[FFmpeg-devel] [PATCH] avformat/mpegts: Check the next sync byte to avoid incorrectt detected raw packet size
lance.lmwang at gmail.com
lance.lmwang at gmail.com
Sun May 17 13:13:38 EEST 2020
On Sat, May 16, 2020 at 07:36:45PM +0200, Marton Balint wrote:
>
>
> On Sat, 16 May 2020, lance.lmwang at gmail.com wrote:
>
> > On Sat, May 16, 2020 at 11:44:01AM +0200, Marton Balint wrote:
> > >
> > >
> > > On Sat, 16 May 2020, lance.lmwang at gmail.com wrote:
> > >
> > > > On Fri, May 15, 2020 at 06:52:55PM +0200, Marton Balint wrote:
> > > > > > > > > On Fri, 15 May 2020, lance.lmwang at gmail.com wrote:
> > > > > > > > On Fri, May 15, 2020 at 08:02:44PM +0800, mypopy at gmail.com
> > > wrote:
> > > > > > > On Fri, May 15, 2020 at 6:23 PM <lance.lmwang at gmail.com> wrote:
> > > > > > > >
> > > > > > > > From: Limin Wang <lance.lmwang at gmail.com>
> > > > > > > >
> > > > > > > > reanalyze() may misdetect the new packet size as 204, but it's 188 still actualy,
> > > > > > > > it'll cause many cc errors report and cannot be recovered. So it's better to check
> > > > > > > > the next sync byte before skip the extra unused bytes.
> > > > > > > >
> > > > > > > > Also, it is best to change SIZE_STAT_THRESHOLD from 10 to 100? If the input stream has
> > > > > > > > a master/slave switch serveral times, the raw size can be easily detected by mistake.
> > > > > > > >
> > > > > > > > Signed-off-by: Limin Wang <lance.lmwang at gmail.com>
> > > > > > > > ---
> > > > > > > > libavformat/mpegts.c | 13 +++++++------
> > > > > > > > 1 file changed, 7 insertions(+), 6 deletions(-)
> > > > > > > >
> > > > > > > > diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c
> > > > > > > > index 0833d62..049555c 100644
> > > > > > > > --- a/libavformat/mpegts.c
> > > > > > > > +++ b/libavformat/mpegts.c
> > > > > > > > @@ -2932,11 +2932,12 @@ static int read_packet(AVFormatContext *s, uint8_t *buf, int raw_packet_size,
> > > > > > > > return 0;
> > > > > > > > }
> > > > > > > >
> > > > > > > > -static void finished_reading_packet(AVFormatContext *s, int raw_packet_size)
> > > > > > > > +static void finished_reading_packet(AVFormatContext *s, const uint8_t *data, int raw_packet_size)
> > > > > > > > {
> > > > > > > > AVIOContext *pb = s->pb;
> > > > > > > > int skip = raw_packet_size - TS_PACKET_SIZE;
> > > > > > > > - if (skip > 0)
> > > > > > > > + /* Check the next sync byte to avoid incorrectt detected raw packet size */
> > > > > > > > + if (skip > 0 && data[TS_PACKET_SIZE] != 0x47)
> > > > > > > > avio_skip(pb, skip);
> > > > > > > > }
> > > > > > > >
> > > > > > > > @@ -2985,7 +2986,7 @@ static int handle_packets(MpegTSContext *ts, int64_t nb_packets)
> > > > > > > > if (ret != 0)
> > > > > > > > break;
> > > > > > > > ret = handle_packet(ts, data, avio_tell(s->pb));
> > > > > > > > - finished_reading_packet(s, ts->raw_packet_size);
> > > > > > > > + finished_reading_packet(s, data, ts->raw_packet_size);
> > > > > > > > if (ret != 0)
> > > > > > > > break;
> > > > > > > > }
> > > > > > > > @@ -3137,7 +3138,7 @@ static int mpegts_read_header(AVFormatContext *s)
> > > > > > > > pid = AV_RB16(data + 1) & 0x1fff;
> > > > > > > > if ((pcr_pid == -1 || pcr_pid == pid) &&
> > > > > > > > parse_pcr(&pcr_h, &pcr_l, data) == 0) {
> > > > > > > > - finished_reading_packet(s, ts->raw_packet_size);
> > > > > > > > + finished_reading_packet(s, data, ts->raw_packet_size);
> > > > > > > > pcr_pid = pid;
> > > > > > > > packet_count[nb_pcrs] = nb_packets;
> > > > > > > > pcrs[nb_pcrs] = pcr_h * 300 + pcr_l;
> > > > > > > > @@ -3154,7 +3155,7 @@ static int mpegts_read_header(AVFormatContext *s)
> > > > > > > > }
> > > > > > > > }
> > > > > > > > } else {
> > > > > > > > - finished_reading_packet(s, ts->raw_packet_size);
> > > > > > > > + finished_reading_packet(s, data, ts->raw_packet_size);
> > > > > > > > }
> > > > > > > > nb_packets++;
> > > > > > > > }
> > > > > > > > @@ -3194,7 +3195,7 @@ static int mpegts_raw_read_packet(AVFormatContext *s, AVPacket *pkt)
> > > > > > > > }
> > > > > > > > if (data != pkt->data)
> > > > > > > > memcpy(pkt->data, data, ts->raw_packet_size);
> > > > > > > > - finished_reading_packet(s, ts->raw_packet_size);
> > > > > > > > + finished_reading_packet(s, data, ts->raw_packet_size);
> > > > > > > > if (ts->mpeg2ts_compute_pcr) {
> > > > > > > > /* compute exact PCR for each packet */
> > > > > > > > if (parse_pcr(&pcr_h, &pcr_l, pkt->data) == 0) {
> > > > > > > > --
> > > > > > > > 1.8.3.1
> > > > > > > >
> > > > > > > Do you have a case to reproduce the cc errors report?
> > > > > > > Yes, it's real case which can be reproduced in lab.
> > > > > > > Can you share the sample?
> > > > > No, tested with master and slave udp ts stream which switch
> > > between the master and slave stream
> > > > more than five times, it'll cause tons of cc error report and can't be recovered.
> > >
> > > I suggest you capture the input, so this issue can be properly reproduced
> > > and share it. It may even make sense to create a fate test from it.
> >
> > Have tried, the issue can't be reproduced by capture offset file. I guess it's
> > caused by live stream seek isn't same as off line file.
>
> If that is the case then you can override the seekability of files by using
> -seekable 0 option. Alternatively you might find some other means to replay
> the recorded ts, anyhow this should be reproduced, because I have a feeling
> we don't have the whole picture of what is going on.
I have spend more time to investigate it, I have try to capture a pcap file to
reproduce the issue, with tcprelay, it can be reproduced every time, however
if export to ts, I failed to reproduce it.
>
> >
> > >
> > > Anyway, your patch does not seem right, because it seems to revert back the
> > > packet size as soon as the first byte to be skipped is 0x47. That will
> > > surely cause issues for normal streams having a packet size > 188.
> >
> > I haven't sample to test such case, I think 0x47 is sync byte, if the next 188
> > byte is 0x47, it's more possible it's sync byte as sync byte checking is always
> > make sure the next 188/192/204 payload is 0x47.
>
> No, you can only involve any resync logic if you came across a sync byte
> which is not 0x47. You cannot make assumptions about packet size by checking
> bytes of packet data as long as you are in sync, because that would mean
> that packet data can affect sync decisions even for perfectly synced
> streams.
Thanks for the advices, I spend more time to investigate and try to fix it in the
resync logic, with more debug info, I notice the old reanalyze() has one drawback,
the pos isn't one of 188/192/204, so it'll cause the stat will reset all stats
ahead of one of stats[i] which cause normal 188 failed to detected anymore. I
think it's better to return if pos isn't one of 188/192/204, it'll fix my issue
by testing, please help to review whether it's reasonable or not.
my debug log change:
diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c
index 0833d62..9a13146 100644
--- a/libavformat/mpegts.c
+++ b/libavformat/mpegts.c
@@ -2855,6 +2855,8 @@ static void reanalyze(MpegTSContext *ts) {
}
ts->size_stat_count ++;
+ av_log(ts->stream, AV_LOG_INFO, "reanalyze: stat: %d, stat[0]: %d, stat[1]: %d, stat[2]: %d, pos: %lld\n",
+ ts->size_stat_count, ts->size_stat[0], ts->size_stat[1], ts->size_stat[2], pos);
if (ts->size_stat_count > SIZE_STAT_THRESHOLD) {
int newsize = 0;
if (ts->size_stat[0] > SIZE_STAT_THRESHOLD) {
The bug trigger log:
[mpegts @ 0x3ef0180] reanalyze: stat: 0, stat[0]: 0, stat[1]: 1, stat[2]: 0, raw_packet_size: 188, pos: 192
[mpegts @ 0x3ef0180] PES packet size mismatch
[mpegts @ 0x3ef0180] Packet corrupt (stream = 0, dts = 1320433).
[mpegts @ 0x3ef0180] DTS 8590011941 < 8591255025 out of orderN/A speed=1.11x
[mpegts @ 0x3ef0180] reanalyze: stat: 1, stat[0]: 0, stat[1]: 2, stat[2]: 0, raw_packet_size: 188, pos: 192
[mpegts @ 0x3ef0180] reanalyze: stat: 2, stat[0]: 0, stat[1]: 3, stat[2]: 0, raw_packet_size: 188, pos: 192
[mpegts @ 0x3ef0180] reanalyze: stat: 3, stat[0]: 0, stat[1]: 4, stat[2]: 0, raw_packet_size: 188, pos: 192
[mpegts @ 0x3ef0180] PES packet size mismatch
[mpegts @ 0x3ef0180] Packet corrupt (stream = 0, dts = 1229349).
[mpegts @ 0x3ef0180] DTS 8590128272 < 8591163941 out of orderN/A speed=1.07x
[mpegts @ 0x3ef0180] reanalyze: stat: 4, stat[0]: 0, stat[1]: 5, stat[2]: 0, raw_packet_size: 188, pos: 192
[mpegts @ 0x3ef0180] reanalyze: stat: 5, stat[0]: 0, stat[1]: 6, stat[2]: 0, raw_packet_size: 188, pos: 192
[mpegts @ 0x3ef0180] reanalyze: stat: 6, stat[0]: 0, stat[1]: 7, stat[2]: 0, raw_packet_size: 188, pos: 192
[mpegts @ 0x3ef0180] PES packet size mismatch
[mpegts @ 0x3ef0180] Packet corrupt (stream = 0, dts = 1464480).
[mpegts @ 0x3ef0180] DTS 8590009421 < 8591399072 out of orderN/A speed=1.06x
[mpegts @ 0x3ef0180] reanalyze: stat: 7, stat[0]: 0, stat[1]: 8, stat[2]: 0, raw_packet_size: 188, pos: 192
[mpegts @ 0x3ef0180] reanalyze: stat: 8, stat[0]: 0, stat[1]: 9, stat[2]: 0, raw_packet_size: 188, pos: 192
[mpegts @ 0x3ef0180] reanalyze: stat: 9, stat[0]: 0, stat[1]: 10, stat[2]: 0, raw_packet_size: 188, pos: 192
[mpegts @ 0x3ef0180] PES packet size mismatch
[mpegts @ 0x3ef0180] Packet corrupt (stream = 0, dts = 1828029).
[mpegts @ 0x3ef0180] DTS 8590030653 < 8591762621 out of orderN/A speed=1.02x
[mpegts @ 0x3ef0180] reanalyze: stat: 10, stat[0]: 0, stat[1]: 11, stat[2]: 0, raw_packet_size: 188, pos: 192
[mpegts @ 0x3ef0180] changing packet size to 192
[mpegts @ 0x3ef0180] reanalyze: stat: 0, stat[0]: 1, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 188
[mpegts @ 0x3ef0180] PES packet size mismatch
[mpegts @ 0x3ef0180] Packet corrupt (stream = 0, dts = 1442461).
[mpegts @ 0x3ef0180] reanalyze: stat: 1, stat[0]: 2, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 188
[mpegts @ 0x3ef0180] reanalyze: stat: 2, stat[0]: 3, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 188
[mpegts @ 0x3ef0180] reanalyze: stat: 3, stat[0]: 4, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 188
[mpegts @ 0x3ef0180] reanalyze: stat: 4, stat[0]: 5, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 188
the log which explain why it failed to detect back to 188:
[mpegts @ 0x3ef0180] reanalyze: stat: 1, stat[0]: 1, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 188
[mpegts @ 0x3ef0180] reanalyze: stat: 2, stat[0]: 2, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 188
[mpegts @ 0x3ef0180] reanalyze: stat: 3, stat[0]: 3, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 188
[mpegts @ 0x3ef0180] reanalyze: stat: 4, stat[0]: 4, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 188
[mpegts @ 0x3ef0180] reanalyze: stat: 5, stat[0]: 4, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 564
[mpegts @ 0x3ef0180] reanalyze: stat: 6, stat[0]: 5, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 188
[mpegts @ 0x3ef0180] reanalyze: stat: 7, stat[0]: 6, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 188
[mpegts @ 0x3ef0180] reanalyze: stat: 8, stat[0]: 6, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 376
[mpegts @ 0x3ef0180] reanalyze: stat: 9, stat[0]: 7, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 188
[mpegts @ 0x3ef0180] reanalyze: stat: 10, stat[0]: 7, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 474
[mpegts @ 0x3ef0180] reanalyze: stat: 0, stat[0]: 0, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 752
[mpegts @ 0x3ef0180] reanalyze: stat: 1, stat[0]: 0, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 940
[mpegts @ 0x3ef0180] reanalyze: stat: 2, stat[0]: 1, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 188
[mpegts @ 0x3ef0180] reanalyze: stat: 3, stat[0]: 2, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 188
[mpegts @ 0x3ef0180] reanalyze: stat: 4, stat[0]: 2, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 737
[mpegts @ 0x3ef0180] reanalyze: stat: 5, stat[0]: 2, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 203
[mpegts @ 0x3ef0180] reanalyze: stat: 6, stat[0]: 3, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 188
[mpegts @ 0x3ef0180] reanalyze: stat: 7, stat[0]: 4, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 188
[mpegts @ 0x3ef0180] reanalyze: stat: 8, stat[0]: 4, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 376
[mpegts @ 0x3ef0180] reanalyze: stat: 9, stat[0]: 4, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 564
[mpegts @ 0x3ef0180] reanalyze: stat: 10, stat[0]: 5, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 188
[mpegts @ 0x3ef0180] reanalyze: stat: 0, stat[0]: 1, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 188
[mpegts @ 0x3ef0180] reanalyze: stat: 1, stat[0]: 1, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 376
[mpegts @ 0x3ef0180] reanalyze: stat: 2, stat[0]: 2, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 188
[mpegts @ 0x3ef0180] reanalyze: stat: 3, stat[0]: 2, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 564
[mpegts @ 0x3ef0180] reanalyze: stat: 4, stat[0]: 3, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 188
[mpegts @ 0x3ef0180] reanalyze: stat: 5, stat[0]: 4, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 188
[mpegts @ 0x3ef0180] reanalyze: stat: 6, stat[0]: 4, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 376
[mpegts @ 0x3ef0180] reanalyze: stat: 7, stat[0]: 5, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 188
[mpegts @ 0x3ef0180] reanalyze: stat: 8, stat[0]: 5, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 564
[mpegts @ 0x3ef0180] reanalyze: stat: 9, stat[0]: 6, stat[1]: 0, stat[2]: 0, raw_packet_size: 192, pos: 188
....
>
> Regards,
> Marton
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--
Thanks,
Limin Wang
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