[FFmpeg-devel] [PATCH v3 00/10] avcodec/vc1: Arm optimisations

[Martin Storsjö]

On Thu, 31 Mar 2022, Ben Avison wrote:

> The VC1 decoder was missing lots of important fast paths for Arm, especially
> for 64-bit Arm. This submission fills in implementations for all functions
> where a fast path already existed and the fallback C implementation was
> taking 1% or more of the runtime, and adds a new fast path to permit
> vc1_unescape_buffer() to be overridden.
>
> I've measured the playback speed on a 1.5 GHz Cortex-A72 (Raspberry Pi 4)
> using `ffmpeg -i <bitstream> -f null -` for a couple of example streams:
>
> Architecture:  AArch32    AArch32    AArch64    AArch64
> Stream:        1          2          1          2
> Before speed:  1.22x      0.82x      1.00x      0.67x
> After speed:   1.31x      0.98x      1.39x      1.06x
> Improvement:   7.4%       20%        39%        58%
>
> `make fate` passes on both AArch32 and AArch64.
>
> Changes in v2:
>
> * Refactor checkasm tests to convert some macros into functions.
> * Remove cast-to-void of checked_call.
> * Limit 16-bit values in idctdsp checkasm test to +/-0x100.
> * Reinstate ff_add_pixels_clamped_arm.
> * Adapt vc1 deblocking filters to specify stride as ptrdiff_t.
> * Add align specifiers to a few VLD/VST instructions for AArch32 deblocking
>  filter, and adapt checkasm test not to test with tighter alignment than is
>  encountered in normal use.
> * Correct unescape buffer memcmp length.
> * Update benchmarks for AArch64 idctdsp.

Thanks! From a quick readthrough, this version of the patchset seems good 
to me! I'll run it through some more testing, and push it if everything 
seems to work fine (tomorrow or so).

// Martin