MediaCodec

部分简单#xff0c;越读越发现自己的无知#xff0c;Android

源码真…

onRequestInputBuffers();virtual

bool

等等方法这时候可能就会有人有疑问了我上层调用的这些接口为什么底层却没有了呢其实在之前的文章中我们已经对部分接口做了解释这里就不再赘述。

构造函数传入一个

type、surface、secure、width、height、crypto、csd

等等信息创建

设定上层传下的参数pause这个方法其实并没有用后面详细了解它为什么没有用setRenderer设定

renderdecoder

的解码流程initiateShutdown停止解码流程并释放相关资源getStats获取当前

Decoder

信息当前解出的帧数丢弃的帧数等等信息。

其他onConfigure

Decoder

NuPlayer::instantiateDecoder(bool

audio,

mSource-getFormat(audio);*decoder

new

mCCDecoder);(*decoder)-init();(*decoder)-configure(format);

}init

{mDecoderLooper-registerHandler(this);

}后面

NuPlayer::DecoderBase::onRequestInputBuffers()

{....spAMessage

AMessage(kWhatRequestInputBuffers,

this);msg-post(10

NuPlayer::Decoder::onConfigure(const

spAMessage

mime;CHECK(format-findString(mime,

mime));mIsAudio

MediaCodec::CreateByType(mCodecLooper,

mime.c_str(),

{mCodec-getName(mComponentName);mComponentName.append(.secure);mCodec-release();mCodec

MediaCodec::CreateByComponentName(mCodecLooper,

NULL

*/);rememberCodecSpecificData(format);spAMessage

reply

this);mCodec-setCallback(reply);err

mCodec-start();

mBufferGeneration这个东西是干什么的呢其实我们之前已经说过

Media

NuPlayer::Decoder::isStaleReply(const

spAMessage

generation;CHECK(msg-findInt32(generation,

generation));return

NuPlayer::Decoder::onMessageReceived(const

spAMessage

ACodec、NuPlayer::Source、Renderer

generation

发送消息NuPlayer、Renderer、MediaCodec

Decoder

index);reply-setInt32(generation,

mBufferGeneration);reply-setSize(size,

size);Decoder

起着状态记录的作用当状态发生改变后依赖该状态的消息将会不再处理。

它和一些具体的状态例如

MediaPlayer.cpp

NuPlayer::Decoder::onMessageReceived(const

spAMessage

cbID;CHECK(msg-findInt32(callbackID,

cbID));switch

MediaCodec::CB_INPUT_AVAILABLE:{int32_t

index;CHECK(msg-findInt32(index,

index));handleAnInputBuffer(index);break;}case

MediaCodec::CB_OUTPUT_AVAILABLE:{int32_t

index;size_t

flags;CHECK(msg-findInt32(index,

index));CHECK(msg-findSize(offset,

offset));CHECK(msg-findSize(size,

size));CHECK(msg-findInt64(timeUs,

timeUs));CHECK(msg-findInt32(flags,

flags));handleAnOutputBuffer(index,

offset,

CB_INPUT_AVAILABLE、CB_OUTPUT_AVAILABLE、CB_ERROR、CB_OUTPUT_FORMAT_CHANGED

这四个我们这里只看

NuPlayer::Decoder::handleAnInputBuffer(size_t

index)

buffer;mCodec-getInputBuffer(index,

buffer);if

{mInputBuffers.add();mInputBufferIsDequeued.add();mMediaBuffers.editItemAt(i)

NULL;mInputBufferIsDequeued.editItemAt(i)

false;}}mInputBuffers.editItemAt(index)

buffer;mInputBufferIsDequeued.editItemAt(index)

true;//

AMessage();msg-setSize(buffer-ix,

index);spABuffer

mCSDsToSubmit.itemAt(0);msg-setBuffer(buffer,

buffer);mCSDsToSubmit.removeAt(0);if

{handleError(UNKNOWN_ERROR);return

false;}return

(!mPendingInputMessages.empty())

{spAMessage

*mPendingInputMessages.begin();if

{break;}mPendingInputMessages.erase(mPendingInputMessages.begin());}//

如果在

(!mInputBufferIsDequeued.editItemAt(index))

{return

中mDequeuedInputBuffers.push_back(index);//

尝试从

decoderonRequestInputBuffers();return

true;

datadoRequestBuffersonRequestInputBuffers

内部实现onInputBufferFetched成功从Source

获取到数据填充到

MediaCodecfetchInputDataonInputBufferFetched

我们从

NuPlayer::DecoderBase::onRequestInputBuffers()

{//

获取数据的调用mRequestInputBuffersPending

true;spAMessage

AMessage(kWhatRequestInputBuffers,

this);msg-post(10

doRequestBuffers所以它们的作用是相同的但是一个是基类的方法一个是子类的方法。

这么设计有什么用呢我的理解是这样每个

Decoder

方法使用父类定义的数据读取流程流程中调用子类的数据读取实现这样就一举两得既统一了读取流程又区分了读取方式。

另外这里还有

获取数据失败了那么需要做延时等待并且重新尝试获取等待的过程中我们并不希望外部能够再调用到

doRequestBuffers

NuPlayer::Decoder::doRequestBuffers()

{if

!mDequeuedInputBuffers.empty())

{size_t

*mDequeuedInputBuffers.begin();spAMessage

msg

AMessage();msg-setSize(buffer-ix,

bufferIx);err

bufferbreak;}mDequeuedInputBuffers.erase(mDequeuedInputBuffers.begin());if

(!mPendingInputMessages.empty()||

{mPendingInputMessages.push_back(msg);}}return

err

NuPlayer::Decoder::fetchInputData(spAMessage

reply)

mSource-dequeueAccessUnit(mIsAudio,

accessUnit);//

获取码流不连续的原因CHECK(accessUnit-meta()-findInt32(discontinuity,

type));bool

ATSParser::DISCONTINUITY_AUDIO_FORMAT))||

(!mIsAudio

ATSParser::DISCONTINUITY_VIDEO_FORMAT));bool

timeChange

判断当前播放的码流格式是否支持无缝切换seamlessFormatChange

supportsSeamlessFormatChange(newFormat);//

treat

bufferrememberCodecSpecificData(newFormat);mTimeChangePending

true;err

bufferrememberCodecSpecificData(newFormat);continue;}

else

100ms视频为avc并且不是参考帧那么就drop掉当前读取的内容if

100000LL

!IsAVCReferenceFrame(accessUnit))

{dropAccessUnit

(dropAccessUnit);reply-setBuffer(buffer,

accessUnit);return

不仅仅是获取了数据还对码流的异常情况做了处理。

dequeueAccessUnit

四种返回值

OK获取到有效数据-EWOULDBLOCK未能读取到数据INFO_DISCONTINUITY码流不连续ERROR_END_OF_STREAM读到文件末尾

返回值为

DISCONTINUITY_VIDEO_FORMAT格式变化分别宽高变化和mime

selectTrack

DISCONTINUITY_TIME这种情况出现在直播的回播中比较多。

无缝切换adaptive-playback如果支持则不对该事件做处理如果不支持把返回值设置为

pts不连续

ERROR_END_OF_STREAM那么重新开始播放之后需要先填充

csd

MediaCodec这里比较简单就是做了数据拷贝而已要看的只有

EOS

事件处理完成后才会写入下一个序列的数据这部分我们放到下一小节来看。

bool

NuPlayer::Decoder::isDiscontinuityPending()

const

NuPlayer::Decoder::handleAnOutputBuffer(size_t

index,size_t

buffermCodec-getOutputBuffer(index,

buffer);int64_t

buffer-meta()-findInt64(frameIndex,

frameIndex);buffer-setRange(offset,

size);//

ptsbuffer-meta()-clear();buffer-meta()-setInt64(timeUs,

timeUs);if

{buffer-meta()-setInt64(frameIndex,

frameIndex);}//

index);reply-setInt32(generation,

mBufferGeneration);reply-setSize(size,

size);//

video);buffer-meta()-setInt32(eos,

!mIsAudio;//

(mSkipRenderingUntilMediaTimeUs

{if

mSkipRenderingUntilMediaTimeUs)

{ALOGV([%s]

requested.,mComponentName.c_str(),

(long

{notifyResumeCompleteIfNecessary();if

(mRenderer

true;}mSkipRenderingUntilMediaTimeUs

-1;}//

播放停止后重新恢复播放等待第一帧到达后上抛消息在seek时用到notifyResumeCompleteIfNecessary();if

(mRenderer

avsyncmRenderer-queueBuffer(mIsAudio,

buffer,

NuPlayer::Decoder::handleOutputFormatChange(const

spAMessage

autolock(mStatsLock);mStats-setInt32(width,

height);}spAMessage

mNotify-dup();notify-setInt32(what,

kWhatVideoSizeChanged);notify-setMessage(format,

else

(mSource-getDuration(durationUs)

durationUs

AUDIO_SINK_MIN_DEEP_BUFFER_DURATION_US))

{flags

AUDIO_OUTPUT_FLAG_DEEP_BUFFER;}

else

AUDIO_OUTPUT_FLAG_NONE;}spAMessage

reply

AMessage(kWhatAudioOutputFormatChanged,

this);reply-setInt32(generation,

mBufferGeneration);mRenderer-changeAudioFormat(format,

false

{onRenderBuffer(msg);}break;}isStaleReply

onRenderBuffer

NuPlayer::Decoder::onRenderBuffer(const

spAMessage

indexCHECK(msg-findSize(buffer-ix,

bufferIx));if

timestampNs;CHECK(msg-findInt64(timestampNs,

timestampNs));

mCodec-renderOutputBufferAndRelease(bufferIx,

timestampNs);}

mCodec-releaseOutputBuffer(bufferIx);}//

(msg-findInt32(eos,

{finishHandleDiscontinuity(true

flushOnTimeChange

renderOutputBufferAndRelease否则调用

reply

NuPlayer::Decoder::finishHandleDiscontinuity(bool

flushOnTimeChange)

{ALOGV(finishHandleDiscontinuity:

format

mNotify-dup();msg-setInt32(what,

kWhatInputDiscontinuity);msg-setInt32(formatChange,

mFormatChangePending);msg-post();mFormatChangePending

false;

DecoderBase::kWhatInputDiscontinuity)

{int32_t

formatChange;CHECK(msg-findInt32(formatChange,

discontinuity:

{mDeferredActions.push_back(new

FLUSH_CMD_SHUTDOWN

FLUSH_CMD_SHUTDOWN));}mDeferredActions.push_back(new

SimpleAction(NuPlayer::performScanSources));processDeferredActions();}

NuPlayer

NuPlayer::Decoder::doFlush(bool

notifyComplete)

notifyComplete);mRenderer-signalTimeDiscontinuity();}status_t

err

fails.}releaseAndResetMediaBuffers();mPaused

true;

handled.finishHandleDiscontinuity(false

flushOnTimeChange

mNotify-dup();notify-setInt32(what,

kWhatFlushCompleted);notify-post();

}flush

NuPlayer::Decoder::onShutdown(bool

notifyComplete)

nownotifyResumeCompleteIfNecessary();if

(mCodec

nativeWindowConnect(mSurface.get(),

NO_ERROR,[%s]

error%d,mComponentName.c_str(),

decoder;}//

listreleaseAndResetMediaBuffers();if

(err

mNotify-dup();notify-setInt32(what,

kWhatShutdownCompleted);notify-post();//

停止处理

NuPlayer::Decoder::onResume(bool

notifyComplete)

mComponentName.c_str());handleError(NO_INIT);return;}mCodec-start();

}flush

机制领悟的还不够深刻设计模式也不会接下来会继续加强这部分的学习

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如需阅读其他

https://blog.csdn.net/qq_41828351?spm1000.2115.3001.5343