There is one rare case where calling handle_messages() more than once can cause a deadlock
in the video decoder element:
- sink pad thread starts the src pad task (gst_omx_video_dec_loop())
- _video_dec_loop() calls gst_omx_port_acquire_buffer() on dec_out_port
- blocks in gst_omx_component_wait_message() releasing comp->lock and comp->messages_lock
(initially, there are no buffers configured on that port, so it waits for OMX_EventPortSettingsChanged)
- the sink pad thread pushes a buffer to the decoder with gst_omx_port_release_buffer()
- _release_buffer() grabs comp->lock and sends the buffer to OMX, which consumes it immediately
- EmptyBufferDone gets called at this point, which signals _wait_message() to unblock
- the message from EmptyBufferDone is processed in gst_omx_component_handle_messages()
called from gst_omx_port_release_buffer()
- gst_omx_port_release_buffer releases comp->lock
- the src pad thread now gets to run, grabbing comp->lock while it exits from _wait_message()
- _acquire_buffer() calls the _handle_messages() on the next line after _wait_message(),
which does nothing (no pending messages)
- then it goes to "retry:" and calls _handle_messages() again, which also does nothing
(still no pending messages)
- scheduler switches to a videocore thread that calls EventHandler, informing us about the
OMX_EventPortSettingsChanged event that just arrived
- EventHandler graps comp->messages_lock, but not comp->lock, so it can run in parallel at
this point just fine.
- scheduler switches back to the src pad thread (which is in the middle of _acquire_buffer())
- the next _handle_messages() which is right before if (g_queue_is_empty (&port->pending_buffers))
processes the OMX_EventPortSettingsChanged
- the buffer queue is still empty, so that thread blocks again in _wait_message()
- the sink pad thread tries to acquire the next input port buffer
- _acquire_buffer() also blocks this thread in:
if (comp->pending_reconfigure_outports) { ... _wait_message() ... }
- DEADLOCK. gstreamer is waiting for omx to do something, omx waits for gstreamer to do something.
By removing those extra _handle_messages() calls, we can ensure that all the checks of
_acquire_buffer() will re-run. In the above case, after the scheduler switches back to
the middle of _acquire_buffer(), the code will enter _wait_message(), which will see that
there are pending messages and will return immediately, going back to "retry:" and
re-doing all the checks properly.
https://bugzilla.gnome.org/show_bug.cgi?id=741854
- append a glfilter just before fakesink
So that we get gltexture or eglimages
- propagate our EGLDisplay to the pipeline
see GST_QUERY_CONTEXT
- share our EGLContext with the iternal gl context
of the pipeline, see GST_QUERY_ALLOCATION
- use GstVideoGLTextureUploadMeta to upload
the incoming gltexture or eglimage to our gl texture
TODO: convert from GLESv1 to GLESv2
See https://bugzilla.gnome.org/show_bug.cgi?id=728940
Interlaced stream could make the decoder use two input frames to produce
one output frame causing the gstvideodecoder frame list to grow.
Assuming the video decoder output frame in display order rather than in
decoding order, this commit add a way to release frames with PTS less
than current output frame.
https://bugzilla.gnome.org/show_bug.cgi?id=730995
