[XviD-devel] Simple profile level 0

suxen_drol suxen_drol at hotmail.com
Wed Jun 4 19:22:25 CEST 2003


On Tue, 3 Jun 2003 09:53:50 +0200 <R.Schramp at telecom.tno.nl> wrote:
> Hello All,
> 
> I am building mpeg-4 files dedicated for low bandwidth mobile phones.
> These phones support mpeg-4 simple profile @ level 0.
> 
> Currently I have patched ffmpeg for this purpose but I am wondering if
> Xvid is capable of creating this type of mpeg-4 and if not what needs
> to be patched.

code within libxvidcore-0.9.2 and the CVS_HEAD _always_ set the 
"profile_and_level_indication" field to 0x03 (simple at level3). this is
hardcoded in xvidcore/src/bitstream/bitstream.c

in the dev-api-4 branch, i've recently made some changes to both the
core lib and the vfw gui to make using profiles/levels easier:

* there is a "enc_create_t.profile" field which lets the encoding
application specifiy the profile level.

* vfw gui includes list of profiles, and enables/disable mpeg-4 tools
accordingly. NOTE: simple at level0 permits dquant or ac prediction, but
not both. xvid *always* performs ac prediction, so to be simple profile 
compliant, do not use adaptive quantiziation.

* important: our rate control algos lack vbv, and therefore do not alway
abide by the specified bitrate. level0 is very low bitrate: 64kbps max,
with a buffer capacity of 20460 bytes.
vbv is on my todo list, but time is my time is limited (and theres more
higher priority stuff).

cheers,
-- pete




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