[FFmpeg-devel] [PATCH] avcodec/av1dec: fix loading PrevGmParams for frames with primary_ref_frame none

[Mark Thompson]

On 17/10/2020 20:30, James Almer wrote:
> Signed-off-by: James Almer <jamrial at gmail.com>
> ---
>   libavcodec/av1dec.c | 9 +++++++--
>   1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/libavcodec/av1dec.c b/libavcodec/av1dec.c
> index 54aeba1812..04aaf5d148 100644
> --- a/libavcodec/av1dec.c
> +++ b/libavcodec/av1dec.c
> @@ -109,13 +109,18 @@ static void read_global_param(AV1DecContext *s, int type, int ref, int idx)
>   {
>       uint8_t primary_frame, prev_frame;
>       uint32_t abs_bits, prec_bits, round, prec_diff, sub, mx;
> -    int32_t r;
> +    int32_t r, prev_gm_param;
>   
>       primary_frame = s->raw_frame_header->primary_ref_frame;
>       prev_frame = s->raw_frame_header->ref_frame_idx[primary_frame];
>       abs_bits = AV1_GM_ABS_ALPHA_BITS;
>       prec_bits = AV1_GM_ALPHA_PREC_BITS;
>   
> +    if (s->raw_frame_header->primary_ref_frame == AV1_PRIMARY_REF_NONE)
> +        prev_gm_param = s->cur_frame.gm_params[ref][idx];

To clarify that I'm reading the standard correctly here, this is the value set for PrevGmParams by setup_past_independance(), which then matches the default for gm_params at the top of global_motion_params() so you've reused it here?

> +    else
> +        prev_gm_param = s->ref[prev_frame].gm_params[ref][idx];
> +
>       if (idx < 2) {
>           if (type == AV1_WARP_MODEL_TRANSLATION) {
>               abs_bits = AV1_GM_ABS_TRANS_ONLY_BITS -
> @@ -131,7 +136,7 @@ static void read_global_param(AV1DecContext *s, int type, int ref, int idx)
>       prec_diff = AV1_WARPEDMODEL_PREC_BITS - prec_bits;
>       sub = (idx % 3) == 2 ? (1 << prec_bits) : 0;
>       mx = 1 << abs_bits;
> -    r = (s->ref[prev_frame].gm_params[ref][idx] >> prec_diff) - sub;
> +    r = (prev_gm_param >> prec_diff) - sub;
>   
>       s->cur_frame.gm_params[ref][idx] =
>           (decode_signed_subexp_with_ref(s->raw_frame_header->gm_params[ref][idx],
> 

- Mark