When PES are not aligned and a tiny nal-encoded frame is contained in a single
TS packet,
the first NAL startcode may be split by the PES boundary, making the packet
unworkable.
This patch shift the PES boundaries to avoid this.
Signed-off-by: Nicolas Gaullier <nicolas.gaullier@cji.paris>
---
libavformat/mpegts.c | 41 +++++++++++++++++++++++++++++++++++++++--
1 file changed, 39 insertions(+), 2 deletions(-)
diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c
index bef00c88e7..4b4cf82fb9 100644
--- a/libavformat/mpegts.c
+++ b/libavformat/mpegts.c
@@ -1149,6 +1149,7 @@ static int mpegts_push_data(MpegTSFilter *filter,
PESContext *pes = filter->u.pes_filter.opaque;
MpegTSContext *ts = pes->ts;
const uint8_t *p;
+ int pes_align_shift = 0;
int ret, len;
if (!ts->pkt)
@@ -1156,6 +1157,37 @@ static int mpegts_push_data(MpegTSFilter *filter,
if (is_start) {
if (pes->state == MPEGTS_PAYLOAD && pes->data_index > 0) {
+ if ((pes->st->codecpar->codec_id == AV_CODEC_ID_H264
+ || pes->st->codecpar->codec_id == AV_CODEC_ID_HEVC)
+ && pes->data_index < TS_PACKET_SIZE - 4 - PES_HEADER_SIZE
+ && pes->data_index >= 4
+ && buf_size >= 4 ) {
+ /* check/avoid spliting the start code + first byte of the
first NAL unit in two different packets.
+ * this could happen with a tiny unaligned PES that fits
in a single ts packet. */
+ uint8_t *last_p_end = pes->buffer->data + pes->data_index
- 4;
+ p = buf + PES_HEADER_SIZE + buf[PES_HEADER_SIZE - 1];
+ if (last_p_end[3] == 0x00 && AV_RB24(p) == 0x000001)
+ pes_align_shift = 4;
+ else if (AV_RB16(last_p_end + 2)== 0x0000 && AV_RB16(p) ==
0x0001)
+ pes_align_shift = 3;
+ else if (AV_RB24(last_p_end + 1)== 0x000000 && *p == 0x01)
+ pes_align_shift = 2;
+ else if (AV_RB32(last_p_end) == 0x00000001)
+ pes_align_shift = 1;
+ if (pes_align_shift)
+ {
+ last_p_end += 4;
+ if (pes_align_shift > 3)
+ *last_p_end++ = 0x00;
+ if (pes_align_shift > 2)
+ *last_p_end++ = 0x00;
+ if (pes_align_shift > 1)
+ *last_p_end++ = 0x01;
+ *last_p_end = *(p + pes_align_shift - 1);
+ pes->data_index += pes_align_shift;
+ buf_size -= pes_align_shift;
+ }
+ }
ret = new_pes_packet(pes, ts->pkt);
if (ret < 0)
return ret;
@@ -1301,6 +1333,7 @@ skip:
/* we got the full header. We parse it and get the payload */
pes->state = MPEGTS_PAYLOAD;
pes->data_index = 0;
+ p += pes_align_shift;
if (pes->stream_type == 0x12 && buf_size > 0) {
int sl_header_bytes = read_sl_header(pes, &pes->sl, p,
buf_size);
@@ -1409,9 +1442,13 @@ skip:
pes->data_index += buf_size;
/* emit complete packets with known packet size
* decreases demuxer delay for infrequent packets like
subtitles from
- * a couple of seconds to milliseconds for properly muxed
files. */
+ * a couple of seconds to milliseconds for properly muxed
files.
+ * disabled for video/NALs because at this point it could
split/break the first NAL start code.
+ */
if (!ts->stop_parse && pes->PES_packet_length &&
- pes->pes_header_size + pes->data_index ==
pes->PES_packet_length + PES_START_SIZE) {
+ pes->pes_header_size + pes->data_index ==
pes->PES_packet_length + PES_START_SIZE &&
+ pes->st->codecpar->codec_id != AV_CODEC_ID_H264 &&
+ pes->st->codecpar->codec_id != AV_CODEC_ID_HEVC) {
ts->stop_parse = 1;
ret = new_pes_packet(pes, ts->pkt);
pes->state = MPEGTS_SKIP;
--
2.30.2
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