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

[Luca Piccarreta]

Wasn't it intended for N-bit coding?

----- Original Message ----- 
From: "Chandra Sekhar Reddy" <gchandra at tataelxsi.co.in>
To: <xvid-devel at xvid.org>
Sent: Saturday, July 26, 2003 4:32 PM
Subject: [XviD-devel] [Fwd: [M4IF Technotes] resync_marker emulation]


> 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
> >
> > _______________________________________________
> > Technotes mailing list
> > Technotes at lists.m4if.org
> > http://lists.m4if.org/mailman/listinfo/technotes
>
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