[FFmpeg-devel] [PATCH 13/23] lavc/hevc/hevcdec: implement MV-HEVC inter-layer prediction
Anton Khirnov
anton at khirnov.net
Sat Sep 14 13:45:38 EEST 2024
The per-frame reference picture set contains two more lists -
INTER_LAYER[01]. Assuming at most two layers, INTER_LAYER1 is always
empty, but is added anyway for completeness.
When inter-layer prediction is enabled, INTER_LAYER0 for the
second-layer frame will contain the base-layer frame from the same
access unit, if it exists.
The new lists are then used in per-slice reference picture set
construction as per F.8.3.4 "Decoding process for reference picture
lists construction".
---
libavcodec/hevc/hevcdec.c | 7 ++++-
libavcodec/hevc/hevcdec.h | 8 ++++--
libavcodec/hevc/refs.c | 58 ++++++++++++++++++++++++++++++---------
libavcodec/nvdec_hevc.c | 2 +-
libavcodec/vdpau_hevc.c | 2 +-
5 files changed, 59 insertions(+), 18 deletions(-)
diff --git a/libavcodec/hevc/hevcdec.c b/libavcodec/hevc/hevcdec.c
index d3a47b65f4..cbf763b8be 100644
--- a/libavcodec/hevc/hevcdec.c
+++ b/libavcodec/hevc/hevcdec.c
@@ -784,7 +784,7 @@ static int hls_slice_header(SliceHeader *sh, const HEVCContext *s, GetBitContext
sh->rpl_modification_flag[0] = 0;
sh->rpl_modification_flag[1] = 0;
- nb_refs = ff_hevc_frame_nb_refs(sh, pps);
+ nb_refs = ff_hevc_frame_nb_refs(sh, pps, layer_idx);
if (!nb_refs) {
av_log(s->avctx, AV_LOG_ERROR, "Zero refs for a frame with P or B slices.\n");
return AVERROR_INVALIDDATA;
@@ -3356,6 +3356,11 @@ static int decode_nal_units(HEVCContext *s, const uint8_t *buf, int length)
s->eos = 0;
s->slice_initialized = 0;
+ for (int i = 0; i < FF_ARRAY_ELEMS(s->layers); i++) {
+ HEVCLayerContext *l = &s->layers[i];
+ l->cur_frame = NULL;
+ }
+
/* split the input packet into NAL units, so we know the upper bound on the
* number of slices in the frame */
ret = ff_h2645_packet_split(&s->pkt, buf, length, s->avctx,
diff --git a/libavcodec/hevc/hevcdec.h b/libavcodec/hevc/hevcdec.h
index 16b1d1ce92..57bf5aa599 100644
--- a/libavcodec/hevc/hevcdec.h
+++ b/libavcodec/hevc/hevcdec.h
@@ -84,6 +84,8 @@ enum RPSType {
ST_FOLL,
LT_CURR,
LT_FOLL,
+ INTER_LAYER0,
+ INTER_LAYER1,
NB_RPS_TYPE,
};
@@ -442,6 +444,7 @@ typedef struct HEVCLocalContext {
typedef struct HEVCLayerContext {
HEVCFrame DPB[32];
+ HEVCFrame *cur_frame;
const HEVCSPS *sps; // RefStruct reference
@@ -498,7 +501,7 @@ typedef struct HEVCContext {
struct AVMD5 *md5_ctx;
///< candidate references for the current frame
- RefPicList rps[5];
+ RefPicList rps[NB_RPS_TYPE];
const HEVCVPS *vps; ///< RefStruct reference
const HEVCPPS *pps; ///< RefStruct reference
@@ -615,7 +618,8 @@ int ff_hevc_res_scale_sign_flag(HEVCLocalContext *lc, int idx);
/**
* Get the number of candidate references for the current frame.
*/
-int ff_hevc_frame_nb_refs(const SliceHeader *sh, const HEVCPPS *pps);
+int ff_hevc_frame_nb_refs(const SliceHeader *sh, const HEVCPPS *pps,
+ unsigned layer_idx);
int ff_hevc_set_new_ref(HEVCContext *s, HEVCLayerContext *l, int poc);
diff --git a/libavcodec/hevc/refs.c b/libavcodec/hevc/refs.c
index 20fdbb5794..625ac68aaa 100644
--- a/libavcodec/hevc/refs.c
+++ b/libavcodec/hevc/refs.c
@@ -149,6 +149,7 @@ int ff_hevc_set_new_ref(HEVCContext *s, HEVCLayerContext *l, int poc)
return AVERROR(ENOMEM);
s->cur_frame = ref;
+ l->cur_frame = ref;
s->collocated_ref = NULL;
if (s->sh.pic_output_flag)
@@ -248,7 +249,9 @@ int ff_hevc_slice_rpl(HEVCContext *s)
return ret;
if (!(s->rps[ST_CURR_BEF].nb_refs + s->rps[ST_CURR_AFT].nb_refs +
- s->rps[LT_CURR].nb_refs) && !s->pps->pps_curr_pic_ref_enabled_flag) {
+ s->rps[LT_CURR].nb_refs +
+ s->rps[INTER_LAYER0].nb_refs + s->rps[INTER_LAYER1].nb_refs) &&
+ !s->pps->pps_curr_pic_ref_enabled_flag) {
av_log(s->avctx, AV_LOG_ERROR, "Zero refs in the frame RPS.\n");
return AVERROR_INVALIDDATA;
}
@@ -258,11 +261,14 @@ int ff_hevc_slice_rpl(HEVCContext *s)
RefPicList *rpl = &s->cur_frame->refPicList[list_idx];
/* The order of the elements is
- * ST_CURR_BEF - ST_CURR_AFT - LT_CURR for the L0 and
- * ST_CURR_AFT - ST_CURR_BEF - LT_CURR for the L1 */
- int cand_lists[3] = { list_idx ? ST_CURR_AFT : ST_CURR_BEF,
- list_idx ? ST_CURR_BEF : ST_CURR_AFT,
- LT_CURR };
+ * ST_CURR_BEF - INTER_LAYER0 - ST_CURR_AFT - LT_CURR - INTER_LAYER1 for the L0 and
+ * ST_CURR_AFT - INTER_LAYER1 - ST_CURR_BEF - LT_CURR - INTER_LAYER0 for the L1 */
+ int cand_lists[] = { list_idx ? ST_CURR_AFT : ST_CURR_BEF,
+ list_idx ? INTER_LAYER1 : INTER_LAYER0,
+ list_idx ? ST_CURR_BEF : ST_CURR_AFT,
+ LT_CURR,
+ list_idx ? INTER_LAYER0 : INTER_LAYER1
+ };
/* concatenate the candidate lists for the current frame */
while (rpl_tmp.nb_refs < sh->nb_refs[list_idx]) {
@@ -271,7 +277,11 @@ int ff_hevc_slice_rpl(HEVCContext *s)
for (j = 0; j < rps->nb_refs && rpl_tmp.nb_refs < HEVC_MAX_REFS; j++) {
rpl_tmp.list[rpl_tmp.nb_refs] = rps->list[j];
rpl_tmp.ref[rpl_tmp.nb_refs] = rps->ref[j];
- rpl_tmp.isLongTerm[rpl_tmp.nb_refs] = i == 2;
+ // multiview inter-layer refs are treated as long-term here,
+ // cf. G.8.1.3
+ rpl_tmp.isLongTerm[rpl_tmp.nb_refs] = cand_lists[i] == LT_CURR ||
+ cand_lists[i] == INTER_LAYER0 ||
+ cand_lists[i] == INTER_LAYER1;
rpl_tmp.nb_refs++;
}
}
@@ -410,11 +420,6 @@ int ff_hevc_frame_rps(HEVCContext *s, HEVCLayerContext *l)
RefPicList *rps = s->rps;
int i, ret = 0;
- if (!short_rps) {
- rps[0].nb_refs = rps[1].nb_refs = 0;
- return 0;
- }
-
unref_missing_refs(l);
/* clear the reference flags on all frames except the current one */
@@ -430,6 +435,9 @@ int ff_hevc_frame_rps(HEVCContext *s, HEVCLayerContext *l)
for (i = 0; i < NB_RPS_TYPE; i++)
rps[i].nb_refs = 0;
+ if (!short_rps)
+ goto inter_layer;
+
/* add the short refs */
for (i = 0; i < short_rps->num_delta_pocs; i++) {
int poc = s->poc + short_rps->delta_poc[i];
@@ -459,6 +467,24 @@ int ff_hevc_frame_rps(HEVCContext *s, HEVCLayerContext *l)
goto fail;
}
+inter_layer:
+ /* add inter-layer refs */
+ if (s->sh.inter_layer_pred) {
+ HEVCLayerContext *l0 = &s->layers[0];
+
+ av_assert0(l != l0);
+
+ /* Given the assumption of at most two layers, refPicSet0Flag is
+ * always 1, so only RefPicSetInterLayer0 can ever contain a frame. */
+ if (l0->cur_frame) {
+ // inter-layer refs are treated as short-term here, cf. F.8.1.6
+ ret = add_candidate_ref(s, l0, &rps[INTER_LAYER0], l0->cur_frame->poc,
+ HEVC_FRAME_FLAG_SHORT_REF, 1);
+ if (ret < 0)
+ goto fail;
+ }
+ }
+
fail:
/* release any frames that are now unused */
for (i = 0; i < FF_ARRAY_ELEMS(l->DPB); i++)
@@ -467,7 +493,8 @@ fail:
return ret;
}
-int ff_hevc_frame_nb_refs(const SliceHeader *sh, const HEVCPPS *pps)
+int ff_hevc_frame_nb_refs(const SliceHeader *sh, const HEVCPPS *pps,
+ unsigned layer_idx)
{
int ret = 0;
int i;
@@ -486,6 +513,11 @@ int ff_hevc_frame_nb_refs(const SliceHeader *sh, const HEVCPPS *pps)
ret += !!long_rps->used[i];
}
+ if (sh->inter_layer_pred) {
+ av_assert0(pps->sps->vps->num_direct_ref_layers[layer_idx] < 2);
+ ret++;
+ }
+
if (pps->pps_curr_pic_ref_enabled_flag)
ret++;
diff --git a/libavcodec/nvdec_hevc.c b/libavcodec/nvdec_hevc.c
index 6888507535..e01ce4c782 100644
--- a/libavcodec/nvdec_hevc.c
+++ b/libavcodec/nvdec_hevc.c
@@ -188,7 +188,7 @@ static int nvdec_hevc_start_frame(AVCodecContext *avctx,
.NumBitsForShortTermRPSInSlice = s->sh.short_term_rps ? s->sh.short_term_ref_pic_set_size : 0,
.NumDeltaPocsOfRefRpsIdx = s->sh.short_term_rps ? s->sh.short_term_rps->rps_idx_num_delta_pocs : 0,
- .NumPocTotalCurr = ff_hevc_frame_nb_refs(&s->sh, pps),
+ .NumPocTotalCurr = ff_hevc_frame_nb_refs(&s->sh, pps, s->cur_layer),
.NumPocStCurrBefore = s->rps[ST_CURR_BEF].nb_refs,
.NumPocStCurrAfter = s->rps[ST_CURR_AFT].nb_refs,
.NumPocLtCurr = s->rps[LT_CURR].nb_refs,
diff --git a/libavcodec/vdpau_hevc.c b/libavcodec/vdpau_hevc.c
index affb7e7f5a..0ddcafd897 100644
--- a/libavcodec/vdpau_hevc.c
+++ b/libavcodec/vdpau_hevc.c
@@ -206,7 +206,7 @@ static int vdpau_hevc_start_frame(AVCodecContext *avctx,
}
}
/* See section 7.4.7.2 of the specification. */
- info->NumPocTotalCurr = ff_hevc_frame_nb_refs(&h->sh, pps);
+ info->NumPocTotalCurr = ff_hevc_frame_nb_refs(&h->sh, pps, h->cur_layer);
if (sh->short_term_ref_pic_set_sps_flag == 0 && sh->short_term_rps) {
/* Corresponds to specification field, NumDeltaPocs[RefRpsIdx].
Only applicable when short_term_ref_pic_set_sps_flag == 0.
--
2.43.0
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