Android-7.0-Nuplayer-启动流程

原帖地址：

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 NuPlayerDriver
participant NuPlayer
participant DecoderBase
participant Decoder
participant MediaCodec
participant ACodec
participant BaseState
participant UninitializedState
participant LoadedState
participant LoadedToIdleState
participant IdleToExecutingState
participant ExecutingState
participant OMX


opt 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: kWhatScanSources
end 


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:
end


opt 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:
end


loop 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()
end


loop 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