On Wed, 20 May 2020, lance.lmw...@gmail.com wrote:
On Tue, May 19, 2020 at 09:06:59PM +0200, Marton Balint wrote:
pos47_full is not updated for every packet, and for unseekable inputs the
resync logic might simply skip some 0x47 sync bytes. In order to detect these
let's check for modulo instead of exact value.
Before modifying and returning directly, I considered whether pos is a multiple
of raw_packet_size, by the debug information, it's not true.
Not always, because sometimes there are 0x47 sync bytes in the packet
payload as well. But we siply ignore that case because of the return later
originated from your patch. Checking for modulo allows faster detection
and it also allows detection when UDP packets contain a single MPEGTS
packet.
Also it's possible
for the pos of two sync byte > 188/192/204 * n. If that's true, it's not correct
to look it as stats hit by the modulo logic.
I don't understand what you mean here.
Regards,
Marton
Also skip unrecognized sync byte distances instead of considering them as a
failure of detection. It only delays the detection of the new packet size.
Also note that AVIO only buffers a single packet (for UDP/mpegts, that usually
means 1316 bytes), so among every ten consecutive 188-byte MPEGTS packets there
will always be a seek failure, and that caused the old code to not find the 188
byte pattern across 10 consecutive packets.
Signed-off-by: Marton Balint <c...@passwd.hu>
---
libavformat/mpegts.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c
index a065c61c40..f2b2c05d86 100644
--- a/libavformat/mpegts.c
+++ b/libavformat/mpegts.c
@@ -2846,12 +2846,14 @@ static void reanalyze(MpegTSContext *ts) {
if (pos < 0)
return;
pos -= ts->pos47_full;
- if (pos == TS_PACKET_SIZE) {
+ if (pos % TS_PACKET_SIZE == 0) {
ts->size_stat[0] ++;
- } else if (pos == TS_DVHS_PACKET_SIZE) {
+ } if (pos % TS_DVHS_PACKET_SIZE == 0) {
ts->size_stat[1] ++;
- } else if (pos == TS_FEC_PACKET_SIZE) {
+ } if (pos % TS_FEC_PACKET_SIZE == 0) {
ts->size_stat[2] ++;
+ } else {
+ return;
}
ts->size_stat_count ++;
--
2.26.1
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--
Thanks,
Limin Wang
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