On Wed, Sep 24, 2014 at 10:43:40AM +0300, Mika Raento wrote: > Dear all > > This mail is meant mainly as a note to other potential users, but > possibly as input to development - time allowing I might be able to pick > up some of the pieces myself. It's also a thank-you for all the hard > work in ffmpeg. > > I've successfully implemented a transcoding pipeline for producing > multi-bitrate fragmented mp4 files from broadcast DVB input. More > concretely, I'm taking in broadcast TS captures with either mpeg2 video > and mp2 audio (SD, varying aspect ratio) or h264 video and aac audio, > both potentially with dvbsub. From that I'm producing ISMV output with > multiple bitrate h264 video at fixed 16:9 aspect ratio and multiple > bitrate aac audio, with burned subtitles. The ISMV outputs are > post-processed with tools/ismindex and with the hls muxer. > > There are number of limitations in ffmpeg that I've had to work around: > > - I haven't gotten sub2video or async working without reasonably > monotonous DTS. Broadcast TS streams can easily contain backward jumps > in time (e.g., a cheapo source that plays mp4 files and starts each file > at 0). The fix is to cut the TS into pieces at timestamp jump locations > and using '-itsoffset' to rewrite the timestamps and then concatenate. > I'm using the segment and concat muxers for that. > - Sub2video doesn't work with negative timestamps, so I use '-itsoffset' > to get positive timestamps > - For HD streams, I need to scale up the sub2video results from SD to > HD. Sub2video doesn't handle the HD subtitle geometries. I'm not > enough of an expert to know whether that's the issue, or whether that's > just the way it's supposed to work with SD subs (typical) with HD video. > - For columnboxing, I use the scale, pad and setdar video filters. These > work fine, but their parameters are only evaluated at start, so I need > to cut the video into pieces with a single aspect ratio first and > concatenate later. > - Audio sync (using aresample) gets confused if the input contains > errors, so I need to first re-encode audio (with '-copyts') and only > after that synchronize. > - The TS PIDs are not kept over the segment muxer, so I given them on > the command line with '-streamid'.
a bit late reply but bug reports or feature requests for all these are welcome unless there are already tickets for them assuming these issues still exist thx [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB Why not whip the teacher when the pupil misbehaves? -- Diogenes of Sinope
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