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MEDIA DECODER STATE MACHINE Play and Pause

Alastor Wu 2015/03/27

OUTLINE

2

Overview !

Code flow !

Special mechanisms

PLAY OVERVIEW

3

Download + Decode + Playback

DECODE + PLAYBACK

4

Video queue

MediaDecoderStateMachine

Audio queue

Decoded data

Render &

Player

Command

DECODING FLOW

5

Media Decoder

Media Decoder

State Machine

Media Omx

Reader

Omx Decoder

Codec &

Codec Proxy

!

HW/SW Decoder

PlayRequestData

DecodeDataReadData

Read

BufferBufferFrame

Data

MODULES CONCEPT

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Media Decoder

Media Decoder

State Machine

Media Omx

Reader

!

Omx Decoder

Codec &

Codec Proxy

HW/SW Decoder

Command Data control Manage decoders Decoding!

Communicate with

decoderGet

decoded data

Load

PLAY() CALL FLOW

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MediaDecoderStateMachineMediaDecoder MediaOmxReader OmxDecoderMediaElement

Play()

RequestAudio/VideoData()EnsureAudio/VideoDecodeTaskQueued

DecodedAudio/VideoFrame()ReadAudio/Video()

OnAudio/VideoDecode() OnAudio/VideoNotDecode()

Resolve/Reject

Play()

MaybeFinishDecode

Decoding task

Decoding taskProm

ise

DispatchDecodeTasksIfNeeded()

StartDecoding()

RunStateMachine()MaybeStartPlayback()

AdvanceFrame()

Loop

ScheduleStateMachine()

Load()

PAUSE() CALL FLOW

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MediaDecoderStateMachineMediaDecoderMediaElement

Pause()

Pause()

MediaOmxReader OmxDecoder

StopPlaying()

RunStateMachine()

DispatchDecodeTasksIfNeeded()

SetReaderIdle()

SetIdle()Pause()

ScheduleStateMachine()

Low Video Threshold

SKIP TO NEXT KEY FRAME

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Timeline

Current timeLast decoded frame time

Next key frame

Drop frames!

AUDIO & VIDEO SYNCHRONIZATION

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Video queue

Checking Time-step

(Audio/system clock)

Image container

Discarding !

Video data Video data

too early

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END