[FFmpeg-user] maintaining full swing when encoding in 10 bit (want to preserve all values from 0-1023)

[Paul B Mahol]

On 11/9/15, Marwan Daar <marwan.daar at gmail.com> wrote:
> I'm doing some experimentation with different displays, and I need to be
> able to encode 10 bit images (scaled to a 16 bit png) into an mp4.
>
> I'm using madVR to render the 10 bit content. When I view, for example,
> a 10 bit gradient that goes from pixel value 0 to pixel value 7 (with
> the highest pixel value being 1023), it renders perfectly when I render
> the image with madVR - I see 8 distinct bars.
>
> However, when I use the 10 bit ffmpeg build found here:
> https://ffmpeg.zeranoe.com/blog/?p=435 (static, win32), there are
> artifacts in the encoding that seem to arise from a compression into
> 64-940 when the RGB is transformed into YUV (similar to how 0-255 is
> transformed to 16-235 in 8 bit). This is a problem in my case, as I need
> all 1023 distinct values to work with.
>
> Here is the code I'm using:
>
> *ffmpeg -i %d.png test.mp4*
>
>
> I originally thought this was a bug, and submitted a ticket:
> https://trac.ffmpeg.org/ticket/4986
>
> I was told the following,
>
> *Use the input option **-color_range mpeg**to force 0->0. It appears
> that this fails for rgb48 but please also try the output option
> **-dst_range 1*
>
> however this didn't work at all. -dst_range 1 just turned the whole
> frame into a uniform patch of color, rather than 8 distinct ones.
>
> I could really use some guidance here.
>

That are swscale bug(s). Compile with z.img and use zscale.

> thanks,
> Marwan
>
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