From: Xu Guangxin <guangxin...@intel.com>
Currently find_ref_idx() would trigger 2 scans in DPB to find the
requested POC:
1. Firstly, ignore MSB of ref->poc and search for the requested POC;
2. Secondly, compare the entire ref->poc with requested POC;
For long term reference, we are able to only check LSB if MSB is not
presented(e.g. delta_poc_msb_present_flag == 0). However, for short
term reference, we should never ignore poc's MSB and it should be
kind of bit-exact. (Details in 8.3.2)
Otherwise this leads to decoding failures like:
[hevc @ 0x5638f4328600] Error constructing the frame RPS.
[hevc @ 0x5638f4328600] Error parsing NAL unit #2.
[hevc @ 0x5638f4338a80] Could not find ref with POC 21
Error while decoding stream #0:0: Invalid data found when processing input
Search the requested POC based on whether MSB is used, and avoid
the 2-times scan for DPB buffer. This benefits both native HEVC
decoder and integrated HW decoders.
Signed-off-by: Linjie Fu <linjie...@intel.com>
---
Since it's kind of difficult to generate an identical bitstream for
fate or test, I'd like to elaborate more about one of the failures:
requested POC = 5;
LtMask = (1 << 4) - 1 = 15;
ref[0]->poc = 21; // unexpected ref for poc = 5 (short term)
ref[1]->poc = 5; // expected ref for poc = 5 (short term)
Hence find_ref_idx() would wrongly return a ref with poc = 21, which
leads to the decoding error.
libavcodec/hevc_refs.c | 38 ++++++++++++++++++++------------------
1 file changed, 20 insertions(+), 18 deletions(-)
diff --git a/libavcodec/hevc_refs.c b/libavcodec/hevc_refs.c
index 7870a72..73aa6d8 100644
--- a/libavcodec/hevc_refs.c
+++ b/libavcodec/hevc_refs.c
@@ -358,24 +358,26 @@ int ff_hevc_slice_rpl(HEVCContext *s)
return 0;
}
-static HEVCFrame *find_ref_idx(HEVCContext *s, int poc)
+static HEVCFrame *find_ref_idx(HEVCContext *s, int poc, uint8_t use_msb)
{
int i;
- int LtMask = (1 << s->ps.sps->log2_max_poc_lsb) - 1;
- for (i = 0; i < FF_ARRAY_ELEMS(s->DPB); i++) {
- HEVCFrame *ref = &s->DPB[i];
- if (ref->frame->buf[0] && (ref->sequence == s->seq_decode)) {
- if ((ref->poc & LtMask) == poc)
- return ref;
+ if (use_msb) {
+ for (i = 0; i < FF_ARRAY_ELEMS(s->DPB); i++) {
+ HEVCFrame *ref = &s->DPB[i];
+ if (ref->frame->buf[0] && (ref->sequence == s->seq_decode)) {
+ if (ref->poc == poc)
+ return ref;
+ }
}
- }
-
- for (i = 0; i < FF_ARRAY_ELEMS(s->DPB); i++) {
- HEVCFrame *ref = &s->DPB[i];
- if (ref->frame->buf[0] && ref->sequence == s->seq_decode) {
- if (ref->poc == poc || (ref->poc & LtMask) == poc)
- return ref;
+ } else {
+ int LtMask = (1 << s->ps.sps->log2_max_poc_lsb) - 1;
+ for (i = 0; i < FF_ARRAY_ELEMS(s->DPB); i++) {
+ HEVCFrame *ref = &s->DPB[i];
+ if (ref->frame->buf[0] && ref->sequence == s->seq_decode) {
+ if ((ref->poc & LtMask) == poc)
+ return ref;
+ }
}
}
@@ -427,9 +429,9 @@ static HEVCFrame *generate_missing_ref(HEVCContext *s, int
poc)
/* add a reference with the given poc to the list and mark it as used in DPB */
static int add_candidate_ref(HEVCContext *s, RefPicList *list,
- int poc, int ref_flag)
+ int poc, int ref_flag, uint8_t use_msb)
{
- HEVCFrame *ref = find_ref_idx(s, poc);
+ HEVCFrame *ref = find_ref_idx(s, poc, use_msb);
if (ref == s->ref || list->nb_refs >= HEVC_MAX_REFS)
return AVERROR_INVALIDDATA;
@@ -485,7 +487,7 @@ int ff_hevc_frame_rps(HEVCContext *s)
else
list = ST_CURR_AFT;
- ret = add_candidate_ref(s, &rps[list], poc, HEVC_FRAME_FLAG_SHORT_REF);
+ ret = add_candidate_ref(s, &rps[list], poc, HEVC_FRAME_FLAG_SHORT_REF,
1);
if (ret < 0)
goto fail;
}
@@ -495,7 +497,7 @@ int ff_hevc_frame_rps(HEVCContext *s)
int poc = long_rps->poc[i];
int list = long_rps->used[i] ? LT_CURR : LT_FOLL;
- ret = add_candidate_ref(s, &rps[list], poc, HEVC_FRAME_FLAG_LONG_REF);
+ ret = add_candidate_ref(s, &rps[list], poc, HEVC_FRAME_FLAG_LONG_REF,
long_rps->poc_msb_present[i]);
if (ret < 0)
goto fail;
}
--
2.7.4
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