Re: [FFmpeg-devel] [PATCH v3 5/5] lavc: implement a Vulkan-based VC-2 encoder Implements a Vulkan based dirac encoder. Supports Haar and Legall wavelets and should work with all wavelet depths.

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

IndecisiveTurtle:
> From: IndecisiveTurtle <geoster3d@gmail.com>
> 
> Performance wise, encoding a 1080p 1-minute video is performed in about 2.5 minutes with the cpu encoder running on my Ryzen 5 4600H, while it takes about 30 seconds on my NVIDIA GTX 1650
> 
> Haar shader has a subgroup optimized variant that applies when configured wavelet depth allows it
> ---



> +
> +void put_vc2_ue_uint(inout PutBitContext pb, uint val)
> +{
> +    int pbits = 0, topbit = 1, maxval = 1, bits = 0;
> +    if (val == 0)
> +    {
> +        put_bits(pb, 1, 1);
> +        return;
> +    }
> +    val++;
> +
> +    while (val > maxval)
> +    {
> +        topbit <<= 1;
> +        bits++;
> +        maxval <<= 1;
> +        maxval |=  1;
> +    }
> +
> +    for (int i = 0; i < bits; i++)
> +    {
> +        topbit >>= 1;
> +        pbits <<= 2;
> +        if ((val & topbit) != 0)
> +            pbits |= 1;
> +    }
> +
> +    put_bits(pb, bits * 2 + 1, (pbits << 1) | 1);
> +}
> +

You are still using the old and inefficient way to write VC-2
exponential coded integers. Improving this gave a nice speed boost to
the software encoder.

- Andreas

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