[XviD-devel] [Fwd: [M4IF Technotes] resync_marker emulation]

[Chandra Sekhar Reddy]

Hi,

One of my team-mate raised this issue on M4IF-technotes, but got no responces.
What is XVID codec doing to take care of this situation?

Regards,
Chandra



Dhinesh wrote:

> Dear experts,
>
> Reference : Section "6.2.7 Block - ISO/IEC 14496-2:2001(E)"
> "In Block decoding if the dct_dc_size_chrominance > 8  a marker_bit
>  is inserted to avoid the resync_marker emulation."
>
> If the encoders follow the above statement,
> it will still lead to resync_marker emulation in some cases as explained
> below.
>
> We fould atleast two cases,
> in case the first part of the emulated resync_marker starts at
> byte-boundary.
>
> Should the encoder take care of this emulation problem by
> re-encoding the probematic-macroblock/block with changed parameters
> to avoid emulation?
>
>         or
>
> Replace the text in the Section "6.2.7 Block - ISO/IEC 14496-2:2001(E)"
> ****************************************************************************
> *****
> "In Block decoding if the dct_dc_size_chrominance > 8
>  a marker_bit is inserted to avoid the resync_marker emulation."
> ****************************************************************************
> *****
> with
> ****************************************************************************
> *****
> " dct_dc_size_chrominance >= 8 "
> ****************************************************************************
> *****
>
> ****************************************************************************
> *****
> EMULATION COMBINATION - 1
> ****************************************************************************
> *****
> First part of the emulated resync_marker
> -----------------------------------------
> Table B-16 -- VLC Table for Intra Luminance and Chrominance TCOEF
> VLC-CODE        LAST    RUN     LEVEL
> 0010 000s       1       4       1
>
> Second part of the emulated resync_marker
> -----------------------------------------
> Table B-14 -- Variable length codes for dct_dc_size_chrominance
> Variable-length-code    dct_dc_size_chrominance
> 0000 0000 0001                  12
>
>         TCOEF      dct_dc_size_chrominance
>         (s = 0)
>         0010 0000    0000 0000 0001
> ****************************************************************************
> *****
>
> ****************************************************************************
> *****
> EMULATION COMBINATION - 2
> ****************************************************************************
> *****
> First part of the emulated resync_marker
> -----------------------------------------------------------
> Table B-15 -- Differential DC additional codes
> Additional-code         Differential-DC         Size
> 00000000 to 01111111    -255 to -128            8
>
> Second part of the emulated resync_marker
> -----------------------------------------------------------
> Table B-16 -- VLC Table for Intra Luminance and Chrominance TCOEF
> VLC-CODE        LAST    RUN     LEVEL
> 0000 0000 111s  0       0       21
> or
> 0000 0000 110s  0       0       22
> or
> 0000 0000 101s  1       0        6
> or
> 0000 0000 100s  1       0        7
>
>         Differential-DC     TCOEF
>         (-255)
>         00000000           0000 0000 111s
> ****************************************************************************
> *****
>
> Waiting for comments .
>
> Best Regards
> Dhinesh
>
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