[FFmpeg-devel] [PATCH] hevc: If hwccel avoid creation/use of s/w only arrays

[Anton Khirnov]

Quoting John Cox (2022-05-27 15:51:17)
> Hwaccel doesn't use any of the block strength, pcm, slice address, etc.
> arrays which can be >100k each for 4k video. Patch to avoid initial
> allocation and zeroing at the start of every frame. On a Pi4 the memsets
> can use 10% CPU on 4k 60Hz decode, this fixes that.
> 
> Signed-off-by: John Cox <jc at kynesim.co.uk>
> ---
>  libavcodec/hevc_refs.c | 35 +++++++++++++++++++++--------------
>  libavcodec/hevcdec.c   | 42 +++++++++++++++++++++++++++++-------------
>  2 files changed, 50 insertions(+), 27 deletions(-)
> 
> diff --git a/libavcodec/hevcdec.c b/libavcodec/hevcdec.c
> index f782ea6394..48b059ce45 100644
> --- a/libavcodec/hevcdec.c
> +++ b/libavcodec/hevcdec.c
> @@ -504,6 +504,16 @@ static int set_sps(HEVCContext *s, const HEVCSPS *sps,
>      if (!sps)
>          return 0;
> 
> +    // If hwaccel then we don't need all the s/w decode helper arrays
> +    if (s->avctx->hwaccel) {
> +        export_stream_params(s, sps);
> +
> +        s->avctx->pix_fmt = pix_fmt;
> +        s->ps.sps = sps;
> +        s->ps.vps = (HEVCVPS*) s->ps.vps_list[s->ps.sps->vps_id]->data;

This duplication is ugly. This code should be commutative, so you can
either move it all above pic_arrays_init() and add an early return
after, or move it all to the end and jump to it with goto.

Otherwise looks reasonable.

-- 
Anton Khirnov