1498440 - Refactor the logic of seamless looping audio

Status: RESOLVED FIXED

(Core :: Audio/Video: Playback, enhancement, P2)

Description

[Alastor Wu [:alwu]]

The purpose of this bug is to move out the codes for seamless audio from DecodingState::Step().

Comment 1

[Alastor Wu [:alwu]]

Attachment: Bug 1498440 - part1 : return fake EOS when we cancel looping and the previoud EOS had been hidden by ReaderProxy

If we're in seamless looping, ReaderProxy will not tell MDSM about EOS error which reader returned, so MDSM will stay at `decoding state` all the time.
We can say that the ReaderProxy hides EOS in this case.

When canceling seamless looping, if the playback position does not reach the EOS position yet and we had already hidden EOS, we need to create another
EOS to notify MDSM the demuxing has ended.

   playback   hidden    fake
   position    EOS      EOS
 ----|---------|---------|-------> (Increasing timeline)

Comment 2

[Alastor Wu [:alwu]]

Attachment: Bug 1498440 - part2 : discard redudant looping data.

When we cancel seamless looping, we should discard the audio data whose time are later than the last
audio frame's time in the audio track.

Comment 3

[Alastor Wu [:alwu]]

Attachment: Bug 1498440 - part3 : move MediaPlaybackEvent::Loop dispatching to UpdatePlaybackPositionPeriodically().

No need to check whether we need to dispatch looping event everytime when entering the DecodingState::Step().

Comment 4

[Alastor Wu [:alwu]]

Attachment: Bug 1498440 - part4 : rename PopEvent() to PopFrontEvent().

We only have a interest in the data which is popped out from the front side of the queue.

Comment 5

[Alastor Wu [:alwu]]

Attachment: Bug 1498440 - part1 : implement MDSM's 'LoopingDecodingState'.

This state is used to handle decoding when the media is in seamless looping.

It will be responsible for
(1) time adjustment
(2) handle EOS and seek to the first sample

Comment 6

[Alastor Wu [:alwu]]

Attachment: Bug 1498440 - part2 : implement state transition.

Comment 7

[Alastor Wu [:alwu]]

Attachment: Bug 1498440 - part3 : remove time-adjustment related codes in ReaderProxy.

Comment 8

[Alastor Wu [:alwu]]

Attachment: Bug 1498440 - part4 : discard redudant looping data when cancel looping.

When we cancel seamless looping, we should discard audio data whose time are later than the last
audio frame's time in the audio track.

Comment 9

[Alastor Wu [:alwu]]

Attachment: Bug 1498440 - part5 : rename PopEvent() to PopFrontEvent().

We only have a interest in the data which is popped out from the front side of the queue.

Comment 10

[Alastor Wu [:alwu]]

Attachment: Bug 1498440 - part6 : only enable 'loopingDecodingState' for audio seamless looping

We don't have any implementation for video seamless looping yet, so we only use 'loopingDecodingState' for
audio for now.

Comment 11

[Alastor Wu [:alwu]]

Attachment: Bug 1498440 - part7 : disconnect all Then() before exit the 'loopingDecoding' state

Ensure we disconnect all Then() before exit the state.

Comment 12

[Alastor Wu [:alwu]]

https://treeherder.mozilla.org/#/jobs?repo=try&revision=20b3c8c04771a6814185e836e58ac579ff413bc5

Comment 13

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/8937fe137441
part1 : implement MDSM's 'LoopingDecodingState'. r=jya
https://hg.mozilla.org/integration/autoland/rev/f47b8fef7cc7
part2 : implement state transition. r=jya
https://hg.mozilla.org/integration/autoland/rev/c67e483b4ab4
part3 : remove time-adjustment related codes in ReaderProxy. r=jya
https://hg.mozilla.org/integration/autoland/rev/2e61ba5a50f2
part4 : discard redudant looping data when cancel looping. r=jya
https://hg.mozilla.org/integration/autoland/rev/1cd5c63b4182
part5 : rename PopEvent() to PopFrontEvent(). r=jya
https://hg.mozilla.org/integration/autoland/rev/93cfc552f067
part6 : only enable 'loopingDecodingState' for audio seamless looping r=jya

Comment 14

[Raul Gurzau (:RaulG)]

https://hg.mozilla.org/mozilla-central/rev/8937fe137441
https://hg.mozilla.org/mozilla-central/rev/f47b8fef7cc7
https://hg.mozilla.org/mozilla-central/rev/c67e483b4ab4
https://hg.mozilla.org/mozilla-central/rev/2e61ba5a50f2
https://hg.mozilla.org/mozilla-central/rev/1cd5c63b4182
https://hg.mozilla.org/mozilla-central/rev/93cfc552f067