[FFmpeg-devel] [PATCH] avcodec: add Actimagine VX video decoder

[Lynne]

Mar 15, 2021, 19:37 by fnouwt2 at gmail.com:

> I'll have a look if functions can be reused. If it's the case, the same
> could likely be done to the mobiclip decoder too since that one does a lot
> of stuff in a similar way.
> The "idct" looks very similar to "ff_h264_idct_add" in h264idct_template.c.
> Which would make sense since the codec is largely based on techniques used
> in h264. In that function the order seems to be reversed though
> (column->row, row->row instead of row->column, row->row) and I wonder if
> that can have any impact on the output? (Rounding errors or so)
> I think there's a good chance that h264 prediction functions can also be
> used. I will check if they are 100% equal.
>

The order doesn't matter, and rounding errors shouldn't occur as all your
coefficients are left-shifted by 6.


> I have a question about the color space btw. This format uses a yuv
> approximation based on bit shifting as I described in the init function.
> Currently it is not supported by ffmpeg. Would there be a way to add it or
> so? The regular yuv coefficients do look alright, but it is not correct.
> Everything is a bit less saturated or so.
>

Are there any docs or code on what the encoder uses? In general we don't
do colorspace conversions in decoders, but if it's close enough that some
correction can make it fit into bt601 or bt709, I think it would be okay.