EP0768006A1 - Procede de synchronisation de systemes de compression/decompression video numerique successive - Google Patents

Procede de synchronisation de systemes de compression/decompression video numerique successive

Info

Publication number
EP0768006A1
EP0768006A1 EP95922678A EP95922678A EP0768006A1 EP 0768006 A1 EP0768006 A1 EP 0768006A1 EP 95922678 A EP95922678 A EP 95922678A EP 95922678 A EP95922678 A EP 95922678A EP 0768006 A1 EP0768006 A1 EP 0768006A1
Authority
EP
European Patent Office
Prior art keywords
coding
video signal
signal
added information
information
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
EP95922678A
Other languages
German (de)
English (en)
Inventor
Alois Martin Bock
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
National Transcommunications Ltd
Original Assignee
National Transcommunications Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by National Transcommunications Ltd filed Critical National Transcommunications Ltd
Publication of EP0768006A1 publication Critical patent/EP0768006A1/fr
Ceased legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/40—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using video transcoding, i.e. partial or full decoding of a coded input stream followed by re-encoding of the decoded output stream

Definitions

  • the present invention relates to the processing of digital signals and more particularly to digital video signals.
  • Digital video compression algorithms such as those disclosed in ISO/IEC 11172-2 (MPEGl) and 13818-2 (MPEG2) have already been proposed and are used to reduce the bandwidth necessary for the transmission of video signals in digitally coded format.
  • MPEGl digitally coded television frames
  • MPEG2 13818-2
  • coding schemes usually predict future pictures (e.g. digitally coded television frames) from previously decoded ones. By predicting pictures more than one frame into the future, it is possible to code intermediate frames by predictive processes from past as well as future frames as outlined in the standards MPEGl and MPEG2. This predictive coding process is then, often at regular intervals, replaced by a complete reconstruction of the current frame (intra-frame coding) in order to constrain the propagation and accumulation of coding errors and to provide unambiguous start points for the decoding process.
  • intra-frame coding Intra-frame coding
  • FIG. 1 shows an example of a cascade of two successive compression-decompression systems currently being used, with the intermediate signal (c) stored, for example, on a video cassette recorder. This process of compression/decompression storage and/or transmission could be repeated several times. If the compression systems in such a cascade of successive coding schemes operate entirely independently of one another the picture quality rapidly deteriorates. It is, therefore, important that, if transcoded frames are used for refresh in such a cascade the same frames are intra-coded throughout the entire chain of encoders and decoders.
  • the present invention proposes a method which makes it possible to synchronise cascaded compression systems in such a way that frames which have been intra- coded in the first coding system will then be intra- coded by the second and, therefore, all following coding systems.
  • a method for conveying information in a video signal comprising the steps of adding code signals to the video signal at certain points in a succession of video signals representing a frame of video, said code signals relating to the process used to create said frames, and using said code signals for choosing a coding scheme for said signal coding said video signal using said coding scheme, decoding said video signal such that the resulting decoded video signal comprises said code signals.
  • Figure 1 shows an example of a cascade of two successive compression systems with intermediate storage device.
  • Figure 2 shows a block diagram of the proposed method using a cascade of two successive compression/ decompression systems.
  • Figure 3 shows a block diagram of proposed method B, with detector and inserter prior to the encoder.
  • Figure 4 shows the temporal alignment of signalling waveform with coding blocks.
  • FIG. 2 shows a cascade of two successive compression systems, each consisting of an encoder and a decoder.
  • a signal to be processed (a) is fed to an encoder (1) and the encoded signal (b) is then fed to a decoder (2) of the first system.
  • the decoder (2) of the first system sends the coding information (d) of the first system to the signal inserter (3).
  • Signal inserter (3) codes the information on the video signal (e) as described below. This information is then conveyed together with the video signal (e) to the signal detector (4) of the second compression system.
  • Signal detector (4) extracts the information from the video signal (e) and passes this information on to the encoder (6) of the second compression system. Since signal inserters are used at the output of all decoders, several of such systems can be cascaded. In this simple mode of operation the blanking unit (5) simply passes the video signal on to the second encoder (6).
  • the signalling information is coded in the vertical blanking interval at the top of the frame to which the signalling information applies.
  • An example of such an application is the use of a user data field as defined in ITU-R Rec. 656 digital video standards for the transmission of the intra-frame signalling bit.
  • this simple method is all that is needed to synchronise successive video compression systems.
  • the disadvantage of the embodiment described above is that it relies on the transmission/ storage medium being transparent to the vertical blanking interval. If such transparency cannot be guaranteed the signalling information should be coded in the active part of the video signal itself as described below.
  • the signal waveform is chosen such that it survives most commonly used analogue and digital recording and transmission formats under worst-case broadcast quality signal-to-noise conditions. It could consist, for example, of a series of luminance pulses, such as raised-cosine pulses, with a width of 0.3 us or more. These could be located at the beginning of the last active line of the video frame prior to the frame to which the signalling information applies. This line is normally hidden in the over-scan region of display monitors. By putting the information into the last line of the previous frame the second encoder (6) has enough time to synchronise its intra-coding frames to that of the previous coding system.
  • the signal detector (4) needs to detect not only the signalling bit itself but it must also make a decision as to whether signalling information is present at all and, if it is, whether it is of sufficient quality in terms of its error rate to be used for controlling the encoder (6).
  • a further advantage of automatic signalling detection is the possibility of removing the signalling information in the blanking unit (5) prior to re- encoding in (6). This structure makes it possible to hide the signalling waveform from the viewer even in cases where the display monitor is not over-scanning the picture.
  • FIG. 3 shows a proposed third embodiment in block diagrammatic form.
  • the detector (2) If the detector (2) detects the presence of a signalling waveform, it passes the information (c) both to the encoder and to the inserter (1). If no signal is detected, the coding information (d) is entirely determined by the encoder (3) .
  • the proposed signal consists of a series of raised- cosine pulses, each, for example, 32 pixels wide.
  • the centre pixels of each symbol e.g. 16 pixels
  • Figure 4 shows how the signalling waveform is aligned with respect to coding blocks of the compression system.
  • the essential feature of the signalling waveform is that it is kept at a constant value for the duration of one or more complete compression blocks so as to minimise the distortion compression would have on the waveform.
  • By inserting guard intervals between successive bit levels cross-talk between symbols is minimised. Since all symbols have to be aligned with the coding structure, the guard intervals must have a minimum period equal to the horizontal size of at least one coding block.
  • the waveform between symbols is less important but would normally be chosen to have low spectral content.
  • intra-frame coding and forward predictive coding coding schemes such as those described in ISO/IEC 11172-1, MPEG-1, Coding of Moving Pictures and Associated Audio, Part 2, Video and ISO/IEC 13818-2, MPEG-2, Coding of Moving Pictures and Associated Audio, Part 2, Video, allow the definition of bi-directionally predicted pictures. These are pictures which are predicted both from a past and a future reference picture. In order to achieve the best picture quality after several cycles of compression and decompression in systems using bi-directional prediction it may be desirable that the entire sequence of intra, bi-directional and forward predictive coding is faithfully repeated in all coding/decoding cycles.
  • Additional coding parameters which might be signalled from one compression system to the next are the use of field or frame coding, the type of block scanning pattern and the quantisation table used in the first encoding process.

Landscapes

  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Compression Or Coding Systems Of Tv Signals (AREA)

Abstract

Procédé de codage et de décodage répétés de signaux vidéo numériques permettant d'éviter les problèmes de dégradation de la qualité des images causés par des codages internes répétés de trames. Grâce au présent procédé, le codage/décodage répété de trames à l'aide de systèmes de codage interne permet de toujours utiliser les mêmes trames en tant que trames non interpolées, de manière qu'à chaque génération, une quantité importante des informations originales soit présente et ne soit pas approchée par approximation de manière répétitive, comme dans les systèmes en vigueur. L'invention consiste à ajouter des signaux de code au signal vidéo décodé, lesdits signaux de code contenant les informations relatives aux trames non interpolées dans des codages précédents, de manière que lors du codage à nouveau dudit signal, le même codage soit utilisé, évitant ainsi de perdre beaucoup moins d'informations.
EP95922678A 1994-06-28 1995-06-27 Procede de synchronisation de systemes de compression/decompression video numerique successive Ceased EP0768006A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB9413001 1994-06-28
GB9413001A GB9413001D0 (en) 1994-06-28 1994-06-28 Methods for the synchronisation of successive digital video compression/decompression systems
PCT/GB1995/001507 WO1996001023A1 (fr) 1994-06-28 1995-06-27 Procede de synchronisation de systemes de compression/decompression video numerique successive

Publications (1)

Publication Number Publication Date
EP0768006A1 true EP0768006A1 (fr) 1997-04-16

Family

ID=10757469

Family Applications (1)

Application Number Title Priority Date Filing Date
EP95922678A Ceased EP0768006A1 (fr) 1994-06-28 1995-06-27 Procede de synchronisation de systemes de compression/decompression video numerique successive

Country Status (4)

Country Link
EP (1) EP0768006A1 (fr)
JP (1) JPH10506505A (fr)
GB (1) GB9413001D0 (fr)
WO (1) WO1996001023A1 (fr)

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5715009A (en) 1994-03-29 1998-02-03 Sony Corporation Picture signal transmitting method and apparatus
GB9501736D0 (en) * 1995-01-30 1995-03-22 Snell & Wilcox Ltd Video signal processing
US6885702B1 (en) 1997-10-06 2005-04-26 Telediffusion De France Method for spatial synchronization of a digitally coded video image and/or for identification of the syntax of a video sequence
FR2769453B1 (fr) 1997-10-06 2000-01-07 Telediffusion Fse Procede d'evaluation de la degradation d'une image video introduite par un systeme de codage et/ou de stockage et/ou de transmission numerique
FR2769452B1 (fr) * 1997-10-06 2000-01-14 Telediffusion Fse Procede de synchronisation spatiale d'une image video codee numeriquement et/ou d'identification de la syntaxe d'une sequence video
CA2265089C (fr) 1998-03-10 2007-07-10 Sony Corporation Systeme de transcodage utilisant les informations d'encodage
KR100571307B1 (ko) 1999-02-09 2006-04-17 소니 가부시끼 가이샤 코딩 시스템 및 방법, 부호화 장치 및 방법, 복호화 장치및 방법, 기록 장치 및 방법, 및 재생 장치 및 방법
JP3694888B2 (ja) 1999-12-03 2005-09-14 ソニー株式会社 復号装置および方法、符号化装置および方法、情報処理装置および方法、並びに記録媒体
JP4196726B2 (ja) 2003-05-14 2008-12-17 ソニー株式会社 画像処理装置および画像処理方法、記録媒体、並びに、プログラム

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5200749A (en) * 1991-05-28 1993-04-06 Tektronix, Inc. Format converter architecture
JP3196906B2 (ja) * 1992-08-21 2001-08-06 富士ゼロックス株式会社 画像信号の符号化装置
JP3163830B2 (ja) * 1993-03-29 2001-05-08 ソニー株式会社 画像信号伝送方法及び装置

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9601023A1 *

Also Published As

Publication number Publication date
JPH10506505A (ja) 1998-06-23
GB9413001D0 (en) 1994-08-17
WO1996001023A1 (fr) 1996-01-11

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