Steve Lhomme pushed to branch 3.0.x at VideoLAN / VLC
Commits:
292c4756 by Russell Greene at 2023-05-10T07:59:08+00:00
demux: ts: fix seek issues in some streams
Fixes #27646
Currently, VLC's SeekToTime algorithm for MPEG Transport Streams involves a
number of arbitrary restrictions when searching for PCR timestamps. It rejects
packets whose PIDs are not included in the current program and it also rejects
packets that do not contain a payload as well as packets that do not contain
the payload start indicator.
However, per the official documentation describing the MPEG-TS format (ITU-T
H.222.0 version 7.0) there are no such restrictions placed on where the PCR can
be set (nor are there official recommendations on it). It specifies that the
PCR is part of the adaptation field, and it's perfectly valid to make a
packet with "adaptation field only" and no payload.
References:
* Chapter 2.4.3.3:
- Table 2-3: "The transport packets with PID values 0x0000, 0x0001, and
0x0010-0x1FFE are allowed to carry a PCR."
- Table 2-5: "'10': Adaptation_field only, no payload"
- Table 2-6: PCR is an optional part of the adaptation field, see 2.4.3.5
for details
* Chapter 2.4.4.10: See PCR_PID
Our observation of the existing algorithm is that the restrictions on the
contents of the packet and the type of stream are intended more for the
subsequent "ParsePESHeader" call, as those restrictions make sense
when using that mechanism as a fallback method to find the PCR. However, by
including these restrictions prior to the line that gets the PCR if
"p_pmt->i_pid_pcr == i_pid", it's rejecting packets that could
have otherwise provided PCR information.
By moving the restrictions to later within the algorithm, we allow for any
packets containing a matching PCR_PID to potentially supply that PCR
information. This resolves seeking issues on any video that was created with
PCRs set on packets without payloads.
(cherry picked from commit 80c4515fac992580486967c724ef56d8cbfd0246)
Signed-off-by: Francois Cartegnie <fcvlc...@free.fr>
- - - - -
1 changed file:
- modules/demux/mpeg/ts.c
Changes:
=====================================
modules/demux/mpeg/ts.c
=====================================
@@ -1946,11 +1946,7 @@ static int SeekToTime( demux_t *p_demux, const ts_pmt_t
*p_pmt, int64_t i_scaled
int i_pid = PIDGet( p_pkt );
ts_pid_t *p_pid = GetPID(p_sys, i_pid);
- if( i_pid != 0x1FFF && p_pid->type == TYPE_STREAM &&
- ts_stream_Find_es( p_pid->u.p_stream, p_pmt ) &&
- (p_pkt->p_buffer[1] & 0xC0) == 0x40 && /* Payload start but not
corrupt */
- (p_pkt->p_buffer[3] & 0xD0) == 0x10 /* Has payload but is
not encrypted */
- )
+ if( i_pid != 0x1FFF )
{
unsigned i_skip = 4;
if ( p_pkt->p_buffer[3] & 0x20 ) // adaptation field
@@ -1963,7 +1959,11 @@ static int SeekToTime( demux_t *p_demux, const ts_pmt_t
*p_pmt, int64_t i_scaled
}
}
- if( i_pcr == -1 )
+ if( i_pcr == -1 && p_pid->type == TYPE_STREAM &&
+ ts_stream_Find_es( p_pid->u.p_stream, p_pmt ) &&
+ (p_pkt->p_buffer[1] & 0xC0) == 0x40 && /* Payload start but
not corrupt */
+ (p_pkt->p_buffer[3] & 0xD0) == 0x10 /* Has payload but
is not encrypted */
+ )
{
vlc_tick_t i_dts = -1;
vlc_tick_t i_pts = -1;
View it on GitLab:
https://code.videolan.org/videolan/vlc/-/commit/292c4756f79a9bd3097eaef234737e274bde3f68
--
View it on GitLab:
https://code.videolan.org/videolan/vlc/-/commit/292c4756f79a9bd3097eaef234737e274bde3f68
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