Fixes issue 1520.

* cus/stable:
  ffplay: if there is no audio stream, use external clock by default
  ffplay: use get_master_sync_type where necessary
  ffplay: add get_master_sync_type function
  ffplay: only check external clock if current frame serial matches the displayed frame serial
  ffplay: add serial field to PacketQueue entry and populate it
  ffplay: fix external time sync mode
  ffplay: initialize audio and video pts drift
  ffplay: fix nosync threshold check in synchronize_audio
  ffplay: use framedrop by default when sync is not done to video
Merged-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Marton Balint <cus@passwd.hu>
Reviewed-by: Kieran Kunhya <kierank@ob-encoder.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

This commit introduces a new AVPacket side data type:
AV_PKT_DATA_STRINGS_METADATA. Its main goal is to provide a way to
transmit the metadata from the AVFilterBufferRef up to the AVFrame. This
is at the moment "only" useful for lavfi input from libavdevice:
lavd/lavfi only outputs packets, and the metadata from the buffer ref
kept in its context needs to be transmitted from the packet to the frame
by the decoders. The buffer ref can be destroyed at any time (along with
the metadata), and a duplication of the AVPacket needs to duplicate the
metadata as well, so the choice of using the side data to store them was
selected.

Making sure lavd/lavfi raises the metadata is useful to allow tools like
ffprobe to access the filters metadata (it is at the moment the only
way); ffprobe will now automatically show the AVFrame metadata in any
customizable output format for users. API users will also be able to
access the AVFrame->metadata pointer the same way ffprobe does
(av_frame_get_metadata).

All the changes are done in this single commit to avoid some memory
leaks: for instances, the changes in lavfi/avcodec.c are meant to
duplicate the metadata from the buffer ref into the AVFrame. Unless we
have an internal way of freeing the AVFrame->metadata automatically, it
will leak in most of the user apps. To fix this problem, we introduce
AVCodecContext->metadata and link avctx->metadata to the current
frame->metadata and free it at each decode frame call (and in the codec
closing callback for the last one). But doing this also means to update
the way the tiff decoder already handles the AVFrame->metadata (it's the
only one decoder with frame metadata at the moment), by making sure it
is not trying to free a pointer already freed by the lavc internals.

The lavfi/avcodec.c buffer ref code is based on an old Thomas Kühnel
work, the rest of the code belongs to the commit author.
Signed-off-by: Thomas Kühnel <kuehnelth@googlemail.com>
Signed-off-by: Clément Bœsch <ubitux@gmail.com>

Otherwise playing the video could be much slower than realtime if the system
can't decode or display the frames fast enough.
Signed-off-by: Marton Balint <cus@passwd.hu>

We should make decisions based on the real sync type. This also simplifies
the code.
Signed-off-by: Marton Balint <cus@passwd.hu>

The real av_sync_type may be different to VideoState->av_sync_type, because the
required audio or video stream for audio or video clock may not be available.
We will use a function to query the real av_sync_type which is used for
determining the master clock.
Signed-off-by: Marton Balint <cus@passwd.hu>

This way we avoid updating the external clocks with timestamps beloging to
frames before seek.
Signed-off-by: Marton Balint <cus@passwd.hu>

The purpose of the serial field is to accompany the decoded data during the
decoding process to know if the decoded data belongs to the data stream after
the latest packet queue flush.
Signed-off-by: Marton Balint <cus@passwd.hu>

We now initalize the external clock to 0 and, we use the system clock to
regulate the timings of audio and video in external clock sync mode.  We
recover from external clock sync loss, when the delay to external clock is
bigger than AV_NOSYNC_THRESHOLD.
Signed-off-by: Marton Balint <cus@passwd.hu>

This makes sensible audio and video clock values even before displaying the
first frame.
Signed-off-by: Marton Balint <cus@passwd.hu>

Signed-off-by: Marton Balint <cus@passwd.hu>

When using external sync, framedrop is perfectly fine.
Signed-off-by: Marton Balint <cus@passwd.hu>

* qatar/master:
  fate: adpcm: cosmetics: Sort test entries
  fate: adpcm: Add dependencies
  svq3: cosmetics: Drop useless parentheses

Conflicts:
	libavcodec/svq3.c
Merged-by: Michael Niedermayer <michaelni@gmx.at>

* commit 'a7d2861d':
  svq3: K&R formatting cosmetics
  fate: Introduce ENCMUX macro for tests that require encoders and a muxer
  ffv1: Add missing #includes to header file

Conflicts:
	libavcodec/ffv1.h
	libavcodec/svq3.c
Merged-by: Michael Niedermayer <michaelni@gmx.at>

* commit '2d09b36c':
  doc/platform: Add info on shared builds with MSVC
  doc/platform: Move a caveat down to the notes section
  ARM: reinstate optimised intmath.h
  ffv1: update to ffv1 version 3

Conflicts:
	doc/platform.texi
	libavcodec/ffv1.c
	libavcodec/ffv1.h
	libavcodec/ffv1dec.c
	libavcodec/ffv1enc.c
Merged-by: Michael Niedermayer <michaelni@gmx.at>

* commit '4a2a4524':
  ffv1: propagate errors

Conflicts:
	libavcodec/ffv1dec.c
	libavcodec/ffv1enc.c
Merged-by: Michael Niedermayer <michaelni@gmx.at>

* commit '71f7b22d':
  ffv1: split decoder and encoder

Conflicts:
	libavcodec/Makefile
	libavcodec/ffv1.c
	libavcodec/ffv1.h
	libavcodec/ffv1dec.c
	libavcodec/ffv1enc.c
Merged-by: Michael Niedermayer <michaelni@gmx.at>

This is not based on lucas work due to code divergence (its less work this way
than trying to merge from a split based on 2 years outdated code)
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

* commit 'd15c21e5':
  avutil: Add a copy of ff_sqrt_tab back into avutil to restore ABI compatibility
  avutil: make some tables visible again
  avutil: remove inline av_log2 from public API
  celp_math: rename ff_log2 to ff_log2_q15

Conflicts:
	libavutil/libavutil.v
Merged-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

The libav code depends on mp3 startcodes only occuring at the start of
frames. But there is nothing in mp3 that prevents them occuring elsewhere
by chance. Thus the code would fail randomly, the new code searches for 3
consecutive valid frames. If this turns out to be still insufficient the
number can be raised further, or additional checks added.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

This should also fix CID717889.

Should fix CID733781 and CID733782.

Should fix CID733779 and CID733780.

Fixes CID703688
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Fixes CID733715
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Fixes CID732199
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>