[mythtv] Plextor ConvertX MPEG4 skip ahead/back not seeking to keyframe

Jack Porter jack at porter.net.au
Tue May 17 13:09:03 UTC 2005


Hi,

I'm using a Plextor ConvertX with latest CVS and when I press the skip 
ahead/back button while watching recordings (or live TV), I get around 1 
second of blocky MPEG4 junk before the video plays normally again.

Looking at NuppelVideoRecorder.cpp, I can see it's requesting a key 
frame to be generated every 30 frames, and sure enough if I reduce the 
"gop_size" passed to the GO7007IOC_S_COMP_PARAMS ioctl, the length of 
time I get blockyness is reduced accordingly.  Looking at the plextor 
docs, the only other thing I could think of trying was the 
GO7007_MPEG_REPEAT_SEQHEADER flag but it didn't make any difference.


I also have a WinTV PVR-350 and I don't see this problem on recordings 
made with this and then transcoded to MPEG4.

Is there some code in the skip ahead/back handling that seeks to the 
nearest keyframe when skipping, and it's failing for some reason with 
the GO7007-generated MPEG4 streams?

If anyone has any suggestions on where I should look to fix this, please 
let me know.

Cheers
Jack

-- 
Jack Porter                       Seoul
jack at porter.net.au                South Korea


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