Commit Graph

6 Commits

Author SHA1 Message Date
Anton Khirnov
e9a868e9ee fftools/sync_queue: add debug logging 2023-05-28 10:47:59 +02:00
Anton Khirnov
f9d3c06533 fftools/sync_queue: allow requesting a specific number of audio samples
This will be made useful in following commits.
2023-04-09 15:47:45 +02:00
Anton Khirnov
98b41d0bd2 fftools/sync_queue: document overall design 2023-04-09 15:47:45 +02:00
Anton Khirnov
090950f832 fftools/sync_queue: use timebase from input frames/packets
They are always properly set now. Avoid a separate timebase-setting
call, which duplicates the knowledge of the timebase being used.
2023-04-09 15:47:45 +02:00
Anton Khirnov
587081a179 fftools/ffmpeg: use the sync queues to handle -frames
Same issues apply to it as to -shortest.

Changes the results of the following tests:
- matroska-flac-extradata-update
  The test reencodes two input FLAC streams into three output FLAC
  streams. The last output stream is limited to 8 frames. The current
  code results in the first two output streams having 12 frames, after
  this commit all three streams have 8 frames and are the same length.
  This new result is better, since it is predictable.
- mkv-1242
  The test streamcopies one video and one audio stream, video is limited
  to 11 frames. The new result shortens the audio stream so that it is
  not longer than the video.
2022-07-23 11:53:19 +02:00
Anton Khirnov
4740fea7dd fftools/ffmpeg: rework -shortest implementation
The -shortest option (which finishes the output file at the time the
shortest stream ends) is currently implemented by faking the -t option
when an output stream ends. This approach is fragile, since it depends
on the frames/packets being processed in a specific order. E.g. there
are currently some situations in which the output file length will
depend unpredictably on unrelated factors like encoder delay. More
importantly, the present work aiming at splitting various ffmpeg
components into different threads will make this approach completely
unworkable, since the frames/packets will arrive in effectively random
order.

This commit introduces a "sync queue", which is essentially a collection
of FIFOs, one per stream. Frames/packets are submitted to these FIFOs
and are then released for further processing (encoding or muxing) when
it is ensured that the frame in question will not cause its stream to
get ahead of the other streams (the logic is similar to libavformat's
interleaving queue).

These sync queues are then used for encoding and/or muxing when the
-shortest option is specified.

A new option – -shortest_buf_duration – controls the maximum number of
queued packets, to avoid runaway memory usage.

This commit changes the results of the following tests:
- copy-shortest[12]: the last audio frame is now gone. This is
  correct, since it actually outlasts the last video frame.
- shortest-sub: the video packets following the last subtitle packet are
  now gone. This is also correct.
2022-07-23 11:53:19 +02:00