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docs/design/part-element-sink.txt: Pseudo code overview of desired sink behaviour regarding preroll.
Original commit message from CVS: * docs/design/part-element-sink.txt: Pseudo code overview of desired sink behaviour regarding preroll.
This commit is contained in:
Wim Taymans
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2 changed files with 172 additions and 2 deletions
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@ -1,3 +1,9 @@
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2006-01-30 Wim Taymans <wim@fluendo.com>
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* docs/design/part-element-sink.txt:
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Pseudo code overview of desired sink behaviour regarding
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preroll.
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2006-01-29 Sebastien Moutte <sebastien@moutte.net>
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* win32/vs6/grammar.dsp:
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fix some bugs in Release mode for autogenerated files
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@ -20,13 +20,177 @@ includes a state change from READY->PAUSED and PLAYING->PAUSED. The
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reason for this is that this way we can detect when the first buffer
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or event arrives in the sink when the state change completes.
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A sink should block on the first event or buffer received in the
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PAUSED state before commiting the state to PAUSED.
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A sink should block on the first EOS event or buffer received in the
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READY->PAUSED state before commiting the state to PAUSED.
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FLUSHING events have to be handled out of sync with the buffer flow
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and take no part in the preroll procedure.
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Events other than EOS do not complete the preroll stage.
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sink overview
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-------------
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/* commit the state. We return TRUE if we can continue
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* streaming, FALSE in the case we go to a READY or NULL state.
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* if we go to PLAYING, we don't need to block on preroll.
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*/
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commit
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LOCK
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switch (pending) {
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case PLAYING:
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need_preroll = FALSE;
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break;
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case PAUSED:
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break;
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case READY:
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case NULL:
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return FALSE;
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case VOID:
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return TRUE;
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}
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/* update state */
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state = pending;
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next = VOID;
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pending = VOID;
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UNLOCK
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return TRUE;
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/* handle a prerollable item (EOS or buffer). It is
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* always called with the PREROLL_LOCK helt.
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* need_preroll indicates that we must perform, commit and
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* potentially block on preroll.
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*/
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handle (time)
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again:
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while (need_preroll) {
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preroll
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if (!commit)
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return WRONG_STATE
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/* commit could have made us not need preroll anymore. */
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if (need_preroll) {
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/* release PREROLL_LOCK and wait. prerolled can be observed
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* and will be TRUE */
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prerolled = TRUE;
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PREROLL_WAIT (releasing PREROLL_LOCK)
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prerolled = FALSE;
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if (flushing)
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return WRONG_STATE
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}
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}
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if (clock && sync) {
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/* the only way we can regain the prerolled state is when
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* the clock entry gets unscheduled, we then preroll (again) on the
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* current item, else we render and preroll on the next buffer. */
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PREROLL_UNLOCK
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ret = wait_clock;
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PREROLL_LOCK
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if (flushing) | /* sinks that sync on buffer contents do like this */
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return WRONG_STATE | while (more_to_render) {
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if (ret == UNSCHEDULED) | ret = render
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goto again; | if (ret == interrupted)
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} | prerolled = TRUE;
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render ----->| PREROLL_WAIT (releasing PREROLL_LOCK)
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| prerolled = FALSE;
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| if (flushing)
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| return WRONG_STATE
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| }
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/* various event functions */
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event
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EOS:
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STREAM_LOCK
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PREROLL_LOCK
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if (flushing)
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return FALSE
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ret = handle (end_time);
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if (ret == WRONG_STATE)
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return FALSE
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post_eos
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eos = TRUE;
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PREROLL_UNLOCK
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STREAM_UNLOCK
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break;
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NEWSEGMENT:
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STREAM_LOCK
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PREROLL_LOCK
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if (flushing)
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return FALSE
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set_clip
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event
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PREROLL_UNLOCK
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STREAM_UNLOCK
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break;
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FLUSH_START:
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event ----> subclasses can interrupt render
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PREROLL_LOCK
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flushing = TRUE
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unlock_clock
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PREROLL_SIGNAL
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PREROLL_UNLOCK
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STREAM_LOCK
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lost_state
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STREAM_UNLOCK
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break;
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FLUSH_END:
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STREAM_LOCK
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event
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PREROLL_LOCK
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flushing = FALSE
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eos = FALSE;
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PREROLL_UNLOCK
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STREAM_UNLOCK
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break;
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chain
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STREAM_LOCK
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PREROLL_LOCK
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if (flushing)
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return WRONG_STATE
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if (clip)
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handle (time);
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PREROLL_UNLOCK
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STREAM_UNLOCK
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state
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switch (transition)
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READY_PAUSED:
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ret = ASYNC;
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eos = FALSE
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flushing = FALSE
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need_preroll = TRUE;
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prerolled = FALSE;
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break;
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PAUSED_PLAYING:
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PREROLL_LOCK
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if (prerolled || eos)
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PREROLL_SIGNAL
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ret = OK;
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need_preroll = FALSE;
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if (eos)
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post_eos
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else
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need_preroll = TRUE;
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ret = ASYNC;
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PREROLL_UNLOCK
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break;
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PLAYING_PAUSED:
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---> subclass can interrupt render
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PREROLL_LOCK
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need_preroll = TRUE;
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unlock_clock
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if (prerolled || eos)
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ret = OK;
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else
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ret = ASYNC;
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PREROLL_UNLOCK
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break;
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PAUSED_READY:
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---> subclass can interrupt render
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PREROLL_LOCK
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flushing = TRUE
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unlock_clock
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PREROLL_SIGNAL
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ret = OK;
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PREROLL_UNLOCK
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break;
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