[FFmpeg-user] ProRes XQ 12-bit support

Elliott Balsley elliottbalsley at gmail.com
Wed Apr 25 00:32:04 EEST 2018

>> Looking at the source code here, I see that PRORES_BITS_PER_SAMPLE is
>> defined as 10.  So it sounds like ffmpeg simply decodes all ProRes as
>> 10-bit.  I would like to request the option to decode ProRes with 12-bit
>> precision, but unfortunately I do not have any programming knowledge to
>> contribute.
>> https://github.com/FFmpeg/FFmpeg/blob/master/libavcodec/proresdsp.h
>> <https://github.com/FFmpeg/FFmpeg/blob/master/libavcodec/proresdsp.h <https://github.com/FFmpeg/FFmpeg/blob/master/libavcodec/proresdsp.h>>
>> Sample footage is here if anybody is interested:
>> http://www.arri.com/camera/alexa/learn/alexa_sample_footage/ <http://www.arri.com/camera/alexa/learn/alexa_sample_footage/>
> There is no 12 bit codec.
> There is only possible 16 bit alpha, which is downconverted to 10 bit.
> _______________________________________________

Here are a few sources stating there is a 12-bit codec.  Are you suggesting they are all wrong?

Apple’s white paper:
The new Apple ProRes 4444 codec preserves motion image sequences originating in either 4:4:4 RGB or 4:4:4 Y’CBCR color spaces. At its remarkably low data rate as compared to uncompressed 4:4:4 HD, Apple ProRes 4444 supports 12-bit pixel depth with an optional, mathematically lossless alpha channel for true 4:4:4:4 support. 
https://images.apple.com/support/finalcutpro/docs/Apple-ProRes-White-Paper-July-2009.pdf <https://images.apple.com/support/finalcutpro/docs/Apple-ProRes-White-Paper-July-2009.pdf>

Arri Alexa camera specs:
ProRes 4444 XQ preserves dynamic ranges several times greater than the dynamic range of Rec. 709 imagery. Like standard ProRes 4444, this version supports up to 12 bits per image channel. ProRes 4444 XQ features a target data rate of approximately 500 Mb/s for 4:4:4 sources at 1920 x 1080.
http://www.arri.com/news/news/alexa-xrxt-supports-new-prores-4444-xq/ <http://www.arri.com/news/news/alexa-xrxt-supports-new-prores-4444-xq/>

Rohit Gupta, software engineer for DaVinci Resolve: "PR4444 exports are always 12-bit. There is no way to limit it to 10-bit."
https://forum.blackmagicdesign.com/viewtopic.php?f=3&t=22488 <https://forum.blackmagicdesign.com/viewtopic.php?f=3&t=22488>

Sound Devices PIX 260i recorder specs:
Using Apple ProRes and Avid DNxHD codecs, the PIX 260i records and plays high-quality 12-bit 4:4:4 high definition video as well as 32 tracks of 48 kHz audio.
http://cdn.sounddevices.com/download/lit/pix260i_lit.pdf <http://cdn.sounddevices.com/download/lit/pix260i_lit.pdf>

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