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design: gstbin: add missing markup

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Also fix some minor grammar issues.
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Reynaldo H. Verdejo Pinochet 2016-12-21 23:25:41 -08:00
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markdown/design/gstbin.md
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# GstBin # GstBin
GstBin is a container element for other GstElements. This makes it `GstBin` is a container element for other `GstElements`. This makes it
possible to group elements together so that they can be treated as one possible to group elements together so that they can be treated as one
single GstElement. A GstBin provides a GstBus for the children and single `GstElement`. A `GstBin` provides a `GstBus` for the children and
collates messages from them. collates messages from them.
## Add/removing elements ## Add/removing elements
@ -16,7 +16,7 @@ The bin maintains a parent-child relationship with its elements (see
## Retrieving elements ## Retrieving elements
GstBin provides a number of functions to retrieve one or more children `GstBin` provides a number of functions to retrieve one or more children
from itself. A few examples of the provided functions: from itself. A few examples of the provided functions:
* `gst_bin_get_by_name()` retrieves an element by name. * `gst_bin_get_by_name()` retrieves an element by name.
@ -24,8 +24,8 @@ from itself. A few examples of the provided functions:
## element management ## element management
The most important function of the GstBin is to distribute all The most important function of the `GstBin` is to distribute all
GstElement operations on itself to all of its children. This includes: `GstElement` operations on itself to all of its children. This includes:
- state changes - state changes
@ -38,20 +38,20 @@ The state change distribution is the most complex and is explained in
## GstBus ## GstBus
The GstBin creates a GstBus for its children and distributes it when The `GstBin` creates a `GstBus` for its children and distributes it when
child elements are added to the bin. The bin attaches a sync handler to child elements are added to the bin. The bin attaches a sync handler to
receive messages from children. The bus for receiving messages from receive messages from children. The bus for receiving messages from
children is distinct from the bin’s own externally-visible GstBus. children is distinct from the bin’s own externally-visible `GstBus`.
Messages received from children are forwarded intact onto the bin’s Messages received from children are forwarded intact onto the bin’s
external message bus, except for EOS and SEGMENT_START/DONE which are external message bus, except for EOS and `SEGMENT_START`/`DONE` which are
handled specially. handled specially.
ASYNC_START/ASYNC_STOP messages received from the children are used to `ASYNC_START`/`ASYNC_STOP` messages received from the children are used to
trigger a recalculation of the current state of the bin, as described in trigger a recalculation of the current state of the bin, as described in
[states](design/states.md). [states](design/states.md).
The application can retrieve the external GstBus and integrate it in the The application can retrieve the external `GstBus` and integrate it in the
mainloop or it can just `pop()` messages off in its own thread. mainloop or it can just `pop()` messages off in its own thread.
When a bin goes to READY it will clear all cached messages. When a bin goes to READY it will clear all cached messages.
@ -74,16 +74,16 @@ going to PLAYING again.
A bin collects `SEGMENT_START` messages but does not post them to the A bin collects `SEGMENT_START` messages but does not post them to the
application. It counts the number of `SEGMENT_START` messages and posts a application. It counts the number of `SEGMENT_START` messages and posts a
`SEGMENT_STOP` message to the application when an equal number of `SEGMENT_STOP` message to the application when an equal number of
`SEGMENT_STOP` messages where received. `SEGMENT_STOP` messages were received.
The cached SEGMENT_START/STOP messages are cleared when going to READY. The cached `SEGMENT_START`/`STOP` messages are cleared when going to READY.
## DURATION ## DURATION
When a DURATION query is performed on a bin, it will forward the query When a DURATION query is performed on a bin, it will forward the query
to all its sink elements. The bin will calculate the total duration as to all its sink elements. The bin will calculate the total duration as
the MAX of all returned durations and will then cache the result so that the MAX of all returned durations and will then cache the result so that
any further query can use the cached version. The reason for caching the any further queries can use the cached version. The reason for caching the
result is because the duration of a stream typically does not change result is because the duration of a stream typically does not change
that often. that often.
@ -96,10 +96,10 @@ application, which can then fetch the updated DURATION.
## Subclassing ## Subclassing
Subclasses of GstBin are free to implement their own add/remove Subclasses of `GstBin` are free to implement their own add/remove
implementations. It is a good idea to update the GList of children so functions. It is a good idea to update the `GList` of children so
that the `_iterate()` functions can still be used if the custom bin that the `_iterate()` functions can still be used if the custom bin
allows access to its children. allows access to its children.
Any bin subclass can also implement a custom message handler by Any bin subclass can also implement a custom message handler by
overriding the default message handler. overriding the default one.