[FFmpeg-user] Apple live HTTP streaming: video slows down if processed with ffmpeg

[Baptiste Coudurier]

Hi,

On 04/21/2011 07:12 PM, i-love-spam wrote:
> 
> I'm trying to make live http streaming working with and iPhone 4. For
> live http streaming I have to use mpegts segments that contain h264
> and mp3/aac for audio. I use 10 sec segments and I use opensource
> segmenter.c that uses libavformat/avcodec to segment videos into
> mpegts chunks.
> 
> What I noticed, is that many of my segmented videos didn't play
> properly: after playing for 30 seconds or so video starts to play
> twice slower while sound plays at normal speed. So I tried to
> investigate what's wrong and I came to conclusion that chunks
> generated from flv/mp4 etc always have this problem and segments
> generated from other ts files do not have the problem. I tried to
> different tests, and it looks that ffmpeg somehow modifies bitstream
> so that live http streaming does not work on iPhone.
> 
> I have an original family guy mpegts video clip. If I use this clip
> for segmenting then live http streaming works perfectly. If I convert
> this file with ffmpeg -i famili_guy.ts -acodec copy -vcodec copy
> family_guy.flv (or mp4) then if I try to segment that resulting file
> then iPhone will have video slowdown problem (at the beginning it
> plays it normally, but after 30 seconds or so video starts to play
> approx twice slower). What I also observed, is that if I take that
> family_guy.flv or mp4 and convert it back to family_guy2.ts then this
> new famili_guy2.ts will also have the same problem as mp4 or flv
> file. I used binary compare tool to check and it looks like after
> mpegts -> mp4 -> mpegts h264 bitstream becomes somewhat different and
> doesn't play normally on iPhone 4.
> 
> Did anybody had the same problem, any idea what I could do to "fix"
> some of these video to make them segmentable with ffmpeg and
> segmenter?
> 
> 
> thank you.
> 
> 
> PS. just to clarify, I do use -vbsf h264_mp4toannexb to convert from
> mp4 back to ts file, I think the problem is somehow related to that
> bitstream re-format.

You need to use -absf aac_adtstoasc when going from ts to mp4/flv.

-- 
Baptiste COUDURIER
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