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66 lines
2.5 KiB
Text
66 lines
2.5 KiB
Text
There are a number of different ways of coding a GstSrc. I'll try to
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outline them and how the function here:
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1a) Simple push-function based with single output
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This is the style that all the existing sources use. There is a single
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output pad, and a _push function that's global to the whole element. The
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_push function simple constructs buffer and pushes them out the pad.
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Chained:
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Typically this will be the/an entry into the Bin. The Bin's iterate
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function simply calls the Src's _push function. When the _push function
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pushes a buffer out it's pad, the chain function of the peer pad is
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called, presumably causing a push out the other side of that element, and
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eventually data gets to the other end. The stack unrolls, and the
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iteration ends for that Src.
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Cothreaded:
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Again, the source would generally be an entry into the Bin. A loopfunc
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will be constructed around it, which will simply loop calling the Src's
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_push function as in the non-cothreaded case. When the _push function
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pushes a buffer, it finds a pushfunc attached to the pad, drops the buffer
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in the pen, and calls the pushfunc provided by the Bin. This causes a
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switch to the next element, then the next, to the end, at which point a
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buffer pull will travel back down the chain. The _push function gets
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context and finishes, at which point the loopfunc wrapper simply calls it
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again in the next iteration.
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1b) Simple push-function based with multiple output
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Chained:
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Similar to the single output variant, except several chains are spawned
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off, one per push, hanging off whichever pad the buffer is pushed off of.
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The stack will grow and unwind as many times as buffers are pushed out.
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Cothreaded:
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Also similar to the single output variant. When the pull winds its way
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back from the first push, execution returns to the Src's _push function,
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which simply goes off and pushes out another buffer, causing another
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series of context switches. Eventually the loopfunc wrapper starts over,
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round and round we go.
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2) Pull-function based with single output
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Similar to a regular filter with a chain function associated with each
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pad, this kind of source doesn't provide a src-wide push function, but
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does provide pullfuncs for its pad. A pullfunc puts a buffer in the pen
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and exits.
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Chained:
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As usual, is likely to be an entry into a Bin. The Bin iterate code must
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explicitely pull a buffer and pass it on to the peer.
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Cothreaded:
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---- ok, I'll finish this tomorrow when my brain's working again.... ----
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