[Libav-user] Fwd: mpeg2video low quality iframes

[Zach Swena]

Hi,

I am working on encoding parameters for use in broadcast TV.  I am having
problems with FFmpeg not allocating enough bandwidth for the I frames in
the stream.  Image quality is acceptable for the most part, but there are
poorly encoded blocky frames with the same period as the GOP length.  This
would indicate that too much bandwidth is being used by the P and B frames
and too high of compression is used for the I frames in relation to P and B
frames.  Is there some setting I can add or change to fix this, or do I
need to report this as a bug?  Attached is the test file I am using.

Zach

My Command:
ffmpeg -y -i test.mov -f mpegts -vcodec mpeg2video -mbd bits -lmin
QP2LAMBDA -vf fps=29.97,scale=704x480 -pix_fmt yuv420p -b:v 3400k
-minrate:v 3400k -maxrate:v 3400k -bufsize 120k -me_method epzs -bf 2
-b_strategy 1 -flags +cgop -mpv_flags +strict_gop -trellis 2 -cmp 2 -subcmp
2 -sc_threshold 1000000k -g 45 -an -threads 0 test.ts
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