Advertisement
Not a member of Pastebin yet?
Sign Up,
it unlocks many cool features!
- From 37f1a07904d164ada5dd0af82cca3742e916bd82 Mon Sep 17 00:00:00 2001
- From: Nicolas Gaullier <nicolas.gaullier@cji.paris>
- Date: Fri, 2 Feb 2024 12:34:39 +0100
- Subject: [PATCH] avformat/mpegts: fix first NAL start code splited in two
- different packets
- 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.
- ---
- libavformat/mpegts.c | 45 ++++++++++++++++++++++++++++++++++++++++++--
- 1 file changed, 43 insertions(+), 2 deletions(-)
- diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c
- index 836d5dd5a3..8f3bdfc690 100644
- --- a/libavformat/mpegts.c
- +++ b/libavformat/mpegts.c
- @@ -1148,6 +1148,7 @@ 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)
- @@ -1155,6 +1156,39 @@ 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)
- + {
- + if (pes->PES_packet_length)
- + pes->PES_packet_length += 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;
- @@ -1206,6 +1240,8 @@ static int mpegts_push_data(MpegTSFilter *filter,
- }
- pes->PES_packet_length = AV_RB16(pes->header + 4);
- + if (pes->PES_packet_length)
- + pes->PES_packet_length -= pes_align_shift;
- /* NOTE: zero length means the PES size is unbounded */
- if (pes->stream_id != STREAM_ID_PROGRAM_STREAM_MAP &&
- @@ -1300,6 +1336,7 @@ 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);
- @@ -1408,9 +1445,13 @@ 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
Advertisement
Add Comment
Please, Sign In to add comment
Advertisement
