[vlc-devel] [PATCH] videotoolbox: fix HEVC 10bits on iOS 14

[Alexandre Janniaux]

Hi,

On Mon, Sep 28, 2020 at 03:27:35PM +0200, Thomas Guillem wrote:
> iOS 14 adds support for 10bits YUV output. Unfortunately, it can only be
> rendered with Metal, so force BGRA output for now (waiting for a
> possible MetalAngle integration?).

I've started MetalANGLE integration, just for notification. :)

> ---
>  modules/codec/videotoolbox.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/modules/codec/videotoolbox.c b/modules/codec/videotoolbox.c
> index 02e009a42dd..673fc21dd2d 100644
> --- a/modules/codec/videotoolbox.c
> +++ b/modules/codec/videotoolbox.c
> @@ -180,12 +180,16 @@ static void HXXXGetBestChroma(decoder_t *p_dec)
>      {
>          if (i_depth_luma == 8 && i_depth_chroma == 8)
>              p_sys->i_cvpx_format = kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange;
> -#if !TARGET_OS_IPHONE
> -        /* Not for iOS since there is no 10bits textures with the old iOS
> -         * openGLES version, and therefore no P010 shaders */
>          else if (i_depth_luma == 10 && i_depth_chroma == 10 && deviceSupportsHEVC())
> +        {
> +#if !TARGET_OS_IPHONE
>              p_sys->i_cvpx_format = kCVPixelFormatType_420YpCbCr10BiPlanarVideoRange;
> +#else
> +            /* Force BGRA output (and let VT handle the tone mapping) on iOS
> +             * since the old openGLES version can't handle 16 bit textures. */
> +            p_sys->i_cvpx_format = kCVPixelFormatType_32BGRA;
>  #endif
> +        }

LGTM for now, but I don't think that's completely correct. Since we're
testing the availability of 16bit textures, you could instead use the
updateFormat callback to check whether we can have a vout with the 10bit
format, and if it fails, falls back to kCVPixelFormatType_32BGRA.

It would means that adding MetalANGLE won't need a modification to
videotoolbox and unavailability of MetalANGLE won't re-trigger the bug.

It's ok for 3.0 and 4.0 but I'd like this to change on 4.0.

>      }
>  }
>
> --
> 2.28.0
>
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