What are bitrate settings of H264 Export window?

[lindenbaum]

Hello everyone,

I have one small question about the Export window of DCP-o-matic, which lets you make either ProRes of H264 from DCPs.

If you choose H264, it lets you decide of a "quality" between 0 (being the best) and 51 (being the worst).

Does anyone know more precisely what those numbers correspond to in terms of bitrate?

I would like to be able to make calculations in order to get a 5gb file.

Thanks a lot for your inputs,
Best,
lindenbaum

PS: Long live DCP-o-matic and its maker!

[Carsten]

I think there is no straight relationship - other than with J2K, you can not calculate the bitrate for this export. In the past, it was always a trial and error thing for me. If you need to target a specific file size for the export, you probably need to use a different tool to postprocess the DCP-o-matic export, like e.g. Handbrake.


- Carsten

[carl]

That H264 quality setting is described in a bit more detail here, if that helps. One interesting note is:

The range is exponential, so increasing the CRF value +6 results in roughly half the bitrate / file size, while -6 leads to roughly twice the bitrate

which might help you to hit your size target.

[Carsten]

One could try to trim the project temporarily to a 'typical' footage segment, e.g. 1min from the middle (under Timing), do a test export, and extrapolate full project size from there. That could bring you towards a useful number. Very rough, but...