mirror of
https://gitlab.freedesktop.org/gstreamer/gstreamer.git
synced 2024-12-27 02:30:35 +00:00
49 lines
1.5 KiB
Text
49 lines
1.5 KiB
Text
|
Capsnego patterns
|
||
|
|
-----------------
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
src negotiation recovery
|
||
|
|
------------------------
|
||
|
|
|
||
|
|
common pipelines like
|
||
|
|
|
||
|
|
filesrc -> mad -> osssink
|
||
|
|
|
||
|
|
perform negotiation strictly left to right. At some point during
|
||
|
|
iterate, mad will know the caps of the media stream and will need
|
||
|
|
to inform osssink of this before pushing out a buffer.
|
||
|
|
mad only has one set of fixed caps.
|
||
|
|
|
||
|
|
1) try_set_caps
|
||
|
|
|
||
|
|
mad does a try_set_caps with the caps if all goes well, osssink
|
||
|
|
accepts and negotiation succeeds.
|
||
|
|
|
||
|
|
if the try_set_caps function fails, the application should have
|
||
|
|
a change to recover.
|
||
|
|
|
||
|
|
- mad therefore calls gst_pad_caps_error_try_recover, this will
|
||
|
|
emit a signal on the pad that the app can catch. One of the
|
||
|
|
signal arguments will contain a list of possible caps.
|
||
|
|
|
||
|
|
- the app can use the allowed caps to find another element that
|
||
|
|
is compatible with the caps and the peer element caps.
|
||
|
|
|
||
|
|
- the app will connect the new element with mad, negotiation
|
||
|
|
will happen again, the link will fail or succeed, if it fails,
|
||
|
|
thr app knows because the link function returns FALSE.
|
||
|
|
|
||
|
|
- if the link succeeds, pad caps are set and the try_recover
|
||
|
|
function returns TRUE, mad then knows the issue was resolved
|
||
|
|
and can continue. It will have received the final caps in its
|
||
|
|
srclink function.
|
||
|
|
|
||
|
|
- if no signal handler is connected to the caps_nego_failure signal
|
||
|
|
the issue will remain unresolved and a big debug warning is
|
||
|
|
printed on the console to debug the issue. mad will get a
|
||
|
|
return value of FALSE and may stop.
|
||
|
|
|
||
|
|
|