Hi In my fiddling with fragmented indexes in mov.c I ran cross mov_fix_index(), which has been in the codebase since September 2016. The intent of this function is to implement limited support for edit lists (elst). More rudely one could say it implements half-assed support for edit lists. Besides the way it's implemented being incredibly cursed, I feel strongly that this is not something that a demuxer should do, partly because it's not something a demuxer *can* do. There are a number of reasons why:
1) demuxers are not part of the presentation layer 2) the demuxer must lie about what the file actually contains 3) the ISOBMFF spec mandates being able to cut on samples, not just frames. for audio, there is no way to do that from a demuxer 4) similarly, there is no way (I think) to implement "dwell" segments The second point becomes painfully clear when one looks at mov_fix_index(). FFStream.index_entries is completely replaced. The function is not idempotent. For the kind of work I'm doing right now this is a huge problem. As I see it, the way forward is: 1) introduce API for edit lists, so that users can decide themselves what to do 2) implement basic support for edit lists in the ffmpeg CLI 3) remove edit list hacks from all demuxers, especially mov.c The main issue I see with this is that it risks turning ffmpeg into an NLE tool, which would be a waste of developer effort better spent on melt and related tools (kdenlive, shotcut etc). The present level of edit list support could be reimplemented by just fiddling with the -ss and -t options. That is, the ffmpeg CLI could automatically derive -ss and -t from the edit list extracted by lavf. If this stuff is done correctly then it should be possible to remux MOV to MXF while keeping the edit lists and the original uncut essence. And of course back again to MOV if so desired. I haven't sketched out any API yet, but it would probably closely mirror how elst works in MOV. Care should be taken that MXF operational pattern 3a can also fit into this API. Possibly even OP3c. Thoughts? /Tomas _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
