[Ffmpeg-devel] MP3 decoding from RTP stream. Getting "invalid new backstep"

Martin Thielen marthi
Tue Oct 31 10:41:01 CET 2006

>>I'm using ffmpeg to encode MP3 data transmit it over RTP and decode it.
>>If I start the RTP sender before the receiver I get warnings on the
>>decoder side from the ffmpeg library (only at the very beginning):
>>backstep:452, lastbuf:0
>>invalid new backstep 381
>>overread, skip -5 enddists: -4 -4
>>overread, skip -9 enddists: -1 -1
>>invalid new backstep 382
>>The sound is distorted as well (just for 1 second or so). Is it somehow
>>possible to tell the AVParser or the decoder to discard the frames that
>>leads to the distortion?
> yes if you implement it and send a patch, and yes i fully agree that the
> mp3 decoder should discard such packets instead of annoying the user
> with the noise
> just look at the code which outputs the error messages and silence the
> output somehowm shouldnt be too hard
> [...]


I'm trying to silence the distorted output now. What would you consider
the best way:
1) Return a value that indicates a problem
2) Set a flag (which one?) in AVCodecContext that indicates a problem
3) Changing the buffer values to 0? Is 0 the right value for silence?


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