Expose the internally used methods for locking and unlocking the object. Pass
the access mode to the unlock function for extra checks and because we need it
for the EXCLUSIVE locks.
Make some new defines to specify the desired locking.
Add a new EXCLUSIVE lock mode which will increment the shared counter. Objects
with a shared counter > 1 will not be lockable in WRITE mode.
Make GstSeekFlag to GstSegmentFlag conversion explicit, and
set only those seek flags in the segment flags which are
mapped. This makes sure we don't have extraneous flags
littering our segment flag field, which also fixes the
debug printing/serialisation of segment events in the
debug log.
Make a gst_buffer_append_region() function that allows you to append a memory
region from one buffer to another. This is a more general version of
gst_buffer_append().
Some tag parsers and writers use same datetime format based on ISO 8601.
We can reduce some code by creating some general functions for it.
API: gst_date_time_to_iso8601_string()
API: gst_date_time_new_from_iso8601_string()
https://bugzilla.gnome.org/show_bug.cgi?id=678031
Let's keep it simple for now:
gst_toc_setter_reset_toc() -> gst_toc_setter_reset()
gst_toc_setter_get_toc_copy() -> removed
gst_toc_setter_get_toc() -> returns a ref now
gst_toc_setter_get_toc_entry_copy() -> removed,
use TOC functions instead
gst_toc_setter_get_toc_entry() -> removed,
use TOC functions instead
gst_toc_setter_add_toc_entry() -> removed,
to avoid problems with (refcount-dependent)
writability of TOC; use TOC functions instead
They can be used to select snapping behavior (to previous, next, or
nearest location, where relevant) when seeking.
The seeking implementation (eg, demuxer) may currently ignore some
or all of these flags.
It's only used internally, most other users will likely
want to use gst_registry_find_plugin() directly instead
(and if not, they can easily walk the list and doing the
strcmp themselves).
This is an implementation detail really, and it's not
clear what anyone would do with this. It's unused as
far as I'm aware, so just remove it for now.
Rename the _get_value_array() functions to _get_g_value_array() and reintroduce
the former to operate on plain unboxed c datatypes (like in 0.10). The _g_value
variants are for bindings while the _value ones are more suited to processing
in elements.
Add gst_element_class_{add,set}_metadata() variants for static strings,
so we can avoid unnecessary g_strdup()s.
API: gst_element_class_add_static_metadata()
API: gst_element_class_set_static_metadata()
Remove GST_MAJORMINOR and replace it by GST_API_VERSION
Also set GST_VERSION_{MAJOR,MINOR,MICRO,NANO} explicitely
now.
All versions are at 1.0.0 now for the release soon but
API/ABI can still change until the 1.0.0 release.
Next release versions until 1.0.0 will be 0.10.9X and
these will be release candidates. GST_VERSION_* will
nonetheless stay at 1.0.0.0.
gst_buffer_take_memory -> gst_buffer_insert_memory because insert is what the
method does.
Make all methods deal with ranges so that we can replace, merge, remove and map
a certain subset of the memory in a buffer. With the new methods we can make
some code nicer and reuse more code. Being able to deal with a subset of the
buffer memory allows us to optimize more cases later (most notably RTP headers
and payload that could be in different memory objects).
Make some more convenient macros that call the more generic range methods.
Add gst_buffer_append() which appends the memory blocks from one buffer to
another. Remove the old inefficient _merge() and _join() methods which forced a
premature memcpy in most cases.
Remove the _is_span() and _span() methods they are not needed anymore now that
we can _append(). Merging and spanning will be delayed until mapping or maybe
not at all when the element can deal with the different memory blocks.
Rename _do_simplify() to _simplify(). The name was introduced as a replacement
method for a deprecated method but we can now rename it again.
Fix some docs.
Rework some caps operations so they don't rely on writable caps but instead take
ownership of the input caps and do _make_writable() only when needed.
Remove some const from caps functions, it does not make much sense for
refcounted objects and does not allow us to return a refcount to the const input
caps.
Rework the base classes fixate vmethods to not operate on the caps in-place.
All this saves us around 30% of caps and structure copy and new operations.
There isn't really any need to provide public API for that. It's not
used anywhere in practice, and we aim to provide an API that works
for GstCaps, not some kind of generic set manipulation API based on
GValue. Making this private also makes it easier to optimise this
later. We can always put it back if someone actually needs it.
We introduced our own when GLib didn't want to add a GType
for GError. But now that there is one, we can use GLib's
unconditionally and remove our version.
Make the memory object simply manage the data pointer and the maxsize and move
the offset and size handling to common functionality.
Use the READONLY flag to set a readonly lock.
Remove the data and size fields from the unmap method. We need an explicit
resize operation instead of using the unmap function.
Make internal helper lock and unlock functions.
Update unit test and users of the old API.
Which we had to add because GLib didn't have it
back in the day. Port everything to plain old
G_TYPE_DATE, which is also a boxed type. Ideally
we'd just use GDateTime for everything, but it
doesn't support not setting some of the fields
unfortuntely (which would be very useful for
tag handling in general, if we could express
2012-01 for example).
https://bugzilla.gnome.org/show_bug.cgi?id=666351
Count how many mappings are currently active and also with what access pattern.
Update the design doc with restrictions on the access patterns for nested
mappings.
Check if nested mappings obey the access mode restrictions of the design doc.
Add various unit tests to check the desired behaviour.
There are many good use cases for GstIndex and we want
to add it back again in some form, but possibly not with
the current API, which is very powerful (maybe too powerful),
but also a bit confusing. At the very least we'd need to
make the API bindings-friendly.
Add a GstControlBinding class. This is a preparation for making the
controlsources generate double valued control curves and do the gparamspec
mapping in the control binding. Now the API in GstObject is again mostly
for convenience.
Move most of the code to a GstTimedValueControlSource. Split out the trigger
'interpolation mode' to a new control source class. Move tests and examples to
new api. Update docs.
Fixes#610338
An extra application preset dir help to organize presets created for special
purposes. Fixes#660760
API: gst_preset_set_app_dir(), gst_preset_get_app_dir()
Rename the last-buffer property to last-sample and make it return the new
GstSample type so that we can include caps and timing info in one nice bundle.
Add _full variants of the pad function setters that take a destroy notify.
Make some macros that make the old method name pass NULL to this new
function.
Add the pad mode to the activate function so that we can reuse the same function
for all activation modes. This makes the core logic smaller and allows for some
elements to make their activation code easier. It would allow us to add more
scheduling modes later without having to add more activate functions.
Remove the getcaps function on the pad and use the CAPS query for
the same effect.
Add PROXY_CAPS to the pad flags. This instructs the default caps event and query
handlers to pass on the CAPS related queries and events. This simplifies a lot
of elements that passtrough caps negotiation.
Make two utility functions to proxy caps queries and aggregate the result. Needs
to use the pad forward function instead later.
Make the _query_peer_ utility functions use the gst_pad_peer_query() function to
make sure the probes are emited properly.
Make that implizit with attaching/detaching controlsources. This is a lot easier
and has less invalid state (controlled property without control source).
No one but filesrc used that API. Should probably be replaced by
requiring an "uri" property instead, and then objects can do a
notify on that. Also removed interface structure padding, it's
not needed.
This make the controller even more lightweight (no extra object, no extra lock,
less indirections). For object that don't use the controller the only 'overhead'
is a 3 unused fields in the gst_object structure.
The fixate caps function was not used externally and we have vmethods in the
base classes where it is needed.
Update some docs.
simplify some fixate functions in the base classes. Also pass the untruncated
caps to the vmethod.
Better now than later in the cycle. These might come in handy:
sed -i -e 's/GstProbeReturn/GstPadProbeReturn/g' `git grep GstProbeReturn | sed -e 's/:.*//' | sort -u`
sed -i -e 's/GST_PROBE_/GST_PAD_PROBE_/g' `git grep GST_PROBE_ | sed -e 's/:.*//' | sort -u`
sed -i -e 's/GstProbeType/GstPadProbeType/g' `git grep GstProbeType | sed -e 's/:.*//' | sort -u`
No one uses this or should ever need to use it, since
the size is architecture-specific anyway. If normal
integers don't do, one should use 64-bit integers.
There's no code that uses it other than multiqueue, so make it private
to multiqueue for now. That way we can also do optimisations that
require API/ABI breaks. If anyone ever wants to use it, we can still
make it public again.
No point removin those empty override files from git, they'll
just be re-created later, so let's tell gtk-doc about them, so
it can clean them up properly.
The idea was originally that if one passed &dest_fmt with
dest_fmt=GST_FORMAT_DEFAULT, then the code answering the query
could change dest_fmt to the actual default format used. However,
in more than half a decade of GStreamer 0.10 no piece of code in
GStreamer has ever used that feature, nor are there that many
users of this API that actually check whether the format returned
is the original format passed before using the values returned.
Also, it's just annoying-to-use API in its own right.
For all these reasons, make it so that the destination format is
passed directly and can't be changed by the element queried.
It was a bit too clever, and didn't really work as an API,
confusing people to no end. Better implement specific methods
whether an interface is usable/available/ready on the interface
itself, or even add GError arguments, rather than try to have
per-instance interfaces.
This is an ad-hoc release that is almost identical to 0.10.34:
* work around GLib atomic ops API change
* some minor win32/mingw fixes
* don't use G_CONST_RETURN in public headers
Require the memory implementations to implement a share operation. This allows
us to remove the fallback share implementation which uses a different allocator
implementation and complicates things too much.
Update design doc a bit.
Instead of passing it structure by structure. This allows
better optimized transform_caps functions and allows better
transformation decisions.
See bug #619844.
Update the design docs with some clear rules for how sticky events are
handled.
Reimplement the sticky tags, use a small structure to hold the event and its
current state (active or inactive).
Events on sinkpads only become active when the event function returned success
for the event.
When linking, only update events that are different.
Avoid making a copy of the event array, use the object lock to protect the event
array and release it only to call the event function. This will need to check
if something changed, later.
Disable a test in the unit test, it can't work yet.
gst_pad_template_get_caps(), gst_pad_get_pad_template_caps()
and gst_pad_get_pad_template() return a new reference of the
caps or template now and the return value needs to be
unreffed after usage.
Improve GstSegment, rename some fields. The idea is to have the GstSegment
structure represent the timing structure of the buffers as they are generated by
the source or demuxer element.
gst_segment_set_seek() -> gst_segment_do_seek()
Rename the NEWSEGMENT event to SEGMENT.
Make parsing of the SEGMENT event into a GstSegment structure.
Pass a GstSegment structure when making a new SEGMENT event. This allows us to
pass the timing info directly to the next element. No accumulation is needed in
the receiving element, all the info is inside the element.
Remove gst_segment_set_newsegment(): This function as used to accumulate
segments received from upstream, which is now not needed anymore because the
segment event contains the complete timing information.
This allows to get the internal pad of ghostpads and
proxypads without using gst_pad_iterate_internal_links()
and is much more convenient.
The internal pad of a ghostpad is the pad of the opposite direction
that is used to link to the ghostpad target.
Highlights:
- new parser base class: GstBaseParse
- new core element: funnel
- OSX multi-arch fixes
- new QoS type for QoS events
- new progress message API to notify applications of asynchronous operations
- countless other fixes and improvements
Add a query to request allocation parameters and optionally a bufferpool as
well. This should allow elements to discover downstream capabilities and also
use the downstream allocators.
This allows to add pad templates and set metadata in class_init instead of
base_init. base_init is a concept that is not supported by almost all
languages and copying the templates/metadata for subclasses is the more
intuitive way of doing things.
Subclasses can override pad templates of parent classes by adding a new
template with the same now.
Also gst_element_class_add_pad_template() now takes ownership of the
pad template, which was assumed by all code before anyway.
Fixes bug #491501.
Seems like the best fit to what it does, and is shorter than
set_frame_properties() which might also have been confusing
because of GstBaseParseFrame.
https://bugzilla.gnome.org/show_bug.cgi?id=518857
This is more in line with e.g. GstBaseTransform's API, and makes for nicer
to read code. No getters for now since I don't see any use case for them,
the API is for subclasses, which usually know what format they're
dealing with already and hence know what they've set.
https://bugzilla.gnome.org/show_bug.cgi?id=518857
Add first implementation of arbitrary buffer metadata. We use a simple linked
linked of slice allocated metadata chunks. Future implementations could use
something more performant.
Add get, remove, iterate methods to handle the metadata.
Add function that (unlike the GLib equivalent) also accepts paths that
aren't absolute and will clean up relative markers such as ./ and ../
before forming a URI.
Fixes warnings with e.g. filesrc location=foo ! typefind caused by the
recent switch to g_filename_to_uri(), but also actually creates valid
URIs for the first time.
Windows code paths could need some more work, e.g. we don't clean up
the relative markers there for now (because path could have \ and /
as separators).
API: gst_filename_to_uri()
Add a first draft with some ideas and use cases for the implementation
for bufferpools. The purpose is to be able to make elements negotiate
their buffer requirements as well as provide an infrastructure to
preallocate and reuse buffers in an easy way.
So the encoding of the original document is respected and
displays properly in browsers where the encoding autodetection
fails to recognise that it's utf-8.
https://bugzilla.gnome.org/show_bug.cgi?id=639448
The new request_new_pad_full vmethod provides an additional caps field,
which allows elements to take better decision process.
Also, add a gst_element_request_pad() function to allow developers to be
able to specify which pad template they want a pad of.
Convert gstutils to use that new method instead of the old one when more
efficient.
This is useful for being able to request pads in a more flexible way,
especially when the element can provide pads whose caps depend on
runtime configuration and therefore can't provide pre-registered
pad templates.
API: GstElement::request_new_pad_full
API: gst_element_request_pad
https://bugzilla.gnome.org/show_bug.cgi?id=637300
Make GstObject extend from GInitiallyUnowned, remove the FLOATING flag and use
GObject methods for managing the floating ref.
Remove class lock, it was a workaround for a glib < 2.8 bug.
Remove the parent-set and parent-unset signals, attempt to implement with notify
but disabled because deadlocks in deep-notify.
Fix wrongly placed example and weirdly phrased 'note' lacking proper
formatting. Fix missing hint for autogen.sh location and rephrase
'built and installed' sentence. Fix wrongly phrased and redundant
paragraph in PWG
https://bugzilla.gnome.org/show_bug.cgi?id=634921
Add minimal math-compath.h header where we can define fallback
versions for miscellaneous math functions that aren't always
available, so we don't have to duplicate this in plugins.
The header is not included by default, so needs to be
included explicitly for now.
https://bugzilla.gnome.org/show_bug.cgi?id=630802
Adds a new tag to indicate the error in horizontal positioning
in meters. This is one of the available 'gps error' fields in
exif, for example.
API: GST_TAG_GEO_LOCATION_HORIZONTAL_ERROR
Add a function to retrieve a list of buffers containing the first N bytes from
the adapter. This can be done without a memcpy and should make it possible to
transfer the list to a GstBufferList later.
Add _set_value() variants that take ownership of the value passed
instead of making a copy of the value. This is useful for setting
values to things that aren't refcounted (e.g. GValueArrays or
strings or string arrays, etc.).
API: gst_structure_take_value()
API: gst_structure_id_take_value()
https://bugzilla.gnome.org/show_bug.cgi?id=629831
Add a GstStructure to GstElementClass and GstElementFactory. Add setters/getter.
Handle it in the registry code. Print items in gst-inspect.
Fixes#396774.
API: gst_element_class_set_meta_data(), gst_element_factory_get_meta_data_detail()
Added a new query type to retrieve informations about the areas of the
media currently buffered. See bug 623121.
API: gst_query_add_buffering_range
API: gst_query_get_n_buffering_ranges
API: gst_query_parse_nth_buffering_range
Make code including GStreamer headers compile with -Wcast-qual by
maintaining const-ness when casting. Also fix function signature of
gst_byte_writer_set_pos(): the byte writer should not be marked as
const.
https://bugzilla.gnome.org/show_bug.cgi?id=627910
Adds GST_TAG_APPLICATION_DATA for representing arbitrary private
data that applications might want to store into tags. Exif/id3,
for example, have tags for this.
API: GST_TAG_APPLICATION_DATA
Fixes#626651
For some reason the static inline function GST_CAT_LEVEL_LOG_valist is
now picked up, which then breaks the build because it's not documented,
so add it to the sections file.
Based on patch by Víctor Manuel Jáquez Leal <vjaquez@igalia.com>.
Fixes#625862.
Adds a new tag to inform about the image orientation and how
to rotate and flip it before display.
Note that this tag is a string with a predefined set of
possible values.
API: GST_TAG_IMAGE_ORIENTATION
Fixes#619508
A pad is 'negotiable' when its container element is in a state greater
than GST_STATE_READY
API:gst_pad_is_negotiable
API:gst_pad_set_negotiable
API:GST_PAD_NEGOTIABLE
https://bugzilla.gnome.org/show_bug.cgi?id=618644
This allows removing structures from caps without them being freed. Helpful when
plugins need to move around structures without having to do an expensive structure
copy.
API:gst_caps_steal_structure
https://bugzilla.gnome.org/show_bug.cgi?id=621527
This makes it possible to easily get a *:5 debug log without all
the refcounting noise, and drastically reduces the number of lines
output for a normal log (46m to 28m for a 20min video). The full log
including refcounting information can still be gotten using *:7.
Fixes#620460.
Adds 3 new geo location tags involving direction and
movement of capture. Those are:
API: GST_TAG_GEO_LOCATION_CAPTURE_DIRECTION
API: GST_TAG_GEO_LOCATION_MOVEMENT_DIRECTION
API: GST_TAG_GEO_LOCATION_MOVEMENT_SPEED
Fixes#617223
Adds those new tags to describe the device manufacturer and
model used to create medias.
API: GST_TAG_DEVICE_MANUFACTURER
API: GST_TAG_DEVICE_MODEL
Fixes#615941
Use .NOTPARALLEL when building docs. This avoids intermittent
make distcheck failures like 'cp: cannot create regular file
`build/image.entities': File exists' when using -jN.
Fixes#590718.
Adds a new tag for user favorite media rating.
User rating informs how much (from 0 to 100) a user
'likes' a media.
Having an percent uint range for this is easy to map into other scales,
like some players that allow users to attribute 'stars' to its
media.
API: GST_TAG_USER_RATING
Fixes#520697
Adds that warning to configure.ac
Includes a tiny change of the GST_BOILERPLATE_FULL() macro:
The get_type() function is no longer declared before being defined.
https://bugzilla.gnome.org/show_bug.cgi?id=611692
The functions are called gst_byte_writer_put_{float32|float64}_*() and not
gst_byte_writer_put_{float|double}_*().
Spotted by: Benjamin Otte <otte@redhat.com>
Adds a new function to GstByteWriter that writes
a constant value to a memory area (aka memset).
Useful for adding padding to buffers.
Also updates .def file and docs.
API: gst_byte_writer_fill()
gst_byte_writer_reset_and_get_buffer wasn't declared
in .h, instead there was _reset_and_get_data_as_buffer.
Replace it with the real function name, that is smaller
and matches gst_byte_writer_free_and_get_buffer
https://bugzilla.gnome.org/show_bug.cgi?id=608726
Fix link to gst-uninstalled now that it's been moved, and fix a typo
while we're at it. Also add a new section to 'Building GStreamer from
git' that points to the 'How do I develop against an uninstalled copy
of GStreamer' section.
Add a method to perform get_range typefinding that also uses the
uri/location extension as an extra hint. It will first try to call the
typefind functions of the factories that handle the given extension. The result
is that in the common case, we only call one typefind function, which speeds up
the typefinding a lot.
The only reason these two functions are still around is that at some
point in the past they were in a public header, so we can't really
remove them now even though they should have been private all along
(and aren't really particularly useful). Since these are just empty
stubs now that do nothing but return FALSE and will be removed in
0.11 anyway, we may just as well deprecate them formally.
Add a method to install a clipping function that is called when a buffer is
received. Users of collectpads can then perform clipping on the incomming
buffers.
Also retab the header file a little.
See #590265
Adds the following new tags:
GST_TAG_SHOW_NAME
GST_TAG_SHOW_SORTNAME
GST_TAG_SHOW_EPISODE_NUMBER
GST_TAG_SHOW_SEASON_NUMBER
GST_TAG_LYRICS
GST_TAG_COMPOSER_SORTNAME
GST_TAG_GROUPING
Fixes#599759
Mention that elements implementing GstMixer and GstTuner need to be
in the right state before they can be used. Also mention GLib
functions for converting filenames to and from URIs.
Fixes#602877.
gst_event_new_sink_message()
gst_event_parse_sink_message()
This event is used for sending a GstMessage downstream and synchronized
with the stream, to be posted by the sink once it reaches the sink.
Fixes bug #602275.
and install into a different directory $(libexecdir/gstreamer-0.10) so that
everything is versioned properly.
NOTE: run 'make clean' after updating; if you are running an uninstalled setup,
you will need to update your gst-uninstalled script (unless it's symlinked
to gstreamer core master) and exit/enter your uninstalled environment to get
the updated environment. If you are running an installed setup, you should
run 'make uninstall' before merging this change or remove the old
plugin-scanner binary manually.
Fixes#601698.
gst_util_greatest_common_divisor()
gst_util_double_to_fraction()
gst_util_fraction_to_double()
Using these instead of going over GValue has much lower overhead.
Also add float<->fraction transform functions for GValue.
This returns the internal feature list cookie, which changes every
time a feature is added or removed. This can be used by elements
to check if they should update their cached feature lists.
We currently do a little too much work when we push the first buffer around
resulting in excessive caps checking. We can probably make this a little less
expensive.
This patch adds gst_caps_set_value() and allows gst_caps_set_simple() to
work on non-simple caps. See the API documentation for the functions
about what they do.
The intention of these changes is to ease working with caps in caps
transform functions. An example for this would be ffmpegcolorspace,
where the caps transform function could be changed to look roughly like
this (pseudocode ahead):
result = gst_caps_copy (template_caps);
value = gst_structure_get_value (gst_caps_get_structure (caps, 0),
"widh");
gst_caps_set_value (result, value);
/* same for height, framerate and par */
return caps;
which is much cleaner and easier to understand than the current code.
https://bugzilla.gnome.org/show_bug.cgi?id=597690
In most places in core and baseclasses we just need the caps to do caps-
intersections. In that case ref'ed caps are enough (no need to copy).
This patch also switches the code to use the new functions.
API: gst_pad_get_caps_refed(), gst_pad_peer_get_caps_refed()
Add a simple version check when starting the plugin-scanner so we can
verify we're talking to one that talks the same language.
First try a plugin-scanner in the installed path, then try one via the
GST_PLUGIN_SCANNER env var if that doesn't work.
Update the uninstalled script.
Install the plugin-scanner to the libexec dir
Often we don't need the result of the intersection. Add a variant that only
tries to intersect. It can break out earlier and does less GValue copying.
API: gst_caps_can_intersect()
Use more refined search paths for our plugin modules. Not only does
this make things much faster in an uninstalled setup, it also makes
sure we're not accidentally using out-of-date plugins built ages
ago as part of a (failed) 'make distcheck' when we forget to clean
up the distcheck build directory.
There's no need to have GstStreamConsistency in a public header for
the time being, so make it private. While we're at it, add a gtk-doc
blurb for it though. Re-fixes #588744.
Add a new macro GST_DEBUG_CATEGORY_GET to get a log category by name. This
allows plugins to use e.g. core categories like PERFORMANCE or CLOCK.
API: GST_DEBUG_CATEGORY_GET
Add new method to iterate a bufferlist without having to allocate an iterator.
Add convenience method for getting an item from the list based on the group and
index.
Remove redundant _do_data callback and method.
Update unit-tests and add some more for the new methods.
Add functions to create a new tag list and set tags in one go, which
is nice for use in combination with functions that take ownership of
the taglist, such as gst_event_new_tag() or gst_element_found_tags().
API: add gst_tag_list_new_full()
API: add gst_tag_list_new_full_valist()
Add a pattern scan function similar to the one recently added to
GstAdapter, and a unit test (based on the adapter one).
Fixes#585592.
API: add gst_byte_reader_masked_scan_uint32()
Update design doc with step-start docs.
Add eos field to step done message
when stepping in reverse, update the segment time field.
Flush out the current step when we are flushing.
Add a bunch of vararg getter convenience functions to complement
the vararg setter functions, and a basic unit test. Fixes#534208.
API: gst_structure_get()
API: gst_structure_id_get()
API: gst_structure_get_valist()
API: gst_structure_id_get_valist()
Note in the docs that a flushing step in PLAYING brings the pipeline to the lost
state and skips the data before prerolling again.
Implement the flushing step correctly by invalidating the current step
operation, which would activate the new step operation.
Add gst_segment_to_position() that converts a running_time to a position in the
segment. A faulty variant of this function is currently used in inputselector
but we'll need it for frame stepping too.
API: GstSegment::gst_segment_to_position()
Update framestep document, we want to pass the flush flag in the step-done
message.
Add flush flag to the gstmessage.
Update examples to use the new step-done message api.
Implement framestep with playback rates < 0.0 too.
Add new STEP event and methods for creating/parsing the event
Update design docs.
Add new STEP_DONE message and method to create/parse.
API: GstEvent::gst_event_new_step()
API: GstEvent::gst_event_parse_step()
API: GstMessage::gst_message_new_step_done()
API: GstMessage::gst_message_parse_step_done()
