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. }
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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<max_size; 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 ===================
