WO2004023820A1 - Dispositif et systeme de changement d'un signal video - Google Patents

Dispositif et systeme de changement d'un signal video Download PDF

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Publication number
WO2004023820A1
WO2004023820A1 PCT/SE2003/001378 SE0301378W WO2004023820A1 WO 2004023820 A1 WO2004023820 A1 WO 2004023820A1 SE 0301378 W SE0301378 W SE 0301378W WO 2004023820 A1 WO2004023820 A1 WO 2004023820A1
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WO
WIPO (PCT)
Prior art keywords
video signal
dct
components
transform
coder
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Application number
PCT/SE2003/001378
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English (en)
Inventor
Harald Brusewitz
Original Assignee
Iqc Transcoding Ab
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 Iqc Transcoding Ab filed Critical Iqc Transcoding Ab
Priority to AU2003256213A priority Critical patent/AU2003256213A1/en
Publication of WO2004023820A1 publication Critical patent/WO2004023820A1/fr

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    • 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
    • H04N19/90—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using coding techniques not provided for in groups H04N19/10-H04N19/85, e.g. fractals
    • 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 refers to a device for providing a video signal, which is transformed by quantised transform com- ponents, e.g. lev and/or run, and contains or can be supplied with supporting information, e.g. image type, macro- block, movement vectors, etc.
  • quantised transform com- ponents e.g. lev and/or run
  • supporting information e.g. image type, macro- block, movement vectors, etc.
  • the invention also refers to a system constructed by or including one or several such devices.
  • Video signals may be changed or influenced, e.g. digitally, by various methods for conversion, reduction and compression, and the present invention is specifically directed to the case where transform technique is included.
  • a common example of transform that hereby may be used is the Discrete Cosines Transform (DCT).
  • DCT Discrete Cosines Transform
  • the invention is however applicable on other types of transforms.
  • Common for actual compression methods is that the transform components are quantised and that a variable length code (VLC) is used for creating code words representing the quantised value (frequently called "lev") of the transform component.
  • VLC variable length code
  • run- length coding which means that a particular code word is used for representing the number of transform components (frequently called "run") that is quantised to the value zero (0) prior to a transform component having a value differing from zero.
  • VLC variable length code
  • run- length coding which means that a particular code word is used for representing the number of transform components (frequently called "run") that is quantised to the value zero
  • a straight and well known method of changing the bit rate in a coded bit stream is firstly to decode the bit stream and then to code the resulting video signal by a new bit rate, compare the following Fig 1 .
  • the information in the bit stream which becomes known during the decoding procedure, is used.
  • This information is less complex and may be transmitted via a side channel (compare the following Fig 2) to the coder, and may thus be used for simplifying the coder and for improving the performance of the rate conversion.
  • Said side information may consist of image type, macro-block type, movement vectors etc. (Compare the standards mentioned above for image compression for definition of these items). An important property in this method is to save bits there through.
  • This re-quantisation involves a deterioration of the image quality when the resulting bit stream later on is decoded.
  • the decoder and the following coder have been integrated in one loop. This method is described in scientific literature.
  • desiderata are inter alia present saying that the bit rate could be decreased substantially in a coded video, so-called rate conversion, without deteriorating substantially the content in an actual video signal, i. e. without the image perception is experienced as deteriorated or substantially better than when using known technique.
  • rate conversion a desideratum of reducing substantially the number of bits or the bandwidth from an already coded or compressed still image or video signal without said deterioration occurring.
  • the object of the invention is to solve inter alia the whole or parts of these problems.
  • the values "lev” of the transform components should alternatively be possible to change individually according to a particular criterion. This criteria should possibly be based on the fact that a large bit saving can be made at the same time as a resulting loss in the image quality is limited. There is also a desideratum of being able to reuse a part of the information in the incoming bit stream in the outgoing bit stream, and of being able to operate the device or the system with or without loop in the video case. The invention intends to solve also the whole or parts of this complex of problems.
  • the feature which may be regarded as essentially characterising a device according to the invention is that it is arranged to modify, during the change of the video signal, substantially solely the transform components in one of the following two cases, namely where the device forms a unit converting or reducing the video signal includes a decoder, preferably a VLD, which receives the video signal, and a coder, preferably a VLC, which effectuates a change in the front of a conversion or reduction of the video signal received, wherein said modification results in at least substantially no influence on the supporting information, and where the device forms a coder receiving the video signal arranged to provide by itself a change in the form of a compression of the video signal received and to generate the supporting information substantially independently of the compression.
  • a decoder preferably a VLD
  • a coder preferably a VLC
  • the video buffer verification (vbv)-delay in the PIC-header is subjected to a change function.
  • macro-block type and movement vectors may be subjected to change functions, which is valid in the case that the incoming bit stream is erroneous.
  • the device may operate in a circuit arrangement with or without feedback circuit. When using a feedback circuit, the latter is provided to avoid error propagation from image to image. When modifying the transform component or transform components, the device may operate with or without re-quantisation.
  • the device may also be provided to permit change of the value of one or several transform components, e. g. lev, according to a selected criteria, e. g. a criteria based on a large bit saving with simultaneous small reduction or substantially maintained image quality.
  • the device is arranged not to modify any transform component in an individual DCT-block, to modify an individual transform component in an individual DCT- block, to modify several transform components, but not all, in an individual DCT-block, to modify all transform components in an individual DCT-block, and/or to modify all transform components in an individual macro-block.
  • an individual transform component e.g. lev
  • an individual transform component e.g. lev
  • an individual transform component may be changeable by more than one unit, e.g. from 2 (two) to 0 (zero) or e.g. from -3 (minus three) to 0 (zero) or e.g. 4 (four) to 2 (two), if this involves a bit saving with a predetermined minimum number of bits.
  • several transform components e.g. lev
  • a system according to the invention may essentially be characterised in that the respective device for providing an influence or change of the video signal either includes a decoder or a coder or itself forms a coder which compresses the received video signal, and that one or several of said devices are provided to modify substantially solely the transform components and that the supporting information thus is substantially not influenced.
  • the respective device concerned may be included in or connectable to any of the following function alternative, recording on digital storing media for providing a memory saving and/or a modified image quality, relay transmission in or to a transmission network with smaller bandwidth, multiplexing of two or several video channels, transfer from variable to constant bit rate, transfer from constant to variable bit rate, transfer from constant to constant lower bit rate, transfer from variable to variable lower bit rate, or compression of the video signal between transmission and receiving equipment.
  • the bit rate may, with a substantially maintained image quality, be decreased in an advantageous manner and the construction may to a large extent be based on known and technically simple means.
  • Functions and parameters may be optimised and varied by means of program and computer controls, for instance via tele and/or data communication connections, also Internet.
  • the invention may if so desired be based on standards and known techniques.
  • the selection of criteria or parameters for determining or adjusting values of the transform components and thus the bit-saving and image quality may be performed by means of buffer control, for instance provided by a module.
  • the invention also enables device and system constructions with less complexity than previously. Certain bits in the incoming bit stream may be used in the outgoing bit stream. No loop is required in the video case and the value of "lev" in certain selected DCT-components may be changed without the need of re-quantisation.
  • Fig 1 discloses in a block diagram and principally conversion of the bit rate by a decoder and coder according to known technique.
  • Fig 2 discloses in a block diagram and principally conversion of the bit rate by a decoder, a coder and supplementary information according to known technique. discloses in a block diagram and principally a decoder followed by a coder for still image according to known technique.
  • Fig 1 defines symbolically a decoder 1 , a coder 2 and an incoming coded video signal 3 with a certain bit rate.
  • a decoded video signal 4 is delivered from the decoder to the coder 2.
  • a coded video signal 5 with a lower bit rate than the first mentioned bit rate is obtained at the output of the coder.
  • Fig 2 corresponds to the case according to Fig 1 with the difference that supplementary information, in addition to the uncoded information, is transferred between the decoder and the coder.
  • the decoder is in this case defined by 6 and the coder by 7.
  • a coded video signal has the reference sign 8 and a decoded, video signal has been defined by 9.
  • By 10 is referred to a coded video signal with a lower bit rate than the one related to in Fig 1 .
  • 1 1 refers to side information or a side information signal.
  • Fig 3 illustrates more in detail a case corresponding to Fig 1 for a still image.
  • a variable length decoder is disclosed by 12 and an inverse quantiser 1 by 13.
  • An Inverse Discrete Cosinus Transform (IDCT) 14 is connected to the latter component.
  • 15 refers to a Discrete Cosinus Transform and 16 to a quantiser 2.
  • a variable length coder is defined by 17. In the figure, the components are also defined by their respective abbreviations.
  • a coded still image 18 is supplied and the component is outputting quantised DCT-components 19.
  • inverse quantised DCT-components 20 are obtained.
  • 21 intends to symbolise a decoded still image supplied to the component 15.
  • This delivers re-quantised DCT- components 22 to the component 16 which in its turn provides re-quantised DCT-components 23.
  • 24 intends to illustrate a recorded still image with fewer bits than the coded still image in point 18.
  • Fig 4 the embodiment according to Fig 2 has been replaced by a simplified loop.
  • An inverse quantiser 28 has been connected to the output of the quantiser 27 and connected to a subtracter which is also connected to the incoming signal to the quantiser 27.
  • IDCT Inverse Discrete Cosine Transform
  • a variable length decoder VLD is defined by 25
  • an inverse quantiser 1 by IQ ⁇ which has the reference sign 26.
  • a quantiser 2 (Q 2 ) is defined by 27 and an inverse quantiser IQ 2 by 28. 29 refers to an Inverse Discrete Cosinus Transform (IDCT) 29.
  • IDCT Inverse Discrete Cosinus Transform
  • DCT Discrete Cosinus Transform
  • VLC variable length coder
  • a coded video signal has the reference sign 33 and quantised DCT-components 34.
  • Inverse quantised DCT- components have the reference sign 35 and DCT-components compensated for quantising errors in previous images, via a subtracter, have the reference sign 36.
  • Re-quantised DCT- components have the reference sign 37 and inverse re- quantised DCT-components have been defined by 38.
  • Quantising errors of DCT-components are defined by 39 and 40 intends to disclose a feedback inverse transformed quantising error.
  • 41 is a movement compensated quantising error whereas 42 defines a DCT-transformed and movement compensated feedback signal.
  • a re-coded video signal 43 demonstrates lower bit rate than in point 33.
  • Fig 4, 44 is side information.
  • a modifying unit for DCT-components is utilised between the decoder and the coder.
  • a supervising unit is provided for further information.
  • This embodiment operates without loop, compare Fig 4.
  • a variable length decoder VLD is defined by 45 and a modified DCT-unit is disclosed by 46.
  • DCT means Discrete Cosines Transform.
  • This component is essential for the present invention since certain selected quantised DCT-components obtain a changed value in a predetermined criteria.
  • 47 defines a variable length coder VLC.
  • a coded video signal 48 is introduced to the variable length decoder 45, which transfers quantised DCT- components to the component 46.
  • Quantised modified DCT- components are disclosed by 50.
  • 51 defines a re-coded video signal with lower bit rate than said coded video signal 48.
  • 52 refers to side information.
  • Fig 6 discloses the case without loop and with re-quantisation.
  • a variable length decoder VLD is defined by 53 and a variable length coder VLC by 57.
  • An inverse quantiser 1 (IQ 2 ) is disclosed by 54 and a quantiser 2 (Q 2 ) is defined by 55.
  • a core component as defined above is used, which core component has the reference sign 56 and refers to a modification of DCT-components.
  • the invention operates in this case with certain selected quantised DCT-components which obtain a changed value according to a predetermined criteria.
  • 58 refers to a coded video signal and 59 to quantised DCT- components.
  • Inverse quantised DCT-components are defined by 60 and re-quantised DCT-components are defined by 61 .
  • 62 refers to re-quantised and modified DCT-components and 63 defines a re-coded video signal which demonstrates a bit rate that is lower than the bit rate of the coded video signal 48.
  • a side information is defined by 64.
  • Fig 7 intends to disclose the case with image conversion with loop and re-quantisation.
  • the construction corresponds to the embodiment of Fig 4 except for the fact that the quantiser is followed by a unit that modifies DCT.
  • a variable length decoder VLD is defined by 65, an inverse quantiser 1 (IQ-i) by 66, and a quantiser 2 (Q 2 ) by 67.
  • Modification of DCT- components takes place in 68, and similarly to the embodiment above, is a core component in the present invention since certain selected quantised DCT-components obtain a changed value according to a predetermined criterion.
  • An inverse quantiser 2 (IQ 2 ) is disclosed by 69, an Inverse Discrete Cosines Transform (IDCT) by 70, a movement compensator MC using part of the side information by 71 , a Discrete Cosines Transform (DCT) by 72 and a variable length coder (VLC) by 73.
  • a coded video signal has the reference sign 74, quantised DCT- components are defined by 75, inverse quantised DCT- components are defined by 76 and inverse quantised DCT- components are defined by 77 and provided to compensate for quantising errors in previous images.
  • Re-quantised DCT- components have the reference sign 78 and re-quantised and modified DCT-components have the reference sign 79.
  • Modified and inverse quantised DCT-components are defined by 80, and a quantising error of DCT-components is defined by 81 .
  • An inverse transformed quantising error has the reference sign 82, and a movement compensated and inverse transformed quantising error has the reference sign 83.
  • a feedback, movement compensated and DCT-transformed quantising error has been defined by 84.
  • 85 refers to a re-coded video signal with lower bit rate than the one in point 74.
  • a side information is in this case defined by 86.
  • a Discrete Cosines Transform DCT is defined by 87, a quantiser Q by 88, an inverse quantiser IQ by 89, an Inverse Discrete Cosines Transform IDCT by 90, a movement compensator MC using part of the side information by 91 , a decision module ME including movement estimation by 92, and a variable length coder VLC by 93.
  • An uncompress video signal is defined by 94, a prediction error by 95, DCT-components of transformed prediction error by 96, quantised DCT-components by 97, inverse quantised DCT- components by 98, inverse. transformed DCT-components by 99, reconstructed video by 100, prediction, movement compensated reconstructed video by 101 , side information by 102 and coded video by 103.
  • a Discrete Cosines Transform DCT is defined by 104, a quantiser Q by 105, and modifying of DCT-components by 106.
  • the latter component is a core component in the present invention, in which certain selected quantised DCT-components obtain a changed value according to a predetermined criterion.
  • an inverse quantiser is defined, by 108 an inverse Discrete Cosines Transform IDCT, by 109 a movement compensator MC using part of the side information, by 1 10 a decision module ME including movement estimation, by 1 1 1 a variable length coder VLC, by 1 12 a video signal, by 1 13 a prediction error, by 1 14 DCT-components of transformed prediction error, by 1 15 quantised DCT-components by 1 16 modified DCT-components, by 1 17 inverse quantised and modified DCT-components, by 1 18 inverse transformed DCT- components, by 1 19 reconstructed video, by 120 prediction and movement compensated reconstructed video, by 121 side information, and by 122 coded video.
  • the method and the arrangement to change the value of quantised transform components, e. g. lev, is useful also in a coder, i. e. a device where uncompressed, analogue or digital, video is converted to compressed form.
  • a coder according to known technique is illustrated in Fig 8
  • a coder supplemented according to the present invention is illustrated in Fig 9.
  • the unit 106 in Fig 9 is thus characterised in that the value of lev is changed to a new value if this involves a saving of at least a predetermined value.
  • 1 12 may also be regarded to symbolise receiving equipment, which receives an uncompressed video signal, and 122 may be regarded to symbolise transmitting equipment, which transmits a compressed video signal.
  • a parabolic antenna 123 is included.
  • a "Set-top-box" for digital TV- receivers 124, a television apparatus 125, a rate converter 126 according to the present invention, and a digital storing medium 127, for instance a hard disc, are used.
  • 128 illustrates a signal from the parabolic antenna, 129 a decoded video signal, 130 a coded video signal and 131 a converted video signal with lower bandwidth than the coded video signal 130.
  • Fig 1 1 discloses an example of relay transmission to a transmission network with lower bandwidth.
  • a parabolic antenna 132 a module 133 for extracting the coded video signal, a rate converter 134 according to the present invention, and a transmission network 135, e. g. Internet, are used.
  • 136 constitutes the signal from the parabolic antenna, 137 a coded video signal, and 138 a converted video signal with lower bandwidth than the coded video signal 137.
  • 139 constitutes a parabolic antenna
  • 140 a module for extracting a coded video signal 150
  • 141 a rate converter according to the present invention
  • 142 an antenna for ground transmitted digital-TV
  • 143 a module for extracting a coded video signal 153, 144 a rate converter according to the present invention
  • 145 a TV-camera
  • 146 a video coder 147 a rate converter according to the present invention
  • 148 a multiplexor constitutes a parabolic antenna
  • 140 a module for extracting a coded video signal 150
  • 141 a rate converter according to the present invention
  • 142 an antenna for ground transmitted digital-TV
  • 143 a module for extracting a coded video signal 153, 144 a rate converter according to the present invention
  • 145 a TV-camera
  • 148 a multiplexor.
  • 149 constitutes the signal from the parabolic antenna, 150 a coded video signal, 151 a converted video signal with lower bandwidth than the coded video signal 150, 152 a signal from the TV-antenna, 153 a coded video signal, 154 a converted video signal with lower bandwidth than the last mentioned coded video signal 153, 155 a video signal, 156 a coded video signal, 157 a converted video signal with lower bandwidth than the video signal 156, and the coded and bite rate converted video signals multiplexed to a bit stream 158.
  • the invention may thus in accordance with the embodiments above use the fact that certain information from an incoming bit stream is reused in the outgoing bit stream. No loop is required, for instance in the video case according to Fig 5, although a loop as disclosed may be used in certain embodiments.
  • the value of "lev" in certain selected DCT-components is changed without the need of re-quantisation.
  • bit stream may contain errors, for instance due to poor receiving conditions.
  • An erroneous bit stream may contain unallowable values of the side information, and it may then be appropriate to assign allowable values to the erroneous parameters.
  • a feedback loop is used for avoiding error propagation from image to image.
  • Such a loop may be avoided if intra coding is frequently used in the incoming (and thus outgoing) bit stream.
  • the transform components do not need to be re-quantised but the same value of "quant” may be transmitted for each macro- block. It is however possible to combine the present invention with re-quantisation. Instead, the values "lev" of the transform components are changed individually according to a particular criterion.
  • the invention may operate with various criteria for changing of "lev".
  • An individual "lev” may be changed by one unit, e.g. from the value 1 (one) to 0 (zero), if this involves a bit saving of at least ki bits.
  • Two or several adjacent "lev” may be changed by one unit each, e. g. from the value 1 (one) to 0 (zero), if this involves a bit-saving of at least k 2 bits
  • "lev” may also be changed from e. g. 2 to 0 or from 2 to 1 if this involves a bit- saving by at least k 3 and k 4 bits, respectively.
  • An individual "lev” may be changed from the value 0 (zero) to 1 (one) if this involves a bit saving of at least k 5 bits.
  • the criteria may be selected at use in different cases. The selection of criteria for changing the values of the transform components determines the bit saving and the image quality that are achieved. This may be effectuated by or in a module called buffer control.
  • VLC - Variable Length Coder 18. Coded still image.
  • MC - Movemnet Compensator uses parts of the side information.
  • mod DCT - the core component in the present invention in which certain selected quantised DCT- components receive a changed value according to a predetermined criteria 47.
  • VLC - Variable Length Coder VLC - Variable Length Coder.
  • MC - Movement compensater uses parts of the side information.
  • MC - Movemnet compensator uses parts of the side information.
  • VLC - Variable Length Coder 94. Video signal.
  • mod DCT - the core component in the present invention in which certain selected quantised DCT- components receive a changed value according to a predetermined criteria
  • MC - Movement compensator uses parts of the side information.
  • ME - Decision module including movement estimation.
  • VLC - Variable Length Coder 1 1 1 1 .
  • Rate converter according to the present invention.
  • Digital storing medium e.g. a hard disc.
  • Digital storing medium e.g. a hard disc.
  • 128. Signal from a parabolic antenna.
  • Parabolic antenna 133 Module for extracting of ceded video signal.
  • Rate converter according to the present invention.
  • Transmission network e.g. internet.
  • Rate converter according to the present invention.
  • Rate converter according to the present invention.
  • Rate converter according to the present invention.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Compression Or Coding Systems Of Tv Signals (AREA)
  • Compression, Expansion, Code Conversion, And Decoders (AREA)
  • Color Television Systems (AREA)

Abstract

L'invention concerne un dispositif et un système de conversion ou de réduction du débit binaire d'un signal vidéo numérique, ou de compression d'un signal vidéo numérique. Le signal vidéo est soumis à une transformation à l'aide de composantes de transformation quantifiée, et d'informations de support. Le dispositif, séparé ou intégré dans le système, peut comprendre un décodeur qui reçoit le signal vidéo destiné à être converti, et un codeur qui fournit le signal numérique sous forme convertie ou réduite. En variante, le dispositif est formé d'un codeur. Le dispositif est destiné à modifier seulement les composantes de transformation, ce qui signifie que les informations de support ne sont pas sensiblement influencées. Le dispositif permet une réduction du débit binaire dans une image vidéo codée ou une compression du signal vidéo sans occurrence d'une quelconque détérioration substantielle de la qualité de l'image ou du signal.
PCT/SE2003/001378 2002-09-04 2003-09-04 Dispositif et systeme de changement d'un signal video WO2004023820A1 (fr)

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Application Number Priority Date Filing Date Title
AU2003256213A AU2003256213A1 (en) 2002-09-04 2003-09-04 A device and a system for providing a change of a video signal

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SE0202614A SE525615C2 (sv) 2002-09-04 2002-09-04 Anordning för att åstadkomma förändring av videosignal
SE0202614-4 2002-09-04

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1708510A2 (fr) * 2005-03-29 2006-10-04 Fujitsu Limited Appareil de codage d'image

Citations (4)

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Publication number Priority date Publication date Assignee Title
US5905846A (en) * 1996-05-31 1999-05-18 Sony Corporation Image decoding apparatus and process thereof and image reproduction apparatus
US6263021B1 (en) * 1998-09-18 2001-07-17 Sarnoff Corporation Treating non-zero quantized transform coefficients as zeros during video compression processing
US20020067768A1 (en) * 2000-10-10 2002-06-06 Hurst Robert N. Rate control for bitstream re-encoding
US20020118760A1 (en) * 1996-07-15 2002-08-29 Michael James Knee Video signal compression

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5905846A (en) * 1996-05-31 1999-05-18 Sony Corporation Image decoding apparatus and process thereof and image reproduction apparatus
US20020118760A1 (en) * 1996-07-15 2002-08-29 Michael James Knee Video signal compression
US6263021B1 (en) * 1998-09-18 2001-07-17 Sarnoff Corporation Treating non-zero quantized transform coefficients as zeros during video compression processing
US20020067768A1 (en) * 2000-10-10 2002-06-06 Hurst Robert N. Rate control for bitstream re-encoding

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1708510A2 (fr) * 2005-03-29 2006-10-04 Fujitsu Limited Appareil de codage d'image
EP1708510A3 (fr) * 2005-03-29 2009-09-02 Fujitsu Limited Appareil de codage d'image
US7646926B2 (en) 2005-03-29 2010-01-12 Fujitsu Limited Image encoding apparatus

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SE0202614L (sv) 2004-03-05
SE525615C2 (sv) 2005-03-22
AU2003256213A1 (en) 2004-03-29
SE0202614D0 (sv) 2002-09-04

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