[FFmpeg-devel] [PATCH 1/4] avcodec/av1dec: expose skip mode frame index

[Mark Thompson]

On 09/11/2020 16:30, Timo Rothenpieler wrote:
> Signed-off-by: Timo Rothenpieler <timo at rothenpieler.org>
> Co-authored-by: James Almer <jamrial at gmail.com>
> ---
>   libavcodec/av1dec.c | 89 +++++++++++++++++++++++++++++++++++++++++++++
>   libavcodec/av1dec.h |  3 ++
>   2 files changed, 92 insertions(+)
> 
> diff --git a/libavcodec/av1dec.c b/libavcodec/av1dec.c
> index 56712279aa..83295699e1 100644
> --- a/libavcodec/av1dec.c
> +++ b/libavcodec/av1dec.c
> @@ -145,6 +145,87 @@ static void global_motion_params(AV1DecContext *s)
>       }
>   }
>   
> +static int get_relative_dist(const AV1RawSequenceHeader *seq,
> +                             unsigned int a, unsigned int b)
> +{
> +    unsigned int diff, m;
> +    if (!seq->enable_order_hint)
> +        return 0;

This never gets called if !enable_order_hint, so the argument isn't needed.

> +    diff = a - b;
> +    m = 1 << seq->order_hint_bits_minus_1;
> +    diff = (diff & (m - 1)) - (diff & m);
> +    return diff;
> +}
> +
> +static void skip_mode_params(AV1DecContext *s)
> +{
> +    const AV1RawFrameHeader *header = s->raw_frame_header;
> +    const AV1RawSequenceHeader *seq = s->raw_seq;
> +
> +    int forward_idx,  backward_idx;
> +    int forward_hint, backward_hint;
> +    int second_forward_idx, second_forward_hint;
> +    int ref_hint, dist, i;
> +
> +    s->cur_frame.skip_mode_frame_idx[0] = 0;
> +    s->cur_frame.skip_mode_frame_idx[1] = 0;

0 is AV1_REF_FRAME_INTRA, which doesn't make sense for skip.  Does this value actually get used?

> +
> +    if (header->frame_type == AV1_FRAME_KEY ||
> +        header->frame_type == AV1_FRAME_INTRA_ONLY ||
> +        !header->reference_select || !seq->enable_order_hint)

if (!header->skip_mode_present)

would be much simpler and short-cut some empty cases that this condition misses.

> +        return;
> +
> +    forward_idx  = -1;
> +    backward_idx = -1;
> +    for (i = 0; i < AV1_REFS_PER_FRAME; i++) {
> +        ref_hint = s->ref[header->ref_frame_idx[i]].order_hint;
> +        dist = get_relative_dist(seq, ref_hint, header->order_hint);
> +        if (dist < 0) {
> +            if (forward_idx < 0 ||
> +                get_relative_dist(seq, ref_hint, forward_hint) > 0) {
> +                forward_idx  = i;
> +                forward_hint = ref_hint;
> +            }
> +        } else if (dist > 0) {
> +            if (backward_idx < 0 ||
> +                get_relative_dist(seq, ref_hint, backward_hint) < 0) {
> +                backward_idx  = i;
> +                backward_hint = ref_hint;
> +            }
> +        }
> +    }
> +
> +    if (forward_idx < 0) {
> +        return;
> +    } else if (backward_idx >= 0) {
> +        s->cur_frame.skip_mode_frame_idx[0] =
> +            AV1_REF_FRAME_LAST + FFMIN(forward_idx, backward_idx);
> +        s->cur_frame.skip_mode_frame_idx[1] =
> +            AV1_REF_FRAME_LAST + FFMAX(forward_idx, backward_idx);
> +        return;
> +    }
> +
> +    second_forward_idx = -1;
> +    for (i = 0; i < AV1_REFS_PER_FRAME; i++) {
> +        ref_hint = s->ref[header->ref_frame_idx[i]].order_hint;
> +        if (get_relative_dist(seq, ref_hint, forward_hint) < 0) {
> +            if (second_forward_idx < 0 ||
> +                get_relative_dist(seq, ref_hint, second_forward_hint) > 0) {
> +                second_forward_idx  = i;
> +                second_forward_hint = ref_hint;
> +            }
> +        }
> +    }
> +
> +    if (second_forward_idx < 0)
> +        return;
> +
> +    s->cur_frame.skip_mode_frame_idx[0] =
> +        AV1_REF_FRAME_LAST + FFMIN(forward_idx, second_forward_idx);
> +    s->cur_frame.skip_mode_frame_idx[1] =
> +        AV1_REF_FRAME_LAST + FFMAX(forward_idx, second_forward_idx);
> +}
> +
>   static int init_tile_data(AV1DecContext *s)
>   
>   {
> @@ -318,6 +399,7 @@ static void av1_frame_unref(AVCodecContext *avctx, AV1Frame *f)
>       av_buffer_unref(&f->hwaccel_priv_buf);
>       f->hwaccel_picture_private = NULL;
>       f->spatial_id = f->temporal_id = 0;
> +    f->order_hint = 0;
>   }
>   
>   static int av1_frame_ref(AVCodecContext *avctx, AV1Frame *dst, const AV1Frame *src)
> @@ -337,12 +419,16 @@ static int av1_frame_ref(AVCodecContext *avctx, AV1Frame *dst, const AV1Frame *s
>   
>       dst->spatial_id = src->spatial_id;
>       dst->temporal_id = src->temporal_id;
> +    memcpy(dst->skip_mode_frame_idx,
> +           src->skip_mode_frame_idx,
> +           2 * sizeof(uint8_t));

Keeping this in the same order as the structure would make it easier to check that all fields are copied.

>       memcpy(dst->gm_type,
>              src->gm_type,
>              AV1_NUM_REF_FRAMES * sizeof(uint8_t));
>       memcpy(dst->gm_params,
>              src->gm_params,
>              AV1_NUM_REF_FRAMES * 6 * sizeof(int32_t));
> +    dst->order_hint = src->order_hint;
>   
>       return 0;
>   
> @@ -613,6 +699,7 @@ static int get_current_frame(AVCodecContext *avctx)
>       }
>   
>       global_motion_params(s);
> +    skip_mode_params(s);
>   
>       return ret;
>   }
> @@ -740,6 +827,8 @@ static int av1_decode_frame(AVCodecContext *avctx, void *frame,
>               s->cur_frame.spatial_id  = header->spatial_id;
>               s->cur_frame.temporal_id = header->temporal_id;
>   
> +            s->cur_frame.order_hint = s->raw_frame_header->order_hint;
> +
>               if (avctx->hwaccel) {
>                   ret = avctx->hwaccel->start_frame(avctx, unit->data,
>                                                     unit->data_size);
> diff --git a/libavcodec/av1dec.h b/libavcodec/av1dec.h
> index b58bc53961..8cf50f0d59 100644
> --- a/libavcodec/av1dec.h
> +++ b/libavcodec/av1dec.h
> @@ -41,6 +41,9 @@ typedef struct AV1Frame {
>   
>       uint8_t gm_type[AV1_NUM_REF_FRAMES];
>       int32_t gm_params[AV1_NUM_REF_FRAMES][6];
> +
> +    uint8_t order_hint;
> +    uint8_t skip_mode_frame_idx[2];
>   } AV1Frame;
>   
>   typedef struct TileGroupInfo {
> 

- Mark