Android Camera预览时输出的帧率控制
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= 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());
}
public void onPreviewFrame(byte[] _data, Camera _camera) {
mRingBuffer.enqueue(_data);
}====================2017-05-15 更新 ===================