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