On 12/28/2021 7:01 PM, Hendrik Leppkes wrote:
On Tue, Dec 28, 2021 at 3:26 PM James Almer <jamr...@gmail.com> wrote:
On 12/28/2021 10:49 AM, Hendrik Leppkes wrote:
Aborting decoding of the entire packet on a missing PPS can result in
missing the actual PPS on streams with badly ordered NALs, where the
SPS/PPS/VPS are stitched to the back of the previous frame, instead of
the beginning of the next frame.
Instead, skip the undecodable slice, and let the decoder process further
NALs in the same packet.
---
libavcodec/hevcdec.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/libavcodec/hevcdec.c b/libavcodec/hevcdec.c
index 3aa70e2245..c2451d682e 100644
--- a/libavcodec/hevcdec.c
+++ b/libavcodec/hevcdec.c
@@ -575,7 +575,7 @@ static int hls_slice_header(HEVCContext *s)
sh->pps_id = get_ue_golomb_long(gb);
if (sh->pps_id >= HEVC_MAX_PPS_COUNT || !s->ps.pps_list[sh->pps_id]) {
av_log(s->avctx, AV_LOG_ERROR, "PPS id out of range: %d\n",
sh->pps_id);
- return AVERROR_INVALIDDATA;
+ return 1; // skip slice with missing PPS
The decoder should IMO also set the output frame's decode_error_flags to
FF_DECODE_ERROR_DECODE_SLICES in this scenario.
There is a variety of error conditions that can lead to a slice being
skipped, not just this one. I can potentially add it here, but it
won't be a very exhaustive flag.
If its also the first slice, the frame will fail to decode entirely as
well, although the point primarily here is to allow parsing of
non-image NALs.
What h264 does is set an internal flag on any kind of slice error at
assorted places, then set the AVFrame one before returning it based on
that (Needed because of frame threading).
It's not a blocker in any case. But even if it's just set at this point
for the time being, it would at least be a start.
- Hendrik
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