JP2009117930A

JP2009117930A - Video signal converter, video display device, video signal conversion method

Info

Publication number: JP2009117930A
Application number: JP2007285753A
Authority: JP
Inventors: Naoko Kondo; 尚子近藤; Xiaomang Zhang; 小▲忙▼ 張; Toshiyuki Goto; 俊之後藤
Original assignee: Sharp Corp
Current assignee: Sharp Corp
Priority date: 2007-11-02
Filing date: 2007-11-02
Publication date: 2009-05-28
Anticipated expiration: 2027-11-02
Also published as: JP4861294B2

Abstract

<P>PROBLEM TO BE SOLVED: To correctly reproduce color in a color gamut of a video display section when a primary video signal having a color gamut wider than a color gamut that is displayed by the video display section is converted into a secondary video signal in the color gamut of the video display section, and to perform signal processing of other colors with a low operation load while ensuring continuity of color. <P>SOLUTION: If the signal values Xr, Xg and Xb of RGB in a primary video signal deviate from an output range, the signal state is divided into any of the three states, a formula is selected depending on the state, and the primary video signal is converted into secondary video signals Yr, Yg, and Yb based on a selected formula. Smin and Smax represent lower-limit and upper-limit values of output, and Xmax and Xmin represent maximum and minimum values of Xr-Xb. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

本発明は，所定の出力範囲を一部に含む（出力範囲よりも広い）拡張範囲の信号値をとり得るＲＧＢ各原色の輝度信号からなる映像信号を，前記出力範囲の値をとり得るＲＧＢ各原色の輝度信号からなる映像信号へ変換する映像信号変換装置及びその方法，並びにその映像信号変換装置を備えた映像表示装置に関するものである。 According to the present invention, a video signal composed of luminance signals of RGB primary colors that can take a signal value of an extended range that includes a predetermined output range in part (wider than the output range) is converted into a RGB signal that can take the value of the output range. The present invention relates to a video signal conversion apparatus and method for converting into a video signal composed of luminance signals of primary colors, and a video display apparatus including the video signal conversion apparatus.

テレビジョン受像機等の映像表示装置において，液晶ディスプレイ等の映像表示部は，ＲＧＢ３原色それぞれの輝度信号からなる映像信号（以下，出力側映像信号という）に基づいて映像を表示する。一般に，前記出力側映像信号におけるＲＧＢ３原色の輝度信号は，その組合せが映像表示部により表示可能（再現可能）な色域（色再現領域又は色再現範囲ともいう）内の色と対応するように，信号値（ＲＧＢ３原色の輝度信号の値）が予め定められた下限値（以下，出力下限値という）からそれより大きい上限値（以下，出力上限値という）までの出力範囲（例えば，０〜２５５或いは０〜１等）内で正規化されている。
ところで，映像表示装置に入力される映像信号（以下，入力映像信号という）により表現可能な色域が，映像表示部により再現可能（表示可能）な色域に含まれる場合（一致する場合又は一部に含まれる場合），前記入力映像信号の信号値そのもの若しくは前記入力信号に対して既知の色域変換処理を施した映像信号（以下，入力側映像信号という）の信号値は，前記出力範囲内の値となり，それを前記出力側映像信号として採用すれば，映像表示部により前記入力映像信号に対応した映像（色）が表示される。
一方，前記入力映像信号により表現可能な色域が，映像表示部により再現可能（表示可能）な色域から外れている場合（映像表示部の色域よりも広い場合等），前記入力側映像信号の信号値は前記出力範囲から外れた値をとり得ることとなり，それを前記出力側映像信号として採用することができない場合が生じる。例えば，映像表示部の色域に対応する映像信号の３原色の輝度値の範囲（前記出力範囲）が０〜１であるのに対し，前記入力側映像信号の信号値が負の値となる場合や１を超える値となる場合があり，そのような場合には，前記入力側映像信号を，信号値が前記出力範囲に収まる前記出力側映像信号へ変換しなければならない。このような状況としては，例えば，前記入力側映像信号がＩＥＣ６１９６６−２−４規格（通称，ｘｖＹＣＣ規格）やＩＥＣ６１９６６−２−１規格に準拠した映像信号であるのに対し，前記出力側映像信号がＩＴＵ−ＲＢＴ．７０９規格に準拠した映像信号である状況が考えられる。
ここで，前記入力側映像信号の信号値が前記出力範囲から外れている場合の信号変換方法としては，最も簡易な方法として，前記入力側映像信号の信号値に前記出力範囲でのクリップ処理（リミッタ処理といってもよい）を施すことによって前記出力側映像信号に変換する処理が考えられる。
また，特許文献１には，出力系の色域（映像表示部の色域に相当）が入力系の色域（前記入力側映像信号の色域に相当）よりも小さい場合に，入力系の色域を明度及び彩度の２次元平面上において領域分割し，分割領域ごとに色相を一定にしつつ色域の圧縮（信号値の圧縮）を行うことについて示されている。このように，色域圧縮の前後の映像信号において色相を一定に維持することにより，色域圧縮後の映像信号が表す色の色味を，色域圧縮前の映像信号が表す色（元の色）の色味に近づけることができ，元の色に対してより忠実な色の再現（表示）が可能となり好適である。
特開平９−９８２９８号公報 In a video display device such as a television receiver, a video display unit such as a liquid crystal display displays a video based on a video signal (hereinafter referred to as an output-side video signal) composed of luminance signals of the three primary colors of RGB. In general, the luminance signals of the three primary colors RGB in the output-side video signal correspond to colors in a color gamut (also referred to as color reproduction region or color reproduction range) whose combination can be displayed (reproducible) by the video display unit. , An output range (for example, 0 to 0) of signal values (values of luminance signals of RGB three primary colors) from a predetermined lower limit value (hereinafter referred to as output lower limit value) to a higher upper limit value (hereinafter referred to as output upper limit value). 255 or 0-1 etc.).
By the way, when the color gamut that can be expressed by the video signal input to the video display device (hereinafter referred to as the input video signal) is included in the color gamut that can be reproduced (displayed) by the video display unit (if they match, A signal value of the input video signal itself or a video signal obtained by performing a known color gamut conversion process on the input signal (hereinafter referred to as an input-side video signal) If this value is adopted as the output-side video signal, the video (color) corresponding to the input video signal is displayed by the video display unit.
On the other hand, when the color gamut that can be represented by the input video signal is out of the color gamut that can be reproduced (displayed) by the video display unit (such as when it is wider than the color gamut of the video display unit), The signal value of the signal can take a value out of the output range, and there are cases where it cannot be adopted as the output-side video signal. For example, the range of the luminance values of the three primary colors of the video signal corresponding to the color gamut of the video display unit (the output range) is 0 to 1, whereas the signal value of the input video signal is a negative value. In some cases, the value may exceed 1, and in such a case, the input-side video signal must be converted into the output-side video signal whose signal value falls within the output range. As such a situation, for example, the input side video signal is a video signal conforming to the IEC 61966-2-4 standard (common name, xvYCC standard) or the IEC 61966-2-1 standard, while the output side video signal is The video signal is ITU-R BT. A situation in which the video signal conforms to the 709 standard can be considered.
Here, as a signal conversion method when the signal value of the input-side video signal is out of the output range, as a simplest method, the signal value of the input-side video signal is clipped in the output range ( A process of converting to the output-side video signal by performing a limiter process may be considered.
Further, in Patent Document 1, when the output color gamut (corresponding to the color gamut of the video display unit) is smaller than the input color gamut (corresponding to the color gamut of the input-side video signal), It is shown that the color gamut is divided into regions on a two-dimensional plane of lightness and saturation, and the color gamut is compressed (signal value compression) while keeping the hue constant for each divided region. In this way, by maintaining the hue constant in the video signal before and after the color gamut compression, the color tone represented by the video signal after the color gamut compression represents the color represented by the video signal before the color gamut compression (the original Color), and it is possible to reproduce (display) a color more faithful to the original color.
JP-A-9-98298

しかしながら，前記入力側映像信号をクリップ処理によって前記出力側映像信号に変換した場合，前記出力範囲を超える前記入力側映像信号の信号値が全て前記出力下限値又は前記出力上限値に置き換えられるため，前記入力側映像信号における色の連続性が著しく損なわれてしまう（グラデーションの破綻が生じる）という問題点があった。
また，特許文献１に示される技術は，映像信号を明度及び彩度の２次元平面上のデータとして処理するため，色相を一定にしつつ色域圧縮（信号変換）を行う処理が，三角関数を用いた演算処理となって演算負荷が高いという問題点もあった。
従って，本発明は上記事情に鑑みてなされたものであり，その目的とするところは，映像表示部により表示可能な色域よりも色域の広い映像信号（前記入力側映像信号に相当）が与えられ，その映像信号を映像表示部の色域内の色を表す映像信号（前記出力側映像信号に相当）に変換する際に，与えられた映像信号が映像表示部の色域外の領域の色を表す信号であっても，その領域の色の連続性を極力確保できる（グラデーションの破綻を回避できる）とともに，元の映像信号が表す色に対してより忠実な色の再現（表示）を可能とし，さらに，低い演算負荷で信号変換処理を実行できる映像信号変換装置及びその方法，並びに映像表示装置を提供することにある。 However, when the input-side video signal is converted to the output-side video signal by clipping, all the signal values of the input-side video signal exceeding the output range are replaced with the output lower limit value or the output upper limit value. There is a problem in that the color continuity in the input video signal is significantly impaired (gradation failure occurs).
In addition, the technique disclosed in Patent Document 1 processes a video signal as data on a two-dimensional plane of lightness and saturation, so that processing for performing color gamut compression (signal conversion) while maintaining a constant hue is a trigonometric function. There is also a problem that the calculation load is high due to the calculation processing used.
Therefore, the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a video signal (corresponding to the input-side video signal) having a wider color gamut than the color gamut that can be displayed by the video display unit. When the given video signal is converted into a video signal representing a color within the color gamut of the video display unit (corresponding to the output side video signal), the given video signal is converted into a color outside the color gamut of the video display unit. Even if it is a signal representing the color, the continuity of the color in that area can be secured as much as possible (a gradation failure can be avoided), and more accurate color reproduction (display) of the color represented by the original video signal is possible Furthermore, another object of the present invention is to provide a video signal conversion apparatus and method, and a video display apparatus capable of executing signal conversion processing with a low calculation load.

上記目的を達成するために本発明に係る映像信号変換装置は，予め定められた出力下限値から出力上限値までの出力範囲を一部に含む拡張範囲の信号値をとり得るＲＧＢ各原色の輝度信号からなる映像信号（以下，一次映像信号という）を，所定の映像表示手段に入力される映像信号であり，前記出力範囲の値をとり得るＲＧＢ各原色の輝度信号からなる映像信号（以下，二次映像信号という）へ変換して出力する装置であり，次の（１）〜（５）に示す各構成要素を備えるものである。
（１）前記一次映像信号におけるＲＧＢ各原色の輝度信号の値の最小値Ｘmin及び最大値Ｘmaxと前記出力下限値Ｓmin及び前記出力上限値Ｓmaxとの比較により，「Ｓmin≦ＸminかつＳmax＜Ｘmax」である第１の信号状態と，「Ｘmin＜ＳminかつＳmax＜Ｘmax」である第２の信号状態と，「Ｘmin＜ＳminかつＸmax≦Ｓmax」である第３の信号状態と，その他の信号状態とのいずれであるかを判別する信号状態判別手段。
（２）前記第１の信号状態である場合に以下の（Ａ１）式によって得られる信号値Ｙr，Ｙg，Ｙbを算出してそれらをＲＧＢ各原色の輝度信号の値とする前記二次映像信号を出力する第１の信号変換出力手段。
（３）前記第２の信号状態である場合に以下の（Ａ２）式によって得られる信号値Ｙr，Ｙg，Ｙbを算出してそれらをＲＧＢ各原色の輝度信号の値とする前記二次映像信号を出力する第２の信号変換出力手段。
（４）前記第３の信号状態である場合に以下の（Ａ３）式によって得られる信号値Ｙr，Ｙg，Ｙbを算出してそれらをＲＧＢ各原色の輝度信号の値とする前記二次映像信号を出力する第３の信号変換出力手段。
（５）前記その他の信号状態である場合に前記一次映像信号と同じＲＧＢ各原色の輝度信号からなる前記二次映像信号を出力する第４の信号変換出力手段。

但し，Ｓminは前記出力下限値(前記二次映像信号の各輝度信号の下限値)，Ｓmaxは前記出力上限値(前記二次映像信号の各輝度信号の上限値)，Ｘrは前記一次映像信号におけるＲ輝度信号の値，Ｘgは前記一次映像信号におけるＧ輝度信号の値，Ｘbは前記一次映像信号におけるＢ輝度信号の値，ＸmaxはＸr，Ｘg及びＸbのうちの最大値，ＸminはＸr，Ｘg及びＸbのうちの最小値，Ｙrは前記二次映像信号におけるＲ輝度信号の値，Ｙgは前記二次映像信号におけるＧ輝度信号の値，Ｙbは前記二次映像信号におけるＢ輝度信号の値，ｋ1，ｋ2及びｋ3は変換係数である。
なお，本発明は，必ずしも前記（Ａ１）式乃至（Ａ３）式に従って信号変換処理を実行することを要件とするものではなく，前記（Ａ１）式乃至（Ａ３）式に従った信号変換処理と同等の結果が得られる信号変換処理を実行するものであればよい。例えば，前記（Ａ１）式乃至（Ａ３）式に従った信号変換処理と同等の結果が得られる他の変換式に基づく信号変換処理，或いは，予め設定された信号変換テーブルに基づく信号変換処理等を実行することも考えられる。
また，前記一次映像信号は，前記映像表示手段により表示（再現）可能な色域に対応するように色域変換がなされた後の信号であるものとする。従って，前記一次映像信号の信号値が前記出力範囲内である場合，その一次映像信号をそのまま前記二次映像信号とすれば，前記一次映像信号が表す本来の色が前記映像表示手段によって正しく再現（表示）される。 In order to achieve the above object, the video signal conversion apparatus according to the present invention provides the luminance of each primary color of RGB that can take a signal value in an extended range including a part of the output range from a predetermined output lower limit value to an output upper limit value. A video signal consisting of a signal (hereinafter referred to as a primary video signal) is a video signal inputted to a predetermined video display means, and a video signal consisting of a luminance signal of each primary color of RGB that can take the value of the output range (hereinafter referred to as a video signal). Device (hereinafter referred to as secondary video signal) for output, and includes the following components (1) to (5).
(1) By comparing the minimum value Xmin and the maximum value Xmax of the luminance signals of RGB primary colors in the primary video signal with the output lower limit value Smin and the output upper limit value Smax, “Smin ≦ Xmin and Smax <Xmax” A first signal state of “Xmin <Smin and Smax <Xmax”, a third signal state of “Xmin <Smin and Xmax ≦ Smax”, and other signal states Signal state determination means for determining which of the above.
(2) The secondary video signal in which the signal values Yr, Yg, Yb obtained by the following equation (A1) in the first signal state are calculated and used as luminance signal values of RGB primary colors. First signal conversion output means for outputting.
(3) The secondary video signal in which the signal values Yr, Yg, Yb obtained by the following equation (A2) in the second signal state are calculated and used as the luminance signal values of RGB primary colors 2nd signal conversion output means to output.
(4) The secondary video signal in which the signal values Yr, Yg, Yb obtained by the following equation (A3) in the third signal state are calculated and used as the luminance signal values of RGB primary colors 3rd signal conversion output means to output.
(5) Fourth signal conversion output means for outputting the secondary video signal composed of luminance signals of the same primary colors of RGB as the primary video signal in the other signal states.

Where Smin is the output lower limit value (lower limit value of each luminance signal of the secondary video signal), Smax is the output upper limit value (upper limit value of each luminance signal of the secondary video signal), and Xr is the primary video signal. R luminance signal value, Xg is a G luminance signal value in the primary video signal, Xb is a B luminance signal value in the primary video signal, Xmax is a maximum value among Xr, Xg and Xb, Xmin is Xr, The minimum value of Xg and Xb, Yr is the value of the R luminance signal in the secondary video signal, Yg is the value of the G luminance signal in the secondary video signal, and Yb is the value of the B luminance signal in the secondary video signal. , K1, k2 and k3 are transform coefficients.
Note that the present invention does not necessarily require that the signal conversion processing is executed according to the above equations (A1) to (A3), and the signal conversion processing according to the above equations (A1) to (A3) What is necessary is just to perform the signal conversion process in which the equivalent result is obtained. For example, a signal conversion process based on another conversion expression that can obtain a result equivalent to the signal conversion process according to the expressions (A1) to (A3), or a signal conversion process based on a preset signal conversion table, etc. It is also possible to execute.
The primary video signal is a signal after color gamut conversion is performed so as to correspond to a color gamut that can be displayed (reproduced) by the video display means. Accordingly, when the signal value of the primary video signal is within the output range, if the primary video signal is directly used as the secondary video signal, the original color represented by the primary video signal is correctly reproduced by the video display means. (Is displayed.

本発明によれば，前記一次映像信号の信号値（Ｘr，Ｘg，Ｘb）が前記出力範囲内である場合，その一次映像信号がそのまま前記二次映像信号となるため，前記一次映像信号が表す本来の色（元の色）が前記映像表示手段によって正しく再現（表示）される。
また，本発明によれば，後述するように，前記一次映像信号が表す色（元の色）の色相と，前記二次映像信号が表す色の色相とを常に一致させること（色相の維持）ができ，元の色と色味の近い色を前記映像表示手段において再現（表示）できる。
さらに，本発明によれば，後述するように，前記一次映像信号の信号値が少なくとも前記第１の信号状態及び前記第３の信号状態のいずれかである場合，前記一次映像信号が表す色の変化に対する前記二次映像信号が表す色の変化の連続性を確保できる（グラデーションの破綻を回避できる）。なお，前記一次映像信号の信号値が前記第２の信号状態となる頻度は比較的低いので，多くの場合，前記色の連続性を確保できる。
また，本発明における映像信号の変換処理は，演算負荷の高い三角関数の演算を行うことなく，ＲＧＢ各原色の信号値に基づく簡易な（演算負荷の低い）四則演算により実現できる。
ここで，前記一次映像信号の例としては，ＩＥＣ６１９６６−２−４規格（いわゆる新動画用拡張色空間国際規格であるｘｖＹＣＣ）若しくはＩＥＣ６１９６６−２−１規格に準拠した映像信号や，その映像信号にガンマ処理が施された信号が考えられる。なお，ＩＥＣは，International Electrotechnical Commission（国際電気標準会議）の略である。
一方，前記二次映像信号又はその二次映像信号にガンマ処理が施された信号の例として，ＩＴＵ−ＲＢＴ．７０９規格又はＩＴＵ−ＲＢＴ．６０１−５規格に準拠した映像信号が考えられる。なお，ＩＴＵは，International Telecommunication Union（国際電気通信連合）の略である。
また，本発明は，以上に示した本発明に係る映像信号変換装置及びその映像信号変換装置により生成された前記二次映像信号に基づく映像を表示する映像表示手段を備えた映像表示装置として捉えることもできる。
また，本発明は，以上に示した本発明に係る映像信号変換装置における各手段が実行する処理をプロセッサ（演算手段或いはコンピュータといってもよい）によって実行する映像信号変換方法として捉えることもできる。 According to the present invention, when the signal value (Xr, Xg, Xb) of the primary video signal is within the output range, the primary video signal is directly used as the secondary video signal. The original color (original color) is correctly reproduced (displayed) by the video display means.
In addition, according to the present invention, as will be described later, the hue of the color (original color) represented by the primary video signal and the hue of the color represented by the secondary video signal are always matched (maintain hue). The video display means can reproduce (display) a color close to the original color.
Further, according to the present invention, as will be described later, when the signal value of the primary video signal is at least one of the first signal state and the third signal state, the color of the color represented by the primary video signal is The continuity of the color change represented by the secondary video signal with respect to the change can be secured (a gradation failure can be avoided). In addition, since the frequency with which the signal value of the primary video signal is in the second signal state is relatively low, the continuity of the color can be ensured in many cases.
Further, the video signal conversion processing according to the present invention can be realized by simple (low calculation load) four arithmetic operations based on the signal values of RGB primary colors without performing a trigonometric function calculation with a high calculation load.
Here, examples of the primary video signal include a video signal conforming to the IEC 61966-2-4 standard (xvYCC which is an international standard for extended color space for new moving images) or the IEC 61966-2-1 standard, and the video thereof. A signal obtained by performing gamma processing on the signal is considered. IEC stands for International Electrotechnical Commission.
Meanwhile, as an example of the secondary video signal or a signal obtained by performing gamma processing on the secondary video signal, ITU-R BT. 709 standard or ITU-R BT. A video signal conforming to the 601-5 standard is conceivable. Note that ITU is an abbreviation for International Telecommunication Union.
Further, the present invention is understood as a video display device including the video signal conversion device according to the present invention described above and a video display means for displaying a video based on the secondary video signal generated by the video signal conversion device. You can also
Further, the present invention can also be understood as a video signal conversion method in which processing executed by each means in the video signal conversion apparatus according to the present invention described above is executed by a processor (may be called arithmetic means or a computer). .

本発明によれば，前記一次映像信号の信号値（Ｘr，Ｘg，Ｘb）が前記出力範囲内（映像表示手段に入力される前記二次映像信号の信号値がとり得る範囲内）である場合，その一次映像信号がそのまま前記二次映像信号となるため，前記一次映像信号が表す本来の色が前記映像表示手段によって正しく再現（表示）される。
また，本発明によれば，多くの場合，前記一次映像信号が表す色の変化に対する前記二次映像信号が表す色の変化の連続性を確保できる（グラデーションの破綻を回避できる）。
また，本発明によれば，多くの場合，前記一次映像信号が表す色（元の色）の色相と，前記二次映像信号が表す色の色相とを一致させること（色相の維持）ができ，元の色と色味の近い色を前記映像表示手段において再現（表示）できる。
さらに，本発明における映像信号の変換処理は，ＲＧＢ各原色の信号値に基づく簡易な（演算負荷の低い）四則演算により実現できるので，比較的低い性能のプロセッサにより実現できる。 According to the present invention, when the signal values (Xr, Xg, Xb) of the primary video signal are within the output range (within the possible range of the signal value of the secondary video signal input to the video display means). Since the primary video signal becomes the secondary video signal as it is, the original color represented by the primary video signal is correctly reproduced (displayed) by the video display means.
Further, according to the present invention, in many cases, it is possible to ensure the continuity of the color change represented by the secondary video signal with respect to the color change represented by the primary video signal (a gradation failure can be avoided).
Further, according to the present invention, in many cases, the hue of the color represented by the primary video signal (original color) and the hue of the color represented by the secondary video signal can be matched (maintain hue). , A color close to the original color can be reproduced (displayed) by the video display means.
Furthermore, since the video signal conversion processing according to the present invention can be realized by simple four arithmetic operations based on the signal values of RGB primary colors (low calculation load), it can be realized by a processor with relatively low performance.

以下添付図面を参照しながら，本発明の実施の形態について説明し，本発明の理解に供する。尚，以下の実施の形態は，本発明を具体化した一例であって，本発明の技術的範囲を限定する性格のものではない。
ここに，図１は本発明の実施形態に係る映像表示装置Ｚの主要部の概略構成を表すブロック図，図２は映像表示装置Ｚの変形例である映像表示装置Ｚ’の主要部の概略構成を表す図，図３はＹｃｂｃｒ信号に対応するＲＧＢ信号の信号値が出力範囲に収まる色域をＹＵＶ空間において表した図，図４はＹｃｂｃｒ信号に対応するＲＧＢ信号の複数の状態に対応するＹＵＶ空間における色域の領域を表した図，図５は映像信号変換装置Ｑによる信号変換の様子をＹＵＶ空間において表した図である。 Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
FIG. 1 is a block diagram showing a schematic configuration of a main part of a video display device Z according to an embodiment of the present invention. FIG. 2 is a schematic diagram of a main part of a video display device Z ′ which is a modification of the video display device Z. FIG. 3 is a diagram showing the configuration, FIG. 3 is a diagram showing a color gamut in the YUV space where the signal value of the RGB signal corresponding to the Ycbcr signal falls within the output range, and FIG. 4 corresponds to a plurality of states of the RGB signal corresponding to the Ycbcr signal. FIG. 5 is a diagram showing a color gamut region in the YUV space, and FIG. 5 is a diagram showing how the video signal conversion device Q performs signal conversion in the YUV space.

本発明の実施形態に係る映像表示装置Ｚは，図１に示すように，映像表示手段であるディスプレイ５と，入力された映像信号を前記ディスプレイ５に供給するＲＧＢ信号（映像信号）に変換する映像信号変換装置Ｑとを備えている。
前記ディスプレイ５は，ＲＧＢ各原色の輝度信号（Ｒ信号，Ｇ信号及びＢ信号）からなる映像信号が入力され，その映像信号に基づく映像を表示する液晶ディスプレイやＣＲＴ等のデバイスである。このディスプレイ５に入力される映像信号（ＲＧＢ信号）は，例えば，ＩＴＵ−ＲＢＴ．７０９規格やＩＴＵ−ＲＢＴ．６０１−５規格に準拠したＲＧＢ信号等であり，予め定められた出力下限値Ｓminから出力上限値Ｓmaxまで（ここで，Ｓmin＜Ｓmax）の範囲（以下，出力範囲Ｗという）の値をとり得るＲＧＢ各原色の輝度信号からなる映像信号（以下，非線形二次映像信号Ｖ2’という）である。なお，前記非線形二次映像信号Ｖ2’は，前記ディスプレイ５により表示可能（再現可能）な色域内の色と対応するように，信号値（ＧＢ３原色の輝度信号の値）が前記出力範囲Ｗ（例えば，０〜２５５或いは０〜１等）内で正規化された映像信号である。
そして，映像表示装置Ｚには，前記ディスプレイ５が表示（再現）可能な色域よりも広く拡張された色域を表現可能な映像信号が入力される。この映像信号のことを，以下，入力映像信号Ｖ0という。
前記映像信号変換装置Ｑは，外部から入力される前記入力映像信号Ｖ0を，ＲＧＢ信号（ＲＧＢ各原色の輝度信号からなる映像信号，以下，非線形一次映像信号Ｖ1’という）に変換するとともに，さらに，その非線形一次映像信号Ｖ1’を，前記ディスプレイ５に入力される前記非線形二次映像信号Ｖ2’（前記出力範囲Ｗの値をとり得るＲＧＢ各原色の輝度信号からなる映像信号）へ変換する処理を実行するものである。 As shown in FIG. 1, a video display device Z according to an embodiment of the present invention converts a display 5 as video display means and an RGB signal (video signal) to be supplied to the display 5 into an input video signal. And a video signal converter Q.
The display 5 is a device such as a liquid crystal display or a CRT that receives a video signal composed of luminance signals (R signal, G signal, and B signal) of RGB primary colors and displays an image based on the video signal. The video signal (RGB signal) input to the display 5 is, for example, ITU-R BT. 709 standard and ITU-R BT. The RGB signal conforms to the 601-5 standard and can take a value in a range (hereinafter, referred to as an output range W) from a predetermined output lower limit value Smin to an output upper limit value Smax (herein, Smin <Smax). This is a video signal (hereinafter referred to as a non-linear secondary video signal V2 ') composed of luminance signals of RGB primary colors. The nonlinear secondary video signal V2 ′ has a signal value (value of a luminance signal of GB3 primary colors) corresponding to a color in a color gamut that can be displayed (reproducible) on the display 5 in the output range W ( For example, it is a video signal normalized within 0-255 or 0-1).
A video signal that can express a color gamut that is wider than the color gamut that the display 5 can display (reproduce) is input to the video display device Z. This video signal is hereinafter referred to as an input video signal V0.
The video signal conversion device Q converts the input video signal V0 input from the outside into an RGB signal (video signal composed of luminance signals of RGB primary colors, hereinafter referred to as a non-linear primary video signal V1 ′), and further The non-linear primary video signal V1 ′ is converted into the non-linear secondary video signal V2 ′ (video signal composed of luminance signals of RGB primary colors that can take the value of the output range W) input to the display 5. Is to execute.

また，前記映像信号変換装置Ｑは，例えば，ＤＳＰ（Digital Signal Processor）やＡＳＩＣ等のデジタル処理回路（素子）であり，演算用のプロセッサ（演算手段）及びそのプロセッサにより実行されるプログラムが記憶されたＲＯＭ等の記憶手段，並びにＲＡＭ等のその他の周辺装置を備えて構成されている。そして，前記映像信号変換装置Ｑが備える各構成要素（ＲＧＢ信号生成部１，一次側ガンマ処理部２，信号範囲調整部３及び二次側ガンマ処理部４）は，それぞれの処理に対応したプログラムを実行する前記プロセッサによって具現されている。
なお，前記映像信号変換装置Ｑが備える各構成要素は，前段の構成要素がメモリに記録した信号値（信号処理の結果）を，後段の構成要素がそのメモリから読み出して参照することにより，処理結果（信号値）の受け渡しを行う。 The video signal conversion device Q is, for example, a digital processing circuit (element) such as a DSP (Digital Signal Processor) or ASIC, and stores a processor for calculation (arithmetic means) and a program executed by the processor. Further, it is configured to include storage means such as a ROM and other peripheral devices such as a RAM. Each component (RGB signal generation unit 1, primary gamma processing unit 2, signal range adjustment unit 3 and secondary gamma processing unit 4) included in the video signal conversion device Q is a program corresponding to each process. It is embodied by the processor that executes
Each component included in the video signal conversion apparatus Q is processed by reading the signal value (result of signal processing) recorded in the memory by the preceding component into the memory and referring to the component after reading from the memory. The result (signal value) is transferred.

続いて，前記映像信号変換装置ＱにおけるＲＧＢ信号生成部１，一次側ガンマ処理部２，信号範囲調整部３及び二次側ガンマ処理部４の処理について説明する。
前記ＲＧＢ信号生成部１は，外部から入力される前記入力映像信号Ｖ0を，ＲＧＢ各原色の輝度信号からなる映像信号（以下，非線形一次映像信号Ｖ1’という）に変換する処理（即ち，ＲＧＢ信号を生成する処理）を実行する。
前記入力映像信号Ｖ0は，例えば，ＩＥＣ６１９６６−２−４規格，或いはＩＥＣ６１９６６−２−１規格に準拠したＹＵＶ信号やＹｃｂｃｒ信号等の映像信号であり，その色域は，前記ディスプレイ５により表示（再現）可能な色域よりも広く拡張されている。
そして，前記ディスプレイ５の色域（前記入力映像信号Ｖ0により表現可能な色域）よりも前記入力映像信号Ｖ0により表現可能な色域の方が広いため，前記非線形一次映像信号Ｖ1’は，前記出力範囲Ｗ（出力下限値Ｓminから出力上限値Ｓmaxまで）を一部に含む拡張範囲Ｗ’の信号値をとり得るＲＧＢ信号（ＲＧＢ各原色の輝度信号からなる映像信号）となる。
なお，ＩＥＣ６１９６６−２−４規格及びＩＥＣ６１９６６−２−１規格において，各規格に準拠したＹＵＶ信号やＹｃｂｃｒ信号を同規格に準拠したＲＧＢ信号に変換する規則（変換式）が規定されており，前記ＲＧＢ信号生成部１は，その規則（変換式）に従った信号変換処理を行う。このため，前記入力映像信号Ｖ0が，ＩＥＣ６１９６６−２−４規格，或いはＩＥＣ６１９６６−２−１規格に準拠したＹＵＶ信号やＹｃｂｃｒ信号等の映像信号である場合，前記非線形一次映像信号Ｖ1も，ＩＥＣ６１９６６−２−４規格，或いはＩＥＣ６１９６６−２−１規格に準拠したＲＧＢ信号となる。 Next, processing of the RGB signal generation unit 1, the primary side gamma processing unit 2, the signal range adjustment unit 3, and the secondary side gamma processing unit 4 in the video signal conversion apparatus Q will be described.
The RGB signal generation unit 1 converts the input video signal V0 input from the outside into a video signal (hereinafter referred to as a non-linear primary video signal V1 ′) composed of luminance signals of RGB primary colors (that is, an RGB signal). Process to generate).
The input video signal V0 is a video signal such as a YUV signal or a Ycbcr signal conforming to the IEC 61966-2-4 standard or the IEC 61966-2-1 standard, and the color gamut thereof is displayed on the display 5. (Reproduction) Widened wider than possible color gamut.
Since the color gamut that can be expressed by the input video signal V0 is wider than the color gamut of the display 5 (color gamut that can be expressed by the input video signal V0), the nonlinear primary video signal V1 ' This is an RGB signal (a video signal composed of luminance signals of RGB primary colors) that can take a signal value of the extended range W ′ partially including the output range W (from the output lower limit value Smin to the output upper limit value Smax).
In the IEC 61966-2-4 standard and the IEC 61966-2-1 standard, rules (conversion formulas) for converting YUV signals and Ycbcr signals compliant with each standard into RGB signals compliant with the standard are defined. The RGB signal generation unit 1 performs signal conversion processing according to the rule (conversion formula). Therefore, when the input video signal V0 is a video signal such as a YUV signal or a Ycbcr signal conforming to the IEC 61966-2-4 standard or the IEC 61966-2-1 standard, the nonlinear primary video signal V1 is The RGB signal conforms to the IEC 61966-2-4 standard or the IEC 61966-2-1 standard.

ところで，前記非線形一次映像信号Ｖ1’及び前記非線形二次映像信号Ｖ2’は，信号値（輝度の階調値）とその信号値に対応する実際の色の輝度との対応関係が非線形である映像信号である。以下，前記非線形一次映像信号Ｖ1’及び前記非線形二次映像信号Ｖ2’それぞれについて，信号値とその信号値に対応する実際の色の輝度との対応関係が線形となるように修正（補正）された信号を，それぞれ線形一次映像信号Ｖ1及び線形二次映像信号Ｖ2という。
前記一次側ガンマ処理部２は，前記非線形一次映像信号Ｖ1’に対して周知のガンマ処理（ガンマ補正処理ともいう）を施すことにより，信号値（輝度の階調値）とその信号値に対応する実際の色の輝度との対応関係が非線形である前記非線形一次映像信号Ｖ1’を，信号値とその信号値に対応する実際の色の輝度との対応関係が線形である線形一次映像信号Ｖ1に変換する処理を実行する。通常，この一次側ガンマ処理部２は，ガンマ値が（１／２．２）であるガンマカーブに従ってガンマ処理を行う。なお，前記線形一次映像信号Ｖ1も，その信号値が前記拡張範囲Ｗ’内の値をとり得る映像信号である。また，前記一次側ガンマ処理部２が参照する前記非線形一次映像信号Ｖ1’から前記線形一次映像信号Ｖ1への信号変換テーブル又は変換式は，映像信号変換装置Ｑが備えるメモリ（ＲＯＭ等）に予め記憶されている。 By the way, the nonlinear primary video signal V1 ′ and the nonlinear secondary video signal V2 ′ are images in which the correspondence between the signal value (luminance gradation value) and the luminance of the actual color corresponding to the signal value is nonlinear. Signal. Hereinafter, for each of the non-linear primary video signal V1 ′ and the non-linear secondary video signal V2 ′, the correspondence between the signal value and the luminance of the actual color corresponding to the signal value is corrected (corrected). These signals are called linear primary video signal V1 and linear secondary video signal V2, respectively.
The primary-side gamma processing unit 2 applies a known gamma process (also referred to as a gamma correction process) to the nonlinear primary video signal V1 ′, thereby corresponding to a signal value (luminance gradation value) and the signal value. The non-linear primary video signal V1 ′ having a non-linear correspondence with the actual color luminance is a linear primary video signal V1 with a linear relationship between the signal value and the actual color luminance corresponding to the signal value. Execute the process of converting to. Normally, the primary side gamma processing unit 2 performs gamma processing according to a gamma curve having a gamma value of (1 / 2.2). The linear primary video signal V1 is also a video signal whose signal value can take a value within the extended range W ′. A signal conversion table or conversion formula from the nonlinear primary video signal V1 ′ to the linear primary video signal V1 referred to by the primary side gamma processing unit 2 is stored in advance in a memory (ROM or the like) provided in the video signal converter Q. It is remembered.

また，前記信号範囲調整部３は，前記出力範囲Ｗを一部に含む前記拡張範囲Ｗ’の信号値をとり得るＲＧＢ各原色の輝度信号からなる前記線形一次映像信号Ｖ1を，前記出力範囲Ｗの値をとり得るＲＧＢ各原色の輝度信号からなる前記線形二次映像信号へ変換する処理を実行するものである。以下，前記信号範囲調整部３が実行する処理の詳細について説明する。
なお，前記信号変換装置Ｑにおける前記信号範囲調整部３の処理に関する以下の説明においては，一次映像信号及び二次映像信号という用語は，それぞれ前記線形一次映像信号Ｖ1及び前記線形二次映像信号Ｖ2と同義であるものとする。
まず，前記信号範囲調整部３は，前記一次映像信号におけるＲＧＢ各原色の輝度信号の値の最小値Ｘmin及び最大値Ｘmaxを特定し，その情報を一次記憶する。
次に，前記信号範囲調整部３は，前記一次映像信号における信号値の最小値Ｘmin及び最大値Ｘmaxと，前記出力下限値Ｓmin及び前記出力上限値Ｓmaxとを比較し，その比較結果に基づいて，前記一次映像信号の値が，以下に示す第１の信号状態〜第４の信号状態のうちのいずれの状態であるかを判別する（前記信号状態判別手段の一例）。
ここで，前記第１の信号状態は，「Ｓmin≦Ｘmin」かつ「Ｓmax＜Ｘmax」の状態である。
また，前記第２の信号状態は，「Ｘmin＜Ｓmin」かつ「Ｓmax＜Ｘmax」の状態である。
また，前記第３の信号状態は，「Ｘmin＜Ｓmin」かつ「Ｘmax≦Ｓmax」の状態である。
そして，前記第１の信号状態〜前記第３の信号状態のいずれでもない状態，即ち，「Ｓmin≦Ｘmin」かつ「Ｘmax≦Ｓmax」である状態が，前記第４の信号状態（前記その他の状態）である。 Further, the signal range adjustment unit 3 converts the linear primary video signal V1 composed of luminance signals of RGB primary colors that can take signal values of the extended range W ′ including the output range W as a part thereof into the output range W The process of converting to the linear secondary video signal composed of the luminance signals of the RGB primary colors that can take the above values is executed. Hereinafter, details of the processing executed by the signal range adjustment unit 3 will be described.
In the following description regarding the processing of the signal range adjusting unit 3 in the signal conversion device Q, the terms primary video signal and secondary video signal are the linear primary video signal V1 and the linear secondary video signal V2, respectively. It shall be synonymous with.
First, the signal range adjustment unit 3 specifies the minimum value Xmin and the maximum value Xmax of the luminance signal values of RGB primary colors in the primary video signal, and primarily stores the information.
Next, the signal range adjustment unit 3 compares the minimum value Xmin and the maximum value Xmax of the signal value in the primary video signal with the output lower limit value Smin and the output upper limit value Smax, and based on the comparison result. , It is determined whether the value of the primary video signal is one of the following first to fourth signal states (an example of the signal state determination unit).
Here, the first signal state is a state of “Smin ≦ Xmin” and “Smax <Xmax”.
The second signal state is a state of “Xmin <Smin” and “Smax <Xmax”.
The third signal state is a state of “Xmin <Smin” and “Xmax ≦ Smax”.
A state that is not one of the first signal state to the third signal state, that is, a state that “Smin ≦ Xmin” and “Xmax ≦ Smax” is the fourth signal state (the other state). ).

次に，前記信号範囲調整部３は，前記一次映像信号の状態の判別結果（前記第１の信号状態〜前記第４の信号状態）に応じて，予め定められた４種類の信号変換規則（信号値の変換式）の中から１つの信号変換規則を選択し，選択した信号変換規則に前記一次映像信号の信号値Ｘr，Ｘg，Ｘbを適用することにより，ＲＧＢ３原色の輝度信号の値Ｙr，Ｙg，Ｙbを算出し，その算出値Ｙr，Ｙg，ＹbをＲＧＢ各原色の輝度信号の値とする前記二次映像信号を後段のデバイスへ出力（信号伝送）する。
即ち，前記信号範囲調整部３は，前記第１の信号状態である場合に以下の（Ａ１）式を，前記第２の信号状態である場合に以下の（Ａ２）式を，前記第３の信号状態である場合に以下の（Ａ３）式を信号変換式（信号変換規則）として選択し，選択した信号変換式に前記一次映像信号の信号値Ｘr，Ｘg，Ｘbを適用することにより，前記二次映像信号の信号値Ｙr，Ｙg，Ｙbを算出する（前記第１の信号変換手段，前記第２の信号変換手段及び前記第３の信号変換手段の一例）。

また，前記信号範囲調整部３は，前記第４の信号状態（その他の信号状態）である場合には，前記一次映像信号と同じＲＧＢ各原色の輝度信号からなる前記二次映像信号を後段のデバイスへ出力する（前記第４の信号変換出力手段の一例）。即ち，前記信号範囲調整部３は，（Ｙr，Ｙg，Ｙb）＝（Ｘr，Ｘg，Ｘb）として前記二次映像信号の出力を行う。
以上のようにして前記信号範囲調整部３により出力される前記二次映像信号（ここでは，前記線形二次映像信号Ｖ2）は，その信号値（Ｙr，Ｙg，Ｙb）が前記出力範囲Ｗ1に収まる信号となる。 Next, the signal range adjusting unit 3 determines four types of signal conversion rules (predetermined in accordance with the determination result of the state of the primary video signal (the first signal state to the fourth signal state)). By selecting one signal conversion rule from the signal value conversion formula) and applying the signal values Xr, Xg, Xb of the primary video signal to the selected signal conversion rule, the luminance signal value Yr of the RGB three primary colors is applied. , Yg, Yb are calculated, and the secondary video signal having the calculated values Yr, Yg, Yb as the luminance signal values of RGB primary colors is output (signal transmission) to the subsequent device.
That is, the signal range adjustment unit 3 calculates the following equation (A1) when the signal state is the first signal state, and calculates the following equation (A2) when the signal state is the second signal state: The following equation (A3) is selected as a signal conversion equation (signal conversion rule) in the signal state, and the signal values Xr, Xg, Xb of the primary video signal are applied to the selected signal conversion equation, thereby Signal values Yr, Yg, Yb of the secondary video signal are calculated (an example of the first signal conversion unit, the second signal conversion unit, and the third signal conversion unit).

Further, the signal range adjustment unit 3, when in the fourth signal state (other signal state), converts the secondary video signal composed of luminance signals of the same primary colors of RGB as the primary video signal to the subsequent stage. Output to the device (an example of the fourth signal conversion output means). That is, the signal range adjustment unit 3 outputs the secondary video signal as (Yr, Yg, Yb) = (Xr, Xg, Xb).
As described above, the secondary video signal (here, the linear secondary video signal V2) output by the signal range adjusting unit 3 has its signal value (Yr, Yg, Yb) in the output range W1. It becomes a signal that falls.

また，前記二次側ガンマ処理部４は，前記信号範囲調整部３により出力（生成）された前記線形二次映像信号Ｖ2に周知のガンマ処理を施すことにより，前記線形二次映像信号Ｖ2を前記非線形二次映像信号Ｖ2’（ＲＧＢ３原色の輝度信号）に変換する。通常，この二次側ガンマ処理部４は，ガンマ値が２．２（前記一次側ガンマ処理部２でのガンマ値の逆数）であるガンマカーブに従ってガンマ処理を行う。
なお，この前記二次側ガンマ処理部４が出力する前記非線形二次映像信号Ｖ2’も，その信号値（Ｙr’，Ｙg’，Ｙb’）が前記出力範囲Ｗ1に収まる信号となる。そして，前記ディスプレイ５は，前記二次側ガンマ処理部４から出力される前記非線形二次映像信号Ｖ2’に基づく映像を出力する。 Further, the secondary side gamma processing unit 4 performs known gamma processing on the linear secondary video signal V2 output (generated) by the signal range adjustment unit 3 to obtain the linear secondary video signal V2. The nonlinear secondary video signal V2 '(RGB three primary color luminance signals) is converted. Normally, the secondary side gamma processing unit 4 performs gamma processing according to a gamma curve whose gamma value is 2.2 (the reciprocal of the gamma value in the primary side gamma processing unit 2).
The nonlinear secondary video signal V2 ′ output from the secondary gamma processing unit 4 is also a signal whose signal values (Yr ′, Yg ′, Yb ′) fall within the output range W1. The display 5 outputs an image based on the nonlinear secondary image signal V2 ′ output from the secondary side gamma processing unit 4.

以下，映像信号変換装置Ｑによる映像信号の変換処理の効果について説明する。
［色相の維持について］
周知の通り，２つのＹｃｂｃｒ信号について，色差信号値の比（Ｃｒ／Ｃｂ及びＣｒ’／Ｃｂ’）が一致すれば，それら２つのＹｃｂｃｒ信号それぞれにより表される色は，色相が同一である。
ここで，前記出力下限値が０となるように前記一次映像信号及び前記二次映像信号の信号値が換算されている場合，前記一次映像信号及び前記二次映像信号におけるＲＧＢの信号値（Ｘr，Ｘg，Ｘb）及び（Ｙr，Ｙg，Ｙb）それぞれを，対応するＹｃｂｃｒ信号の信号値（Ｙ，Ｃｂ，Ｃｒ）及び（Ｙ’，Ｃｂ’，Ｃｒ’）それぞれに変換する式は，次の（Ｂ１）式により表される。

なお，映像信号の形式変換の規則を定めるＩＴＵ−ＲＢＴ．６０１規格では，（Ｂ１）式における変換係数ｈ1〜ｈ9が，次の（Ｂ２）式を満たすことが規定されている。

そして，映像信号変換装置Ｑにおいては，前記一次映像信号の値が前記第１の信号状態である場合，その一次映像信号（ＲＧＢ信号）に対応するＹｃｂｃｒ信号（ＲＧＢ信号の形式からＹｃｂｃｒ信号の形式に変換された映像信号）の色差Ｃｂ，Ｃｒと，前記二次映像信号（ＲＧＢ信号）に対応するＹｃｂｃｒ信号の色差Ｃｂ’，Ｃｒ’との関係は，前記（Ａ１）式と前記（Ｂ１）式とにより導かれる次の（Ｂ３）式の関係を満たす。

同様に，映像信号変換装置Ｑにおいては，前記一次映像信号の値が前記第２の信号状態である場合，その一次映像信号に対応するＹｃｂｃｒ信号の色差Ｃｂ，Ｃｒと，前記二次映像信号に対応するＹｃｂｃｒ信号の色差Ｃｂ’，Ｃｒ’との関係は，前記（Ａ２）式と前記（Ｂ１）式及び前記（Ｂ２）式とにより導かれる次の（Ｂ４）式の関係を満たす。

同様に，映像信号変換装置Ｑにおいては，前記一次映像信号の値が前記第３の信号状態である場合，その一次映像信号に対応するＹｃｂｃｒ信号の色差Ｃｂ，Ｃｒと，前記二次映像信号に対応するＹｃｂｃｒ信号の色差Ｃｂ’，Ｃｒ’との関係は，前記（Ａ３）式と前記（Ｂ１）式及び前記（Ｂ２）式とにより導かれる次の（Ｂ５）式の関係を満たす。

また，映像信号変換装置Ｑにおいては，前記一次映像信号の値が前記第４の信号状態である場合，その一次映像信号と前記二次映像信号とは同じ色を表す。
従って，映像信号変換装置Ｑにおいては，前記信号範囲調整部３による信号変換（信号値の範囲の調整）の前後において，映像信号が表す色の色相を常に維持する（一致させる）ことができ，元の色と色味の近い色を前記ディスプレイ５において再現（表示）できる。 Hereinafter, the effect of the video signal conversion processing by the video signal conversion device Q will be described.
[Hue maintenance]
As is well known, if two Ycbcr signals have the same color difference signal value ratio (Cr / Cb and Cr ′ / Cb ′), the colors represented by the two Ycbcr signals have the same hue.
Here, when the signal values of the primary video signal and the secondary video signal are converted so that the output lower limit value becomes 0, RGB signal values (Xr) in the primary video signal and the secondary video signal , Xg, Xb) and (Yr, Yg, Yb), respectively, are converted into signal values (Y, Cb, Cr) and (Y ′, Cb ′, Cr ′) of the corresponding Ycbcr signal, respectively. It is represented by the formula (B1).

It should be noted that ITU-R BT. The 601 standard stipulates that the conversion coefficients h1 to h9 in the equation (B1) satisfy the following equation (B2).

In the video signal conversion device Q, when the value of the primary video signal is in the first signal state, the Ycbcr signal corresponding to the primary video signal (RGB signal) (from the RGB signal format to the Ycbcr signal format). The relationship between the color differences Cb and Cr of the video signal converted into (2) and the color differences Cb ′ and Cr ′ of the Ycbcr signal corresponding to the secondary video signal (RGB signal) is expressed by the equation (A1) and the equation (B1). The following relationship (B3) derived from the equation is satisfied.

Similarly, in the video signal conversion apparatus Q, when the value of the primary video signal is in the second signal state, the color differences Cb and Cr of the Ycbcr signal corresponding to the primary video signal and the secondary video signal The relationship between the color differences Cb ′ and Cr ′ of the corresponding Ycbcr signal satisfies the relationship of the following equation (B4) derived from the equation (A2), the equation (B1), and the equation (B2).

Similarly, in the video signal converter Q, when the value of the primary video signal is in the third signal state, the color differences Cb and Cr of the Ycbcr signal corresponding to the primary video signal and the secondary video signal The relationship between the color differences Cb ′ and Cr ′ of the corresponding Ycbcr signal satisfies the relationship of the following equation (B5) derived from the equation (A3), the equation (B1), and the equation (B2).

Further, in the video signal conversion device Q, when the value of the primary video signal is in the fourth signal state, the primary video signal and the secondary video signal represent the same color.
Therefore, in the video signal conversion device Q, the hue of the color represented by the video signal can always be maintained (matched) before and after the signal conversion (adjustment of the signal value range) by the signal range adjustment unit 3. A color close to the original color can be reproduced (displayed) on the display 5.

［色の連続性確保について］
図３は，色相がある色相θであるＹｃｂｃｒ信号について，そのＹｃｂｃｒ信号をＲＧＢ信号に変換したときの変換後のＲＧＢ信号（Ｙｃｂｃｒ信号に対応するＲＧＢ信号）の信号値が前記出力範囲Ｗに収まる色域Ａ０（色の領域）をＹＵＶ空間において表した図である。
また，図４は，色相がある色相θであるＹｃｂｃｒ信号について，そのＹｃｂｃｒ信号に対応するＲＧＢ信号の複数の状態に対応するＹＵＶ空間における色域の領域を表した図である。
また，図５は，映像信号変換装置Ｑによる信号変換の様子をＹＵＶ空間において表した図である。なお，ＹＵＶ空間は，Ｙ（輝度），Ｃｂ（青の色差）及びＣｒ（赤の色差）を座標軸とする３次元空間であるが，図３〜図５は，３次元のＹＵＶ空間において色相θに対応して特定される平面（輝度Ｙの軸を含む平面）を表している。
図３〜図５において，点Ｅは，ある色相θにおいて，Ｙｃｂｃｒ信号の輝度値（Ｙの値）が最大，かつ，色差Ｃｂ，Ｃｒが最小である色を表す点，点Ｆは，ある色相θにおいて，Ｙｃｂｃｒ信号の輝度値（Ｙの値）が最小，かつ，色差Ｃｂ，Ｃｒが最小である色を表す点，点Ｇは，ある色相θにおいて，彩度が最大である色を表す点である。ＹＵＶ空間において，図３〜図５に示す三角形ＥＦＧを形成する境界線以内の領域Ａ０が，当該Ｙｃｂｃｒ信号から変換されたＲＧＢ信号の信号値が前記出力範囲Ｗに収まる領域（ＲＧＢ信号により再現（表示）可能な色域）であり，その外側の領域（斜線を記した領域）が前記出力範囲Ｗに収まらない領域（即ち，虚色の領域）である。即ち，前記一次映像信号（ＲＧＢ信号）が前記第４の信号状態であるということは，その一次映像信号は，Ｙｃｂｃｒ信号に変換することにより，ＹＵＶ空間において前記領域Ａ０に位置する色の映像信号であることを意味する。 [Ensuring color continuity]
FIG. 3 shows a signal value of an RGB signal (RGB signal corresponding to the Ycbcr signal) obtained by converting the Ycbcr signal into an RGB signal for a Ycbcr signal whose hue is a certain hue θ. It is a figure showing color gamut A0 (color field) in YUV space.
FIG. 4 is a diagram showing a gamut region in the YUV space corresponding to a plurality of states of the RGB signal corresponding to the Ycbcr signal with respect to the Ycbcr signal having a hue θ of a certain hue.
FIG. 5 is a diagram showing the state of signal conversion by the video signal conversion apparatus Q in the YUV space. The YUV space is a three-dimensional space having Y (luminance), Cb (blue color difference), and Cr (red color difference) as coordinate axes, but FIGS. 3 to 5 show the hue θ in the three-dimensional YUV space. The plane (corresponding to the axis of the luminance Y) specified corresponding to is represented.
3 to 5, a point E represents a color having a maximum luminance value (Y value) of the Ycbcr signal and a minimum color difference Cb, Cr in a certain hue θ, and a point F represents a certain hue. A point representing a color having the minimum luminance value (Y value) of the Ycbcr signal at θ and the minimum color differences Cb and Cr, and point G representing a color having the maximum saturation in a certain hue θ It is. In the YUV space, a region A0 within the boundary line forming the triangle EFG shown in FIGS. 3 to 5 is a region where the signal value of the RGB signal converted from the Ycbcr signal is within the output range W (reproduced by the RGB signal ( Display) possible color gamut), and the outer area (the hatched area) is an area that does not fall within the output range W (that is, an imaginary color area). That is, when the primary video signal (RGB signal) is in the fourth signal state, the primary video signal is converted into a Ycbcr signal, and thus the video signal of the color located in the region A0 in the YUV space. It means that.

一方，図４及び図５に示すように，前記一次映像信号（ＲＧＢ信号）が前記第１の信号状態であるということは，その一次映像信号は，Ｙｃｂｃｒ信号に変換することにより，ＹＵＶ空間において点Ｅ及び点Ｇを通る直線Ｌ１より上側，かつ，点Ｆ及び点Ｇを通る直線Ｌ２より上側の領域Ａ１に位置する色の映像信号であることを意味する。
また，前記一次映像信号（ＲＧＢ信号）が前記第２の信号状態であるということは，その一次映像信号は，Ｙｃｂｃｒ信号に変換することにより，ＹＵＶ空間において前記直線Ｌ１より上側，かつ，前記直線Ｌ２より下側の領域Ａ２に位置する色の映像信号であることを意味する。
また，前記一次映像信号（ＲＧＢ信号）が前記第３の信号状態であるということは，その一次映像信号は，Ｙｃｂｃｒ信号に変換することにより，ＹＵＶ空間において前記直線Ｌ１より下側，かつ，前記直線Ｌ２より下側の領域Ａ３に位置する色の映像信号であることを意味する。 On the other hand, as shown in FIGS. 4 and 5, the primary video signal (RGB signal) is in the first signal state, which means that the primary video signal is converted into a Ycbcr signal in the YUV space. This means that the video signal is in a color located in the area A1 above the straight line L1 passing through the points E and G and above the straight line L2 passing through the points F and G.
Further, the primary video signal (RGB signal) is in the second signal state means that the primary video signal is converted into a Ycbcr signal so that it is above the straight line L1 in the YUV space and the straight line. This means that the video signal is in a color located in the area A2 below L2.
In addition, the primary video signal (RGB signal) is in the third signal state means that the primary video signal is converted into a Ycbcr signal so that it is below the straight line L1 in the YUV space, and This means that the video signal is a color located in the area A3 below the straight line L2.

また，映像信号変換装置Ｑにおいて，前記一次映像信号が前記第１の信号状態であるときに前記（Ａ１）式に基づき信号変換を行うということは，図５に示すように，ＹＵＶ空間において，前記領域Ａ１に存在する点Ｐ₁の位置の色を表す映像信号を，点Ｐ₁と点Ｆとを結ぶ直線と前記直線Ｌ１との交点Ｐ１’の位置の色を表す映像信号に変換することと等価である。
また，映像信号変換装置Ｑにおいて，前記一次映像信号が前記第２の信号状態であるときに前記（Ａ２）式に基づき信号変換を行うということは，図５に示すように，ＹＵＶ空間において，前記領域Ａ２に存在する点Ｐ₂の位置の色を表す映像信号を，点Ｇの位置の色を表す映像信号に変換することと等価である。
また，映像信号変換装置Ｑにおいて，前記一次映像信号が前記第３の信号状態であるときに前記（Ａ３）式に基づき信号変換を行うということは，図５に示すように，ＹＵＶ空間において，前記領域Ａ３に存在する点Ｐ₃の位置の色を表す映像信号を，点Ｐ₃と点Ｅとを結ぶ直線と前記直線Ｌ２との交点Ｐ３’の位置の色を表す映像信号に変換することと等価である。
なお，Ｙｃｂｃｒ信号とＲＧＢ信号との対応関係は周知であり，その対応関係に基づいて，以上に示したＹＵＶ空間における領域とＲＧＢ信号の信号状態との対応関係を容易に導き出すことができるので，ここではその説明を省略する。
ＹＵＶ空間において，縦軸Ｙの値が大きいほど明度が大きいことを意味し，横軸ＣｂＣｒの値が大きいほど彩度が大きいことを意味する。そのため，前記領域Ａ１内の点Ｐ₁の色を点Ｐ₁’の色へ変換する場合，元の点Ｐ₁の色の彩度或いは明度が大きくなるほど，変換後の点Ｐ１’の色の彩度或いは明度が大きくなる。同様に，前記領域Ａ３内の点Ｐ₃の色を点Ｐ₃’の色へ変換する場合，元の点Ｐ₃の色の彩度或いは明度が大きくなるほど，変換後の点Ｐ１’の色の彩度或いは明度が大きくなる。
従って，映像信号変換装置Ｑにおいては，前記一次映像信号の信号値が少なくとも前記第１の信号状態（前記領域Ａ１の範囲内）及び前記第３の信号状態（前記領域３の範囲内）のいずれかである場合，その一次映像信号が表す色の変化に対する前記二次映像信号が表す色の変化の連続性を確保できる（グラデーションの破綻を回避できる）。なお，前記一次映像信号の信号値が前記第２の信号状態となる頻度は比較的低い（前記領域Ａ２の範囲が狭い）ので，多くの場合，前記色の連続性を確保できる。 Further, in the video signal conversion device Q, when the primary video signal is in the first signal state, signal conversion is performed based on the equation (A1), as shown in FIG. Converting the video signal representing the color of the position of the point P ₁ existing in the area A1 into a video signal representing the color of the position of the intersection P1 ′ between the straight line L1 and the straight line connecting the point P ₁ and the point F Is equivalent to
Further, in the video signal conversion device Q, when the primary video signal is in the second signal state, signal conversion is performed based on the equation (A2), as shown in FIG. This is equivalent to converting the video signal representing the color at the point P ₂ existing in the area A 2 into a video signal representing the color at the point G 2.
Further, in the video signal conversion device Q, when the primary video signal is in the third signal state, signal conversion is performed based on the equation (A3), as shown in FIG. Converting the video signal representing the color of the position of the point P ₃ existing in the region A3 into a video signal representing the color of the position of the intersection P3 ′ between the straight line L2 and the straight line connecting the point P ₃ and the point E Is equivalent to
The correspondence relationship between the Ycbcr signal and the RGB signal is well known, and based on the correspondence relationship, the correspondence relationship between the above-described region in the YUV space and the signal state of the RGB signal can be easily derived. The description is omitted here.
In YUV space, the larger the value on the vertical axis Y, the greater the brightness, and the larger the value on the horizontal axis CbCr, the greater the saturation. Therefore, when the color of the point P ₁ in the area A1 is converted to the color of the point P ₁ ′, the color saturation of the converted point P1 ′ increases as the saturation or brightness of the original point P ₁ increases. The degree or brightness increases. Similarly, when the color of the point P ₃ in the area A3 is converted to the color of the point P ₃ ′, the color of the converted point P1 ′ increases as the saturation or lightness of the color of the original point P ₃ increases. Saturation or brightness increases.
Therefore, in the video signal conversion apparatus Q, the signal value of the primary video signal is at least one of the first signal state (within the area A1) and the third signal state (within the area 3). In this case, it is possible to ensure the continuity of the color change represented by the secondary video signal with respect to the color change represented by the primary video signal (a gradation failure can be avoided). Since the frequency at which the signal value of the primary video signal is in the second signal state is relatively low (the range of the area A2 is narrow), the continuity of the color can be ensured in many cases.

ところで，信号変換が行われる前後の２つの映像信号について，色相を維持するためには，前述したように，元の映像信号をＹｃｂｃｒ信号で表したときの色差信号の比Ｃｒ／Ｃｂと，変換後の映像信号をＹｃｂｃｒ信号で表したときの色差信号の比Ｃｒ’／Ｃｂ’とを一致させつつ色域の圧縮を行えばよい。
しかしながら，Ｙｃｂｃｒ信号において，Ｃｒ／Ｃｂ＝Ｃｒ’／Ｃｂ’となるように色域の圧縮を行うためには，例えば，θ＝ａｒｃｔａｎ(Ｃｒ／Ｃｂ）＝ａｒｃｔａｎ(Ｃｒ’／Ｃｂ’）などとし，このθに対応する色相について，以下に示す周知の（Ｃ１）式や（Ｃ２）式に基づいて，ＲＧＢの信号値が前記出力範囲を超えないような色域の範囲を特定した上で，その色域の範囲内の色（変換後のＹｃｂｃｒ信号が表す色）を予め定めた規則に従って特定する，といった手順で変換後の映像信号を算出する必要がある。

しかしながら，そのような手順で信号変換処理を行う場合，煩雑な三角関数の演算や二元一次方程式を解く演算を行う必要が生じ，演算負荷が高くなる。
一方，映像信号変換装置Ｑにおいて，前記信号範囲調整部３が実行する映像信号の変換処理は，演算負荷の高い三角関数の演算を行うことなく，ＲＧＢ各原色の信号値に基づく簡易な（演算負荷の低い）四則演算（前記（Ａ１）式乃至（Ａ３）式）により実現できる。 By the way, in order to maintain the hue of the two video signals before and after the signal conversion, as described above, the ratio Cr / Cb of the color difference signal when the original video signal is represented by the Ycbcr signal and the conversion. The color gamut may be compressed while matching the ratio Cr ′ / Cb ′ of the color difference signal when the subsequent video signal is expressed as a Ycbcr signal.
However, in order to compress the color gamut so that Cr / Cb = Cr ′ / Cb ′ in the Ycbcr signal, for example, θ = arctan (Cr / Cb) = arctan (Cr ′ / Cb ′) For the hue corresponding to this θ, based on the well-known formulas (C1) and (C2) shown below, after specifying the color gamut range such that the RGB signal value does not exceed the output range, It is necessary to calculate the converted video signal by a procedure such as specifying a color within the range of the color gamut (a color represented by the converted Ycbcr signal) according to a predetermined rule.

However, when signal conversion processing is performed in such a procedure, it is necessary to perform complicated trigonometric function calculations and calculations that solve binary linear equations, and the calculation load increases.
On the other hand, in the video signal conversion apparatus Q, the video signal conversion processing executed by the signal range adjustment unit 3 is simple (calculation based on the signal values of RGB primary colors without performing trigonometric calculations with a high calculation load. This can be realized by four arithmetic operations (low load) (formulas (A1) to (A3)).

次に，図２に示すブロック図を参照しつつ，前記映像表示装置Ｚの応用例である映像表示装置Ｚ’について説明する。なお，図２において，図１に示した前記映像表示装置Ｚの構成要素と同じ構成要素については同じ符号が付されている。
前記映像表示装置Ｚにおける前記映像信号変換装置Ｑにおいては，信号値の範囲の調整前（信号変換前）の一次映像信号が，ＩＥＣ６１９６６−２−４規格やＩＥＣ６１９６６−２−１規格に準拠した映像信号である前記非線形一次映像信号Ｖ1’に，前記一次側ガンマ処理部２によってガンマ処理が施された線形の映像信号（前記線形一次映像信号Ｖ1）であった。
さらに，前記映像信号変換装置Ｑにおいては，信号値の範囲の調整後（信号変換後）の二次映像信号が線形の映像信号（前記線形二次映像信号Ｖ2）であり，その映像信号に前記二次側ガンマ処理部４によってガンマ処理が施された非線形の信号（前記非線形二次映像信号Ｖ2’）が，ＩＴＵ−ＲＢＴ．７０９規格やＩＴＵ−ＲＢＴ．６０１−５規格等に準拠した映像信号（ＲＧＢ信号）であった。
これにより，信号変換に簡易な線形式（一次式）である前記（Ａ１）式乃至前記（Ａ３）式を採用しても，非線形の映像信号に線形処理を施した場合に生じる画質の低下を招くことがない。 Next, a video display device Z ′, which is an application example of the video display device Z, will be described with reference to the block diagram shown in FIG. In FIG. 2, the same components as those of the image display device Z shown in FIG.
In the video signal conversion device Q in the video display device Z, the primary video signal before adjustment of the signal value range (before signal conversion) conforms to the IEC 61966-2-4 standard or the IEC 61966-2-1 standard. The non-linear primary video signal V1 ′, which is the video signal, is a linear video signal (the linear primary video signal V1) obtained by performing the gamma processing by the primary side gamma processing unit 2.
Further, in the video signal conversion device Q, the secondary video signal after the signal value range adjustment (after signal conversion) is a linear video signal (the linear secondary video signal V2), and the video signal includes A nonlinear signal (the nonlinear secondary video signal V2 ′) that has been subjected to gamma processing by the secondary side gamma processing unit 4 is converted into ITU-R BT. 709 standard and ITU-R BT. It was a video signal (RGB signal) conforming to the 601-5 standard.
As a result, even if the above-described equations (A1) to (A3), which are simple line formats (primary equations) for signal conversion, are employed, the image quality degradation caused when linear processing is performed on a non-linear video signal is reduced. There is no invitation.

一方，前記映像表示装置Ｚ’は，前記映像表示装置Ｚにおける前記映像信号変換装置Ｑに代えて，その映像信号変換装置Ｑから前記一次側ガンマ処理部２及び前記二次側ガンマ処理部３が除かれた映像信号変換装置Ｑ’を備えている。即ち，映像信号変換装置Ｑ’は，前記ＲＧＢ信号生成部１と前記信号範囲調整部３とを備えている。
そして，前記映像信号変換装置Ｑ’における前記信号範囲調整部３は，まず，前記ＲＧＢ信号生成部１により生成された前記非線形一次映像信号Ｖ1’について信号状態（前記第１の信号状態乃至前記第３の信号状態）を判別する。
さらに，前記映像信号変換装置Ｑ’における前記信号範囲調整部３は，前記非線形一次映像信号Ｖ1’について信号状態に応じた変換式（前記（Ａ１）式乃至前記（Ａ３）式）を選択し，選択した変換式に前記非線形一次映像信号Ｖ1’におけるＲＧＢ３原色の輝度信号の値を適用することにより，前記非線形一次映像信号Ｖ1’を前記非線形二次映像信号Ｖ2’に変換する。即ち，当該信号変換装置Ｑ’における前記信号範囲調整部３の処理においては，前記（Ａ１）式乃至前記（Ａ３）式における一次映像信号及び二次映像信号という用語は，それぞれ前記非線形一次映像信号Ｖ1’及び前記非線形二次映像信号Ｖ2’と同義であるものとする。
このように，前記映像信号変換装置Ｑ’においては，信号値の範囲の調整前（信号変換前）の一次映像信号が，ＩＥＣ６１９６６−２−４規格やＩＥＣ６１９６６−２−１規格に準拠した映像信号（前記非線形一次映像信号Ｖ1’）である。
さらに，前記映像信号変換装置Ｑ’においては，信号値の範囲の調整後（信号変換後）の二次映像信号（前記非線形二次映像信号Ｖ2’）が，ＩＴＵ−ＲＢＴ．７０９規格やＩＴＵ−ＲＢＴ．６０１−５規格等に準拠した映像信号（ＲＧＢ信号）である。
前記映像信号変換装置Ｑ’のように，非線形の一次映像信号Ｖ1’に対し，前記（Ａ１）式乃至前記（Ａ３）式のような線形式（一次式）を用いて信号変換を行った場合，多少の画質の低下を招くが，２回のガンマ処理を省略できる点で，演算負荷低減効果が高い。このような映像信号変換装置Ｑ’及びそれを備えた映像表示装置Ｚ’も本発明の実施形態の一例である。 On the other hand, in the video display device Z ′, instead of the video signal conversion device Q in the video display device Z, the primary side gamma processing unit 2 and the secondary side gamma processing unit 3 are connected to the video signal conversion device Q. A video signal conversion device Q ′ is provided. That is, the video signal conversion device Q ′ includes the RGB signal generation unit 1 and the signal range adjustment unit 3.
Then, the signal range adjustment unit 3 in the video signal conversion device Q ′ first sets the signal state (the first signal state to the first signal state) for the nonlinear primary video signal V1 ′ generated by the RGB signal generation unit 1. 3 signal state).
Further, the signal range adjustment unit 3 in the video signal converter Q ′ selects a conversion formula (the formula (A1) to the formula (A3)) according to the signal state for the nonlinear primary video signal V1 ′, The non-linear primary video signal V1 'is converted into the non-linear secondary video signal V2' by applying the luminance signal values of the three primary colors of RGB in the non-linear primary video signal V1 'to the selected conversion formula. That is, in the processing of the signal range adjustment unit 3 in the signal conversion device Q ′, the terms “primary video signal” and “secondary video signal” in the expressions (A1) to (A3) are respectively referred to as the nonlinear primary video signal. It is assumed that V1 'is synonymous with the nonlinear secondary video signal V2'.
As described above, in the video signal conversion device Q ′, the primary video signal before adjustment of the signal value range (before signal conversion) conforms to the IEC 61966-2-4 standard and the IEC 61966-2-1 standard. It is a video signal (the nonlinear primary video signal V1 ′).
Further, in the video signal converter Q ′, the secondary video signal (the nonlinear secondary video signal V2 ′) after adjusting the signal value range (after the signal conversion) is converted into ITU-R BT. 709 standard and ITU-R BT. This is a video signal (RGB signal) compliant with the 601-5 standard.
When the signal conversion is performed on the non-linear primary video signal V1 ′ using the linear form (primary formula) such as the formulas (A1) to (A3) as in the video signal conversion device Q ′. Although the image quality is slightly reduced, the calculation load is greatly reduced in that the two gamma processes can be omitted. Such a video signal conversion device Q ′ and a video display device Z ′ having the same are also examples of the embodiment of the present invention.

本発明は，一次側の映像信号を，その信号値が所定範囲に収まるように二次側の映像信号に変換する信号変換装置及びそれを備えた映像表示装置に利用可能である。 INDUSTRIAL APPLICABILITY The present invention can be used in a signal conversion device that converts a primary-side video signal into a secondary-side video signal so that the signal value falls within a predetermined range, and a video display device including the signal conversion device.

本発明の実施形態に係る映像表示装置Ｚの主要部の概略構成を表すブロック図。The block diagram showing the schematic structure of the principal part of the video display apparatus Z which concerns on embodiment of this invention. 映像表示装置Ｚの変形例である映像表示装置Ｚ’の主要部の概略構成を表す図。The figure showing schematic structure of the principal part of the video display apparatus Z 'which is a modification of the video display apparatus Z. Ｙｃｂｃｒ信号に対応するＲＧＢ信号の信号値が出力範囲に収まる色域をＹＵＶ空間において表した図。The figure which represented in the YUV space the color gamut in which the signal value of the RGB signal corresponding to a Ycbcr signal is settled in an output range. Ｙｃｂｃｒ信号に対応するＲＧＢ信号の複数の状態に対応するＹＵＶ空間における色域の領域を表した図。The figure showing the area | region of the color gamut in YUV space corresponding to the several state of the RGB signal corresponding to a Ycbcr signal. 映像信号変換装置Ｑによる信号変換の様子をＹＵＶ空間において表した図。The figure which represented the mode of the signal conversion by the video signal converter Q in YUV space.

Explanation of symbols

Ｚ，Ｚ’：映像表示装置
Ｑ，Ｑ’：映像信号変換装置
１：ＲＧＢ信号生成部
２：一次側ガンマ処理部
３：信号範囲調整部
４：二次側ガンマ処理部
５：ディスプレイ Z, Z ′: Video display device Q, Q ′: Video signal conversion device 1: RGB signal generation unit 2: Primary side gamma processing unit 3: Signal range adjustment unit 4: Secondary side gamma processing unit 5: Display

Claims

A primary video signal composed of luminance signals of RGB primary colors that can take a signal value in an extended range including a part of an output range from a predetermined output lower limit value to an output upper limit value is input to a predetermined video display means. A video signal conversion device for converting and outputting a secondary video signal composed of luminance signals of RGB primary colors that can take the value of the output range,
A comparison is made between the minimum value Xmin and the maximum value Xmax of the luminance signal values of the primary colors of RGB in the primary video signal and the output lower limit value Smin and the output upper limit value Smax, and the first is Smin ≦ Xmin and Smax <Xmax. A signal for determining whether the signal state is a second signal state where Xmin <Smin and Smax <Xmax, a third signal state where Xmin <Smin and Xmax ≦ Smax, or another signal state State discrimination means;
In the case of the first signal state, signal values Yr, Yg, Yb obtained by the following equation (A1) are calculated, and the secondary video signal having these values as the luminance signal values of RGB primary colors is output. First signal conversion output means;
In the second signal state, signal values Yr, Yg, and Yb obtained by the following equation (A2) are calculated, and the secondary video signal is output with the values of luminance signals of RGB primary colors as the values. Second signal conversion output means;
In the case of the third signal state, signal values Yr, Yg, Yb obtained by the following equation (A3) are calculated, and the secondary video signal having these values as the luminance signal values of RGB primary colors is output. Third signal conversion output means;
Fourth signal conversion output means for outputting the secondary video signal composed of luminance signals of the same primary colors of RGB as the primary video signal when in the other signal state;
A video signal conversion apparatus comprising:

The video signal converter according to claim 1, wherein the primary video signal is a video signal conforming to the IEC 61966-2-4 standard or the IEC 61966-2-1 standard, or a signal obtained by performing gamma processing on the video signal.

The secondary video signal or a signal obtained by performing gamma processing on the secondary video signal is ITU-R BT. 709 or ITU-R BT. The video signal converter according to claim 1, wherein the video signal converter is a video signal conforming to the 601-5 standard.

A video signal conversion device according to any one of claims 1 to 3, and a video display means for displaying a video based on the secondary video signal output by the video signal conversion device. Display device.

A primary video signal composed of luminance signals of RGB primary colors that can take a signal value in an extended range including a part of an output range from a predetermined output lower limit value to an output upper limit value is input to a predetermined video display means. A video signal conversion method for converting to a secondary video signal composed of luminance signals of RGB primary colors that can take the value of the output range and outputting the secondary video signal,
With a given processor
A comparison is made between the minimum value Xmin and the maximum value Xmax of the luminance signal values of RGB primary colors in the primary video signal and the output lower limit value Smin and the output upper limit value Smax. A signal for determining whether the signal state is a second signal state where Xmin <Smin and Smax <Xmax, a third signal state where Xmin <Smin and Xmax ≦ Smax, or another signal state A state determination procedure;
In the case of the first signal state, signal values Yr, Yg, Yb obtained by the following equation (A1) are calculated, and the secondary video signal having these values as the luminance signal values of RGB primary colors is output. A first signal conversion output procedure;
In the second signal state, signal values Yr, Yg, and Yb obtained by the following equation (A2) are calculated, and the secondary video signal is output with the values of luminance signals of RGB primary colors as the values. A second signal conversion output procedure;
In the case of the third signal state, signal values Yr, Yg, Yb obtained by the following equation (A3) are calculated, and the secondary video signal having these values as the luminance signal values of RGB primary colors is output. A third signal conversion output procedure;
A fourth signal conversion output procedure for outputting the secondary video signal composed of luminance signals of the same primary colors of RGB as the primary video signal when in the other signal state;
A video signal conversion method comprising: