JP2002300525A - Digital video recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a digital video recording device which can record image data of higher image quality and caption data of higher quality, in the limit of the maximum transfer rate of a stream and the limit of the capacity of a recording medium. SOLUTION: A caption signal is previously extracted from an inputted video signal, and the extracted caption signal is encoded by a compression encoding system suitable for encoding a character signal, such as runlength system. A stream of an auxiliary video is obtained apart from the video stream of the main video. A caption part is deleted form the video signal, and the video is compressed and encoded, after only the main video part is taken out. Then, the main video stream is obtained. The main video stream and the auxiliary video stream are picketed and multiplexed into a single stream together with a sound stream and on recorded in a digital signal recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital video recording apparatus for recording a digital video signal obtained by compressing and encoding video information on a digital signal recording medium such as an optical disk such as a DVD.

[0002]

2. Description of the Related Art A DVD (Digital Versatile Disk) is a typical system for recording video information (video data) on a digital signal recording medium such as an optical disk. DVDs achieve a large capacity by high-density recording technology, and realize long-time recording of high-quality video data by compressing and recording images and sounds.

[0003] In a DVD recorder (not shown) not according to the present invention, an input analog video signal is converted to an A / D signal.
After being digitally sampled and converted into a digital video signal by a converter, the digital video signal is supplied to a video encoding unit.
The video encoding unit compresses and encodes the digitally sampled video signal to generate a video stream. In DVD, M is used as the video compression encoding method.
A compression coding method called PEG video (ISO / IEC13818-2) is adopted. In this MPEG video system, prediction with motion compensation using the correlation between past and future images (hereinafter, images mean video frames or video fields) and the current image, And DCT (Discrete Cosine Transform) transform, quantization, and variable-length coding (VLC: Variable Length Coding) for such blocks are combined to achieve highly efficient compression coding.

On the other hand, an analog audio signal input to a DVD recorder not according to the present invention is digitally sampled by an A / D converter, converted into a digital audio signal, and supplied to an audio encoding unit. The audio encoding unit compresses and encodes the digitally sampled audio signal to generate an audio stream. In the case of DVD, MPEG audio (ISO / ISO /
IEC13818-3) and Dolby AC-3 (ATSC)
Standard).

[0005] The video stream and the audio stream obtained as described above are input to a multiplexer, and after being packetized for each predetermined size,
The packets are multiplexed and converted into one system stream. This system stream is recorded on a DVD disc. In DVD, MPE is used as this multiplexing method.
G2-System standard (ISO / IEC13818-1)
Is adopted.

[0006]

FIG. 2 (a) shows an example of the above-mentioned "DVD recorder not according to the present invention".
Let us consider a case where a signal in which a subtitle is included in the lower band portion of a letterbox image as shown in FIG. (here,
The “letterbox image” is, for example, an aspect ratio of 4:
A main image having an aspect ratio of 16: 9 is placed in the center of the third image frame, and the upper and lower bands without the main image are filled with a single color such as black. )
Since a portion having a sharp image edge such as a subtitle contains many high frequency components, the compression efficiency using the “spatial frequency characteristic” such as the DCT transform used in the MPEG method is inevitably reduced in compression efficiency. It gets worse.

Further, if the generated code amount is limited so as to satisfy the limitation on the maximum transfer rate of the stream and the limitation on the capacity of the recording medium, the quality of subtitles deteriorates. If an attempt is made to assign a large amount of code to subtitles in order to avoid this, the code amount for the main video must be reduced, which causes problems such as deterioration in image quality of the main video.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object the object of providing higher-quality image data and higher-quality subtitle data under the limitation of the maximum transfer rate of a stream and the capacity of a recording medium. An object of the present invention is to provide a digital video recording device capable of recording.

[0009]

In order to achieve the above object, a digital video recording apparatus according to the present invention extracts a subtitle signal from an input video signal in advance and converts the extracted subtitle signal into a character signal such as a run-length signal. To obtain a sub-picture stream separately from the main video stream. After the subtitle portion is deleted from the video signal and only the main video portion is extracted, video compression encoding is performed to obtain a main video stream. Then, the main video stream and the sub video stream are packet-multiplexed into one stream together with the audio stream, and are recorded on a digital signal recording medium.

As described above, the coding efficiency is increased by removing the subtitle portion from the video signal and reducing high frequency components which are disadvantageous when performing video compression coding.
As a result, it is possible to record higher-quality image data. Also, with regard to subtitles, by performing encoding suitable for character signals such as run-length encoding separately from the main video, higher-quality subtitle data can be recorded. Furthermore, since the main video and subtitles are recorded in separate streams, the user can arbitrarily select whether or not to reproduce subtitles during reproduction.

Further, in the digital video recording apparatus of the present invention, when the input image is in the letterbox format, only the main video portion is cut out, and then the number of scanning lines is returned to the original number of scanning lines, and the aspect ratio is changed to 16. : 9 can be recorded as an image signal.

As described above, by recording a 16: 9 letterbox image (see FIG. 6A) in advance as a full-screen 16: 9 signal, the screen size corresponds to the aspect ratio of 16: 9. When this is displayed on a horizontally long screen receiver (or wide TV), caption data (FIG. 6)
(A) and (b) “Good morning” can be displayed over the main video (see FIG. 6B). Thus, when the letterbox image (see FIG. 5A) is enlarged and displayed on a 16: 9 wide TV, the caption displayed in the upper band portion or the lower band portion ("Good morning" in FIG. 5A). Is missing) (see FIG. 5B).

When a letterbox image is displayed on a conventional 4: 3 receiver, the subtitle is displayed in a band portion because the reproduced subtitle is converted into a letterbox before being superimposed on the main video ( FIG. 5 (a) or FIG. 6 (a)). (D
The VD standard allows recorded 16: 9 video to be 4: 3
In order to display on a receiver, the playback device is required to have the letterbox conversion function. Also, in the digital video recording apparatus of the present invention, when the main video is decompressed and recorded as a 16: 9 image, the subtitle signal extracted from the video signal is bordered by a different color from the subtitle signal. The encoding can also be performed after adding.
By doing so, it is possible to avoid the problem that white character subtitles displayed on the main image on a bright screen are difficult to see.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A digital video recording apparatus according to one embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram illustrating the configuration of a digital video recording device (DVD recording device) according to an embodiment of the present invention.

An analog video signal input to the input terminal 101 of the DVD recorder shown in FIG.
, And is converted into a digital video signal, which is supplied to a subtitle detecting unit 201 and a subtitle erasing unit 202.

The subtitle detecting section 201 detects a subtitle portion from the supplied video signal and extracts a subtitle signal. As a method of detecting the subtitle portion, for example, there is a method of detecting a luminance level portion having a certain level or more as a subtitle signal. The subtitle erasing section 202 uses the subtitle signal extracted by the subtitle detecting section 201 to remove a subtitle signal portion from the supplied video signal. As a method of removing the subtitle signal, for example, there is a method of replacing pixel data detected as a subtitle signal with an average value of peripheral pixel data.

The video signal from which the subtitle signal has been removed is
This is supplied to the video encoding unit 105. Video encoding unit 1
Reference numeral 05 generates a video stream by MPEG-encoding the supplied subtitle-free video signal. On the other hand, the caption signal extracted by the caption detection unit 201 is supplied to the sub-picture encoding unit 203. The sub-picture encoding unit 203 performs run-length compression encoding on the supplied subtitle signal in accordance with a predetermined rule (DVD sub-picture format) to generate a sub-picture stream.

An analog audio signal input to the input terminal 102 of the DVD recorder shown in FIG. 1 is digitally sampled by an A / D converter 104 and converted into a digital audio signal, and then supplied to an audio encoding unit 106. . The audio encoding unit 106 compression-encodes the supplied audio signal to generate an audio stream. This audio compression encoding method includes MPEG audio (ISO / IEC138).
18-3) or Dolby AC-3 (ATSC standard).

The video stream, sub-picture stream, and audio stream obtained as described above are input to the multiplexer 107, and are packetized for each predetermined size, and then packet-multiplexed to form a system stream (MPEG2 program stream). ). This system stream is a DVD disc 1
08 is recorded.

FIG. 2 is a diagram for explaining the operation of the digital video recording apparatus of FIG.

Now, the video signal (input image) input to the input terminal 101 is, for example, as shown in FIG. 2 (a), a main image (two person images) and a subtitle portion ("good morning" characters). Column). In this case, the caption signal extracted by the caption detection unit 201 is the signal shown in FIG.
As shown in FIG. 2B, the data becomes only caption data, and the output of the caption erasing unit 202 becomes image data of only the main video with the caption deleted as shown in FIG.

As a result, a subtitle signal containing many high frequency components (which is disadvantageous in terms of image quality or compression rate in MPEG compression encoding) is removed from the video signal supplied to the video encoding unit 105. Therefore, the video encoding unit 105 can create a video stream from which a higher quality image can be restored.

On the other hand, the subtitle signal extracted from the video signal by the subtitle detection unit 201 is supplied to the sub-picture encoding unit 203, and is encoded based on the sub-picture format of the DVD, and becomes a sub-picture stream to become the multiplexer 107. Supplied to

Here, the sub-picture data format in the DVD standard will be described. FIG. 8 shows the data structure of each of the sub-picture units (SPU1, SPU2, SPU3,...) Of the DVD. The data of the sub-picture unit SPU is obtained by encoding one sub-picture image and includes a sub-picture unit header SPUH, pixel data PXD, and a sub-picture display control sequence table SP_DCSQT.

SPUH is header data that describes the size of sub-picture unit data and the start address of SP_DCSQT. PXD is obtained by run-length encoding pixel data such as a caption signal. Each pixel data is
4 of background pixels, pattern pixels, and two types of emphasized pixels
Can take a value.

SP_DCSQT is a table of control signals (DCSQ) for displaying sub-picture pixel data. Each control signal includes a time at which the control is applied and a control content to be performed at the time. Types of control contents include display start, display end, color setting, contrast setting, display area change, and color / contrast change.

Since one sub-picture unit SPU can have a plurality of control signals (DCSQ), for example, the color of a subtitle can be changed over time, or the contrast can be gradually reduced and faded out.

Returning to the description of FIG. The sub-picture encoding unit 203 in FIG. 1 performs encoding of the sub-picture, for example, as follows. That is, the sub-picture encoding unit 203 binarizes the input subtitle signal into a background portion and a character portion, performs run-length encoding, and creates pixel data PXD.

Sub-picture display control sequence table SP_
In DCSQT, a color setting command for setting the contrast of the background to zero (that is, transparent) and setting the contrast and color of the character portion to predetermined values is described, and a display start command is described after the description of the contrast setting command. At this time, the end time of the caption (how long the display continues) is unknown at the time of encoding, so that the control command of the display end is not described. Then, when the input subtitle is switched, a sub-picture unit is created in the same way, and when the subtitle disappears, a dummy sub-picture unit with only transparent pixels is created to clear the previous subtitle To do it.

On the playback side (DVD player side),
When a new sub-picture unit is decoded, the previously displayed sub-picture is cleared, so that subtitles can be switched or erased without any problem without an end command. It has become.

FIG. 9 is a diagram for explaining a method (example 1) of creating a sub-picture unit by the digital video recording apparatus according to the present invention. FIG. 9 shows a case where subtitles are encoded in a sub-picture.
The state of creating the sub-picture unit SPU is shown along the time axis. Here, subtitle <2> is displayed in a period T2 from time t2 to time t3, and a signal is input from time t3 such that subtitle <2> disappears and nothing is displayed. Is illustrated.

When subtitle <1> is input at time t1, sub-picture encoding, that is, run-length encoding and issuance of a control signal are performed for subtitle <1> to create sub-picture unit SPU1 ( FIG. 9 (a)). Then, when subtitle <1> is switched to subtitle <2> at time t2, subtitle encoding is newly performed on subtitle <2> to create sub-picture unit SPU2 (FIG. 9).
(B)). Further, at time t3, when the subtitle <2> disappears and the subtitle display disappears, a transparent sub-picture unit (a dummy unit having a contrast of all pixels of zero) SPU3 in which nothing is displayed is created (FIG. 9 ( c)).

FIG. 10 is a diagram for explaining a method (example 2) of creating a sub-picture unit by the digital video recording apparatus according to the present invention. FIG. 10 shows another example different from FIG. The caption signal input in the example of FIG. 10 is the same as that of FIG. 9, and the SPU created at time t1 in FIG.
1a is the same as SPU1 in FIG.

However, in the example of FIG. 10, during the display period of the subtitle <1>, the SPU 1 is set at regular intervals (for example, every 0.5 seconds).
The sub-picture units SPU1b and SPU1c that are the same as a are created (the SPU for subtitle <1> is repeatedly created at regular intervals). Also, the subtitle <2> SPU
Similarly, the same SPU 2a as the head SPU 2a is repeatedly created (the SPU for subtitle <2> is repeatedly created at regular intervals).

This is because of the problem of the method of creating the sub-picture unit shown in FIG.
This is to avoid the problem that the subtitle <1> is not displayed when the reproduction is started from behind the subtitle # 1).

That is, as shown in the example of FIG. 10, by inserting a sub-picture unit at regular intervals, even if the access is made not from the beginning of the period T1 but from the middle of the period,
Since the same sub-video unit is repeatedly inserted, subtitles can be reproduced regardless of the position where reproduction is started by decoding the sub-picture unit.

When the display period of subtitle <2> ends, a dummy SPU 3 for deleting subtitle <2> is created (FIG. 10 (c)). This is the same as the case of FIG.

FIG. 5 exemplifies a case where a video with subtitles recorded by a recording apparatus not according to the present invention is displayed on a 4: 3 monitor and a 16: 9 monitor.

When a letterbox image as shown in FIG. 5 (a) is reproduced on a 16: 9 monitor, the main video portion can be enlarged and displayed on many monitors as shown in FIG. 5 (b). However, in this case, the subtitle part (Fig. 5 (a)
"Good morning" character) will not be displayed.

FIG. 3 is a block diagram for explaining the configuration of a digital video recording apparatus which addresses the above problem. Also,
FIG. 4 is a diagram for explaining the operation of the vertical extension unit 204, which is a feature of FIG. The device shown in FIG. 3 has a configuration in which a vertical expansion unit 204 and a selector 205 are inserted between the subtitle erasure unit 202 and the video encoding unit 105 shown in FIG.
In the apparatus shown in FIG. 3, the main image portion in the letterbox image is vertically expanded by the vertical expansion unit 204 in advance.
The image is encoded and recorded as 9 images.

In FIG. 3, the video signal from which the caption signal has been removed by the caption erasing section 202 is supplied to a vertical expansion section 204 and also to one input of a selector 205. The vertical expansion unit 204 cuts out a main image of a letterbox image having an aspect ratio of 16: 9 contained in a video signal having an aspect ratio of 4: 3 as shown in FIG. The main image (FIG. 4B) expanded in the vertical direction is supplied to the other input of the selector 205.

When the video signal is a letterbox signal, the selector 205 outputs the output (1
6: 9 signal), and if the video signal is not a letterbox signal, select a video signal (4: 3 signal) that is not vertically expanded and encode the selected signal into the video encoding unit 10.
5 Accordingly, when the input video signal is a letterbox image having an aspect ratio of 4: 3 (FIG. 4A or FIG. 6A), one of the main video portions in the image signal is displayed.
A 6: 9 image is cut out and recorded on the DVD 108 as a 16: 9 video signal.

FIG. 6 is a diagram exemplifying a case where the video with subtitles recorded by the digital video recording apparatus according to the present invention is displayed on a 4: 3 monitor and a case where it is displayed on a 16: 9 monitor.

FIG. 6 (b) shows 16:
9 shows an image displayed on a 16: 9 monitor by reproducing the video signal recorded at 9. Thus, 1
When an image recorded at 6: 9 is reproduced by a DVD player, the subtitle signal is superimposed on the main video and reproduced. Therefore, the reproduced image can be displayed on the 16: 9 monitor without missing subtitles. Can be displayed.

According to the DVD standard, a 16: 9 video playback image is provided to a 4: 3 letter box so that a video signal recorded at 16: 9 can be viewed on a 4: 3 monitor. It requires that a means for converting to an image be installed. Since the letterbox conversion of the video playback image is performed before the sub-picture playback signal is superimposed on the video playback image, the 4: 3 monitor has the same format as the original input video signal as shown in FIG. Is displayed with.

In summary, in the apparatus shown in FIG. 3, when the input image is in the letterbox format, only the main video portion is cut out, and then the number of scanning lines is returned to the original number of scanning lines, and the aspect ratio is 16: 9. Can be recorded as an image signal.

As described above, by recording a 16: 9 letterbox image (see FIG. 6A) in advance as a full-screen 16: 9 signal, the screen size corresponds to the aspect ratio of 16: 9. When this is displayed on a horizontally long screen receiver (or wide TV), caption data (FIG. 6)
(A) and (b) “Good morning” can be displayed over the main video (see FIG. 6B). Thus, when the letterbox image (see FIG. 5A) is enlarged and displayed on a 16: 9 wide TV, the caption displayed in the upper band portion or the lower band portion ("Good morning" in FIG. 5A). Is missing) (see FIG. 5B).

FIG. 7 is a diagram for explaining the operation of the border adding section 206 of FIG. In the configuration of FIG. 3, the border adding unit 206 performs a border process on the caption signal extracted by the caption detection unit 201. Specifically, as shown in FIG. 7B, a border pixel is added around the character pattern to the character pixel as shown in FIG. 7A.

Further, in the sub-picture encoding unit 203, the subtitle signal subjected to the border processing is ternarized, and sub-picture encoding including run-length encoding is performed. In this sub-picture encoding, for example, the background pixel is made transparent, the subtitle pixel is made white, and the border pixel of the character is made black. Or,
The color of the caption pixel or the color of the border pixel may be different from the color of the background main image. Thus, even when a sub-picture subtitle is superimposed on a bright portion in a 16: 9 main video, the subtitle text has a border, so that the subtitle text does not mix with the background main video and become difficult to see.

Further, a pixel for anti-aliasing is inserted between the body pixel of the caption character and the border pixel or outside the border pixel in the border adding unit 206 in FIG. By creating a sub-video stream in this way, higher-quality subtitle playback can be enabled.

[0052]

As described above, in the digital video recording apparatus according to the present invention, a subtitle signal (including many high frequency components) is separated from a video signal, and the subtitle is encoded separately from the main video. I'm trying to do it. As a result, high-quality caption data can be recorded, and the encoding efficiency of the main video can be improved, so that a high-quality video signal can be recorded.

Since the main video and subtitles are recorded in separate streams, the user can arbitrarily select whether to display subtitles during reproduction.

Further, even when the reproduction is started in the middle of the subtitle display period, the subtitle can be displayed.

When the input video signal is a letter box video, the main video portion is expanded in the vertical direction in advance and recorded as 16: 9 video, so that 16: 9 video is recorded.
It is possible to avoid "subtitle missing" which occurs when the letterbox image is enlarged and displayed on the nine receiver.

Further, it is possible to avoid the problem that the subtitles overlaid on the main video become difficult to see.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a digital video recording device according to an embodiment of the present invention.

FIG. 2 is a view for explaining the operation of the digital video recording device according to the embodiment of the present invention;

FIG. 3 is a block diagram illustrating a configuration of a digital video recording device according to another embodiment of the present invention.

FIG. 4 is a diagram for explaining the operation of the vertical extension unit in FIG. 3;

FIG. 5 shows a case where a video with subtitles recorded by a recording device not according to the present invention is displayed on a 4: 3 monitor and 1
The figure which illustrates each when displaying on a 6: 9 monitor.

FIG. 6 is a diagram exemplifying a case where a video with subtitles recorded by the digital video recording apparatus according to the present invention is displayed on a 4: 3 monitor and a case where it is displayed on a 16: 9 monitor.

FIG. 7 is a diagram for explaining the operation of the border addition unit in FIG. 3;

FIG. 8 is a view for explaining the data structure of a sub-picture unit according to the DVD standard.

FIG. 9 is a view for explaining a method (example 1) of creating a sub-picture unit by the digital video recording device according to the present invention.

FIG. 10 is a view for explaining a method (example 2) of creating a sub-picture unit by the digital video recording device according to the present invention.

[Explanation of symbols]

101, 102: input terminal; 103, 104: A / D converter; 105: video encoder; 106: audio encoder; 107: multiplexer; 108: DVD disk (DVD-ROM disk original, DVD-R Discs, DVD-RW discs, DVD-RAM discs, etc.); 201: Caption detecting section; 202: Caption erasing section; 203: Sub-picture coding section; 204: Vertical expansion section;
05: selector; 206: border adding section.

────────────────────────────────────────────────── ─── of the front page continued (51) Int.Cl. ⁷ identification mark FI theme Court Bu (reference) G11B 27/034 H04N 5/85 Z 5D110 H04N 5/278 5/91 E 5/85 C 5/92 5 / 92 H 7/025 7/08 A 7/03 G11B 27/02 K 7/035 F term (reference) 5C023 AA02 AA18 BA01 BA13 CA02 CA04 CA05 5C052 AA02 CC11 5C053 FA24 GA11 GB11 GB12 GB37 JA16 KA25 5C063 AB05 CA11 DA03 DA05 EB03 EB37 5D044 AB05 AB07 BC02 CC06 DE02 DE03 DE14 DE18 DE92 DE96 FG21 GK08 5D110 AA14 AA29 CA05 CA06 CA07

Claims (7)

[Claims] 1. An apparatus for compressing and encoding an input video signal and recording the signal on a digital signal recording medium, comprising: a subtitle detecting means for extracting a subtitle portion from the input video signal to separate a subtitle signal; Subtitle erasing means for erasing the subtitle signal from the signal to obtain a main video signal; video encoding means for compressing and encoding the main video signal to obtain a main video stream; Sub-picture encoding means for obtaining a video stream;
Multiplexing means for multiplexing the main video stream and the sub-video stream to obtain a multiplexed stream, wherein the multiplexed stream is recorded on a digital signal recording medium. apparatus. 2. A horizontal image is cut out by deleting at least one of an upper part and a lower part of an image from the input video signal or the main video signal, and the cut horizontal image is expanded vertically to obtain an original scanning line. Further comprising vertical expansion means for returning to an image having a number, when the input video is a horizontally long image not including the main image in at least one of an upper part and a lower part of the image, the image is cut out by the vertical expansion means 2. The apparatus according to claim 1, wherein only a horizontally long main video section is supplied to said video encoding means. 3. The subtitle signal separated by the subtitle detection means is added with a border signal having a color or luminance different from the subtitle signal or an anti-aliasing signal. An apparatus according to claim 2. 4. The apparatus according to claim 1, wherein the digital signal recording medium is a DVD disk conforming to a DVD standard. 5. The sub-picture encoding means according to claim 4, wherein the sub-picture encoding means is configured to perform encoding in a sub-picture format of the DVD standard to provide a sub-picture stream of the DVD standard. The described device. 6. The sub-picture encoding means is configured to repeatedly generate data of the same sub-picture unit at regular intervals during a period in which the same subtitle is continuously present in the input video signal. The apparatus according to any one of claims 1 to 5, wherein the apparatus is used. 7. The sub-picture encoding means, when no subtitle exists in the signal of the input video, a sub-display that does not display anything in order to hide the subtitle that existed before. Apparatus according to any one of the preceding claims, configured to create a video unit.