FFmpegx Corrections for Keyframe Interval

[kwag]

Hi major,

Please check the default setting for "Keyframe interval". It's defaulting to 240, instead of 24 (or 18 )
So when an MPEG is created, the maximum frames per GOP can go up to 240 frames (Bs and Ps) before the next I frame.

P.S. I'm heavily testing ffmpeg/ffmpegX at this moment

-kwag

[major4]

Hi kwag,

"Keyframe interval" is a mpeg-4 parameter. It is not used for mpeg-2. Gop values of 240 are normal for mpeg-4.

For mpeg-2, gop size is always set to 12, excepted when kvcd profile is selected.

[kwag]

Quote:

Originally Posted by major4

Hi kwag,

"Keyframe interval" is a mpeg-4 parameter. It is not used for mpeg-2. Gop values of 240 are normal for mpeg-4.

For mpeg-2, gop size is always set to 12, excepted when kvcd profile is selected.

Well, apparently it's going to the command line arguments from ffmpegX to ffmpeg
If I encode an MPEG-1 with the keyframe set to 240, my encoded MPEG has a long GOP
Look at the values going above 24:



And look at the GOP when I change it to 24:



-kwag

[major4]

I meant mpeg-2 with mpeg2enc uses 12 as GOP. For ffmpeg you should go through the "fast mpeg-1" preset which also sets GOP to 12.

[kwag]

Ok, thanks

-kwag