Choose streams by language, instead of streams index

[suntong]

See

• https://stackoverflow.com/questions/57177713/
• https://stackoverflow.com/questions/40937172/mapping-streams-by-language-in-ffmpeg

You can test with,

TestStreams.mov

[suntong]

Here is a better example:

TestStreams2.mov

When run with the current ffcvt:

FFCVT_FTC=TestStreams2.mov

$ ffcvt -f "$FFCVT_FTC" -force
== Transcoding: TestStreams2.mov
] ffmpeg -i TestStreams2.mov -map 0:0 -c:v libvpx-vp9 -b:v 0 -crf 45 -map 0:1 -c:a libopus -b:a 64k -map 0:3 -map 0:4 -map 0:5 -map 0:6 -map 0:7 -map 0:8 -map 0:9 -map 0:10 -map 0:11 -map 0:12 -map 0:13 -map 0:14 -map 0:15 -map 0:16 -map 0:17 -map 0:18 -map 0:19 -map 0:20 -map 0:21 -map 0:22 -map 0:23 -map 0:24 -map 0:25 -map 0:26 -map 0:27 -map 0:28 -map 0:29 -map 0:30 -map 0:31 -map 0:32 -map 0:33 -map 0:34 -map 0:35 -map 0:36 -map 0:37 -c:s copy -y TestStreams2_.mkv
2021/10/09 13:03:55 ffcvt: Exec error - exit status 1
Input #0, matroska,webm, from 'TestStreams2.mov':
  Metadata:
    title           : TestStreams2
    ENCODER         : Lavf58.45.100
  Duration: 00:01:37.39, start: 0.036000, bitrate: 838 kb/s
    Stream #0:0: Video: hevc (Main 10), yuv420p10le(tv), 1280x640, SAR 1:1 DAR 2:1, 23.98 fps, 23.98 tbr, 1k tbn, 23.98 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
      DURATION        : 00:01:37.094000000
    Stream #0:1(eng): Audio: aac (HE-AAC), 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
      DURATION        : 00:01:37.017000000
    Stream #0:2(eng): Audio: aac (HE-AAC), 48000 Hz, stereo, fltp
    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
      DURATION        : 00:01:37.017000000
    Stream #0:3(eng): Subtitle: ass (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
      ENCODER         : Lavc58.91.100 ssa
      DURATION        : 00:01:36.636000000
    Stream #0:4(eng): Subtitle: ass
    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
      ENCODER         : Lavc58.91.100 ssa
      DURATION        : 00:01:36.636000000
    Stream #0:5(ara): Subtitle: ass
    Metadata:
      BPS             : 107
      NUMBER_OF_FRAMES: 652
      NUMBER_OF_BYTES : 40797
      _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 ssa
      DURATION        : 00:01:36.636000000
    Stream #0:6(cze): Subtitle: ass
    Metadata:
      BPS             : 57
      NUMBER_OF_FRAMES: 653
      NUMBER_OF_BYTES : 21810
      _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 ssa
      DURATION        : 00:01:36.636000000
    Stream #0:7(dan): Subtitle: ass
    Metadata:
      BPS             : 52
      NUMBER_OF_FRAMES: 647
      NUMBER_OF_BYTES : 19802
      _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 ssa
      DURATION        : 00:01:36.636000000
    Stream #0:8(ger): Subtitle: ass
    Metadata:
      BPS             : 55
      NUMBER_OF_FRAMES: 649
      NUMBER_OF_BYTES : 21108
      _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 ssa
      DURATION        : 00:01:36.636000000
    Stream #0:9(gre): Subtitle: ass
    Metadata:
      BPS             : 100
      NUMBER_OF_FRAMES: 652
      NUMBER_OF_BYTES : 38303
      _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 ssa
      DURATION        : 00:01:36.636000000
    Stream #0:10(spa): Subtitle: ass
    Metadata:
      BPS             : 56
      NUMBER_OF_FRAMES: 652
      NUMBER_OF_BYTES : 21595
      _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 ssa
      DURATION        : 00:01:36.636000000
    Stream #0:11(spa): Subtitle: ass
    Metadata:
      title           : European
      BPS             : 59
      NUMBER_OF_FRAMES: 653
      NUMBER_OF_BYTES : 22567
      _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 ssa
      DURATION        : 00:01:36.636000000
    Stream #0:12(spa): Subtitle: ass
    Metadata:
      BPS             : 59
      NUMBER_OF_FRAMES: 652
      NUMBER_OF_BYTES : 22686
      _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 ssa
      DURATION        : 00:01:36.636000000
    Stream #0:13(spa): Subtitle: ass
    Metadata:
      title           : Mexican
      BPS             : 55
      NUMBER_OF_FRAMES: 652
      NUMBER_OF_BYTES : 21082
      _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 ssa
      DURATION        : 00:01:36.636000000
    Stream #0:14(fin): Subtitle: ass
    Metadata:
      BPS             : 53
      NUMBER_OF_FRAMES: 523
      NUMBER_OF_BYTES : 20492
      _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 ssa
      DURATION        : 00:01:37.094000000
    Stream #0:15(fre): Subtitle: ass
    Metadata:
      BPS             : 59
      NUMBER_OF_FRAMES: 641
      NUMBER_OF_BYTES : 22540
      _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 ssa
      DURATION        : 00:01:36.636000000
    Stream #0:16(heb): Subtitle: ass
    Metadata:
      BPS             : 101
      NUMBER_OF_FRAMES: 657
      NUMBER_OF_BYTES : 38421
      _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 ssa
      DURATION        : 00:01:36.636000000
    Stream #0:17(hrv): Subtitle: ass
    Metadata:
      BPS             : 52
      NUMBER_OF_FRAMES: 650
      NUMBER_OF_BYTES : 20134
      _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 ssa
      DURATION        : 00:01:36.636000000
    Stream #0:18(hun): Subtitle: ass
    Metadata:
      BPS             : 56
      NUMBER_OF_FRAMES: 651
      NUMBER_OF_BYTES : 21597
      _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 ssa
      DURATION        : 00:01:36.636000000
    Stream #0:19(ind): Subtitle: ass
    Metadata:
      BPS             : 53
      NUMBER_OF_FRAMES: 652
      NUMBER_OF_BYTES : 20336
      _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 ssa
      DURATION        : 00:01:36.636000000
    Stream #0:20(ita): Subtitle: ass
    Metadata:
      BPS             : 59
      NUMBER_OF_FRAMES: 653
      NUMBER_OF_BYTES : 22488
      _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 ssa
      DURATION        : 00:01:36.636000000
    Stream #0:21(jpn): Subtitle: ass
    Metadata:
      BPS             : 61
      NUMBER_OF_FRAMES: 677
      NUMBER_OF_BYTES : 23421
      _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 ssa
      DURATION        : 00:01:36.722000000
    Stream #0:22(kor): Subtitle: ass
    Metadata:
      BPS             : 71
      NUMBER_OF_FRAMES: 655
      NUMBER_OF_BYTES : 27280
      _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 ssa
      DURATION        : 00:01:36.636000000
    Stream #0:23(may): Subtitle: ass
    Metadata:
      BPS             : 62
      NUMBER_OF_FRAMES: 661
      NUMBER_OF_BYTES : 23797
      _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 ssa
      DURATION        : 00:01:37.386000000
    Stream #0:24(nob): Subtitle: ass
    Metadata:
      BPS             : 50
      NUMBER_OF_FRAMES: 507
      NUMBER_OF_BYTES : 19132
      _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 ssa
      DURATION        : 00:01:36.636000000
    Stream #0:25(dut): Subtitle: ass
    Metadata:
      BPS             : 51
      NUMBER_OF_FRAMES: 574
      NUMBER_OF_BYTES : 19598
      _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 ssa
      DURATION        : 00:01:36.636000000
    Stream #0:26(pol): Subtitle: ass
    Metadata:
      BPS             : 56
      NUMBER_OF_FRAMES: 652
      NUMBER_OF_BYTES : 21534
      _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 ssa
      DURATION        : 00:01:36.636000000
    Stream #0:27(por): Subtitle: ass
    Metadata:
      BPS             : 58
      NUMBER_OF_FRAMES: 640
      NUMBER_OF_BYTES : 22369
      _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 ssa
      DURATION        : 00:01:36.886000000
    Stream #0:28(por): Subtitle: ass
    Metadata:
      title           : Brazilian
      BPS             : 57
      NUMBER_OF_FRAMES: 652
      NUMBER_OF_BYTES : 21781
      _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 ssa
      DURATION        : 00:01:36.636000000
    Stream #0:29(rum): Subtitle: ass
    Metadata:
      BPS             : 69
      NUMBER_OF_FRAMES: 652
      NUMBER_OF_BYTES : 26367
      _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 ssa
      DURATION        : 00:01:36.636000000
    Stream #0:30(rus): Subtitle: ass
    Metadata:
      BPS             : 87
      NUMBER_OF_FRAMES: 652
      NUMBER_OF_BYTES : 33318
      _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 ssa
      DURATION        : 00:01:36.636000000
    Stream #0:31(swe): Subtitle: ass
    Metadata:
      BPS             : 57
      NUMBER_OF_FRAMES: 642
      NUMBER_OF_BYTES : 21863
      _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 ssa
      DURATION        : 00:01:36.719000000
    Stream #0:32(tha): Subtitle: ass
    Metadata:
      BPS             : 156
      NUMBER_OF_FRAMES: 651
      NUMBER_OF_BYTES : 59586
      _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 ssa
      DURATION        : 00:01:36.636000000
    Stream #0:33(tur): Subtitle: ass
    Metadata:
      BPS             : 58
      NUMBER_OF_FRAMES: 652
      NUMBER_OF_BYTES : 22353
      _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 ssa
      DURATION        : 00:01:36.636000000
    Stream #0:34(ukr): Subtitle: ass
    Metadata:
      BPS             : 92
      NUMBER_OF_FRAMES: 650
      NUMBER_OF_BYTES : 35166
      _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 ssa
      DURATION        : 00:01:36.636000000
    Stream #0:35(vie): Subtitle: ass
    Metadata:
      BPS             : 85
      NUMBER_OF_FRAMES: 635
      NUMBER_OF_BYTES : 32545
      _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 ssa
      DURATION        : 00:01:36.636000000
    Stream #0:36(chi): Subtitle: ass
    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
      ENCODER         : Lavc58.91.100 ssa
      DURATION        : 00:01:36.636000000
    Stream #0:37(chi): Subtitle: ass
    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
      ENCODER         : Lavc58.91.100 ssa
      DURATION        : 00:01:36.636000000
Stream mapping:
  Stream #0:0 -> #0:0 (hevc (native) -> vp9 (libvpx-vp9))
  Stream #0:1 -> #0:1 (aac (native) -> opus (libopus))
  Stream #0:3 -> #0:2 (copy)
  Stream #0:4 -> #0:3 (copy)
  Stream #0:5 -> #0:4 (copy)
  Stream #0:6 -> #0:5 (copy)
  Stream #0:7 -> #0:6 (copy)
  Stream #0:8 -> #0:7 (copy)
  Stream #0:9 -> #0:8 (copy)
  Stream #0:10 -> #0:9 (copy)
  Stream #0:11 -> #0:10 (copy)
  Stream #0:12 -> #0:11 (copy)
  Stream #0:13 -> #0:12 (copy)
  Stream #0:14 -> #0:13 (copy)
  Stream #0:15 -> #0:14 (copy)
  Stream #0:16 -> #0:15 (copy)
  Stream #0:17 -> #0:16 (copy)
  Stream #0:18 -> #0:17 (copy)
  Stream #0:19 -> #0:18 (copy)
  Stream #0:20 -> #0:19 (copy)
  Stream #0:21 -> #0:20 (copy)
  Stream #0:22 -> #0:21 (copy)
  Stream #0:23 -> #0:22 (copy)
  Stream #0:24 -> #0:23 (copy)
  Stream #0:25 -> #0:24 (copy)
  Stream #0:26 -> #0:25 (copy)
  Stream #0:27 -> #0:26 (copy)
  Stream #0:28 -> #0:27 (copy)
  Stream #0:29 -> #0:28 (copy)
  Stream #0:30 -> #0:29 (copy)
  Stream #0:31 -> #0:30 (copy)
  Stream #0:32 -> #0:31 (copy)
  Stream #0:33 -> #0:32 (copy)
  Stream #0:34 -> #0:33 (copy)
  Stream #0:35 -> #0:34 (copy)
  Stream #0:36 -> #0:35 (copy)
  Stream #0:37 -> #0:36 (copy)
Press [q] to stop, [?] for help
Too many packets buffered for output stream 0:1.
[libopus @ 0x7fffd6bf7fc0] 1 frames left in the queue on closing
Conversion failed!

[suntong]

The above Too many packets buffered for output stream 0:1 "appears to be faulty source file content", and can be fixed with increasing the queue size, like:

-max_muxing_queue_size 1024

Using the following updated TestStreams2.mov, and fixed new ffcvt:

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

== Transcoding: TestStreams2.mov
] ffmpeg -i TestStreams2.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 TestStreams2_.mkv

Done.
Org Size: 9971 KB
New Size: 4151 KB
Saved:    58% with 5820 KB
Time: 2m33.0096667s at 2021-10-09 14:26:24


Transcoding completed in 2m33.0103213s
Org Size: 9 MB
New Size: 4 MB
Saved:    58%

$ ffprobe -i TestStreams2_.mkv
Input #0, matroska,webm, from 'TestStreams2_.mkv':
  Metadata:
    title           : TestStreams2.mov
    ENCODER         : Lavf58.45.100
  Duration: 00:01:37.36, 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        : 00:01:37.063000000
    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        : 00:01:36.988000000
    Stream #0:2(eng): Subtitle: ass (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
      ENCODER         : Lavc58.91.100 ssa
      DURATION        : 00:01:36.607000000
    Stream #0:3(eng): Subtitle: ass
    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
      ENCODER         : Lavc58.91.100 ssa
      DURATION        : 00:01:36.607000000
    Stream #0:4(ara): Subtitle: ass
    Metadata:
      BPS             : 107
      NUMBER_OF_FRAMES: 652
      NUMBER_OF_BYTES : 40797
      _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 ssa
      DURATION        : 00:01:36.607000000
    Stream #0:5(cze): Subtitle: ass
    Metadata:
      BPS             : 57
      NUMBER_OF_FRAMES: 653
      NUMBER_OF_BYTES : 21810
      _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 ssa
      DURATION        : 00:01:36.607000000
    Stream #0:6(dan): Subtitle: ass
    Metadata:
      BPS             : 52
      NUMBER_OF_FRAMES: 647
      NUMBER_OF_BYTES : 19802
      _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 ssa
      DURATION        : 00:01:36.607000000
    Stream #0:7(ger): Subtitle: ass
    Metadata:
      BPS             : 55
      NUMBER_OF_FRAMES: 649
      NUMBER_OF_BYTES : 21108
      _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 ssa
      DURATION        : 00:01:36.607000000
    Stream #0:8(gre): Subtitle: ass
    Metadata:
      BPS             : 100
      NUMBER_OF_FRAMES: 652
      NUMBER_OF_BYTES : 38303
      _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 ssa
      DURATION        : 00:01:36.607000000
    Stream #0:9(spa): Subtitle: ass
    Metadata:
      BPS             : 56
      NUMBER_OF_FRAMES: 652
      NUMBER_OF_BYTES : 21595
      _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 ssa
      DURATION        : 00:01:36.607000000
    Stream #0:10(spa): Subtitle: ass
    Metadata:
      title           : European
      BPS             : 59
      NUMBER_OF_FRAMES: 653
      NUMBER_OF_BYTES : 22567
      _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 ssa
      DURATION        : 00:01:36.607000000
    Stream #0:11(spa): Subtitle: ass
    Metadata:
      BPS             : 59
      NUMBER_OF_FRAMES: 652
      NUMBER_OF_BYTES : 22686
      _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 ssa
      DURATION        : 00:01:36.607000000
    Stream #0:12(spa): Subtitle: ass
    Metadata:
      title           : Mexican
      BPS             : 55
      NUMBER_OF_FRAMES: 652
      NUMBER_OF_BYTES : 21082
      _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 ssa
      DURATION        : 00:01:36.607000000
    Stream #0:13(fin): Subtitle: ass
    Metadata:
      BPS             : 53
      NUMBER_OF_FRAMES: 523
      NUMBER_OF_BYTES : 20492
      _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 ssa
      DURATION        : 00:01:37.065000000
    Stream #0:14(fre): Subtitle: ass
    Metadata:
      BPS             : 59
      NUMBER_OF_FRAMES: 641
      NUMBER_OF_BYTES : 22540
      _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 ssa
      DURATION        : 00:01:36.607000000
    Stream #0:15(heb): Subtitle: ass
    Metadata:
      BPS             : 101
      NUMBER_OF_FRAMES: 657
      NUMBER_OF_BYTES : 38421
      _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 ssa
      DURATION        : 00:01:36.607000000
    Stream #0:16(hrv): Subtitle: ass
    Metadata:
      BPS             : 52
      NUMBER_OF_FRAMES: 650
      NUMBER_OF_BYTES : 20134
      _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 ssa
      DURATION        : 00:01:36.607000000
    Stream #0:17(hun): Subtitle: ass
    Metadata:
      BPS             : 56
      NUMBER_OF_FRAMES: 651
      NUMBER_OF_BYTES : 21597
      _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 ssa
      DURATION        : 00:01:36.607000000
    Stream #0:18(ind): Subtitle: ass
    Metadata:
      BPS             : 53
      NUMBER_OF_FRAMES: 652
      NUMBER_OF_BYTES : 20336
      _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 ssa
      DURATION        : 00:01:36.607000000
    Stream #0:19(ita): Subtitle: ass
    Metadata:
      BPS             : 59
      NUMBER_OF_FRAMES: 653
      NUMBER_OF_BYTES : 22488
      _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 ssa
      DURATION        : 00:01:36.607000000
    Stream #0:20(jpn): Subtitle: ass
    Metadata:
      BPS             : 61
      NUMBER_OF_FRAMES: 677
      NUMBER_OF_BYTES : 23421
      _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 ssa
      DURATION        : 00:01:36.693000000
    Stream #0:21(kor): Subtitle: ass
    Metadata:
      BPS             : 71
      NUMBER_OF_FRAMES: 655
      NUMBER_OF_BYTES : 27280
      _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 ssa
      DURATION        : 00:01:36.607000000
    Stream #0:22(may): Subtitle: ass
    Metadata:
      BPS             : 62
      NUMBER_OF_FRAMES: 661
      NUMBER_OF_BYTES : 23797
      _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 ssa
      DURATION        : 00:01:37.357000000
    Stream #0:23(nob): Subtitle: ass
    Metadata:
      BPS             : 50
      NUMBER_OF_FRAMES: 507
      NUMBER_OF_BYTES : 19132
      _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 ssa
      DURATION        : 00:01:36.607000000
    Stream #0:24(dut): Subtitle: ass
    Metadata:
      BPS             : 51
      NUMBER_OF_FRAMES: 574
      NUMBER_OF_BYTES : 19598
      _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 ssa
      DURATION        : 00:01:36.607000000
    Stream #0:25(pol): Subtitle: ass
    Metadata:
      BPS             : 56
      NUMBER_OF_FRAMES: 652
      NUMBER_OF_BYTES : 21534
      _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 ssa
      DURATION        : 00:01:36.607000000
    Stream #0:26(por): Subtitle: ass
    Metadata:
      BPS             : 58
      NUMBER_OF_FRAMES: 640
      NUMBER_OF_BYTES : 22369
      _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 ssa
      DURATION        : 00:01:36.857000000
    Stream #0:27(por): Subtitle: ass
    Metadata:
      title           : Brazilian
      BPS             : 57
      NUMBER_OF_FRAMES: 652
      NUMBER_OF_BYTES : 21781
      _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 ssa
      DURATION        : 00:01:36.607000000
    Stream #0:28(rum): Subtitle: ass
    Metadata:
      BPS             : 69
      NUMBER_OF_FRAMES: 652
      NUMBER_OF_BYTES : 26367
      _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 ssa
      DURATION        : 00:01:36.607000000
    Stream #0:29(rus): Subtitle: ass
    Metadata:
      BPS             : 87
      NUMBER_OF_FRAMES: 652
      NUMBER_OF_BYTES : 33318
      _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 ssa
      DURATION        : 00:01:36.607000000
    Stream #0:30(swe): Subtitle: ass
    Metadata:
      BPS             : 57
      NUMBER_OF_FRAMES: 642
      NUMBER_OF_BYTES : 21863
      _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 ssa
      DURATION        : 00:01:36.690000000
    Stream #0:31(tha): Subtitle: ass
    Metadata:
      BPS             : 156
      NUMBER_OF_FRAMES: 651
      NUMBER_OF_BYTES : 59586
      _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 ssa
      DURATION        : 00:01:36.607000000
    Stream #0:32(tur): Subtitle: ass
    Metadata:
      BPS             : 58
      NUMBER_OF_FRAMES: 652
      NUMBER_OF_BYTES : 22353
      _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 ssa
      DURATION        : 00:01:36.607000000
    Stream #0:33(ukr): Subtitle: ass
    Metadata:
      BPS             : 92
      NUMBER_OF_FRAMES: 650
      NUMBER_OF_BYTES : 35166
      _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 ssa
      DURATION        : 00:01:36.607000000
    Stream #0:34(vie): Subtitle: ass
    Metadata:
      BPS             : 85
      NUMBER_OF_FRAMES: 635
      NUMBER_OF_BYTES : 32545
      _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 ssa
      DURATION        : 00:01:36.607000000
    Stream #0:35(chi): Subtitle: ass
    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
      ENCODER         : Lavc58.91.100 ssa
      DURATION        : 00:01:36.607000000
    Stream #0:36(chi): Subtitle: ass
    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
      ENCODER         : Lavc58.91.100 ssa
      DURATION        : 00:01:36.607000000

TestStreams2.mov

[suntong]

Here is the converted result:

TestStreams2_.mov