[FFmpeg-trac] #5761(undetermined:new): GOP inconsistencies when transcoding H.264 to MPEG2 MXF

[FFmpeg]

#5761: GOP inconsistencies when transcoding H.264 to MPEG2 MXF
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             Reporter:  edob          |                     Type:  defect
               Status:  new           |                 Priority:  normal
            Component:  undetermined  |                  Version:  3.0.2
             Keywords:                |               Blocked By:
             Blocking:                |  Reproduced by developer:  0
Analyzed by developer:  0             |
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 Hi,

 here's my summary of the bug:

 When transcoding H.264 video files from a GoPro Hero3
 (1920x1080,25fps,High at 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.

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Ticket URL: <https://trac.ffmpeg.org/ticket/5761>
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