JP3809303B2

JP3809303B2 - Image processing apparatus and method

Info

Publication number: JP3809303B2
Application number: JP18421199A
Authority: JP
Inventors: 慎吾野澤
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 1999-06-29
Filing date: 1999-06-29
Publication date: 2006-08-16
Anticipated expiration: 2019-06-29
Also published as: JP2001016583A

Description

【０００１】
【発明の属する技術分野】
本発明は画像処理装置及びその方法に関し、特に画像信号の高能率符号化及び復号を行なう画像処理装置及びその方法に関する。
【０００２】
【従来の技術】
近年、デジタル信号処理技術の進歩により、動画像や静止画像、音声等、大量のデジタル情報を高能率符号化し、小型磁気記録媒体への記録や通信媒体への伝送を行なうことが可能となっている。こうした技術を応用し、動画と静止画、さらには解像度の異なる複数の映像を混在して扱えるマルチメデイア機器の検討が行われている。
【０００３】
図４は、低解像度映像と高解像度映像のいずれも符号化可能な、従来の高能率符号化装置の構成を示すブロック図である。図４において、４０１は映像信号入力端子、４０２は切り替え部、４０３は低解像度映像符号化部、４０４は低解像度映像符号出力端子、４０５は低域通過型フィルタ、４０６はダウンサンプラ、４０７は高域通過型フィルタ、４０８はダウンサンプラ、４０９は高域符号化部、４１０は高域符号出力端子である。
【０００４】
以下、該装置における符号化処理について説明する。映像信号入力端子４０１には低解像度映像信号あるいは、水平／垂直ともに倍の解像度を有する高解像度映像信号のいずれか一方が入力され、切り替え部４０２および低域通過型フィルタ４０３、高域通過型フィルタ４０７に供給される。
【０００５】
入力される高解像度映像信号は低域通過型フィルタ４０５および高域通過型フィルタ４０７によって低域信号と高域信号に分割された後、それぞれダウンサンプラ４０６，４０８に供給される。ここで図６に、低域通過型フィルタ４０５および高域通過型フィルタ４０７による周波数分割の例を示す。低域通過型フィルタ４０５は図６における二次元周波数領域ＬＬ、すなわち、水平／垂直ともに高解像度映像信号の半分の低帯域のみを通過させる。一方の高域通過型フィルタ４０７は図６のＬＨ，ＨＬ，ＨＨ領域のみを通過させる。
【０００６】
ダウンサンプラ４０６は低域通過型フィルタ４０５から供給される低域信号を、水平／垂直とも半分に間引き、低解像度映像と同一画素数の映像信号に変換し、切り替え部４０２に供給する。切り替え部４０２は、映像信号入力端子４０１より直接供給される映像信号と、ダウンサンプラ４０６から供給される映像信号とを選択し、いずれか一方を低解像度映像符号化部４０４に供給する。即ち、映像信号入力端子４０１への入力信号が高解像度映像信号である場合にはダウンサンプラ４０６より供給される映像信号が選択され、該入力信号が低解像度映像信号である場合には映像信号入力端子４０１より供給される映像信号が選択される。
【０００７】
低解像度映像符号化部４０３は、切り替え部４０２より供給される信号に対して、直交変換や量子化可変長符号化等の各処理を施すことにより低解像度映像符号に変換し、低解像度映像符号出力端子４０４に出力する。
【０００８】
ダウンサンプラ４０８は、高域通過型フィルタ４０７から供給される高域信号を水平／垂直ともに間引き、高域符号化部４０９に供給する。高域符号化部４０９は、供給される信号に対して量子化可変長符号化等の各処理を施すことにより高域符号へ変換し、高域符号出力端子４１０に出力する。
【０００９】
図５は、図４に示した従来の高能率符号化装置によって符号化された信号を復号する、従来の高能率復号装置構成を示すブロック図である。図５において、５０１は低解像度映像符号入力端子、５０２は低解像度映像復号部、５０３は切り替え部、５０４は映像信号出力端子、５０５は高域符号入力端子、５０６高域復号部、５０７はアップサンプラ、５０８は低域通過型フィルタ、５０９はアップサンプラ、５１０は高域通過型フィルタ、５１１は加算部である。
【００１０】
低解像度映像符号入力端子５０１に供給される映像符号は、低解像度映像復号部５０２に供給される。尚、符号化の際に高解像度映像を処理した場合、該映像符号は図６に示す周波数帯域ＬＬに相当する。低解像度映像復号部５０２は供給される映像符号に対して可変長復号逆量子化、逆直交変換を施すことによって映像信号を復号し、切り替え部５０３およびアップサンプラ５０７に供給する。
【００１１】
高域符号入力端子５０５に供給される高域符号は、高域復号部５０６に供給される。該高域符号は、高解像度映像を符号化した際に得られる、図６に示す周波数帯域ＬＨ，ＨＬ，ＨＨに相当する。高域復号化部５０６は、該高域符号を可変長復号逆量子化し、アップサンプラ５０９に供給する。
【００１２】
アップサンプラ５０７，５０９は供給される信号列に対して水平／垂直に０を挿入し、それぞれ低域通過型フィルタ５０８、高域通過型フィルタ５１０に供給する。低域通遇型フィルタ５０８はアップサンプラ５０７から供給される信号列における、帯域ＬＬ相当部分のみを通過させ、加算部５１１へ供給する。一方、高域通過型フィルタ５１０はアップサンプラ５０９から供給される信号列における、帯域ＬＨ，ＨＬ，ＨＨ相当部分のみを通過させ、加算部５１１へ供給する。
【００１３】
加算部５１１は、帯域ＬＬ相当部分と帯域ＬＨ，ＨＬ，ＨＨ相当部分とを加算することによって高解像度映像の全帯域を再構成し、切り替え部５０３に供給する。切り替え部５０３は、復号装置に供給される符号が低解像度映像に対する符号である場合には、低解像度映像復号部５０２から供給される信号を選択し、供給される符号が高解像度映像に対する符号である場合には、加算部５１１から供給される信号を選択して、映像信号出力端子５０４に出力する。
【００１４】
以上のように、従来の高能率符号化／復号装置においては、高解像度映像の低域部分の符号化／復号化を行なうために、低解像度映像のみを処理する低解像度映像符号化／復号部（４０３，５０２）を用いることによって、従来の低解像度映像のみを扱う符号化／復号装置との高い互換性を実現している。即ち、低解像度映像符号のみを従来の復号装置に供給すれば、高解像度映像の低域部分を再生することが可能である。
【００１５】
【発明が解決しようとする課題】
しかしながら、上記従来の高能率符号化／復号装置においては、従来の低解像度映像のみを扱う符号化／復号装置との高い互換性を実現する反面、高解像度映像の符号化／復号における画像品質に着目すると、低解像度映像符号化／復号部（４０３，５０２）における劣化が、高解像度映像全体としての符号化／復号に多大な影響を与えてしまい、十分な画質を実現できなかった。
【００１６】
こうした背景において本発明の目的は、低解像度画像のみに対応した装置との互換性を損なうことなく、高解像度画像に対する高品位な符号化処理を可能とする画像処理装置及びその方法を提供することにある。
【００１７】
【課題を解決するための手段】
上述の目的を達成するための一手段として、本発明の画像処理装置は以下の構成を備える。
【００１８】
即ち、本発明の一側面に係る画像処理装置は、画像信号を入力する入力手段と、低域通過型フィルタを用いて前記画像信号をフィルタリングし、ダウンサンプリングすることにより低周波成分信号を抽出する低周波成分抽出手段と、高域通過型フィルタを用いて前記画像信号をフィルタリングし、ダウンサンプリングすることにより第１の高周波成分信号を抽出する第１の高周波成分抽出手段と、高域通過型フィルタを用いて前記低周波成分信号をフィルタリングし、ダウンサンプリングすることにより前記低周波成分信号における高周波成分信号である第２の高周波成分信号を抽出する第２の高周波成分抽出手段と、前記低周波成分信号を符号化する低周波成分符号化手段と、前記第１の高周波成分信号及び前記第２の高周波成分信号を符号化する高周波成分符号化手段と、を有することを特徴とする。
【００１９】
更に、前記入力手段は、前記画像信号の解像度よりも低解像度である低解像度画像信号を入力し、前記低周波成分符号化手段は前記低解像度画像信号を符号化することを特徴とする。
【００２０】
また、本発明の別の側面は、低域通過型フィルタを用いて画像信号をフィルタリングし、ダウンサンプリングすることにより得られた低周波成分信号と、高域通過型フィルタを用いて前記画像信号をフィルタリングし、ダウンサンプリングすることにより得られた第１の高周波成分信号と、高域通過型フィルタを用いて前記低周波成分信号をフィルタリングし、ダウンサンプリングすることにより得られた第２の高周波成分信号とがそれぞれ符号化された符号化信号を復号する画像処理装置に係り、前記低周波成分信号の符号化信号を復号して第１の低周波成分信号を作成する低周波成分復号手段と、低域通過型フィルタを用いて前記第１の低周波成分信号をフィルタリングすることにより第２の低周波成分信号を抽出する低周波成分抽出手段と、前記第１の高周波成分信号の符号化信号を復号して第１の高周波成分信号を出力し、前記第２の高周波成分信号の符号化信号を復号して第２の高周波成分信号を出力する高周波成分復号手段と、第２の高周波成分信号をアップサンプリングし、高域通過型フィルタを用いて第３の高周波成分信号を出力し、前記第２の低周波成分信号と前記第３の高周波成分信号を用いて第３の低周波成分信号を出力し、該第３の低周波成分信号と前記第１の高周波成分信号とを用いて前記画像信号を復元する復元手段と、を有することを特徴とする。
【００２２】
【発明の実施の形態】
以下、本発明に係る一実施形態について、図面を参照して詳細に説明する。
【００２３】
＜第１実施形態＞
図１は本実施形態における高能率符号化装置の構成を示すブロック図である。図１において、１０１は映像信号入力端子、１０２は切り替え部、１０３は低解像度映像符号化部、１０４は低解像度映像符号出力端子、１０５は低域通過型フィルタ、１０６はダウンサンプラ、１０７は高域通過型フィルタ、１０８はダウンサンプラ、１０９は高域符号化部、１１０は高域符号出力端子、１１１は高域通過型フィルタ、１１２はダウンサンプラである。
【００２４】
●低解像度映像の符号化処理
まず、映像入力端子１０１に低解像度映像が入力された場合について説明する。映像入力端子１０１に供給された低解像度映像信号は、切り替え部１０２を経由して低解像度映像符号化部１０３に供給される。低解像度映像符号化部１０３は該低解像映像信号に対して直交変換、量子化可変長符号化の処理を施すことにより低解像度映像符号に変換して、低解像度映像符号出力端子１０４に出力する。
【００２５】
●高解像度映像の符号化処理
続いて、映像入力端子１０１に高解像度の静止画像が入力された場合について説明する。映像入力端子１０１に供給された高解像度映像信号は、低域通過型フィルタ１０５および高域通過型フィルタ１１１に供給される。高解像度映像は低域通過型フィルタおよび高域通過型フィルタによって低域信号と高域信号に分割されて、それぞれダウンサンプラ１０６，１１２に供給される。
【００２６】
ここで図３（ａ）に、低域通過型フィルタ１０５および高域通過型フィルタ１１１による周波数分割の例を示す。低域通過型フィルタ１０５は同図における二次元周波数領域ＬＬ、すなわち、水平／垂直ともに高解像度映像信号の半分の低帯域のみを通過させる。一方の高域通過型フィルタ１１１は同図のＬＨ，ＨＬ，ＨＨ領域のみを通過させる。
【００２７】
ダウンサンプラ１０６は、低域通過型フィルタ１０５から供給される低域信号を水平／垂直とも半分に間引くことによって、本実施形態において入力可能な低解像度映像と同一画素数の低解像度映像に変換した後、切り替え部１０２および高域通過型フィルタ１０７に供給する。切り替え部１０２は、前記ダウンサンプラ１０６から供給される低解像度映像を選択して低解像度映像符号化部１０３に供給する。
【００２８】
低解像度映像符号化部１０３は、低解像度映像符号に対して直交変換、量子化、可変長符号化の処理を施こすことによって低解像度映像符号へ変換し、低解像度映像符号出力端子１０４に出力する。
【００２９】
高域通過型フィルタ１０７はダウンサンプラ１０６から供給される低解像度映像の高域成分のみを、ダウンサンプラ１０８に供給する。ここで図３（ｂ）に、高域通過型フィルタ１０７が通過させる高域成分の例を示す。即ち、同図においてＬＬＬＨ，ＬＬＨＬ，ＬＬＨＨで示す領域のみが、ダウンサンプラ１０８に供給される。
【００３０】
ダウンサンプラ１１２およびダウンサンプラ１０８は、供給された信号列を各領域において水平／垂直とも半分に間引き、高域符号化部１０９に供給する。高域符号化部１０９においては、供給された信号に対して量子化、可変長符号化の各処理を施すことにより高域符号へ変換し、高域符号出力端子１１０に出力する。
【００３１】
以上説明したように本実施形態によれば、高解像度映像信号が入力された際に、その低周波成分（ＬＬ）と高周波成分（ＬＨ，ＨＬ，ＨＨ）を抽出し、該低周波成分（ＬＬ）から更に高周波成分（ＬＬＬＨ，ＬＬＨＬ，ＬＬＨＨ）を抽出して、それぞれを符号化する。従って、高解像度映像を符号化する際に、従来の様に低周波成分（ＬＬ）をそのまま符号化する場合よりも高画質化が実現される。
【００３２】
また、低周波成分に相当する低解像度映像の符号化については一般的な処理を行なうため、従来装置との互換性が維持できる。
【００３３】
尚、本実施形態において低周波成分（ＬＬ）から抽出される高周波成分（ＬＬＬＨ，ＬＬＨＬ，ＬＬＨＨ）の情報量は比較的少ないため、符号化効率を大さく損ねることはない。
【００３４】
＜第２実施形態＞
以下、本発明に係る第２実施形態について説明する。第２実施形態においては、上述した第１実施形態に示した高能率符号化装置に対応する、高能率復号装置について説明する。
【００３５】
図２は、第２実施形態における高能率復号装置の構成を示すブロック図である。図２において、２０１は低解像度映像符号入力端子、２０２は低解像度映像復号部、２０３は切り替え部、２０４は映像信号出力端子、２０５は高域符号入力端子、２０６高域復号部、２０７はアップサンプラ、２０８は低域通過型フィルタ、２０９は加算部、２１０はアップサンプラ、２１１は低域通過型フィルタ、２１２は高域通過型フィルタ、２１３はアップサンプラ、２１４は高域通過型フィルタ、２１５は加算部である。
【００３６】
●低解像映像の復号処理
まず、上述した第１実施形態の高能率符号化装置によって符号化された、低解像度映像の符号が供給される場合について説明する。低解像映像符号入力端子２０１に供給される低解像度映像符号は、低解像度映像復号部２０２に供給され、可変長復号、逆量子化、逆直交変換の各処理が施されることによって映像符号に変換された後、切り替え部２０３に供給される。
【００３７】
そして切り替え部２０３においては、低解像度映像復号部２０２から供給される映像信号を映像信号出力端子２０４に出力する。
【００３８】
●高解像映像の復号処理
続いて、第１実施形態の高能率符号化装置によって符号化された、高解像度映像の符号が供給される場合について説明する。
【００３９】
この場合、まず低解像度映像符号入力端子２０１には図３（ａ）に示す周波数帯域ＬＬに相当する映像符号が供給される。低解像度映像復号部２０２では、供給された映像符号に可変長復号、逆量子化、逆直交変換を施すことで低解像度映像を復号し、低域通過型フィルタ２０８に供給する。低域通過型フィルタ２０８は、供給された低解像度映像の低域信号、すなわち図３（ｂ）に示す周波数帯域ＬＬＬＬ相当を加算部２０９に供給する。
【００４０】
一方、高域符号入力端子２０５に供給される高域符号は、高域復号部２０６に供給される。ここで入力される高域符号は高解像度映像を符号化した際の、図３（ａ）に示す周波数帯域ＬＨ，ＨＬ，ＨＨ及び図３（ｂ）に示す周波数帯域ＬＬＬＨ，ＬＬＨＬ，ＬＬＨＨ領域に相当する。高域復号化部２０６は、該高域符号に対して可変長復号化、逆量子化を施し、周波数帯域ＬＨ，ＨＬ，ＨＨに相当する信号列をアップサンプラ２１３に、周波数帯域ＬＬＬＨ，ＬＬＨＬ，ＬＬＨＨに相当する信号列をアップサンプラ２０７にそれぞれ供給する。
【００４１】
アップサンプラ２０７，２１３は供給される信号列に対して水平／垂直に「０」値を挿入し、それぞれ高域通過型フィルタ２１２，２１４に供給する。高域通過型フィルタ２１２は、供給される信号列における図３（ｂ）に示す周波数帯域ＬＬＬＨ，ＬＬＨＬ，ＬＬＨＨのみを通過させ、加算部２０９に供給する。加算部２０９においては、供給された帯域ＬＬＬＨ，ＬＬＨＬ，ＬＬＨＨと、低域通過型フィルタ２０８から供給された帯域ＬＬＬＬとを加算して、図３（ａ）に示す帯域ＬＬを再構成し、アップサンプラ２１０に供給する。
【００４２】
アップサンプラ２１０は供給された信号列に対して水平／垂直に「０」値を挿入し、低域通過型フィルタ２１１に供給する。低域通過型フィルタ２１１は、アップサンプラ２１０から供給された信号列において図３（ａ）に示す帯域ＬＬのみを通過させ、加算部２１５へ供給する。一方、高域通過型フィルタ２１４は、アップサンプラ２１３から供給された信号列において図３（ａ）に示す帯域ＬＨ，ＨＬ，ＨＨのみを通過させ、加算部２１５へ供給する。加算部２１５は、供給される帯域ＬＬと帯域ＬＨ，ＨＬ，ＨＨを加算し、高解像度映像の全帯域を再構成し、切り替え部２０３に供給する。
【００４３】
そして切り替え部２０３においては、加算部２１５から供給される信号を選択して、映像信号出力端子２０４に出力する。
【００４４】
以上説明したように第２実施形態によれば、従来の復号装置との互換性を保ちつつ、上述した第１実施形態に示す高能率符号化装置によって高能率符号化された映像信号を適切に復号することができる。
【００４５】
尚、第２実施形態においては、高解像度映像を復号する際に、加算部２１５において帯域ＬＬと帯域ＬＨ，ＨＬ，ＨＨを加算することによって高解像度映像の全帯域を再構成し、切り替え部２０３に出力する例について説明した。これを、ここで加算を行なわず、帯域ＬＬのみを切り替え部２０３に出力するように構成すれば、高画質な低解像度映像を出力することができる。
【００４６】
尚、上述した第１及び第２実施形態においては、低解像度映像符号と高域符号とを分離して入出力する例について説明したが、これらを多重化した信号を入出力するような構成としても良い。この場合の多重化方法としては例えば、低解像度映像符号と高域符号を時分割多重化する方法や、周波数多重化する方法等が適用できる。
【００４７】
【他の実施形態】
なお、本発明は、複数の機器（例えばホストコンピュータ、インタフェイス機器、リーダ、プリンタなど）から構成されるシステムに適用しても、一つの機器からなる装置（例えば、複写機、ファクシミリ装置など）に適用してもよい。
【００４８】
また、本発明の目的は、前述した実施形態の機能を実現するソフトウェアのプログラムコードを記録した記憶媒体（または記録媒体）を、システムあるいは装置に供給し、そのシステムあるいは装置のコンピュータ（またはCPUやMPU）が記憶媒体に格納されたプログラムコードを読み出し実行することによっても、達成されることは言うまでもない。この場合、記憶媒体から読み出されたプログラムコード自体が前述した実施形態の機能を実現することになり、そのプログラムコードを記憶した記憶媒体は本発明を構成することになる。また、コンピュータが読み出したプログラムコードを実行することにより、前述した実施形態の機能が実現されるだけでなく、そのプログラムコードの指示に基づき、コンピュータ上で稼働しているオペレーティングシステム(OS)などが実際の処理の一部または全部を行い、その処理によって前述した実施形態の機能が実現される場合も含まれることは言うまでもない。
【００４９】
さらに、記憶媒体から読み出されたプログラムコードが、コンピュータに挿入された機能拡張カードやコンピュータに接続された機能拡張ユニットに備わるメモリに書込まれた後、そのプログラムコードの指示に基づき、その機能拡張カードや機能拡張ユニットに備わるCPUなどが実際の処理の一部または全部を行い、その処理によって前述した実施形態の機能が実現される場合も含まれることは言うまでもない。
【００５０】
【発明の効果】
以上説明したように本発明によれば、低解像度画像のみに対応した装置との互換性を損なうことなく、高解像度画像に対する高品位な符号化処理が可能となる。
【図面の簡単な説明】
【図１】本発明に係る一実施形態における高能率符号化装置の構成を示すブロック図、
【図２】第２実施形態における高能率復号装置の構成を示すブロック図、
【図３】本実施形態における周波数分割の様子を示す図である。
【図４】従来の高能率符号化装置の構成を示すブロック図、
【図５】従来の高能率復号装置の構成を示すブロック図、
【図６】従来装置における周波数分割の様子を示す図、である。
【符号の説明】
１０１映像信号入力端子
１０２切り替え部
１０３低解像度映像符号化部
１０４低解像度映像符号出力端子
１０５低域通過型フィルタ
１０６ダウンサンプラ
１０７高域通過型フィルタ
１０８ダウンサンプラ
１０９高域符号化部
１１０高域符号出力端子
１１１高域通過型フィルタ
１１２ダウンサンプラ
２０１低解像度映像符号入力部
２０２低解像度映像復号部
２０３切り替え部
２０４映像信号出力端子
２０５高域符号入力端子
２０６高域復号部
２０７アップサンプラ
２０８低域通過型フィルタ
２０９加算部
２１０アップサンプラ
２１１低域通過型フィルタ
２１２高域通過型フィルタ
２１３アップサンプラ
２１４高域通過型フィルタ
２１５加算部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image processing apparatus and method, and more particularly, to an image processing apparatus and method for performing highly efficient encoding and decoding of an image signal.
[0002]
[Prior art]
Recent advances in digital signal processing technology have enabled high-efficiency encoding of large amounts of digital information, such as moving images, still images, and audio, and recording to a small magnetic recording medium or transmission to a communication medium. Yes. Applying these technologies, studies are being made on multimedia devices that can handle moving images, still images, and multiple video images with different resolutions.
[0003]
FIG. 4 is a block diagram showing a configuration of a conventional high-efficiency encoding apparatus capable of encoding both low-resolution video and high-resolution video. In FIG. 4, 401 is a video signal input terminal, 402 is a switching unit, 403 is a low resolution video encoding unit, 404 is a low resolution video code output terminal, 405 is a low-pass filter, 406 is a downsampler, and 407 is high. A band-pass filter, 408 is a downsampler, 409 is a high-frequency encoding unit, and 410 is a high-frequency code output terminal.
[0004]
Hereinafter, the encoding process in the apparatus will be described. Either a low-resolution video signal or a high-resolution video signal having double horizontal / vertical resolution is input to the video signal input terminal 401. The switching unit 402, the low-pass filter 403, and the high-pass filter 407.
[0005]
The input high-resolution video signal is divided into a low-frequency signal and a high-frequency signal by a low-pass filter 405 and a high-pass filter 407 and then supplied to down-samplers 406 and 408, respectively. Here, FIG. 6 shows an example of frequency division by the low-pass filter 405 and the high-pass filter 407. The low-pass filter 405 passes only the two-dimensional frequency region LL in FIG. 6, that is, only the low band that is half of the high-resolution video signal in both horizontal and vertical directions. One high-pass filter 407 passes only the LH, HL, and HH regions of FIG.
[0006]
The down sampler 406 thins out the low-frequency signal supplied from the low-pass filter 405 in half both horizontally and vertically, converts it into a video signal having the same number of pixels as the low-resolution video, and supplies the video signal to the switching unit 402. The switching unit 402 selects a video signal directly supplied from the video signal input terminal 401 and a video signal supplied from the downsampler 406, and supplies either one to the low resolution video encoding unit 404. That is, when the input signal to the video signal input terminal 401 is a high resolution video signal, the video signal supplied from the downsampler 406 is selected, and when the input signal is a low resolution video signal, the video signal input is performed. A video signal supplied from the terminal 401 is selected.
[0007]
The low-resolution video encoding unit 403 converts the signal supplied from the switching unit 402 into a low-resolution video code by performing various processes such as orthogonal transform and quantization variable length encoding, and the low-resolution video code Output to the output terminal 404.
[0008]
The downsampler 408 thins out the high-frequency signal supplied from the high-pass filter 407 in both horizontal and vertical directions and supplies the thinned high-frequency signal to the high frequency encoding unit 409. The high frequency encoding unit 409 converts the supplied signal into a high frequency code by performing various processes such as quantization variable length encoding and outputs the signal to the high frequency code output terminal 410.
[0009]
FIG. 5 is a block diagram showing a conventional high-efficiency decoding device configuration that decodes a signal encoded by the conventional high-efficiency encoding device shown in FIG. In FIG. 5, 501 is a low-resolution video code input terminal, 502 is a low-resolution video decoding unit, 503 is a switching unit, 504 is a video signal output terminal, 505 is a high-frequency code input terminal, 506 high-frequency decoding unit, and 507 is up. A sampler, 508 is a low-pass filter, 509 is an up-sampler, 510 is a high-pass filter, and 511 is an adder.
[0010]
The video code supplied to the low resolution video code input terminal 501 is supplied to the low resolution video decoding unit 502. When a high resolution video is processed at the time of encoding, the video code corresponds to the frequency band LL shown in FIG. The low resolution video decoding unit 502 decodes the video signal by performing variable length decoding inverse quantization and inverse orthogonal transform on the supplied video code, and supplies the decoded video signal to the switching unit 503 and the upsampler 507.
[0011]
The high frequency code supplied to the high frequency code input terminal 505 is supplied to the high frequency decoding unit 506. The high-frequency code corresponds to the frequency bands LH, HL, and HH shown in FIG. 6 that are obtained when high-resolution video is encoded. The high frequency decoding unit 506 performs variable length decoding inverse quantization on the high frequency code, and supplies it to the upsampler 509.
[0012]
Up-samplers 507 and 509 insert 0 in the horizontal / vertical direction with respect to the supplied signal sequence, and supply them to low-pass filter 508 and high-pass filter 510, respectively. The low frequency reception type filter 508 passes only the portion corresponding to the band LL in the signal sequence supplied from the upsampler 507, and supplies it to the adder 511. On the other hand, the high-pass filter 510 passes only the portions corresponding to the bands LH, HL, and HH in the signal sequence supplied from the upsampler 509 and supplies them to the adder 511.
[0013]
The adding unit 511 reconstructs the entire band of the high-resolution video by adding the band LL equivalent part and the bands LH, HL, and HH equivalent parts, and supplies the reconfigured band to the switching unit 503. When the code supplied to the decoding device is a code for a low-resolution video, the switching unit 503 selects a signal supplied from the low-resolution video decoding unit 502, and the supplied code is a code for a high-resolution video. In some cases, the signal supplied from the adder 511 is selected and output to the video signal output terminal 504.
[0014]
As described above, in the conventional high-efficiency encoding / decoding device, the low-resolution video encoding / decoding unit that processes only the low-resolution video in order to encode / decode the low-frequency portion of the high-resolution video. By using (403, 502), high compatibility with a conventional encoding / decoding device that handles only low-resolution video is realized. That is, if only the low resolution video code is supplied to the conventional decoding device, the low frequency part of the high resolution video can be reproduced.
[0015]
[Problems to be solved by the invention]
However, while the conventional high-efficiency encoding / decoding device achieves high compatibility with the conventional encoding / decoding device that handles only low-resolution video, the image quality in encoding / decoding of high-resolution video is improved. When paying attention, deterioration in the low-resolution video encoding / decoding unit (403, 502) has a great influence on encoding / decoding of the entire high-resolution video, and sufficient image quality cannot be realized.
[0016]
In such a background, an object of the present invention is to provide an image processing apparatus and method capable of performing high-quality encoding processing for a high-resolution image without impairing compatibility with an apparatus that supports only a low-resolution image. It is in.
[0017]
[Means for Solving the Problems]
As a means for achieving the above object, an image processing apparatus of the present invention has the following arrangement.
[0018]
That is, an image processing apparatus according to one aspect of the present invention extracts a low-frequency component signal by filtering and down-sampling the image signal using an input unit that inputs the image signal and a low-pass filter. and the low frequency component extracting means, and filtering the image signal using the high-pass filter, a first high-frequency component extracting means for extracting a first high frequency component signal by downsampling the high-pass filter A second high-frequency component extracting means for extracting a second high-frequency component signal that is a high-frequency component signal in the low-frequency component signal by filtering and down-sampling the low-frequency component signal using a low-frequency component coding means for coding the signal, marks the first high frequency component signal and the second high frequency component signal Characterized by having a a high-frequency component coding means for reduction.
[0019]
Furthermore, the input means inputs the low-resolution image signal which is at a lower resolution than the resolution of the image signal, the low-frequency component coding means is characterized by encoding the low-resolution image signal.
[0020]
Another aspect of the present invention provides a low-frequency component signal obtained by filtering and down-sampling an image signal using a low-pass filter, and the image signal using a high-pass filter. The first high-frequency component signal obtained by filtering and down-sampling, and the second high-frequency component signal obtained by filtering the low-frequency component signal using a high-pass filter and down-sampling Doo is relates to an image processing apparatus for decoding a coded signal, respectively, wherein the low-frequency component decoding means for generating a first low-frequency component signal by decoding the encoded signal of the low frequency component signal, the low low-frequency component extraction hand for extracting a second low frequency component signal by filtering the first low-frequency component signal by using a band pass filter When the first decoding the coded signal of the high-frequency component signal and outputs a first high frequency component signal, it outputs a second high frequency component signal by decoding the encoded signal of the second high frequency component signal High-frequency component decoding means, up-samples the second high-frequency component signal, outputs a third high-frequency component signal using a high-pass filter, and outputs the second low-frequency component signal and the third high- frequency component signal. Restoration means for outputting a third low-frequency component signal using the component signal and restoring the image signal using the third low-frequency component signal and the first high-frequency component signal. Features.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment according to the present invention will be described in detail with reference to the drawings.
[0023]
<First Embodiment>
FIG. 1 is a block diagram showing a configuration of a high-efficiency encoding apparatus according to this embodiment. In FIG. 1, 101 is a video signal input terminal, 102 is a switching unit, 103 is a low resolution video encoding unit, 104 is a low resolution video code output terminal, 105 is a low-pass filter, 106 is a downsampler, and 107 is high. A band-pass filter, 108 is a downsampler, 109 is a high-frequency encoding unit, 110 is a high-frequency code output terminal, 111 is a high-pass filter, and 112 is a downsampler.
[0024]
● Low-resolution video encoding process First, a case where a low-resolution video is input to the video input terminal 101 will be described. The low resolution video signal supplied to the video input terminal 101 is supplied to the low resolution video encoding unit 103 via the switching unit 102. The low resolution video encoding unit 103 converts the low resolution video signal into a low resolution video code by performing orthogonal transform and quantization variable length encoding processing, and outputs the low resolution video code to the low resolution video code output terminal 104. To do.
[0025]
High-resolution video encoding process Next, a case where a high-resolution still image is input to the video input terminal 101 will be described. The high-resolution video signal supplied to the video input terminal 101 is supplied to the low-pass filter 105 and the high-pass filter 111. The high-resolution video is divided into a low-frequency signal and a high-frequency signal by a low-pass filter and a high-pass filter, and supplied to the down samplers 106 and 112, respectively.
[0026]
Here, FIG. 3A shows an example of frequency division by the low-pass filter 105 and the high-pass filter 111. The low-pass filter 105 passes only the two-dimensional frequency region LL in the figure, that is, the low band that is half of the high-resolution video signal in both horizontal and vertical directions. One high-pass filter 111 passes only the LH, HL, and HH regions shown in FIG.
[0027]
The down-sampler 106 converts the low-frequency signal supplied from the low-pass filter 105 into a low-resolution video having the same number of pixels as the low-resolution video that can be input in this embodiment by thinning out both the horizontal and vertical halves. Thereafter, the signal is supplied to the switching unit 102 and the high-pass filter 107. The switching unit 102 selects the low resolution video supplied from the downsampler 106 and supplies the low resolution video to the low resolution video encoding unit 103.
[0028]
The low resolution video encoding unit 103 converts the low resolution video code into a low resolution video code by performing orthogonal transformation, quantization, and variable length encoding, and outputs the low resolution video code to the low resolution video code output terminal 104. To do.
[0029]
The high-pass filter 107 supplies only the high-frequency component of the low resolution video supplied from the downsampler 106 to the downsampler 108. Here, FIG. 3B shows an example of the high-frequency component that the high-pass filter 107 passes. That is, only the regions indicated by LLLH, LLHL, and LLHH in FIG.
[0030]
The down sampler 112 and the down sampler 108 decimate the supplied signal sequence in both horizontal and vertical directions in each region, and supplies the thinned signal sequence to the high frequency encoding unit 109. The high frequency encoding unit 109 converts the supplied signal into a high frequency code by performing quantization and variable length encoding processes, and outputs the signal to the high frequency code output terminal 110.
[0031]
As described above, according to the present embodiment, when a high-resolution video signal is input, the low frequency component (LL) and the high frequency component (LH, HL, HH) are extracted, and the low frequency component (LL) is extracted. ) Are further extracted from the high frequency components (LLLLH, LLHL, LLHH) and encoded. Therefore, when encoding a high-resolution video, a higher image quality is realized than when the low-frequency component (LL) is encoded as it is in the prior art.
[0032]
In addition, since a general process is performed for encoding a low-resolution video corresponding to a low-frequency component, compatibility with a conventional apparatus can be maintained.
[0033]
In this embodiment, since the information amount of the high frequency components (LLLH, LLHL, LLHH) extracted from the low frequency components (LL) is relatively small, the coding efficiency is not greatly impaired.
[0034]
Second Embodiment
Hereinafter, a second embodiment according to the present invention will be described. In the second embodiment, a high-efficiency decoding device corresponding to the high-efficiency encoding device shown in the first embodiment will be described.
[0035]
FIG. 2 is a block diagram illustrating a configuration of a high-efficiency decoding device according to the second embodiment. In FIG. 2, 201 is a low resolution video code input terminal, 202 is a low resolution video decoding unit, 203 is a switching unit, 204 is a video signal output terminal, 205 is a high frequency code input terminal, 206 is a high frequency decoding unit, and 207 is up. Sampler 208, low-pass filter 208, adder 209, up-sampler 210, low-pass filter 211, high-pass filter 212, up-sampler 213, high-pass filter 214, 215 Is an adder.
[0036]
Low-resolution video decoding process First, the case where a low-resolution video code encoded by the high-efficiency encoding device of the first embodiment described above is supplied will be described. The low-resolution video code supplied to the low-resolution video code input terminal 201 is supplied to the low-resolution video decoding unit 202 and is subjected to variable length decoding, inverse quantization, and inverse orthogonal transform, thereby performing video code processing. Then, the data is supplied to the switching unit 203.
[0037]
Then, the switching unit 203 outputs the video signal supplied from the low resolution video decoding unit 202 to the video signal output terminal 204.
[0038]
High-resolution video decoding process Next, a case where a high-resolution video code encoded by the high-efficiency encoding device of the first embodiment is supplied will be described.
[0039]
In this case, first, a video code corresponding to the frequency band LL shown in FIG. 3A is supplied to the low resolution video code input terminal 201. The low resolution video decoding unit 202 decodes the low resolution video by subjecting the supplied video code to variable length decoding, inverse quantization, and inverse orthogonal transformation, and supplies the low resolution video to the low pass filter 208. The low-pass filter 208 supplies the supplied low-frequency image low-frequency signal, that is, the frequency band LLLL equivalent shown in FIG.
[0040]
On the other hand, the high frequency code supplied to the high frequency code input terminal 205 is supplied to the high frequency decoding unit 206. The high-frequency code input here is in the frequency bands LH, HL, HH shown in FIG. 3A and the frequency bands LLLH, LLHL, LLHH shown in FIG. 3B when a high-resolution video is encoded. Equivalent to. The high frequency decoding unit 206 performs variable length decoding and inverse quantization on the high frequency code, and a signal sequence corresponding to the frequency bands LH, HL, and HH is sent to the upsampler 213 and the frequency bands LLLH, LLHL, A signal sequence corresponding to LLHH is supplied to the upsampler 207, respectively.
[0041]
The up-samplers 207 and 213 insert “0” values horizontally / vertically into the supplied signal sequence, and supply them to the high-pass filters 212 and 214, respectively. The high-pass filter 212 passes only the frequency bands LLLH, LLHL, and LLHH shown in FIG. 3B in the supplied signal sequence and supplies them to the adder 209. In the adding unit 209, the supplied bands LLLH, LLHL, LLHH and the band LLLL supplied from the low-pass filter 208 are added to reconfigure the band LL shown in FIG. The sampler 210 is supplied.
[0042]
The upsampler 210 inserts a “0” value horizontally / vertically into the supplied signal sequence, and supplies it to the low-pass filter 211. The low-pass filter 211 passes only the band LL shown in FIG. 3A in the signal sequence supplied from the upsampler 210 and supplies it to the adder 215. On the other hand, the high-pass filter 214 passes only the bands LH, HL, and HH shown in FIG. 3A in the signal sequence supplied from the upsampler 213, and supplies them to the adder 215. The adding unit 215 adds the supplied band LL and the bands LH, HL, and HH, reconstructs the entire band of the high-resolution video, and supplies the reconfigured band to the switching unit 203.
[0043]
In the switching unit 203, the signal supplied from the adding unit 215 is selected and output to the video signal output terminal 204.
[0044]
As described above, according to the second embodiment, while maintaining compatibility with a conventional decoding device, a video signal that has been highly efficient encoded by the high efficiency encoding device shown in the first embodiment described above is appropriately used. Can be decrypted.
[0045]
In the second embodiment, when the high resolution video is decoded, the addition unit 215 reconstructs the entire band of the high resolution video by adding the band LL and the bands LH, HL, and HH, and the switching unit 203. An example of output to has been described. If this is configured so that only the band LL is output to the switching unit 203 without performing addition, a low-resolution video with high image quality can be output.
[0046]
In the first and second embodiments described above, the example in which the low-resolution video code and the high-frequency code are separately input / output has been described. However, a configuration in which a signal obtained by multiplexing these is input / output is described. Also good. As a multiplexing method in this case, for example, a method of time division multiplexing a low resolution video code and a high frequency code, a frequency multiplexing method, or the like can be applied.
[0047]
[Other Embodiments]
Note that the present invention can be applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, and a printer), and a device (for example, a copying machine and a facsimile device) including a single device. You may apply to.
[0048]
Another object of the present invention is to supply a storage medium (or recording medium) in which a program code of software that realizes the functions of the above-described embodiments is recorded to a system or apparatus, and the computer (or CPU or CPU) of the system or apparatus. Needless to say, this can also be achieved by the MPU) reading and executing the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention. Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an operating system (OS) running on the computer based on the instruction of the program code. It goes without saying that a case where the function of the above-described embodiment is realized by performing part or all of the actual processing and the processing is included.
[0049]
Furthermore, after the program code read from the storage medium is written into a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer, the function is determined based on the instruction of the program code. It goes without saying that the CPU or the like provided in the expansion card or the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.
[0050]
【The invention's effect】
As described above, according to the present invention, it is possible to perform a high-quality encoding process for a high-resolution image without impairing compatibility with an apparatus that supports only a low-resolution image.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a high-efficiency encoding device according to an embodiment of the present invention;
FIG. 2 is a block diagram showing a configuration of a high efficiency decoding device according to the second embodiment;
FIG. 3 is a diagram showing a state of frequency division in the present embodiment.
FIG. 4 is a block diagram showing a configuration of a conventional high-efficiency encoding device;
FIG. 5 is a block diagram showing a configuration of a conventional high-efficiency decoding device;
FIG. 6 is a diagram showing a state of frequency division in a conventional apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 101 Video signal input terminal 102 Switching part 103 Low resolution video encoding part 104 Low resolution video code output terminal 105 Low pass filter 106 Down sampler 107 High pass filter 108 Down sampler 109 High pass encoding part 110 High pass code Output terminal 111 High-pass filter 112 Downsampler 201 Low-resolution video code input unit 202 Low-resolution video decoding unit 203 Switching unit 204 Video signal output terminal 205 High-frequency code input terminal 206 High-frequency decoding unit 207 Up-sampler 208 Low-pass Type filter 209 Adder 210 Upsampler 211 Low pass filter 212 High pass filter 213 Upsampler 214 High pass filter 215 Adder

Claims

An input means for inputting an image signal;
Low -frequency component extraction means for filtering the image signal using a low-pass filter and extracting a low-frequency component signal by down-sampling ;
A first high-frequency component extracting means for filtering the image signal using a high-pass filter and extracting a first high-frequency component signal by down-sampling ;
Second high-frequency component extraction means for extracting a second high-frequency component signal that is a high-frequency component signal in the low-frequency component signal by filtering and down-sampling the low-frequency component signal using a high-pass filter ; ,
Low frequency component encoding means for encoding the low frequency component signal;
High-frequency component encoding means for encoding the first high-frequency component signal and the second high-frequency component signal;
An image processing apparatus comprising:

Wherein the input means further inputs the low-resolution image signal which is at a lower resolution than the resolution of the image signal,
The image processing apparatus according to claim 1 , wherein the low-frequency component encoding unit encodes the low-resolution image signal.

Wherein in the low-resolution image signal resolution respective horizontal and vertical directions, the image processing apparatus according to claim 2, wherein the an integral submultiple of the resolution of the image signal.

The image processing apparatus according to claim 2 , wherein the low-frequency component signal has a resolution equivalent to that of the low-resolution image signal.

The image processing apparatus according to claim 1 , wherein the low-frequency component extraction unit includes a two-dimensional low-pass filter and a two-dimensional downsampler.

The image processing apparatus according to claim 5 , wherein the low-frequency component extracting unit includes a horizontal and vertical low-pass filter and a horizontal and vertical downsampler.

The image processing apparatus according to claim 1 , wherein each of the first and second high-frequency component extraction units includes a two-dimensional high-pass filter and a two-dimensional downsampler.

8. The image processing apparatus according to claim 7 , wherein each of the first and second high-frequency component extracting units includes a horizontal and vertical high-pass filter and a horizontal and vertical downsampler.

The second high-frequency component extracting means extracts, as the second high-frequency component signal, a signal other than a signal composed of a horizontal low range and a vertical low range in the low-frequency component signal. Item 8. The image processing apparatus according to Item 1.

The second high-frequency component extracting means uses, as the second high-frequency component signal, in the low-frequency component signal, a signal sequence composed of a horizontal low range and a vertical high range, and a horizontal high range and a vertical direction. 10. The image processing apparatus according to claim 9 , wherein three sets of signal sequences are extracted: a signal sequence composed of a low frequency region of the above and a signal sequence composed of a high frequency region in the horizontal direction and a high frequency region in the vertical direction.

The image processing apparatus according to claim 10 , wherein each of the three sets of signal sequences has half the resolution of the low-frequency component signal in the horizontal and vertical directions.

2. The first high frequency component extracting means extracts a signal other than a signal composed of a horizontal low range and a vertical low range in the image signal as the first high frequency component signal. the image processing apparatus according to.

The image processing apparatus according to claim 12 , wherein the first high-frequency component extracting unit extracts a signal other than the low-frequency component signal in the image signal as the first high-frequency component signal.

The first high-frequency component extracting means uses, as the first high-frequency component signal, in the image signal, a signal sequence composed of a horizontal low range and a vertical high range, a horizontal high range and a vertical low range. 14. The image processing apparatus according to claim 13 , wherein three sets of signal sequences are extracted: a signal sequence composed of regions and a signal sequence composed of a high region in the horizontal direction and a high region in the vertical direction.

And further comprising selection means for selecting either the low resolution image signal or the low frequency component signal,
The image processing apparatus according to claim 2 , wherein the low-frequency component encoding unit encodes the signal selected by the selection unit.

2. The image processing apparatus according to claim 1 , further comprising multiplexing means for multiplexing the output of the low frequency component encoding means and the output of the high frequency component encoding means.

The image processing apparatus according to claim 16 , wherein the multiplexing unit performs time division multiplexing on the output of the low-frequency component encoding unit and the output of the high-frequency component encoding unit.

The image processing apparatus according to claim 16 , wherein the multiplexing unit frequency-multiplexes the output of the low-frequency component encoding unit and the output of the high-frequency component encoding unit.

Obtained by filtering and down-sampling the low-frequency component signal obtained by filtering and down-sampling the image signal using a low-pass filter, and by filtering the image signal using a high-pass filter. The first high-frequency component signal and the second high-frequency component that is a high-frequency component signal in the low-frequency component signal obtained by filtering and down-sampling the low-frequency component signal using a high-pass filter an image processing apparatus signals and decodes the coded signal respectively encoded,
Wherein the low-frequency component decoding means for generating a first low-frequency component signal by decoding the encoded signal of the low frequency component signal,
Low -frequency component extraction means for extracting a second low-frequency component signal by filtering the first low-frequency component signal using a low-pass filter ;
A high-frequency signal that decodes the encoded signal of the first high-frequency component signal and outputs a first high-frequency component signal, and decodes the encoded signal of the second high-frequency component signal and outputs a second high-frequency component signal Component decoding means;
The second high-frequency component signal is up-sampled, a third high-frequency component signal is output using a high-pass filter, and a third high-frequency component signal is output using the second low-frequency component signal and the third high-frequency component signal. A restoration means for outputting the low-frequency component signal and restoring the image signal using the third low-frequency component signal and the first high-frequency component signal ;
An image processing apparatus comprising:

An input process for inputting an image signal;
A low-frequency component extraction step of filtering the image signal using a low-pass filter and extracting a low-frequency component signal by down-sampling ;
A first high-frequency component extracting step of filtering the image signal using a high-pass filter and extracting a first high-frequency component signal by down-sampling ;
A second high-frequency component extracting step of extracting a second high-frequency component signal that is a high-frequency component signal in the low-frequency component signal by filtering the low-frequency component signal using a high-pass filter and down-sampling ; ,
A low frequency component encoding step for encoding the low frequency component signal;
A high frequency component encoding step for encoding the first high frequency component signal and the second high frequency component signal;
An image processing method comprising:

Furthermore, a low-resolution image input step of inputting the low-resolution image signal which is at a lower resolution than the resolution of the image signal,
A low-resolution image encoding step for encoding the low-resolution image signal,
The image processing method according to claim 20, wherein the low-frequency component signal has a resolution equivalent to that of the low-resolution image signal.

It is obtained by filtering the image signal using a low-pass filter and down-sampling the low-frequency component signal obtained by down-sampling and down-sampling the image signal using a high-pass filter. The first high-frequency component signal and the second high-frequency component which is a high-frequency component signal in the low-frequency component signal obtained by filtering and down-sampling the low-frequency component signal using a high-pass filter An image processing method for decoding an encoded signal in which each signal is encoded,
Wherein the low-frequency component decoding step of creating a first low-frequency component signal by decoding the encoded signal of the low frequency component signal,
A low-frequency component extraction step of extracting a second low-frequency component signal by filtering the first low-frequency component signal using a low-pass filter ;
A high-frequency signal that decodes the encoded signal of the first high-frequency component signal to output a first high-frequency component signal, decodes the encoded signal of the second high-frequency component signal, and outputs a second high-frequency component signal Component decoding step;
The second high-frequency component signal is up-sampled, a third high-frequency component signal is output using a high-pass filter, and a third high-frequency component signal is output using the second low-frequency component signal and the third high-frequency component signal. A restoration step of outputting the low-frequency component signal and restoring the image signal using the third low-frequency component signal and the first high-frequency component signal ;
An image processing method comprising:

A recording medium on which a program code for encoding an image is recorded, wherein the program code is at least
An input process code for inputting an image signal;
Filtering the image signal using a low-pass filter and extracting a low-frequency component signal by down-sampling ,
Filtering the image signal using the high-pass filter, and the code of the first high-frequency component extraction step of extracting a first high frequency component signal by downsampling,
A second high-frequency component extraction step of extracting a second high-frequency component signal that is a high-frequency component signal in the low-frequency component signal by filtering the low-frequency component signal using a high-pass filter and down-sampling Code,
A code of a low frequency component encoding step for encoding the low frequency component signal;
A code of a high frequency component encoding step for encoding the first high frequency component signal and the second high frequency component signal;
A recording medium comprising:

The program code further includes:
And code of the low-resolution image input step of inputting the low-resolution image signal is the image signal of lower resolution than the resolution,
A code of a low resolution image encoding step for encoding the low resolution image signal,
The recording medium according to claim 23, wherein the low frequency component signal has a resolution equivalent to that of the low resolution image signal.

Obtained by filtering and down-sampling the low-frequency component signal obtained by filtering and down-sampling the image signal using a low-pass filter, and by filtering the image signal using a high-pass filter. The first high-frequency component signal and the second high-frequency component that is a high-frequency component signal in the low-frequency component signal obtained by filtering and down-sampling the low-frequency component signal using a high-pass filter A recording medium on which a program code for decoding an encoded signal obtained by encoding each signal is recorded, and the program code is at least
Wherein the low-frequency component decoding step of creating a first low-frequency component signal by decoding the encoded signal of the low frequency component signal code,
A low-frequency component extraction step code for extracting a second low-frequency component signal by filtering the first low-frequency component signal using a low-pass filter ;
A high-frequency signal that decodes the encoded signal of the first high-frequency component signal and outputs a first high-frequency component signal, and decodes the encoded signal of the second high-frequency component signal and outputs a second high-frequency component signal Component decoding process code;
The second high-frequency component signal is up-sampled, a third high-frequency component signal is output using a high-pass filter, and a third high-frequency component signal is output using the second low-frequency component signal and the third high-frequency component signal. outputs a low frequency component signal, and the code restoration step of restoring the image signal by using the first high frequency component signal and the low frequency component signal of the third,
A recording medium comprising: