[FFmpeg-user] skipped frames with 18fps DPX - non monotonically increasing dts to muxer

[Kieran O'Leary]

Hi,

I have encountered some DPX that has an fps of 18. It seems that ffmpeg skips every few frames when decoding - at least when I performed a framemd5 analysis. I noticed that 30522 frames were decoded, 10172 were dropped.

It seems that adding -framerate 18 to as an input option resolves the issue, but should ffmpeg not auto-detect the FPS?

I can replicate the issue with just a few frames (I will see if I can share the samples) - here's 17 frames decoded with nullm followed by the md5 muxer where only 14 frames are processed.:

$ ./ffmpeg -i ffmpeg-1-01_%06d.dpx -f null -

ffmpeg version N-92683-g32601fb821 Copyright (c) 2000-2018 the FFmpeg developers

  built with Apple LLVM version 8.0.0 (clang-800.0.42.1)

  configuration:

  libavutil      56. 24.101 / 56. 24.101

  libavcodec     58. 42.100 / 58. 42.100

  libavformat    58. 24.100 / 58. 24.100

  libavdevice    58.  6.101 / 58.  6.101

  libavfilter     7. 46.101 /  7. 46.101

  libswscale      5.  4.100 /  5.  4.100

  libswresample   3.  4.100 /  3.  4.100

Input #0, image2, from 'ffmpeg-1-01_%06d.dpx':

  Duration: 00:00:00.68, start: 0.000000, bitrate: N/A

    Stream #0:0: Video: dpx, gbrp10le, 3840x2160, 18 tbr, 25 tbn, 18 tbc

Stream mapping:

  Stream #0:0 -> #0:0 (dpx (native) -> wrapped_avframe (native))

Press [q] to stop, [?] for help

Output #0, null, to 'pipe:':

  Metadata:

    encoder         : Lavf58.24.100

    Stream #0:0: Video: wrapped_avframe, gbrp10le, 3840x2160, q=2-31, 200 kb/s, 18 fps, 18 tbn, 18 tbc

    Metadata:

      encoder         : Lavc58.42.100 wrapped_avframe

[null @ 0x7f88d3000600] Application provided invalid, non monotonically increasing dts to muxer in stream 0: 1 >= 1

[null @ 0x7f88d3000600] Application provided invalid, non monotonically increasing dts to muxer in stream 0: 4 >= 4

[null @ 0x7f88d3000600] Application provided invalid, non monotonically increasing dts to muxer in stream 0: 6 >= 6

[null @ 0x7f88d3000600] Application provided invalid, non monotonically increasing dts to muxer in stream 0: 9 >= 9

frame=   17 fps=0.0 q=-0.0 Lsize=N/A time=00:00:00.72 bitrate=N/A speed= 1.1x

video:9kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown


$ ./ffmpeg -i ffmpeg-1-01_%06d.dpx -f md5  -

ffmpeg version N-92683-g32601fb821 Copyright (c) 2000-2018 the FFmpeg developers

  built with Apple LLVM version 8.0.0 (clang-800.0.42.1)

  configuration:

  libavutil      56. 24.101 / 56. 24.101

  libavcodec     58. 42.100 / 58. 42.100

  libavformat    58. 24.100 / 58. 24.100

  libavdevice    58.  6.101 / 58.  6.101

  libavfilter     7. 46.101 /  7. 46.101

  libswscale      5.  4.100 /  5.  4.100

  libswresample   3.  4.100 /  3.  4.100

Input #0, image2, from 'ffmpeg-1-01_%06d.dpx':

  Duration: 00:00:00.68, start: 0.000000, bitrate: N/A

    Stream #0:0: Video: dpx, gbrp10le, 3840x2160, 18 tbr, 25 tbn, 18 tbc

Stream mapping:

  Stream #0:0 -> #0:0 (dpx (native) -> rawvideo (native))

Press [q] to stop, [?] for help

Output #0, md5, to 'pipe:':

  Metadata:

    encoder         : Lavf58.24.100

    Stream #0:0: Video: rawvideo (G3[0][10] / 0xA003347), gbrp10le, 3840x2160, q=2-31, 4478976 kb/s, 18 fps, 18 tbn, 18 tbc

    Metadata:

      encoder         : Lavc58.42.100 rawvideo

frame=    5 fps=0.0 q=-0.0 size=       0kB time=00:00:00.27 bitrate=   0.0kbits/frame=    9 fps=7.5 q=-0.0 size=       0kB time=00:00:00.50 bitrate=   0.0kbits/frame=   12 fps=7.0 q=-0.0 size=       0kB time=00:00:00.66 bitrate=   0.0kbits/MD5=123fb3ff58ca94c842453b518aeb6a9a

frame=   14 fps=6.6 q=-0.0 Lsize=       0kB time=00:00:00.77 bitrate=   0.4kbits/s dup=0 drop=3 speed=0.364x

video:680400kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown



Best,


Kieran O'Leary

Irish Film Institute



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