安卓获取摄像头帧率_Android Camera预览时输出的帧率控制

Android Camera预览时输出的帧率控制

2016年08月16日 14:24:28

阅读数：13250

如果使用MediaCodec硬编码H264，可以使用下面的方法控制编码输出的帧率：

MediaFormat mediaFormat = MediaFormat.createVideoFormat("video/avc", width, height);

mediaFormat.setInteger(MediaFormat.KEY_COLOR_FORMAT, MediaCodecInfo.CodecCapabilities.COLOR_FormatYUV420SemiPlanar);

mediaFormat.setInteger(MediaFormat.KEY_BIT_RATE, width*height*5);

mediaFormat.setInteger(MediaFormat.KEY_FRAME_RATE, 30);

mediaFormat.setInteger(MediaFormat.KEY_I_FRAME_INTERVAL, 1);

try {

mediaCodec = MediaCodec.createEncoderByType("video/avc");

} catch (IOException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

mediaCodec.configure(mediaFormat, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);

mediaCodec.start();

但如果是采用预览模式下得到预览的BITMAP，然后通过x264编码的来实现的方式，则需要应用层控制预览帧的帧帧率，Camera本来提供了两个接口来控制预览帧率，但从多个平台的适配发现，基本上都不能有效的控制Camera预览输出的帧率：

setPreviewFrameRate是在api level1就开始使用了，然后不是简单地设置这个方法就可以让摄像头每秒捕获多少帧数的。

比如我设置2，它一秒不会只捕获2帧数据的，从日志记录来看，相当糟糕，不会是预期的2帧，于是我查找文档，发现这个方法已经废除了。

在api level9时加入了一个方法setPreviewFpsRange (int min, int max)

预览帧数从min到max，这个值再*1000.

这个方法已经在高版本的sdk中取代了旧的setPreviewFrameRate。

====================2017-05-15 更新 ===================

当初把这个问题复杂化了，其实对预览帧的回调做下控制就能达到该目的，代码：

private final static int MAX_FPS = 15;    //视频通话控制在15帧是足够的

private final static int FRAME_PERIOD = (1000 / MAX_FPS); // the frame period

long lastTime = 0;

long timeDiff = 0;

int framesSkipped = 0; // number of frames being skipped

int framesRecevied = 0; // number of frames being skipped

int framesSended = 0; // number of frames being skipped

private PreviewCallback previewCallback = new PreviewCallback() {

public void onPreviewFrame(byte[] _data, Camera _camera) {

timeDiff = System.currentTimeMillis() - lastTime;

framesRecevied++;

if (timeDiff < FRAME_PERIOD){

framesSkipped++;

if (NgnProxyVideoProducer.sAddCallbackBufferSupported) {

// do not use "_data" which could be null (e.g. on GSII)

NgnCameraProducer.addCallbackBuffer(_camera,

_data == null ? mVideoCallbackData : _data);

}

Log.d(TAG, "ii loglized diserved framesSkipped:"+framesSkipped + ",framesRecevied:"+framesRecevied + ", framesSended:"+framesSended);

return;

}

lastTime = System.currentTimeMillis();

framesSended++;

// add end.

//doing other thing.

}

====================2017-05-15 更新 ===================

上面是文章： Android camera 预览帧数和视频通话图片缓存 中提到为什么预览帧设置失效的问题，并且也给出了一个控制预览帧的方式，这里提供另外一种类似的实现：无锁队列的实现。

下面 RingBuffer的定义：

final byte STATU_INIT = 0;

final byte STATU_WAIT_DEQEUE = 1;

class UserDefinedBuffer{

ByteBuffer mVideoFrame;

byte status;

}

//the ring queue

class RingBuffer{

int r_index;

int w_index;

int size;

UserDefinedBuffer[] mUserDefinedBuffer;

long last_time;

public RingBuffer(int max_size, int capacity){

mUserDefinedBuffer = new UserDefinedBuffer[max_size];

r_index = w_index = 0;

size = max_size;

for(int i=0 ;i

mUserDefinedBuffer[i] = new UserDefinedBuffer();

mUserDefinedBuffer[i].mVideoFrame = ByteBuffer.allocateDirect(capacity);

}

}

public UserDefinedBuffer getUserDefinedBuffer(int index){

return mUserDefinedBuffer[index];

}

int getRingW(){

return w_index;

}

int getRingR(){

return r_index;

}

int getRingSize(){

return size;

}

void  setUserDefinedBufferStatus(int index, byte status){

synchronized(mUserDefinedBuffer[index]){

mUserDefinedBuffer[index].status = status;

}

}

byte getUserDefinedBufferStatus(int index){

synchronized(mUserDefinedBuffer[index]){

return mUserDefinedBuffer[index].status;

}

}

void enqueue(byte[] _data){

int index = w_index & (size -1);

Log.i(TAG, "#enqueue, index:"+index);

if (index >= size){

index = 0;

}

if (getUserDefinedBufferStatus(index) != STATU_INIT){

Log.i(TAG, "i enqueue, index:"+index+", not dequeue" + ", STATUS:"+getUserDefinedBufferStatus(index));

return;

}

setUserDefinedBufferStatus(index, STATU_WAIT_DEQEUE);

mUserDefinedBuffer[index].mVideoFrame.rewind();

mUserDefinedBuffer[index].mVideoFrame.put(_data);

w_index += 1;

}

void enqueue(ByteBuffer data){

int index = w_index & (size -1);

Log.i(TAG, "enqueue, index:"+index);

if (index >= size){

index = 0;

}

if (getUserDefinedBufferStatus(index) != STATU_INIT){

Log.i(TAG, "ii enqueue, index:"+index+", not dequeue" + ", STATUS:"+getUserDefinedBufferStatus(index));

return;

}

setUserDefinedBufferStatus(index, STATU_WAIT_DEQEUE);

mUserDefinedBuffer[index].mVideoFrame.rewind();

mUserDefinedBuffer[index].mVideoFrame.put(data);

w_index += 1;

//last_time = System.currentTimeMillis();

}

long getLastTime(){

return last_time;

}

int dequeue(){

int index = r_index & (size -1);

if (index == (w_index & (size -1))){

Log.i(TAG, "dequeue, w_index:"+w_index + ", r_index:"+r_index);

return -1;

}

Log.i(TAG, "dequeue, index:"+index);

r_index += 1;

//ByteBuffer data =  mUserDefinedBuffer[index].mVideoFrame;

//mUserDefinedBuffer[index].mVideoFrame.rewind();

return index;

}

};

出队线程：

class PushVideoThread extends Thread{

boolean mExitFlag = false;

public void setExitFlg(boolean bFlag){

mExitFlag = bFlag;

}

@Override

public void run() {

android.os.Process

.setThreadPriority(android.os.Process.THREAD_PRIORITY_URGENT_AUDIO);

Log.i(TAG, "PushVideoThread() run start.");

final int delay = (100/mFps);//

while(!mExitFlag){

long start=System.currentTimeMillis();

if (mRingBuffer == null){

try {

Thread.sleep(delay);

} catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

continue;

}

int index = mRingBuffer.dequeue();

if (index == -1){

try {

Thread.sleep(delay);

} catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

continue;

}

if (STATU_WAIT_DEQEUE != mRingBuffer.getUserDefinedBufferStatus(index)){

Log.i(TAG, "Ana  dequeue mRingBuffer.getUserDefinedBufferStatus(index):"+mRingBuffer.getUserDefinedBufferStatus(index));

try {

Thread.sleep(delay);

} catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

continue;

}

UserDefinedBuffer userDefindedBuffer = mRingBuffer.getUserDefinedBuffer(index);

ByteBuffer byteBuffer = userDefindedBuffer.mVideoFrame;

if (byteBuffer != null){

framesRendered++;

if ((framesRendered % 100) == 0) {

logStatistics();

framesRendered = 0;

startTimeNs= System.nanoTime();

}

//   Log.i(TAG, "Ana  dequeue getRingW:"+ write +",getRingR:"+ read);

mProducer.push(byteBuffer, mVideoFrame.capacity());

mRingBuffer.setUserDefinedBufferStatus(index, STATU_INIT);

}

long end=System.currentTimeMillis();

if ((end - start) < delay && (end - start) > 0){

try {

long value = delay - (end -start);

if (value > 0){

Thread.sleep(value);

}

} catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

}

Log.i(TAG, "PushVideoThread() run End.");

}

}

RingBuffer的初始化：

static final int MAX_SIZE = 64;//must 2 mul

RingBuffer mRingBuffer;

void initRingBuffer(){

mRingBuffer = new RingBuffer(MAX_SIZE, mVideoFrame.capacity());

}

入队：

public void onPreviewFrame(byte[] _data, Camera _camera){

mRingBuffer.enqueue(_data);

}

====================2017-05-15 更新 ===================