Android-7.0-Nuplayer-启动流程

Nuplayer为异步架构，随处可见的AMessage看代码着实头大，
以下为个人总结，供大家参考，如有错误不吝赐教。

Nuplayer简介

Android2.3时引入流媒体框架，而流媒体框架的核心是NuPlayer。Android4.0之后HttpLive和RTSP协议开始使用NuPlayer播放器，Android5.0（L版本）之后本地播放也开始使用NuPlayer播放器。

启动Nuplayer

1. 发送kWhatStart消息即可启动player
2. 启动Decoder之后是一直polling input buffer

ConfigDecoder流程

1. 初始化Decoder ACodec OMX
2. 将Output Buffer塞给OMX
3. 填充Input Buffer

Input-Output Buffer流程

1. 将Input Buffer送给OMX，并再次填充
2. 将Output Buffer设置给OMX，并取得解码后的data
3. 见解码后的data送给Render做AV同步

完整序列图

完整序列图源码

打开Web Sequence Diagrams网址，直接粘贴进去即可。

Title Start流程participant NuPlayerDriverparticipant NuPlayerparticipant DecoderBaseparticipant Decoderparticipant MediaCodecparticipant ACodecparticipant BaseStateparticipant UninitializedStateparticipant LoadedStateparticipant LoadedToIdleStateparticipant IdleToExecutingStateparticipant ExecutingStateparticipant OMXopt Start    NuPlayerDriver->+NuPlayer: start()        NuPlayer-->NuPlayer: kWhatStart    NuPlayer-->-NuPlayerDriver:    NuPlayer->+NuPlayer: onStart()            NuPlayer->+DecoderBase: setRenderer()            DecoderBase-->DecoderBase: kWhatSetRenderer            DecoderBase-->-NuPlayer:         NuPlayer->NuPlayer: postScanSources()    NuPlayer-->-NuPlayer: kWhatScanSourcesend opt Polling InputBuffer    DecoderBase->+Decoder: onSetRenderer()        loop         Decoder->DecoderBase: onRequestInputBuffers()        DecoderBase->Decoder: doRequestBuffers()        Decoder->Decoder: fetchInputData()        Decoder->Decoder: onInputBufferFetched()        Decoder-->DecoderBase: kWhatRequestInputBuffers        end    Decoder-->-DecoderBase:endopt ConfigDecoder    NuPlayer->+NuPlayer: instantiateDecoder()        NuPlayer->+DecoderBase: init()        DecoderBase-->-NuPlayer:        NuPlayer->+DecoderBase: configure()        DecoderBase-->DecoderBase: kWhatConfigure        DecoderBase-->-NuPlayer:     NuPlayer-->-NuPlayer:    DecoderBase->+Decoder: onConfigure()        Decoder->+MediaCodec: CreateByType()            MediaCodec->MediaCodec: init()            MediaCodec-->MediaCodec: kWhatInit        MediaCodec-->-Decoder:        MediaCodec->+ACodec: initiateAllocateComponent            ACodec-->ACodec:kWhatAllocateComponent        ACodec-->-MediaCodec:         ACodec->+UninitializedState: onAllocateComponent()            UninitializedState->+OMX: allocateNode()            OMX-->-UninitializedState:             UninitializedState->+LoadedState: stateEntered()            LoadedState-->-UninitializedState:         UninitializedState-->-ACodec:         Decoder->+MediaCodec: configure()            MediaCodec-->MediaCodec: kWhatConfigure        MediaCodec-->-Decoder:         MediaCodec->+ACodec:initiateConfigureComponent()            ACodec-->ACodec: kWhatConfigureComponent        ACodec-->-MediaCodec:        ACodec->+LoadedState: onConfigureComponent()        LoadedState->-ACodec: configureCodec()        Decoder->+MediaCodec: setCallback()        MediaCodec-->-Decoder:         Decoder->+MediaCodec: start()            MediaCodec-->MediaCodec: kWhatStart            MediaCodec->+ACodec: initiateStart()                ACodec-->ACodec: kWhatStart            ACodec-->-MediaCodec:        MediaCodec-->-Decoder:    Decoder-->-DecoderBase:    ACodec->+LoadedState: onStart()        LoadedState-->OMX: sendCommand(OMX_StateIdle)        LoadedState->+LoadedToIdleState: stateEntered()            LoadedToIdleState->LoadedToIdleState: allocateBuffers()            LoadedToIdleState->+ACodec: allocateBuffersOnPort()            ACodec-->-LoadedToIdleState:         LoadedToIdleState-->-LoadedState:    LoadedState-->-ACodec:    OMX-->+LoadedToIdleState: OMX_EventCmdComplete        LoadedToIdleState-->OMX: sendCommand(OMX_StateExecuting)        LoadedToIdleState->+IdleToExecutingState: stateEntered()        IdleToExecutingState-->-LoadedToIdleState:    LoadedToIdleState-->-OMX:    OMX-->+IdleToExecutingState: OMX_EventCmdComplete        IdleToExecutingState->+ExecutingState: resume()            ExecutingState->ExecutingState: submitOutputBuffers()            ExecutingState->ExecutingState: submitRegularOutputBuffers            ExecutingState-->OMX: fillBuffer()            ExecutingState-->BaseState: postFillThisBuffer()            IdleToExecutingState->ExecutingState: stateEntered()        ExecutingState-->-IdleToExecutingState:    IdleToExecutingState-->-OMX:endloop InputBuffer    OMX-->+BaseState: omx_message::EMPTY_BUFFER_DONE        BaseState->BaseState: onOMXEmptyBufferDone()        BaseState->BaseState: postFillThisBuffer()        BaseState-->MediaCodec: CodecBase::kWhatFillThisBuffer    BaseState-->-OMX:    MediaCodec->+MediaCodec: onInputBufferAvailable()    MediaCodec-->-Decoder: MediaCodec::CB_INPUT_AVAILABLE    Decoder->+Decoder: handleAnInputBuffer()        Decoder->Decoder: onInputBufferFetched()        Decoder->+MediaCodec: queueInputBuffer()            MediaCodec-->MediaCodec: kWhatQueueInputBuffer        MediaCodec-->-Decoder:    Decoder-->-DecoderBase: onRequestInputBuffers()    MediaCodec->+MediaCodec: onQueueInputBuffer()    MediaCodec-->-BaseState: kWhatInputBufferFilled    BaseState->+BaseState: onInputBufferFilled()    BaseState-->-OMX: emptyBuffer()endloop OutputBuffer    OMX-->+BaseState: omx_message::FILL_BUFFER_DONE        BaseState->BaseState: onOMXEmptyBufferDone()        BaseState-->MediaCodec: CodecBase::kWhatDrainThisBuffer    BaseState-->-OMX:    MediaCodec->+MediaCodec:updateBuffers    MediaCodec->MediaCodec: onOutputBufferAvailable()    MediaCodec-->-Decoder: MediaCodec::CB_OUTPUT_AVAILABLE    Decoder->+Decoder: handleAnOutputBuffer()    Decoder->Decoder: onRenderBuffer()    Decoder->-MediaCodec: renderOutputBufferAndRelease()    MediaCodec-->MediaCodec: kWhatReleaseOutputBuffer    MediaCodec->+MediaCodec: onReleaseOutputBuffer()    MediaCodec-->-BaseState: kWhatOutputBufferDrained    BaseState->+BaseState: onOutputBufferDrained()    BaseState-->-OMX: fillBuffer()end