What does "framerate" mean here? An arbitrary export framerate different from what the DCP was specified as?

Just my opinion - the export function is a functional side track in DOM. Adding every imaginable option to the export means much work. I think it is completely okay if DOM offers only two options - a 'low quality' (screener), and a high quality (re-use), plus optional audio mixdown. Everything else can be created by other tools with a more dedicated feature set (e.g. handbrake).

• Carsten

100% w/Carsten,
we could even abandon the .mov conversion (which btw still doesn’t work on MacOs 10.12.5 & 2.11.19)
in favor of mp4 (which works, including soft-subtitles size and position), and is half as heavy for about the same image
quality. Remember that the main purpose of the DCP to MP4 conversion is to let people perform
fast-forward film previews.

I think it is necessary to have a high quality 'reuse' export option, which the MOV option using ProRes is currently targeting. Some people would say uncompressed/lossless image series would be more appropriate.

I noticed that the MP4 export creates unusually high bit rates, some of my lighter machines can not play without frame losses. I guess it makes sense to lower the bitrate for MP4 (or, sigh, make it selectable (low/mid/high), thus making a higher quality ProRes more useful for those who need it.

• Carsten

Everything else can be created by other tools with a more dedicated feature set (e.g. handbrake).

Hi Carsten, don’t bet on Handbrake for DCP to MP4 conversion. Last year I tried (and failed) to convince its stubborn developer team.
Being stuck to Libav*, they are still unable to convert XYZ to rgb/yuv color space, something that FFmpeg offered to DoM
and the world for years.
--jp

• weird result of the 2011 FFmpeg internal war and split.

I don't count on handbrake to convert from DCP, but to all the other formats mentioned above FROM the exports DOMs creates, so, either from MP4 or Prores.

• Carsten

I think also the option -preset needs to be able to be selected. When I used CRF 17, I got a 100 GB file, which I was able to convert to about 12GB without any perceptible loss in quality.

In the future, exporting to HEVC (x265) might become useful, though it is fairly slow on my computer.

Also, what are the settings for audio? VBR or CBR? What encoder DOM uses, libfdk_aac or aac?

BTW: is not seeting the image size equivalent to this: https://dcpomatic.com/mantis/view.php?id=1793 (there fore that one would be duplicate of this one).

I would add to this, after almost three years, that export would deserve a bit of imrovement. As discussed here, it is quite slow: https://dcpomatic.com/forum/viewtopic.php?f=2&t=1682&p=7545#p7545
and it produces big files. I am not sure what options are used internally for the Prores and MP4 options. When Carsten speaks above about screeners, I think this option is now missing as both mp4 and Prores seem to be more for reuse case.

A screener option would produce a smaller file faster.

Moreover, the naming of the options is confusing - ProRes is a codec (exported to MOV?) and MP4 is a container - I presume the codec used is x264?

I would not care if the default options are tweaked internally to produce a smaller and faster encode, but another way to speed things up would be to use hardware acceleration for this. In my case, I have an NVidia card that could do this via h264_nvenc. An option that would work for me would be being abel to set a custom ffmpeg codec (video, above all) specification. Something like this in my case: "-c:v h264_nvenc -b:v 0 -rc vbr_hq -cq 19 -preset slow -profile:v main". Or "-c:v libx264 -preset slow -crf 16".

I opened two bugs about the name of the codecs here: https://dcpomatic.com/mantis/view.php?id=2067t suer
and a suggestion to improve documentation here: https://dcpomatic.com/mantis/view.php?id=2068

Not sure if I shold open a new bug for the custom ffmpeg commands? I think it could be something set in the preferences. If DOM is run from the console, I guess any erros from ffmpeg would get caught.