GOP inconsistencies when transcoding H.264 to MPEG2 MXF
|Reported by:||edob||Owned by:|
|Blocking:||Reproduced by developer:||no|
|Analyzed by developer:||no|
here's my summary of the bug:
When transcoding H.264 video files from a GoPro Hero3 (1920x1080,25fps,High@L4.1,30Mbps VBR,CABAC, M=1,N=13) to XDCAM HD422-Style MPEG2 video (50Mbps CBR, 1080i25, M=3,N=12), one seems to only get proper files if t<=60.00 seconds, but if t>60 seconds, the GOPs of the output file are of variable length (always multiples of M). I've encountered similar behaviour with other H.264 files as well, but this one is easier to reproduce (because it's not "some file from some guy").
[ Src file can be supplied but is 230M. ]
How to reproduce:
% ffmpeg -i C:\FFMPEG\GOPR_61sec.mp4 -vcodec mpeg2video -b:v 50M -minrate 50M -maxrate 50M -g 12 -bf 2 -vf colormatrix=bt601:bt709 -color_primaries bt709 -color_trc bt709 -colorspace bt709 -flags +ildct+ilme -top 1 -s 1920x1080 -r 25.000 -pix_fmt yuv422p -acodec pcm_s24le -ar 48000 -filter_complex "[0:a]channelsplit=channel_layout=stereo[a1][a2]" -map 0:v:0 -map "[a1]" -map "[a2]" C:\FFMPEG\GOPR_Test.mxf ffmpeg version N-81306-g26695ae built on 08/08/16 (Win32 static by zeranoe)
Please let me know if you need more detail.