This patch enhance the code path when an error is found when rendering a
buffer.
If the video meta doesn't contain a surface proxy or a surface, a warning
message is printed.
If the rendering backend fails, a error message is posted in the bus.
https://bugzilla.gnome.org/show_bug.cgi?id=749382
This fixes the regression introduced in 64acc74.
If a pad supports multiple set of capsfeatures, it needs to add
multiple equal structures with different feature sets to the caps.
Because caps structures with the same name but with a non-equal
set of caps features are not compatible.
Without this patch, playbin will autoplug xvimagesink instead of vaapisink.
https://bugzilla.gnome.org/show_bug.cgi?id=750095
This is a naïve approach to the calculation of the VA-API decoding latency. It
takes into consideration when the frame-rate has some insane value.
https://bugzilla.gnome.org/show_bug.cgi?id=740419
Otherwise wl_display_dispatch_queue() might prevent the pipeline from
shutting down. This can happen e.g. if the wayland compositor exits while
the pipeline is running.
Changes:
* renamed unlock()/unlock_stop() to unblock()/unblock_cancel() in gstvaapiwindow
* splitted the patch removing wl_display_dispatch_queue()
Signed-off-by: Víctor Manuel Jáquez Leal <victorx.jaquez@intel.com>
https://bugzilla.gnome.org/show_bug.cgi?id=747492https://bugzilla.gnome.org/show_bug.cgi?id=749078
This patch fixes several issues found when running the `make distcheck`
target:
- In commit c561b8da, the update of gstcompat.h in Makefile.am was
forgotten.
- In commit c5756a91 add the simple_encoder_source_h in EXTRA_DIST was
forgotten.
- vpx.build.stamp is not generated at all, only vpx.configure.stamp.
- The make target distcleancheck failed because some autogenerated files
were not handled with the DISTCLEANFILES variable.
Note: `make distcheck -jXX` is not currently supported.
Fix link when building plugin elements without HEVC support. e.g. don't
try to call into gst_vaapi_decoder_h265_set_alignment() if there is no
support HEVC enabled in libgstvaapi.
Also, drop disabled codecs from static template caps. Add the missing
HEVC static template caps into vaapidecodebin too.
In commit 97b768, a regression for GStreamer 1.2 was introduced:
GStreamer 1.2 doesn't check, in gst_buffer_pool_set_config() if the
config option is already set. This patch adds an inline function to
first verify if the option is not in the pool config berfore add it.
In order to reduce the noise, the query type log was downgrade from INFO to
DEBUG, and the shared display address log message is assigned to the object.
Fix regression introduced by bd866479, the query after decide_allocation()
always needs a pool in the first slot.
Signed-off-by: Víctor Manuel Jáquez Leal <victorx.jaquez@intel.com>
https://bugzilla.gnome.org/show_bug.cgi?id=748559
This a cosmetic refactor: gst_vaapidecode_internal_flush() removes its only
label; gst_vaapidecode_finish() is more readable and gst_vaapidecode_purge()
shares the same error message of gst_vaapidecode_internal_flush() when flush
fails.
Add the method gst_vaapidecode_purge(). This method releases the
flushed frames from the decoder.
This new method add more readablity to gst_vaapidecode_destroy()
When a frame is rejected by downstream, the message is logged twice. This
patch removes one of those logging messages.
Also, the reject of a frame doesn't mean an alarming error. This patch demotes
the log message from error to info.
This is a mirror of h265parse element in upstream gst-plugins-bad.
There could be additional patches but all should go to upstream.
This is for making development faster.
Note: vaapiparse_h265 will get build only for GStreamer version >= 1.4
The problem with this is that creating the filter causes the display to
be selected, and the caps query happens while linking the element. So,
if the downstream or upstream element is using a specific display
object, it won't be propagated correctly to the postproc as it already
has a display at this point.
https://bugzilla.gnome.org/show_bug.cgi?id=747945
vaapisink inherits from GstVideoSink, in order to use its functionality (such
as ::show-preroll-frame property), we should use its vmethod show_frame(),
rather than call ourselves render() and preroll().
This patch adds the signal ::handoff and the property signal-handoffs. If the
property is set TRUE, the signal ::handoff is emitted just after the buffer is
rendered.
Based on Zhao Halley <halley.zhao@intel.com>
https://bugzilla.gnome.org/show_bug.cgi?id=747905
We get one reference when the frame is passed to decode_handle_frame()
and create another one in gst_vaapi_decoder_push_frame().
Usually the frame is handled in gst_vaapidecode_push_decoded_frame().
Here the frame is always released twice:
gst_video_decoder_finish_frame() + gst_video_codec_frame_unref() or
gst_video_decoder_drop_frame() + gst_video_codec_frame_unref().
In gst_vaapidecode_reset_full() both references to the frame must be
released as well.
Signed-off-by: Víctor Manuel Jáquez Leal <vjaquez@igalia.com>
https://bugzilla.gnome.org/show_bug.cgi?id=743226
The support for GStreamer 1.0 has been obsoleted in 0.5.10 release.
GStreamer 1.2 is the a minimal requirement for building the gstreamer-vaapi.
This patch removes all the pre-processor conditional code compilation guarded
for gstreamer-1.0.
Thus, all the video converters were removed too.
https://bugzilla.gnome.org/show_bug.cgi?id=745728
Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne@intel.com>
Signed-off-by: Sreerenj Balachandran <sreerenj.balachandran@intel.com>
The purpose of gstcompat.h is to couple the API differences among
gstreamer-1.0 and gstreamer-0.10. Since gstreamer-0.10 is obsolete, the code
in this compatibility layer shall be removed.
Nevertheless, the gstcompat.h header should be kept, if new incompatibilites
appear in the future, but it shall live in gst/vaapi, not in gst-libs.
This patch removes the crumbs defined gstcompat.h and moves it to gst/vaapi.
In order to avoid layer violations, gstcompat.h includes sysdeps.h and all
the includes in gst/vaapi of sysdeps.h are replaced with gstcompat.h
https://bugzilla.gnome.org/show_bug.cgi?id=745728
Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne@intel.com>
Signed-off-by: Sreerenj Balachandran <sreerenj.balachandran@intel.com>
This patch only removes the support of gstreamer-1.0 in the autotools
scripts. No other files are touched.
In the automake file all the converters were deprecated.
https://bugzilla.gnome.org/show_bug.cgi?id=745728
Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne@intel.com>
Signed-off-by: Sreerenj Balachandran <sreerenj.balachandran@intel.com>
This library was intended to add the base classes for video decoders which
where not included in gstreamer-0.10.
Since the support of gstreamer-0.10 is deprecated those classes are not
required, thus the whole library is removed.
https://bugzilla.gnome.org/show_bug.cgi?id=745728https://bugzilla.gnome.org/show_bug.cgi?id=732666
Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne@intel.com>
This patch only removes the support of gstreamer-0.10 in the autotools
scripts. No other files are touched.
The configuration parameter --gstreamer-api was deleted since now it is always
auto-detected.
The verification of vmethod query in GstBaseSinkClass was removed since it was
added in gstreamer 0.10.35. The same case for GstVideoOverlayComposition and
its format flags.
The precious variable GST_PLUGIN_PATH was removed, while GST_PLUGIN_PATH_1_0
remained.
The automake files were changed accordingly.
Removed, in debian/control, the vaapiupload and vaapidownload descriptions.
https://bugzilla.gnome.org/show_bug.cgi?id=732666https://bugzilla.gnome.org/show_bug.cgi?id=745728
Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne@intel.com>
In GStremer v1.6 a new vmethod drain() was added in GstVideoDecoder
class. This patch implements this new method.
https://bugzilla.gnome.org/show_bug.cgi?id=742922
Signed-off-by: Víctor Manuel Jáquez Leal <vjaquez@igalia.com>
Signed-off-by: Sreerenj Balachandran <sreerenj.balachandran@intel.com>
Since in bug #745728 the support for GStreamer 1.0 is going to be dropped,
this patch removes the method reset() which was deprecated in GStreamer 1.2.
https://bugzilla.gnome.org/show_bug.cgi?id=742922
Signed-off-by: Víctor Manuel Jáquez Leal <vjaquez@igalia.com>
Signed-off-by: Sreerenj Balachandran <sreerenj.balachandran@intel.com>
Since GStreamer 1.2 the vmethod reset() in GstVideoDecoderClass was deprecated
and flush() was added.
This patch set the vmethod flush() if the installed GStreamer version is 1.2 or
superior. Otherwise, reset() is set.
v2: 1) In order to avoid symbol collision, the old method gst_vaapidecode_flush()
was renamed to gst_vaapidecode_internal_flush().
2) The new vmethod flush() always do a hard full reset.
v3: 1) Call gst_vaapidecode_internal_flush() first in flush() vmethod, in order to
gather all collected data with gst_video_decoder_have_frame()
https://bugzilla.gnome.org/show_bug.cgi?id=742922
Signed-off-by: Víctor Manuel Jáquez Leal <vjaquez@igalia.com>
Signed-off-by: Sreerenj Balachandran <sreerenj.balachandran@intel.com>
In commit 2f8c115 (vaapidecode: use the query virtual methods in 1.4)
a bug was introduced: when calling the parent's query function of the
src pad, the one of the sink pad is called instead. This patch fixes
this issue.
https://bugzilla.gnome.org/show_bug.cgi?id=746248
Sometimes, for example, when switching video streams but keeping
the same sink, the surface will be released after the decoder is
stopped and replaced. This caused a crash because the release
callback was called on an invalid pointer.
The patch adding an additional reference to the decoder object in the buffer.
https://bugzilla.gnome.org/show_bug.cgi?id=745189
Signed-off-by: Olivier Crete <olivier.crete@collabora.com>
Signed-off-by: Sreerenj Balachandran <sreerenj.balachandran@intel.com>
GstVideoDecoder, the base class of vaapidecode, added support for
pad queries as virtual methods. This patch enables the use of that
support, while keeping support for lower versions of gstreamer.
This patch is important because GstVideoDecoder takes care of other
queries that might be important in the pipeline managing.
v2: 1) rebase to current master
2) fix indentation with gst-indent
3) simplify the patch layout
4) fix the context query
5) initialise the filter to NULL
6) improve the query log message for gst-1.2
https://bugzilla.gnome.org/show_bug.cgi?id=744406
The vaapipostproc has a proxy flag to know if the the buffer pool is
already active. But this fails in some situations where it is needed
to renegotiate the buffer pool.
This patch removes that flag so the renegotiation is done whenever is
required.
https://bugzilla.gnome.org/show_bug.cgi?id=745535
The gst_video_colorimetry_to_string() function returns a newly created
string that represents the GstVideoColorimetry value. So, that needs
to be released after usage, in e.g. GST_DEBUG().
Add a "vaapidecodebin" element to vaapi plugins.
Child Elements: "vaapidecode ! queue ! vaapipostproc"
The Reasons for implementing a new bin element:
-- Help to Autoplug Hardware Accelerated Video Postprocessing element in playbin
with out any dependency to upstream gstreamer.
This is to overcome the *unacceptable* delay in upstream gstreamer to get new
features in. Eg: https://bugzilla.gnome.org/show_bug.cgi?id=687182.
Also customers using older gstreamer versions (1.2 and 1.4) will get the
benefit of autoplugging, hardware accelerated deinterlacing support etc.
-- Help to maintain a single thread implementation in vaapidecode.
This will result a dead-lock free vaapidecode in most of the cases.
More details here: https://bugzilla.gnome.org/show_bug.cgi?id=742605https://bugzilla.gnome.org/show_bug.cgi?id=745216
Because the decoder uses the thread from handle_frame() to decode a frame,
the src pad task creates an unsolveable AB-BA deadlock between
handle_frame() waiting for a free surface and decode_loop() pushing
decoded frames out.
Instead, have handle_frame() take responsibility for pushing surfaces,
and remove the deadlock completely. If you need a separate thread
downstream, you can insert a queue between vaapidecode and its downstream
to get one.
Another justification for the single thread implementation is,
there are two many point of locking in gstreamer-vaapi's current
implementation which can lead to deadlocks.
https://bugzilla.gnome.org/show_bug.cgi?id=742605
Signed-off-by: Simon Farnsworth <simon.farnsworth@onelan.co.uk>
Signed-off-by: Víctor Manuel Jáquez Leal <victorx.jaquez@intel.com>
Signed-off-by: Sreerenj Balachandran <sreerenj.balachandran@intel.com>
Improve check for upstream element that requires DMABUF buffer pool,
e.g. v4l2src element. In particular, make sure to traverse through
any additional capsfilter for instance.
Note: the traversal to the top-most upstream element could be made
more generic, but we are insofar only interested in supporting pipes
similar to v4l2src or v4l2src ! capsfilter, e.g. with an explicit
specification for a desired video camera format, or resolution.
The dmabuf allocator would close the DMABUF handle passed in the init
function gst_dmabuf_allocator_alloc(). So, we need to dup() it so that
to avoid a double close, ultimately in the underlying driver that owns
the DMABUF handle.
vaapidecode keeps an output state that use the format
GST_VIDEO_FORMAT_ENCODED, while it crafts a different src caps
for a correct negotiation.
I don't see the rational behind this decoupling, it looks like
unnecessary complexity. This patch simplify this logic keeping
in sync the output state and the src caps.
This patch improves the readability of the function
gst_vaapidecode_update_src_caps() and simplify its logic. Also,
the patch validates if the buffer pool has the configuration for
the GL texture upload meta, in order to set the caps feature
meta:GLTextureUpload. Otherwise, the I420 format is set back.
https://bugzilla.gnome.org/show_bug.cgi?id=744618
Signed-off-by: Víctor Manuel Jáquez Leal <victorx.jaquez@intel.com>
Signed-off-by: Sreerenj Balachandran <sreerenj.balachandran@intel.com>
When vaapidecode finishes the decoding of a frame and pushes it,
if, in the decide_allocation() method, it is determined if the
next element supports the GL texture upload meta feature, the
decoder adds the buffer's meta.
Nonetheless, in the same spirit of the commit 71d3ce4d, the
determination if the next element supports the GL texture upload
meta needs to check both the preferred caps feature *and* if the
allocation query request the API type.
This patch, first removes the unused variable need_pool, and
determines the attribute has_texture_upload_meta using the
preferred caps feature *and* the allocation query.
Also, the feature passed to GstVaapPluginBase is not longer
determined by has_texture_upload_meta, but by the computed
preferred one.
https://bugzilla.gnome.org/show_bug.cgi?id=744618
Signed-off-by: Víctor Manuel Jáquez Leal <victorx.jaquez@intel.com>
Signed-off-by: Sreerenj Balachandran <sreerenj.balachandran@intel.com>
Currently the src caps are set immediately after the sink caps are set, but in
that moment the pipeline might not fully constructed and the video sink has
not negotiated its supported caps and features. As a consequence, in many cases
of playback, the least optimized caps feature is forced. This is partially the
responsible of bug #744039.
Also, vaapidecode doesn't attend the reconfigure events from downstream,
which is a problem too, since the video sink can be changed with different
caps features.
This patch delays the src caps, setting them until the first frame arrives to
the decoder, assuming until that very moment the whole pipeline is already
negotiated. Particularly, it checks if the src pad needs to be reconfigured,
as a consequence of a reconfiguration event from downstream.
A key part of this patch is the new GstVaapiCapsFeature
GST_VAAPI_CAPS_FEATURE_NOT_NEGOTIATED, which is returned when the src pad
doesn't have a peer yet. Also, for a better report of the caps allowed
through the src pad and its peer, this patch uses gst_pad_get_allowed_caps()
instead of gst_pad_peer_query_caps() when looking for the preferred feature.
v3: move the input_state unref to close(), since videodecoder resets at
some events such as navigation.
v4: a) the state_changed() callback replaces the input_state if the media
changed, so this case is also handled.
b) since the parameter ref_state in gst_vaapidecode_update_src_caps() is
always the input_state, the parameter were removed.
c) there were a lot of repeated code handling the input_state, so I
refactored it with the function gst_vaapi_decode_input_state_replace().
https://bugzilla.gnome.org/show_bug.cgi?id=744618
Signed-off-by: Víctor Manuel Jáquez Leal <victorx.jaquez@intel.com>
Signed-off-by: Sreerenj Balachandran <sreerenj.balachandran@intel.com>
Working on bug #743687, I realized that vaapidecode always adds to its buffer
pool the config option GST_BUFFER_POOL_OPTION_VIDEO_GL_TEXTURE_UPLOAD_META if
the decide_allocation()'s query has GST_VIDEO_GL_TEXTURE_UPLOAD_META_API_TYPE.
Nevertheless, there are occasions where the query has the API type, but the
last negotiated caps don't have the feature meta:GstVideoGLTextureUploadMeta.
Under this contradiction, vaapidecode adds the GLTextureUploadMeta API to its
buffer pool configuration, and adds its buffer's meta to each output buffer,
even if the negotiated caps feature is memory:SystemMemory with I420 color
format.
This kind of output buffers chokes ClutterAutoVideosSink, since it uses a map
that relates caps <-> GL upload method. If it receives a buffer with color
format I420, it assumes that it doesn't have a texture upload meta, because
only those with RGB color format has it. Our buffers, with I420 format, say
that they have the upload meta too. In that case the mapped method is a dummy
one which does nothing. I reported this issue in bug #744039 (the patch,
obviously, was rejected).
This patch workarounds the problem: the buffer pool's configuration option
GST_BUFFER_POOL_OPTION_VIDEO_GL_TEXTURE_UPLOAD_META is set if and only if the
query has the GST_VIDEO_GL_TEXTURE_UPLOAD_META_API_TYPE *and* the negotiated
caps feature is meta:GstVideoGLTextureUploadMeta.
I have tested these patches with gst-master (1.5), gst-1.4 and gst-1.2 and
in all they seem to work correctly.
https://bugzilla.gnome.org/show_bug.cgi?id=744618
[adapted to fit current EGL changes]
Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne@intel.com>
Add support for GstVideoGLTextureOrientation modes. In particular,
add orientation flags to the GstVaapiTexture wrapper and the GLX
implementations. Default mode is that texture memory is laid out
with top lines first, left row first. Flags indicate whether the
X or Y axis need to be inverted.
Some frameworks (EFL) expect BGRA textures for storage. However,
adding support for that broadly into GStreamer framework implies
two kinds of hacks: (i) libgstgl helpers currently do not support
BGRA textures correctly, (ii) we need to better parse downstream
suggested caps and intersect them with what the VA plugin elements
can offer to them for GL texturing.
When multiple display servers are available, the glimagesink element
(from GStreamer 1.4) may not be able to derive a global display in
Wayland. Rather, a "window"-specific display is created. In this case,
the GstGLDisplay handle available through GstGLContext is invalid.
So, try to improve heuristics for display server characterisation in
those particular situations.
Add initial support for EGL through GstVideoGLTextureUploadMeta.
Fix gst_vaapi_ensure_display() to allocate a GstVaapiDisplay off the
downstream supplied GstGLContext configuration, i.e. use its native
display handle to create a GstVaapiDisplay of type X11 or Wayland ;
and use the desired OpenGL API to allocate the GstVaapiDisplayEGL
wrapper.
https://bugzilla.gnome.org/show_bug.cgi?id=741079
Sync video texture sizes to GstVideoGLTextureUploadMeta private date,
i.e. GstVaapiVideoMetaTexture, on a regular basis. In particular, we
now update the texture size from the GstVideoMeta, if any, or reset
to some defaults otherwise.
If a GstGLContext is supplied by the downstream element, then make
sure that the VA plugin element gets a compatible display to what
is requested by the GL context. e.g. re-allocate a VA/GLX display
when a GLX context is provided by the downstream element.
Record GL context supplied by downstream elements. This can be useful,
and further needed, to enforce run-time check that the GL context is
compatible for use by libgstvaapi. e.g. check that we don't create a
VA/GLX display for EGL/X11 contexts.
https://bugzilla.gnome.org/show_bug.cgi?id=725643
Original-path-by: Matthew Waters <ystreet00@gmail.com>
Reset the VA decoder after updating the base plugin caps, and most
importantly, after GstVideoDecoder negotiation. The reason behind
this is that the negotiation could trigger a last decide_allocation()
where we could actually derive a new GstVaapiDisplay to use from the
downstream element. e.g. GLX backend.
Query caps filtering should be always done on top of allowed caps instead
of existing fixed caps on a particular pad.
This fixes the mvc stream decoding when there is a base view(high profile)
and non-base view(stereo-high profile).
According to documentation[1] when receiving a GST_QUERY_CAPS
the return value should be all formats that this elements supports,
taking into account limitations of peer elements further downstream
or upstream, sorted by order of preference, highest preference first.
This patch add those limitations intersecting with the received
filter in the query. Also takes into account the already negotiated
caps. Also adds the processing of the query on the SRC pad.
1. http://gstreamer.freedesktop.org/data/doc/gstreamer/head/pwg/html/section-nego-getcaps.htmlhttps://bugzilla.gnome.org/show_bug.cgi?id=744406
Otherwise the condition could become true before the lock
is taken and the g_cond_signal() could be called
before the g_cond_wait(), so the g_cond_wait() is never
awoken.
https://bugzilla.gnome.org/show_bug.cgi?id=740645
GstVaapiVideoMemory quark is not needed any more, and the actual
implementation was already removed bfore the merge. i.e. this is
an oversight for a hunk that was not meant to be pushed.
Allow v4l2src element to connected to vaapipostproc or vaapisink when
"io-mode" is set to "dmabuf-import". In practice, this is a more likely
operational mode with uvcvideo. Supporting v4lsrc with "io-mode" set
to "dmabuf" could work, but with more demanding driver or kernel reqs.
Note: with GStreamer 1.4, v4l2src (gst-plugins-good) needs to be built
with --without-libv4l2.
https://bugzilla.gnome.org/show_bug.cgi?id=743635
Allow imports of v4l2 buffers into VA surfaces for further operation
with vaapi plugins, e.g. vaapipostproc or vaapiencode_* elements.
https://bugzilla.gnome.org/show_bug.cgi?id=735362
[fixed memory leaks, ported to new dma_buf infrastructure, cleanups]
Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne@intel.com>
Reword surface pool allocation helpers so that to allow for a simple
form, e.g. gst_vaapi_surface_pool_new(format, width, height); and a
somewhat more elaborated/flexible form with optional allocation flags
and precise GstVideoInfo specification.
This is an API/ABI change, and SONAME version needs to be bumped.
Add gst_vaapi_display_has_opengl() helper function to help determining
whether the display can support OpenGL context to be bound to it, i.e.
if the class is of type GST_VAAPI_DISPLAY_TYPE_GLX.
Make gst_vaapi_display_get_display_type() return the actual VA display
type. Conversely, add a gst_vaapi_display_get_class_type() function to
return the type of the GstVaapiDisplay instance. The former is used to
identify the display server onto which the application is running, and
the latter to identify the original object class.
GstVaapiTexture is a generic abstraction that could be moved to the
core libgstvaapi library. While doing this, no extra dependency needs
to be added. This means that a GstVaapitextureClass is now available
for any specific code that needs to be added, e.g. creation of the
underlying GL texture objects, or backend dependent ways to upload
a surface to the texture object.
Generic OpenGL data types (GLuint, GLenum) are also replaced with a
plain guint.
https://bugzilla.gnome.org/show_bug.cgi?id=736715
The gst_vaapi_texture_put_surface() function is missing a crop_rect
argument that would be used during transfer for cropping the source
surface to the desired dimensions.
Note: from a user point-of-view, he should create the GstVaapiTexture
object with the cropped size. That's the default behaviour in software
decoding pipelines that we need to cope with.
This is an API/ABI change, and SONAME version needs to be bumped.
https://bugzilla.gnome.org/show_bug.cgi?id=736712
dvbsuboverlay signals no subtitles present by not setting
GstVideoOverlayCompositionMeta on a buffer.
Detect this, and remove subtitles whenever we have no overlay composition to
hand.
Signed-off-by: Simon Farnsworth <simon.farnsworth@onelan.co.uk>
Otherwise restarting may fail because the state of vaapipluginbase and
vaapipostproc don't match. e.g. gst_vaapipostproc_set_caps() will skip
initailization and not call gst_vaapi_plugin_base_set_caps()
Make sure that the GstVaapiPluginBase instance receives the new src
pad caps whenever they get updated from within the GstVaapiDecoder
decode routines.
This also ensures that downstream elements receive correctly sized
SW decoded buffers if needed.
https://bugs.tizen.org/jira/browse/TC-114
Split GstVideoDecoder::set_format() handler to first update the sink
pad caps and reset the active VA decoder instance based on those, and
then update the src pad caps whenever possible, e.g. when the caps
specify a valid video resolution.
In some occasions, a buffer pool is created for pre-initialization
purposes regardless of whether a valid image size is available or
not. However, during actual decode stage, the vaapidecode element
is expected to update the srcpad caps with the new dimensions, thus
also triggering a reset of the underlying bufferpool.
