[FFmpeg-user] V_QUICKTIME used as codec ID for DPX/TIFF rewrapped to Matroska

[Kieran O Leary]

Hi,

When re-wrapping DPX or TIFF images to Matroska, it appears that FFmpeg
uses the V_QUICKTIME codec ID. Why is this used? Would something like
V_UNCOMPRESSED (for raw TIFF anyhow) b more appropriate/

The reason why I'm investigating this is that DPC and TIFF rewrappings to
Matroska appear to be fully reversible with matching whole-file checksums.

To replicate using ffmpeg and mediainfo:

$ ./ffmpeg -f lavfi -i testsrc -c:v tiff -compression_algo raw -y -t 1
1_tiff.mkv && mediainfo --Details=1 1_tiff.mkv|grep -i codec
ffmpeg version N-92521-g737b5f5869 Copyright (c) 2000-2018 the FFmpeg
developers
  built with gcc 7 (Ubuntu 7.3.0-27ubuntu1~18.04)
  configuration:
  libavutil      56. 24.101 / 56. 24.101
  libavcodec     58. 40.100 / 58. 40.100
  libavformat    58. 23.100 / 58. 23.100
  libavdevice    58.  6.100 / 58.  6.100
  libavfilter     7. 46.100 /  7. 46.100
  libswscale      5.  4.100 /  5.  4.100
  libswresample   3.  4.100 /  3.  4.100
Input #0, lavfi, from 'testsrc':
  Duration: N/A, start: 0.000000, bitrate: N/A
    Stream #0:0: Video: rawvideo (RGB[24] / 0x18424752), rgb24, 320x240
[SAR 1:1 DAR 4:3], 25 tbr, 25 tbn, 25 tbc
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo (native) -> tiff (native))
Press [q] to stop, [?] for help
Output #0, matroska, to '1_tiff.mkv':
  Metadata:
    encoder         : Lavf58.23.100
    Stream #0:0: Video: tiff (tiff / 0x66666974), rgb24, 320x240 [SAR 1:1
DAR 4:3], q=2-31, 200 kb/s, 25 fps, 1k tbn, 25 tbc
    Metadata:
      encoder         : Lavc58.40.100 tiff
frame=   25 fps=0.0 q=-0.0 Lsize=    5638kB time=00:00:00.96
bitrate=48061.9kbits/s speed=58.3x
video:5636kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB
muxing overhead: 0.034428%
0001AE    CodecID - V_QUICKTIME (13 bytes)
0001CB    CodecPrivate (93 bytes)
$ ./ffmpeg -f lavfi -i testsrc -c:v dpx  -y -t 1 1_dpx.mkv && mediainfo
--Details=1 1_tiff.mkv|grep -i codec
ffmpeg version N-92521-g737b5f5869 Copyright (c) 2000-2018 the FFmpeg
developers
  built with gcc 7 (Ubuntu 7.3.0-27ubuntu1~18.04)
  configuration:
  libavutil      56. 24.101 / 56. 24.101
  libavcodec     58. 40.100 / 58. 40.100
  libavformat    58. 23.100 / 58. 23.100
  libavdevice    58.  6.100 / 58.  6.100
  libavfilter     7. 46.100 /  7. 46.100
  libswscale      5.  4.100 /  5.  4.100
  libswresample   3.  4.100 /  3.  4.100
Input #0, lavfi, from 'testsrc':
  Duration: N/A, start: 0.000000, bitrate: N/A
    Stream #0:0: Video: rawvideo (RGB[24] / 0x18424752), rgb24, 320x240
[SAR 1:1 DAR 4:3], 25 tbr, 25 tbn, 25 tbc
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo (native) -> dpx (native))
Press [q] to stop, [?] for help
Output #0, matroska, to '1_dpx.mkv':
  Metadata:
    encoder         : Lavf58.23.100
    Stream #0:0: Video: dpx (dpx  / 0x20787064), rgb24, 320x240 [SAR 1:1
DAR 4:3], q=2-31, 200 kb/s, 25 fps, 1k tbn, 25 tbc
    Metadata:
      encoder         : Lavc58.40.100 dpx
frame=   25 fps=0.0 q=-0.0 Lsize=    5668kB time=00:00:00.96
bitrate=48312.5kbits/s speed=57.6x
video:5666kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB
muxing overhead: 0.033439%
0001AE    CodecID - V_QUICKTIME (13 bytes)
0001CB    CodecPrivate (93 bytes)