Matroska requires pts to be >= 0 with a slight exception:
It has a mechanism to deal with codec delay, i.e. with
the data added at the beginning that does not correspond
to actual input data and should be discarded by the player.
Only the audio actually intended to be output needs to have
a timestamp >= 0.
In order to avoid unnecessary timestamp shifting, this patch
allows muxers to inform the shifting code about this so that
it can take it into account.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Mediates between old-style (de)muxers and new-style callers. Will be
removed once all the (de)muxers are converted to the new API.
Signed-off-by: James Almer <jamrial@gmail.com>
Peeking into the muxing queue can improve the estimate of
the lowest timestamp needed for avoid_negative_ts in case
the lowest timestamp is in a packet other than the first packet
to be muxed.
This fixes tickets #4536 and #5784 as well as the output from
the matroska-avoid-negative-ts FATE-test.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
write_packet() has code to shift the packets timestamps
to make them nonnegative or even make them start at ts zero;
this code inspects every packet that is written and if a packet
with negative timestamp (whether this is dts or pts depends upon
another flag; basically: Matroska uses pts, everyone else dts)
is encountered, this is offset to make the timestamp zero.
All further packets will be offset accordingly (with the offset
converted according to the streams' timebases).
This is based around an assumption, namely that the timestamps
are indeed non-decreasing, so that the first packet with negative
timestamps is the first packet with timestamps. This assumption
is often fulfilled given that the default interleavement function
by default interleaves per dts; yet there are scenarios in which
it may not be fulfilled:
a) av_write_frame() instead of av_interleaved_write_frame() is used.
b) The audio_preload option is used.
c) When the timestamps that are made nonnegative/zero are pts
(i.e. with Matroska), because the packet with the smallest dts
is not necessarily the packet with the smallest pts.
d) Possibly with custom interleavement functions.
In these cases the relative sync of the first few packet(s) is offset
relative to the later packets. This contradicts the documentation
("When shifting is enabled, all output timestamps are shifted by
the same amount").
Therefore this commit changes this: As soon as the first packet
with valid timestamps is output, it is checked and recorded whether
the timestamps need to be shifted. Further packets are no longer
checked for needing to be offset; instead they are simply offset.
In the cases above this leads to packets with negative timestamps
(and the appropriate warnings) instead of desync. This will mostly
be fixed in the next commit.
This commit also factors handling the avoid_negative_ts stuff out
of write_packet() in order to be able to return immediately.
Tickets #4536 and #5784 as well as the matroska-avoid-negative-ts-test
are examples of c); as has been said, some timestamps are now negative,
yet the ref file update does not show it because ffmpeg.c sanitizes
the timestamps (-copyts disables it; ffprobe and mkvinfo also show
the original timestamps).
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This assert is based upon the wrong assumption that
the noninterleaved codepath is never used; if it is used,
max_interleave_delta is irrelevant. It furthermore
ignores audio_preload.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Up until now, we had a PacketList structure which is actually
a PacketListEntry; a proper PacketList did not exist
and all the related functions just passed pointers to pointers
to the head and tail elements around. All these pointers were
actually consecutive elements of their containing structs,
i.e. the users already treated them as if they were a struct.
So add a proper PacketList struct and rename the current PacketList
to PacketListEntry; also make the functions use this structure
instead of the pair of pointers.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This function is quite small (96B with GCC 11.2 on x64 Ubuntu 21.10
at -O3), making it more economical to duplicate it into libavformat
instead of exporting it as avpriv: Doing so saves 2x24B in .dynsim,
2x16B in .dynstr, 2x2B .gnu.version, 24B in .rela.plt, 16B in .plt,
16B in .plt.sec (if enabled), 4B .gnu.hash; besides the actual
duplicated code this also adds 2x8B .eh_frame_hdr and 24B .eh_frame.
In other words: Duplicating is neutral size-wise (it is also presumed
neutral for other systems). Given that it avoids the runtime
overhead of dynamic symbols, it is advantageouos to duplicate the
function.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This removes one of the last usages of sizeof(AVPacket)
in the generic muxing code.
Reviewed-by: Tomas Härdin <tjoppen@acc.umu.se>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
For most check_bitstream() functions this just avoids having
to dereference s->streams[pkt->stream_index] themselves; but for
meta-muxers it will allow to forward the packet to stream with
a different stream_index (belonging to a different AVFormatContext)
without using a spare packet.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Reviewed-by: James Almer <jamrial@gmail.com>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
It avoids branches lateron and will allow to easily avoid the overhead
of the linked list currently in use in case there is only one stream.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
The documentation of said packet ("Every user has to ensure that
this packet is blank after using it") perfectly fits how we use said
packet in the generic muxing code. Better than the documentation of pkt.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Currently the interleave_packet functions use a packet for
a new packet to be interleaved (may be NULL if there is none) and
a packet for output; said packet is always a stack packet in
interleaved_write_packet(). But all the interleave_packet functions
in use first move the packet to the packet list and then check whether
a packet can be returned, i.e. the effective lifetime of the new packet
ends before the packet for output is touched.
So one can use one packet both for input and output by adding a new
parameter that indicates whether there is a packet to add to the packet
list; there is just one complication: In case the muxer is flushed,
there is no packet available. This can be solved by reusing one of
the packets from AVFormatInternal. They are currently unused when
flushing in av_interleaved_write_frame().
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
The BSF API treats such packets as signalling EOF and therefore
such a packet might corrupt the BSF state. In such a case,
the guarantee that av_interleaved_write_frame() always frees
the packet is not upheld.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Do this by allocating AVStream together with the data that is
currently in AVStreamInternal; or rather: Put AVStream at the
beginning of a new structure called FFStream (which encompasses
more than just the internal fields and is a proper context in its own
right, hence the name) and remove AVStreamInternal altogether.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This gets rid of ugly "->internal" and is in preparation for removing
AVStreamInternal altogether.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Do this by allocating AVFormatContext together with the data that is
currently in AVFormatInternal; or rather: Put AVFormatContext at the
beginning of a new structure called FFFormatContext (which encompasses
more than just the internal fields and is a proper context in its own
right, hence the name) and remove AVFormatInternal altogether.
The biggest simplifications occured in avformat_alloc_context(), where
one can now simply call avformat_free_context() in case of errors.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This gets rid of ugly "->internal" and is in preparation for removing
AVFormatInternal altogether.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Up until now, ff_write_chained() copied the packet (manually, not with
av_packet_move_ref()) from a packet given to it to a stack packet whose
timing and stream_index is then modified before being sent to another
muxer via av_(interleaved_)write_frame(). Afterwards it is intended to
sync the fields of the packet relevant to freeing again; yet this only
encompasses buf, side_data and side_data_elems and not the newly added
opaque_ref. The other fields are not synced so that the returned packet
can have a size > 0 and data != NULL despite its buf being NULL (this
always happens in the interleaved codepath; before commit
fe251f77c8 it could also happen in the
noninterleaved one). This leads to double-frees if the interleaved
codepath is used and opaque_ref is set.
This commit therefore changes this by directly reusing the packet
instead of a spare packet. Given that av_write_frame() does not
change the packet given to it, one only needs to restore the timing
information to return it as it was; for the interleaved codepath
it is not possible to do likewise*, because av_interleaved_write_frame()
takes ownership of the packets given to it and returns blank packets.
But precisely because of this users of the interleaved codepath
have no legitimate expectation that their packet will be returned
unchanged. In line with av_interleaved_write_frame() ff_write_chained()
therefore returns blank packets when using the interleaved codepath.
Making the only user of said codepath compatible with this was trivial.
*: Unless one wanted to create a full new reference.
Reviewed-by: Lynne <dev@lynne.ee>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
An AVStream's internal AVCodecContext is pretty much unused for muxing:
The only place where any of its fields are set is
avformat_transfer_internal_stream_timing_info() where its time base is
set based upon the desired output format. The max_b_frames field is
never set at all, so don't read it in mux.c.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
The next pointer is kept at the end for backwards compatability until the
major bump, when it should ideally be moved at the front.
Signed-off-by: James Almer <jamrial@gmail.com>
And make it const, so the caller doesn't attempt to change it.
ff_get_muxer_ts_offset() should be used to get the muxer timestamp offset.
Signed-off-by: James Almer <jamrial@gmail.com>
Factor out the code into a separate muxing-specific function.
Stop accessing the deprecated AVStream-embedded codec context, use the
average framerate (if specified) instead.
Those are private fields, no reason to have them exposed in a public
header. Since there are some (semi-)public fields located after these,
even though this section is supposed to be private, keep some dummy
padding there until the next major bump to preserve ABI compatibility.
