Change in frame rate detection in dvvideo in v6.1

[Ian Young]

I have a workflow that involves working with some very old .dv files. With newer versions of ffmpeg, it isn't working.

Testing with the linuxserver/ffmpeg images, I can see the following in versions 4.4, 5.1 and 6.0:

ffprobe clip.dv 
ffprobe version 6.0 Copyright (c) 2007-2023 the FFmpeg developers
  built with gcc 11 (Ubuntu 11.4.0-1ubuntu1~22.04)
  configuration: --disable-debug --disable-doc --disable-ffplay --enable-cuvid --enable-ffprobe --enable-gpl --enable-libaom --enable-libass --enable-libfdk_aac --enable-libfreetype --enable-libkvazaar --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libsvtav1 --enable-libtheora --enable-libv4l2 --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvpl --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-nonfree --enable-nvdec --enable-nvenc --enable-opencl --enable-openssl --enable-stripping --enable-vaapi --enable-vdpau --enable-version3
  libavutil      58.  2.100 / 58.  2.100
  libavcodec     60.  3.100 / 60.  3.100
  libavformat    60.  3.100 / 60.  3.100
  libavdevice    60.  1.100 / 60.  1.100
  libavfilter     9.  3.100 /  9.  3.100
  libswscale      7.  1.100 /  7.  1.100
  libswresample   4. 10.100 /  4. 10.100
  libpostproc    57.  1.100 / 57.  1.100
[dv @ 0x5634ce7c8340] Estimating duration from bitrate, this may be inaccurate
Input #0, dv, from 'clip.dv':
  Metadata:
    timecode        : 00:00:21:04
  Duration: 01:01:20.72, start: 0.000000, bitrate: 28800 kb/s
  Stream #0:0: Video: dvvideo, yuv420p, 720x576 [SAR 64:45 DAR 16:9], 25000 kb/s, 25 fps, 25 tbr, 25 tbn
  Stream #0:1: Audio: pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s

Specifically: 25 fps, 25 tbr, 25 tbn

Now the same under v6.1 and later (also tested under 7.0.1):

ffprobe clip.dv 
ffprobe version 6.1.1 Copyright (c) 2007-2023 the FFmpeg developers
  built with gcc 11 (Ubuntu 11.4.0-1ubuntu1~22.04)
  configuration: --disable-debug --disable-doc --disable-ffplay --enable-alsa --enable-cuvid --enable-ffprobe --enable-gpl --enable-libaom --enable-libass --enable-libfdk_aac --enable-libfreetype --enable-libkvazaar --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libplacebo --enable-librav1e --enable-libshaderc --enable-libsvtav1 --enable-libtheora --enable-libv4l2 --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvpl --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzimg --enable-nonfree --enable-nvdec --enable-nvenc --enable-cuda-llvm --enable-opencl --enable-openssl --enable-stripping --enable-vaapi --enable-vdpau --enable-version3 --enable-vulkan
  libavutil      58. 29.100 / 58. 29.100
  libavcodec     60. 31.102 / 60. 31.102
  libavformat    60. 16.100 / 60. 16.100
  libavdevice    60.  3.100 / 60.  3.100
  libavfilter     9. 12.100 /  9. 12.100
  libswscale      7.  5.100 /  7.  5.100
  libswresample   4. 12.100 /  4. 12.100
  libpostproc    57.  3.100 / 57.  3.100
[dv @ 0x5566f329db40] Estimating duration from bitrate, this may be inaccurate
Input #0, dv, from 'clip.dv':
  Metadata:
    timecode        : 00:00:21:04
  Duration: 01:01:20.72, start: 0.000000, bitrate: 28800 kb/s
  Stream #0:0: Video: dvvideo, yuv420p, 720x576 [SAR 64:45 DAR 16:9], 28800 kb/s, 60k fps, 25 tbr, 60k tbn
  Stream #0:1: Audio: pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s

Difference: 60k fps, 25 tbr, 60k tbn

In my actual workflow, there's an error when ffmpeg attempts to write 60000 into the trailer of a .mov file, but the above seems to indicate where that value is coming from.

The files in question are around 13GB each, but the above behaviour shows up in the first 2MB so I'll try and attach one of those.

[Ian Young]

First 2MB of example file