[FFmpeg-user] ProRes XQ 12-bit support

[Paul B Mahol]

On 4/24/18, Elliott Balsley <elliottbalsley at gmail.com> wrote:
>>> 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>

If you want definite proof, provide export of 12 bit prores into some
other 12 bit format
or 16bit one and give it to compare with ffmpeg decoded output.