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[FFmpeg-devel] lavf/mpegtsdec: fix AVPacket.pos when FEC/DVHS/BDAV data is present

Message ID 20180831052030.86840-1-rodger.combs@gmail.com
State Withdrawn, archived
Headers show

Commit Message

Rodger Combs Aug. 31, 2018, 5:20 a.m. UTC 
We previously set pos to several bytes before the actual packet sync byte,
which meant that seeking to pos relied on resync working, which can fail
if there are 0x47 bytes in the additional data.

The resync issue should probably also be fixed separately.
---
 libavformat/mpegts.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

Comments

Hendrik Leppkes Aug. 31, 2018, 9:47 a.m. UTC | #1 
On Fri, Aug 31, 2018 at 7:28 AM Rodger Combs <rodger.combs@gmail.com> wrote:
>
> We previously set pos to several bytes before the actual packet sync byte,
> which meant that seeking to pos relied on resync working, which can fail
> if there are 0x47 bytes in the additional data.
>
> The resync issue should probably also be fixed separately.
> ---
>  libavformat/mpegts.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c
> index a5cb17ac16..881708b42d 100644
> --- a/libavformat/mpegts.c
> +++ b/libavformat/mpegts.c
> @@ -2581,10 +2581,9 @@ static int handle_packet(MpegTSContext *ts, const uint8_t *packet)
>
>      } else {
>          int ret;
> -        // Note: The position here points actually behind the current packet.

This comment still applies, which is why we substract the packet size
from the position. Probably shouldn't remove it.

>          if (tss->type == MPEGTS_PES) {
>              if ((ret = tss->u.pes_filter.pes_cb(tss, p, p_end - p, is_start,
> -                                                pos - ts->raw_packet_size)) < 0)
> +                                                pos - TS_PACKET_SIZE)) < 0)
>                  return ret;
>          }
>      }

For the record, my code currently relies on AVPacket.pos pointing to
the actual start of BDAV packets from Blu-ray m2ts files so the
position lines up with the Blu-ray playlist metadata, which also has
positions for seamless clip changes etc.
I don't know how all the other cases work, but at least for BDAV the
current value is correct.

- Hendrik
diff mbox

Patch

diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c
index a5cb17ac16..881708b42d 100644
--- a/libavformat/mpegts.c
+++ b/libavformat/mpegts.c
@@ -2581,10 +2581,9 @@  static int handle_packet(MpegTSContext *ts, const uint8_t *packet)
 
     } else {
         int ret;
-        // Note: The position here points actually behind the current packet.
         if (tss->type == MPEGTS_PES) {
             if ((ret = tss->u.pes_filter.pes_cb(tss, p, p_end - p, is_start,
-                                                pos - ts->raw_packet_size)) < 0)
+                                                pos - TS_PACKET_SIZE)) < 0)
                 return ret;
         }
     }