Copy all subtitle streams

[suntong]

The current implementation can only only copy a single subtitle stream, the default one.

Need to be able to copy all subtitle streams.

[suntong]

Here is sample video to test/verify:

TestStreams1.mov

FFCVT_FTC=TestStreams1.mov

$ ffcvt -force -f "$FFCVT_FTC" -- -max_muxing_queue_size 1024

== Transcoding: TestStreams1.mov
] ffmpeg -i TestStreams1.mov -c:v libvpx-vp9 -b:v 0 -crf 45 -c:a libopus -b:a 64k -c:s copy -y -max_muxing_queue_size 1024 TestStreams1_.mkv

Done.
Org Size: 3503 KB
New Size: 1628 KB
Saved:    53% with 1875 KB
Time: 58.8158768s at 2021-10-09 15:11:28


Transcoding completed in 58.8165181s
Org Size: 3 MB
New Size: 1 MB
Saved:    53%

$ ffprobe -i TestStreams1_.mkv
Input #0, matroska,webm, from 'TestStreams1_.mkv':
  Metadata:
    title           : TestStreams1_.mkv
    ENCODER         : Lavf58.45.100
  Duration: 00:00:38.13, start: -0.007000, bitrate: 349 kb/s
    Stream #0:0: Video: vp9 (Profile 0), yuv420p(tv), 1280x640, SAR 1:1 DAR 2:1, 23.98 fps, 23.98 tbr, 1k tbn, 1k tbc (default)
    Metadata:
      BPS             : 624175
      NUMBER_OF_FRAMES: 76003
      NUMBER_OF_BYTES : 247326295
      _STATISTICS_WRITING_APP: mkvmerge v61.0.0 ('So') 64-bit
      _STATISTICS_WRITING_DATE_UTC: 2021-10-02 21:30:34
      _STATISTICS_TAGS: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
      ENCODER         : Lavc58.91.100 libvpx-vp9
      DURATION        : 00:00:38.129000000
    Stream #0:1(eng): Audio: opus, 48000 Hz, stereo, fltp (default)
    Metadata:
      BPS             : 62482
      NUMBER_OF_FRAMES: 74301
      NUMBER_OF_BYTES : 24760063
      _STATISTICS_WRITING_APP: mkvmerge v61.0.0 ('So') 64-bit
      _STATISTICS_WRITING_DATE_UTC: 2021-10-02 21:30:34
      _STATISTICS_TAGS: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
      ENCODER         : Lavc58.91.100 libopus
      DURATION        : 00:00:38.023000000
    Stream #0:2(eng): Subtitle: subrip (default)
    Metadata:
      BPS             : 63
      NUMBER_OF_FRAMES: 652
      NUMBER_OF_BYTES : 23388
      _STATISTICS_WRITING_APP: mkvmerge v61.0.0 ('So') 64-bit
      _STATISTICS_WRITING_DATE_UTC: 2021-10-02 21:30:34
      _STATISTICS_TAGS: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
      DURATION        : 00:00:37.166000000

[suntong]

Fixed:

$ ffcvt -force -f "$FFCVT_FTC" -- -max_muxing_queue_size 1024

== Transcoding: TestStreams1.mov
] ffmpeg -i TestStreams1.mov -map 0:v -c:v libvpx-vp9 -b:v 0 -crf 45 -map 0:a:m:language:eng -c:a libopus -b:a 64k -map 0:s -c:s copy -y -max_muxing_queue_size 1024 TestStreams1_.mkv

Done.
Org Size: 3537 KB
New Size: 1662 KB
Saved:    53% with 1875 KB
Time: 1m1.8415699s at 2021-10-09 15:40:24


Transcoding completed in 1m1.8417472s
Org Size: 3 MB
New Size: 1 MB
Saved:    52%

$ ffprobe -i TestStreams1_.mkv
  Duration: 00:00:39.46, start: -0.007000, bitrate: 345 kb/s
    Stream #0:0: Video: vp9 (Profile 0), yuv420p(tv), 1280x640, SAR 1:1 DAR 2:1, 23.98 fps, 23.98 tbr, 1k tbn, 1k tbc (default)
    Metadata:
      BPS             : 624175
      NUMBER_OF_FRAMES: 76003
      NUMBER_OF_BYTES : 247326295
      _STATISTICS_WRITING_APP: mkvmerge v61.0.0 ('So') 64-bit
      _STATISTICS_WRITING_DATE_UTC: 2021-10-02 21:30:34
      _STATISTICS_TAGS: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
      ENCODER         : Lavc58.91.100 libvpx-vp9
      DURATION        : 00:00:38.129000000
    Stream #0:1(eng): Audio: opus, 48000 Hz, stereo, fltp (default)
    Metadata:
      BPS             : 62482
      NUMBER_OF_FRAMES: 74301
      NUMBER_OF_BYTES : 24760063
      _STATISTICS_WRITING_APP: mkvmerge v61.0.0 ('So') 64-bit
      _STATISTICS_WRITING_DATE_UTC: 2021-10-02 21:30:34
      _STATISTICS_TAGS: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
      ENCODER         : Lavc58.91.100 libopus
      DURATION        : 00:00:38.023000000
    Stream #0:2(eng): Subtitle: subrip (default)
    Metadata:
      BPS             : 63
      NUMBER_OF_FRAMES: 652
      NUMBER_OF_BYTES : 23388
      _STATISTICS_WRITING_APP: mkvmerge v61.0.0 ('So') 64-bit
      _STATISTICS_WRITING_DATE_UTC: 2021-10-02 21:30:34
      _STATISTICS_TAGS: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
      DURATION        : 00:00:37.166000000
    Stream #0:3(eng): Subtitle: subrip
    Metadata:
      title           : SDH
      BPS             : 69
      NUMBER_OF_FRAMES: 746
      NUMBER_OF_BYTES : 26327
      _STATISTICS_WRITING_APP: mkvmerge v61.0.0 ('So') 64-bit
      _STATISTICS_WRITING_DATE_UTC: 2021-10-02 21:30:34
      _STATISTICS_TAGS: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
      DURATION        : 00:00:37.166000000
    Stream #0:4(ara): Subtitle: subrip
    . . .
    Stream #0:35(chi): Subtitle: subrip
    Metadata:
      title           : Simplified
      BPS             : 64
      NUMBER_OF_FRAMES: 653
      NUMBER_OF_BYTES : 24386
      _STATISTICS_WRITING_APP: mkvmerge v61.0.0 ('So') 64-bit
      _STATISTICS_WRITING_DATE_UTC: 2021-10-02 21:30:34
      _STATISTICS_TAGS: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
      DURATION        : 00:00:37.166000000
    Stream #0:36(chi): Subtitle: subrip
    Metadata:
      title           : Traditional
      BPS             : 60
      NUMBER_OF_FRAMES: 652
      NUMBER_OF_BYTES : 23128
      _STATISTICS_WRITING_APP: mkvmerge v61.0.0 ('So') 64-bit
      _STATISTICS_WRITING_DATE_UTC: 2021-10-02 21:30:34
      _STATISTICS_TAGS: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
      DURATION        : 00:00:37.166000000