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Bug 1061046. Part 18: Simplify TrackUnionStream now that there are no rate mismatches. r=karlt

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This commit is contained in:
Robert O'Callahan 2014-09-18 17:13:17 +12:00
parent b6f107855b
commit cddaa7d17c
1 changed files with 9 additions and 85 deletions
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94
dom/media/TrackUnionStream.cpp
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@ -264,15 +264,10 @@ TrackUnionStream::TrackUnionStream(DOMMediaStream* aWrapper) :
if (interval.mStart >= interval.mEnd) {
break;
}
TrackTicks ticks = interval.mEnd - interval.mStart;
next = interval.mEnd;
// Ticks >= startTicks and < endTicks are in the interval
StreamTime outputEnd = GraphTimeToStreamTime(interval.mEnd);
TrackTicks startTicks = outputTrack->GetEnd();
StreamTime outputStart = GraphTimeToStreamTime(interval.mStart);
MOZ_ASSERT(startTicks == outputStart, "Samples missing");
TrackTicks ticks = outputEnd - startTicks;
StreamTime inputStart = source->GraphTimeToStreamTime(interval.mStart);
StreamTime outputStart = outputTrack->GetEnd();
if (interval.mInputIsBlocked) {
// Maybe the input track ended?
@ -280,89 +275,18 @@ TrackUnionStream::TrackUnionStream(DOMMediaStream* aWrapper) :
STREAM_LOG(PR_LOG_DEBUG+1, ("TrackUnionStream %p appending %lld ticks of null data to track %d",
this, (long long)ticks, outputTrack->GetID()));
} else {
// Figuring out which samples to use from the input stream is tricky
// because its start time and our start time may differ by a fraction
// of a tick. Assuming the input track hasn't ended, we have to ensure
// that 'ticks' samples are gathered, even though a tick boundary may
// occur between outputStart and outputEnd but not between inputStart
// and inputEnd.
// These are the properties we need to ensure:
// 1) Exactly 'ticks' ticks of output are produced, i.e.
// inputEndTicks - inputStartTicks = ticks.
// 2) inputEndTicks <= aInputTrack->GetSegment()->GetDuration().
// 3) In any sequence of intervals where neither stream is blocked,
// the content of the input track we use is a contiguous sequence of
// ticks with no gaps or overlaps.
if (map->mEndOfLastInputIntervalInInputStream != inputStart ||
map->mEndOfLastInputIntervalInOutputStream != outputStart) {
// Start of a new series of intervals where neither stream is blocked.
map->mEndOfConsumedInputTicks = inputStart - 1;
}
TrackTicks inputStartTicks = map->mEndOfConsumedInputTicks;
TrackTicks inputEndTicks = inputStartTicks + ticks;
map->mEndOfConsumedInputTicks = inputEndTicks;
map->mEndOfLastInputIntervalInInputStream = inputEnd;
map->mEndOfLastInputIntervalInOutputStream = outputEnd;
if (GraphImpl()->mFlushSourcesNow) {
TrackTicks flushto = inputEndTicks;
STREAM_LOG(PR_LOG_DEBUG, ("TrackUnionStream %p flushing after %lld of %lld ticks of input data from track %d for track %d",
this, flushto, aInputTrack->GetSegment()->GetDuration(), aInputTrack->GetID(), outputTrack->GetID()));
aInputTrack->FlushAfter(flushto);
MOZ_ASSERT(inputTrackEndPoint >= aInputTrack->GetEnd());
}
// Now we prove that the above properties hold:
// Property #1: trivial by construction.
// Property #3: trivial by construction. Between every two
// intervals where both streams are not blocked, the above if condition
// is false and mEndOfConsumedInputTicks advances exactly to match
// the ticks that were consumed.
// Property #2:
// Let originalOutputStart be the value of outputStart and originalInputStart
// be the value of inputStart when the body of the "if" block was last
// executed.
// Let allTicks be the sum of the values of 'ticks' computed since then.
// The interval [originalInputStart/rate, inputEnd/rate) is the
// same length as the interval [originalOutputStart/rate, outputEnd/rate),
// so the latter interval can have at most one more integer in it. Thus
// TimeToTicksRoundUp(rate, outputEnd) - TimeToTicksRoundUp(rate, originalOutputStart)
// <= TimeToTicksRoundDown(rate, inputEnd) - TimeToTicksRoundDown(rate, originalInputStart) + 1
// Then
// inputEndTicks = TimeToTicksRoundDown(rate, originalInputStart) - 1 + allTicks
// = TimeToTicksRoundDown(rate, originalInputStart) - 1 + TimeToTicksRoundUp(rate, outputEnd) - TimeToTicksRoundUp(rate, originalOutputStart)
// <= TimeToTicksRoundDown(rate, originalInputStart) - 1 + TimeToTicksRoundDown(rate, inputEnd) - TimeToTicksRoundDown(rate, originalInputStart) + 1
// = TimeToTicksRoundDown(rate, inputEnd)
// <= inputEnd/rate
// (now using the fact that inputEnd <= track->GetEndTimeRoundDown() for a non-ended track)
// <= TicksToTimeRoundDown(rate, aInputTrack->GetSegment()->GetDuration())/rate
// <= rate*aInputTrack->GetSegment()->GetDuration()/rate
// = aInputTrack->GetSegment()->GetDuration()
// as required.
if (inputStartTicks < 0) {
// Data before the start of the track is just null.
// We have to add a small amount of delay to ensure that there is
// always a sample available if we see an interval that contains a
// tick boundary on the output stream's timeline but does not contain
// a tick boundary on the input stream's timeline. 1 tick delay is
// necessary and sufficient.
segment->AppendNullData(-inputStartTicks);
inputStartTicks = 0;
}
if (inputEndTicks > inputStartTicks) {
segment->AppendSlice(*aInputTrack->GetSegment(),
std::min(inputTrackEndPoint, inputStartTicks),
std::min(inputTrackEndPoint, inputEndTicks));
}
STREAM_LOG(PR_LOG_DEBUG+1, ("TrackUnionStream %p appending %lld ticks of input data to track %d",
this, (long long)(std::min(inputTrackEndPoint, inputEndTicks) - std::min(inputTrackEndPoint, inputStartTicks)),
outputTrack->GetID()));
MOZ_ASSERT(outputTrack->GetEnd() == GraphTimeToStreamTime(interval.mStart),
"Samples missing");
StreamTime inputStart = source->GraphTimeToStreamTime(interval.mStart);
segment->AppendSlice(*aInputTrack->GetSegment(),
std::min(inputTrackEndPoint, inputStart),
std::min(inputTrackEndPoint, inputEnd));
}
ApplyTrackDisabling(outputTrack->GetID(), segment);
for (uint32_t j = 0; j < mListeners.Length(); ++j) {
MediaStreamListener* l = mListeners[j];
l->NotifyQueuedTrackChanges(Graph(), outputTrack->GetID(),
startTicks, 0, *segment);
outputStart, 0, *segment);
}
outputTrack->GetSegment()->AppendFrom(segment);
}