mirror of https://github.com/mpv-player/mpv
7fad173cfd
This commit adds an extension to mpv EDL, which basically allows you to do the same as --audio-file, --external-file, etc. in a single EDL file. This is a relatively quick & dirty implementation. The dirty part lies in the fact that several shortcuts are taken. For example, struct timeline now forms a singly linked list, which is really weird, but also means the other timeline using demuxers (cue, mkv) don't need to be touched. Also, memory management becomes even worse (weird object ownership rules that are just fragile WTFs). There are some other dubious small changes, mostly related to the weird representation of separate streams. demux_timeline.c contains the actual implementation of the separate stream handling. For the most part, most things that used to be on the top level are now in struct virtual_source, of which one for each separate stream exists. This is basically like running multiple demux_edl.c in parallel. Some changes could strictly speaking be split into a separate commit, such as the stream_map type change. Mostly untested. Seems to work for the intended purpose. Potential for regressions for other timeline uses (like ordered chapters) is probably low. One thing which could definitely break and which I didn't test is the pseudo-DASH fragmented EDL code, of which ytdl can trigger various forms in obscure situations. (Uh why don't we have a test suite.) Background: The intention is to use this for the ytdl wrapper. A certain streaming site from a particularly brain damaged and plain evil Silicon Valley company usually provides streams as separate audio and video streams. The ytdl wrapper simply does use audio-add (i.e. adding it as external track, like with --audio-file), which works mostly fine. Unfortunately, mpv manages caching completely separately for external files. This has the following potential problems: 1. Seek ranges are rendered incorrectly. They always use the "main" stream, in this case the video stream. E.g. clicking into a cached range on the OSC could trigger a low level seek if the audio stream is actually not cached at the target position. 2. The stream cache bloats unnecessarily. Each stream may allocate the full configured maximum cache size, which is not what the user intends to do. Cached ranges are not pruned the same way, which creates disjoint cache ranges, which only use memory and won't help with fast seeking or playback. 3. mpv will try to aggressively read from both streams. This is done from different threads, with no regard which stream is more important. So it might happen that one stream starves the other one, especially if they have different bitrates. 4. Every stream will use a separate thread, which is an unnecessary waste of system resources. In theory, the following solutions are available (this commit works towards D): A. Centrally manage reading and caching of all streams. A single thread would do all I/O, and decide from which stream it should read next. As long as the total TCP/socket buffering is not too high, this should be effective to avoid starvation issues. This can also manage the cached ranges better. It would also get rid of the quite useless additional demuxer threads. This solution is conceptually simple, but requires refactoring the entire demuxer middle layer. B. Attempt to coordinate the demuxer threads. This would maintain a shared cache and readahead state to solve the mentioned problems explicitly. While this sounds simple and like an incremental change, it's probably hard to implement, creates more messy special cases, solution A. seems just a better and simpler variant of this. (On the other hand, A. requires refactoring more code.) C. Render an intersection of the seek ranges across all streams. This fixes only problem 1. D. Merge all streams in a dedicated wrapper demuxer. The general demuxer layer remains unchanged, and reading from separate streams is handled as special case. This effectively achieves the same as A. In particular, caching is simply handled by the usual demuxer cache layer, which sees the wrapper demuxer as a single stream of interleaved packets. One implementation variant of this is to reuse the EDL infrastructure, which this commit does. All in all, solution A would be preferable, because it's cleaner and works for all external streams in general. Some previous commit tried to prepare for implementing solution A. This could still happen. But it could take years until this is finally seriously started and finished. In any case, this commit doesn't block or complicate such attempts, which is also why it's the way to go. It's worth mentioning that original mplayer handles external files by creating a wrapper demuxer. This is like a less ideal mixture of A. and D. (The similarity with A. is that extending the mplayer approach to be fully dynamic and without certain disadvantages caused by the wrapper would end up with A. anyway. The similarity with D. is that due to the wrapper, no higher level code needs to be changed.) |
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| .. | ||
| codec_tags.c | ||
| codec_tags.h | ||
| cue.c | ||
| cue.h | ||
| demux.c | ||
| demux.h | ||
| demux_cue.c | ||
| demux_edl.c | ||
| demux_lavf.c | ||
| demux_libarchive.c | ||
| demux_mf.c | ||
| demux_mkv.c | ||
| demux_mkv_timeline.c | ||
| demux_null.c | ||
| demux_playlist.c | ||
| demux_raw.c | ||
| demux_timeline.c | ||
| ebml.c | ||
| ebml.h | ||
| matroska.h | ||
| packet.c | ||
| packet.h | ||
| stheader.h | ||
| timeline.c | ||
| timeline.h | ||