[FFmpeg-user] Support for Prores4444 12bit files

[Paul B Mahol]

On 7/4/13, Robert Krueger <krueger at lesspain.de> wrote:
> Hi,
>
> Apple's whitepaper states that Prores4444 has "up to 12bit" color
> depth. There are no Apple tools that I know of that have a switch to
> produce such a 12bit beast (their professional transcoder "Compressor"
> has the options "16.7 million colors" or "more than 16.7 million
> colors" which is useless in that case as IMO that translates to 8bit
> and more than 8 bit).
>
> Now there exist recorders which explicitly claim to support 10bit
> _and_ 12bit Prores4444 (see
> http://www.sounddevices.com/products/pix240i/sample-files/) and I
> downloaded those and tested transcoding with ffmpeg and the output
> looks fine. Since the pixel formats used by ffmpeg for Prores are 10
> bit only, I am wondering if there is a way to test if the color depth
> is really 12bit and thus reduced in any transcoding.
>
> Could anyone with more intimate knowledge of the decoder(s) shed some
> light on this? Is the current decoder reducing bit depth of these
> files when decoding and if so are there plans to add support for a
> pixel format that allows for 12 bit?
>
> Is there a way of testing such a file if it is 10 or 12bit? Apart from
> the alpha channel (which in this case is not there) neither the header
> documentation at
> http://wiki.multimedia.cx/index.php?title=Apple_ProRes nor the source
> code reveal anything that would be suitable for making that
> distinction? Or is the formulation "up to 12bit" simply wrong and
> Prores4444 is always 12bit?
>
> Best regards,
>
> Robert
>
> P.S.: I am not talking about 10 bit files with a special gamma
> function like Arri Log-C or Sony S-Log but real 12bits of depth.

I think you are confused. There is no 12bit prores.

Why would 12 bit prores file be smaller than 10 bit one?