Constant rate factor

[boxdot]

Is there any possibility to use crf (constant rate factor) instead of bitrate. I tried to change this setting via ffmpeg interface

av_opt_set_double(cc->priv_data, "crf", 22.0, 0);

But it does not work. Could it be that I have to modify this parameter over the OpenMAX Il API? Unfortunately I cannot find any specification in the OpenMAX Pdf.

[dickontoo]

What would that do?

[boxdot]

Here is a good description http://slhck.info/crf.html. It is also the default encoding setting in Handbrake.

[dickontoo]

Ah. If you can see anything likely in firmware/documentation/ilcomponents/video_encode.html (you'll have to find a copy of it; there are plenty around) then possibly. I can't ATM, except for one which takes an unspecified uint32_t and is explicitly stated that it's internal only.

[boxdot]

Hmm. I see. There is no description what exactly OMX_IndexParamRateControlModel is. Sad, Handbrake with crf produces a much smaller file than omxtx.

[sammys]

Anything new found about OMX_IndexParamRateControlModel?

[xlazom00]

raspberrypi/firmware#329 (comment)

[brunogm0]

CRF is a unique technique of x264 software based ratecontrol. Broadcom has its own ratecontrol based on the JM H.264 reference software and so definitely there is no CRF mode. To implement one is basically asking to redo the entire codec! Also nothing could be copied from x264 for licensing issues, which adds complexity yet again.