[M4IF Technotes] ´ð¸´: [M4IF Technotes] Decoder specific info for visual atoms

[lmwang]

Dear Cyril,
See ISO/IEC 14496-2:2001(E) Annex K Decoder Configuration Information
for more.
In my understanding, parsing decoderspecificinfo structure is like parse
VOSH+VO header. So the bitstream like 00 00 01 B0, 00 00 00 01 B5,00 00
01 00 is Video Object sequence start code,visual object start code,video
object start code. By parsing them, you'll get some basic information
like video width,height etc.
You can refer to OSMO4's xvid plugin-in code:
http://www.comelec.enst.fr/osmo4/v1.2.1/Osmo4_SRC.zip
good luck,
Limin
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[mailto:technotes-admin   lists.m4if.org] ?? Stage NexVision
????: 2003?5?7? 16:18
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??: [M4IF Technotes] Decoder specific info for visual atoms
Dear experts,
  I'm trying to encode my own MP4 file.
In order to do this, I've made an MP4 file analyser (atom + descriptor
analysers)
Then, I've found a file called "sorenson.mp4" which is very basic and
plays
well in all player I have (wmp4player from MPEG4IP project, Philips one,
TVM4 one, and MPEGable)
I have extracted the information (ie headers from that file which is
320x240), and modified them accordingly to my analyser.
However, on some players, the image is struck to 320x240 size, while in
some
it's the right size which is read (720x576).
This is the place in the file where I modified the size values:
in the tkhd atom, mp4v atom, esds for the scene description atom, and in
the
visual bitstream header (directly in the frames)
I've understood all the atom information except in 2 places :
  I am missing some information about 2 little parts of the MPEG4
standard.
I've read the ISO 14496-1:1998 document, but I can't find any
information
about the decoder specific info for my 'mp4v' atom (descriptor with tag
0x05)
I've found the good "decoder specific information" for the 'mp4s' scene
description, (in chapter 9.3-4).
In this document, however, for visual track only, they refers to the
"Annex
L", I don't have, or I can't find.
Does any of you can explain me if these 'crazy' 32 bytes contains any
informations about the movie size ?
Decoder specific info
\/
05 80808020 00 00 01 B0 01 00 00 01 B5 0E E0 40 40 AF
00 00 01 00 00 00 01 20 00 84 5D 4C 28 50 20 F0 A3 1F
My second question is where can I find a free BIFS decoder, because I
can't
understand easily the first 10 bytes in the "mdat" atom which are BIFS
commands.
When I try to decompose them, I find some bits that are not described in
Part 2, (or I don't know where).
I know it's quite a long mail, but if you could arrive till this line,
you
might be able to answer me ;-) (please...)
Sincerly
Cyril Russo
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