10bit libkvazaar

[sven-pke]

Hello everyone,

As I was not able to get an 10bit encode with kvazaar and ffmpeg to work I guess that libkvazaar is 8bit only.
Is there a way to get ffmpeg with 10bit kvazaar?
Would be nice to test that on some hdr reference clips.

Greetings

[Jovasa]

The implementation of libkvazaar in FFmpeg is hardcoded to use 8bit encoding, however if you compile and install Kvazaar with changing this

kvazaar/src/kvazaar.h

Line 91 in d8c9688

#define KVZ_BIT_DEPTH 8

to #define KVZ_BIT_DEPTH 10 and apply the patch linked below to FFmpeg version 6.1 and compile FFmpeg, the resulting FFmpeg is hard coded to use 10 bit input for libkvazaar. It's not really an optimal solutions but should work if you just want to test 10 bit encoding. One thing to note is that our AVX2 optimizations are currently designed only for 8 bit encoding, so the 10bit encoding can be a lot slower than the 8 bit encoding.
0001-Hard-code-to-use-10bit-input.patch

[farindk]

We probably need two things:

• there should be an API to query the supported bit depths. Checking KVZ_BIT_DEPTH in a client application is no good idea because the version of kvazaar installed by the end user might use a different bit depth than the kvazaar used during compilation. In the simplest case, this would be a kvz_api_get(bit_depth) returning NULL when the bit_depth differs from the compiled bit depth.
• it should be possible to install 8bit and 10bit kvazaar at the same time and use kvz_api_get() to switch between both.