[MPlayer-users] arm bitstream reader problems with svq3, mjpeg

[Steve Magoun]

Hi,

I'm having some trouble with Sorenson v3 and MJPEG content on ARM  
(XScale LE). It looks like A32_BITSTREAM_READER is broken (causing  
trouble with svq3). I disabled the A32 reader, which in turn broke  
MJPEG playback. Naturally I want both to work.

All Sorenson 3 content is scrambled, and MPlayer outputs lots of  
errors like the following when playing an svq3 movie:
[svq3 @ 0x571c94]warning: first frame is no keyframe
[svq3 @ 0x571c94]error while decoding block
[svq3 @ 0x571c94]error while decoding MB 27 1
Error while decoding frame!

I'm using mplayer svn 23017 with libavcodec and libavformat svn 8738  
(as someone already reported, changes to the ac3 parser break  
compilation in libavcodec/libavformat 8739). Kernel is 2.6.13.4,  
distro is a Montavista Linux derivative. libc is 2.3.2. I'm cross- 
compiling with gcc 3.4.5, though I get the same results compiling  
natively on ARM with gcc 3.3.1. Compiling at -O0 doesn't make a  
difference.

I dug in a bit and found GET_CACHE was returning bad data.  
Specifically, for the sample at http://samples.mplayerhq.hu/V-codecs/ 
SVQ3/blade_2_m480.mov:
In the very first call to svq3_get_ue_golomb for that sample, 'buf'  
is populated with 0x3e25f040. On x86 I observed the value 0xf897c100,  
which is 0x3e25f040<<2.

Disabling A32_BITSTREAM_READER in libavcodec/bitstream.h fixes the  
problem - 'buf' contains 0xf897c100 the first time through, and the  
errors/artifacts are gone.

Unfortunately that change breaks MJPEG playback (other codecs seem  
unaffected). While there are no errors in the console, MJPEG content  
has numerous green + purple vertical lines - it looks like the luma  
is more or less intact, but chroma is completely broken. The same  
MJPEG content works fine when A32_BITSTREAM_READER is enabled.

For the MJPEG content I've been looking at http:// 
samples.mplayerhq.hu/V-codecs/MJPEGs/dancing.avi . When playing that  
sample, the very first call to GET_CACHE inside mjpeg.c's  
decode_block returns 0x2dd2bec1 when A32_BITSTREAM_READER is enabled  
and 0x2dd2bec0 when it's disabled. On x86 the value is 0x2dd2bec0. It  
looks like fixing the broken reader unmasks a bug in the MJPEG decoder??

Could someone familiar with the bitstream reader suggest a fix that  
would work for both formats?


Thanks,
Steve