duration of frame thumbnail track in mkv report is wrong

[dericed]

To recreate:

% ffmpeg -f lavfi -i testsrc -t 60 test.mp4
% qcli -i test.mp4 -o test.mp4.qctools.mkv 
% ffmpeg -i test.mp4 -i test.mp4.qctools.mkv 
[...]
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'test.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.45.100
  Duration: 00:01:00.00, start: 0.000000, bitrate: 38 kb/s
    Stream #0:0(und): Video: h264 (High 4:4:4 Predictive) (avc1 / 0x31637661), yuv444p, 320x240 [SAR 1:1 DAR 4:3], 35 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
    Metadata:
      handler_name    : VideoHandler
[matroska,webm @ 0x7ffabc817800] Could not find codec parameters for stream 1 (Attachment: none): unknown codec
Consider increasing the value for the 'analyzeduration' and 'probesize' options
Input #1, matroska,webm, from 'test.mp4.qctools.mkv':
  Metadata:
    ENCODER         : Lavf58.45.100
  Duration: 00:12:47.49, start: 0.000000, bitrate: 26 kb/s
    Stream #1:0: Video: mjpeg (Baseline), yuvj420p(pc, bt470bg/unknown/unknown), 72x54, 50 fps, 50 tbr, 1k tbn, 1k tbc (default)
    Metadata:
      DURATION        : 00:12:47.488000000
    Stream #1:1: Attachment: none
    Metadata:
      filename        : test.mp4.qctools.xml.gz
      mimetype        : application/x-gzip
At least one output file must be specified

Input duration is 1:00 and frame thumbnail track is 00:12:47.49. So...

[dericed]

So I did a test. With a 100 fps input, the output frame thumbnail track is at 20 fps. If the input is 50 fps, the output thumbs is at 5 fps. 10 fps -> 0.2 fps. 1 fps -> 0.002 fps.

I was trying to reverse engineer the equation that is impacting the fps from input frames to output frame thumbnails. With 100,20 and 50,5 that works for y=0.3 * x-10 but that doesn't apply to 10 -> 0.2 and 1 -> 0.002. But I suspect that there's some sort of NTSC-ish value hard coded that impacts the output pts of the thumbnails.

[dericed]

seems to have been resolved a while ago