Asking decklink to render audio data seems to be based entirely on
the sample counts which completely disregards the timestamps
we pass to decklink. As a result, we need to explicitly check
for late buffers and drop them ourselves.
This is part of a much larger goal to always keep the frames we schedule to
decklink be always increasing. This also allows us to avoid using both the
sync and async frame display functions which aren't recomended to be used
together.
If the output timestatmsp is not always increasing decklink seems to hold
onto the latest frame and may cause a flash in the output if the played
sequence has a framerate less than the video output.
Scenario is play for N seconds, pause, flushing seek to some other position,
play again. Each of the play sequences would normally start at 0 with
the decklink time. As a result, the latest frame from the previous sequence
is kept alive waiting for it's timestamp to pass before either dropping
(if a subsequent frame in the new sequence overrides it) or displayed
causing the out of place frame to be displayed.
This is also supported by the debug logs from the decklink video sink
element where a ScheduledFrameCompleted() callback would not occur for
the frame until the above had happened.
It was timing related as to whether the frame was displayed based
on the decklink refresh cycle (which seems to be 16ms here),
when the frame was scheduled by the sink and the difference between
the 'time since vblank' of the two play requests (and thus start times
of scheduled playback).
https://bugzilla.gnome.org/show_bug.cgi?id=797130
The Decklink and GstAudioBaseSink APIs don't fit very well together,
which causes various problems due to inaccuracies in the clock
calculations and the actual ringbuffer and GStreamer's copy getting of
sync.
Problems are audio drop-outs and A/V sync getting wrong after
pausing/seeking.
https://bugzilla.gnome.org/show_bug.cgi?id=790114
HRESULT is unsigned long on Windows, but the Decklink headers define
it to 'int' on Linux. Confusingly, the defines that talk about the
possible return values for it use long constants. The easy fix would
be to change the linux/LinuxCOM.h header, but that's copied from the
decklink SDK.
Change the logging to always upcast to unsigned long while printing
HRESULT for consistency across platforms.
gstdecklinkvideosrc.cpp:425:7: warning: format '%x' expects argument of type 'unsigned int', but argument 8 has type 'HRESULT {aka long int}' [-Wformat]
[and so on]
gstdecklinkaudiosink.cpp:155:19: error: conflicting type attributes specified for 'virtual HRESULT GStreamerAudioOutputCallback::QueryInterface(const IID&, void**)'
In file included from /var/lib/jenkins/workspace/cerbero-cross-mingw32/workdir/mingw/w32/bin/../lib/gcc/i686-w64-mingw32/4.7.3/../../../../i686-w64-mingw32/include/objbase.h:153:0,
from /var/lib/jenkins/workspace/cerbero-cross-mingw32/workdir/mingw/w32/bin/../lib/gcc/i686-w64-mingw32/4.7.3/../../../../i686-w64-mingw32/include/ole2.h:16,
from /var/lib/jenkins/workspace/cerbero-cross-mingw32/workdir/mingw/w32/bin/../lib/gcc/i686-w64-mingw32/4.7.3/../../../../i686-w64-mingw32/include/windows.h:94,
from /var/lib/jenkins/workspace/cerbero-cross-mingw32/workdir/mingw/w32/bin/../lib/gcc/i686-w64-mingw32/4.7.3/../../../../i686-w64-mingw32/include/rpc.h:16,
from win/DeckLinkAPI.h:27,
from gstdecklink.h:35,
from gstdecklinkaudiosink.h:27,
from gstdecklinkaudiosink.cpp:25:
/var/lib/jenkins/workspace/cerbero-cross-mingw32/workdir/mingw/w32/bin/../lib/gcc/i686-w64-mingw32/4.7.3/../../../../i686-w64-mingw32/include/unknwn.h:67:25: error: overriding 'virtual HRESULT IUnknown::QueryInterface(const IID&, void**)'
(and many more)
https://ci.gstreamer.net/job/cerbero-cross-mingw32/6407/console
This reverts commit 845832263b.
The commit broke cross-mingw CI:
https://ci.gstreamer.net/job/GStreamer-master/8659/console
It seems that cross-mingw on Autotools and native-mingw on Meson
disagree about the size of HRESULT. Revert for now till I can
investigate the Meson side of things some more.
While gint64 and int64_t are always the same, clang does not agree with that.
/Applications/Xcode.app/Contents/Developer/usr/bin/make -C decklink
CXX libgstdecklink_la-gstdecklinkaudiosink.lo
gstdecklinkaudiosink.cpp:675:79: error: cannot initialize a parameter of type 'int64_t *' (aka 'long long *') with an rvalue of type 'gint64 *' (aka 'long *')
ret = buf->output->attributes->GetInt (BMDDeckLinkMaximumAudioChannels, &max_channels);
^~~~~~~~~~~~~
./linux/DeckLinkAPI.h:692:87: note: passing argument to parameter 'value' here
virtual HRESULT GetInt (/* in */ BMDDeckLinkAttributeID cfgID, /* out */ int64_t *value) = 0;
^
The driver has an internal buffer of unspecified and unconfigurable size, and
it will pull data from our ring buffer as fast as it can until that is full.
Unfortunately that means that we pull silence from the ringbuffer unless its
size is by conincidence larger than the driver's internal ringbuffer.
The good news is that it's not required to completely fill the buffer for
proper playback. So we now throttle reading from the ringbuffer whenever
the driver has buffered more than half of our ringbuffer size by waiting
on the clock for the amount of time until it has buffered less than that
again.
The ringbuffer's acquire() is too early, and ringbuffer's start() will only be
called after the clock has advanced a bit... which it won't unless we start
scheduled playback.
Otherwise we might start the scheduled playback before the audio or video streams are
actually enabled, and then error out later because they are enabled to late.
We enable the streams when getting the caps, which might be *after* we were
set to PLAYING state.
