--- /dev/null
+
+
+
+Scheduling:
+
+ - remove loop/get/chain from GstElement and add a "iterate" method.
+ The iterate method is called with the event (or events) that
+ triggered it, performs some action, and resets the events (file
+ descriptors becoming readable, semaphores, pads becoming readable
+ or writable, or a time occurs).
+
+ - Add GstLoopElement, GstChainElement, etc. for compatibility.
+
+ - Remove existing state handling and create 2 states, "playing" and
+ "stopped". "playing" means that the iterate() method of the
+ element may be called, that is, the element is allowed to move
+ buffers, negotiate, etc. "stopped" means that no gstreamer-ish
+ things happen to an element, only gobject-ish. A separate
+ reset() method will handle the difference between READY and NULL.
+
+ - Add a flag "ready" to GstElement that is under the control of the
+ element. If the element is ready to stream, it sets this flag,
+ and the entire pipeline starts streaming. (This is basically
+ the difference between PAUSED and PLAYING.) For example, osssink
+ won't set the ready flag until the device is opened and there is
+ a buffer available to write to the device.
+
+ - Scheduling of elements and movement of buffers will be timed by
+ clocks.
+
+
+
+Example:
+
+ Pipeline: sinesrc ! osssink
+
+ - The application creates the pipeline and sets it to "playing".
+
+ - The clock is created and set to "paused".
+
+ - sinesrc.iterate() decides to watch for the event "src pad
+ negotiation" and sets the available caps on the pad.
+
+ - osssink.iterate() opens device, determines available caps, and
+ sets the available caps on the pad. Then it decides to wait for
+ "sink pad negotiation".
+
+ - The scheduler realizes that the two elements are waiting for
+ negotiation, so it negotiates the link.
+
+ - sinesrc.iterate() sets the "ready" flag (because it needs no more
+ preparation to stream) and decides to watch for the event "src
+ pad ready to accept buffer".
+
+ - osssink.iterate() decides to watch for the event "sink pad has
+ available buffer".
+
+ - The scheduler realizes that sinesrc.srcpad is now ready, so it
+ calls sinesrc.iterate()
+
+ - sinesrc.iterate() creates a buffer and pushes it, and decides to
+ wait for the same event.
+
+ - The scheduler realizes that osssink.sinkpad now has a buffer, so
+ it calls osssink.iterate().
+
+ - osssink.iterate() is now ready to stream, so it sets the "ready"
+ flag and waits for "time 0".
+
+ - The pipeline is now completely ready, so the clock may be
+ started. A signal is fired to let the application know this
+ (and possibly change the default behavior).
+
+ - The clock starts with the time 0. The scheduler realizes this,
+ and decides to schedule osssink.
+
+ - osssink.iterate() is called, and writes the buffer to the device.
+ This starts the clock counting. (Actually, the buffer could be
+ written by the clock code, since presumably the clock is related
+ to osssink.) iterate() then waits for "sink pad has available
+ buffer".
+
+ We're now basically in streaming mode. A streaming cycle:
+
+ - osssink.iterate() decides the audio output buffer is full enough,
+ so it waits for "time X", where X is the time when the output
+ buffer will be below some threshold.
+
+ - osssink.iterate() waits for "sink pad has available buffer"
+
+ - sinesrc.iterate() creates and pushes a buffer, then waits for
+ "src pad ready".
+
+
+ Further ideas:
+
+ - osssink can set a hard deadline time, which means that if it is
+ not scheduled before that time, you'll get a skip. Skipping
+ involves setting osssink to "not ready" and pauses the clock.
+ Then the scheduler needs to go through the same process as above
+ to start the clock.
+
+ - As a shortcut, osssink can say "I need a buffer on the sinkpad
+ at time X". This information can be passed upstream, and be used
+ in filters -- filter.sinkpad says "I need a buffer at time X-N",
+ where N is the latency of the filter.
+
+
+
+
+