Android Camera預覽時輸出的幀率控制
阿新 • • 發佈：2019-02-02
如果使用MediaCodec硬編碼H264，可以使用下面的方法控制編碼輸出的幀率：
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();
但如果是採用預覽模式下得到預覽的BITMAP，然後通過x264編碼的來實現的方式，則需要應用層控制預覽幀的幀幀率，Camera本來提供了兩個介面來控制預覽幀率，但從多個平臺的適配發現，基本上都不能有效的控制Camera預覽輸出的幀率：
setPreviewFrameRate是在api level1就開始使用了，然後不是簡單地設定這個方法就可以讓攝像頭每秒捕獲多少幀數的。 比如我設定2，它一秒不會只捕獲2幀資料的，從日誌記錄來看，相當糟糕，不會是預期的2幀，於是我查詢文件，發現這個方法已經廢除了。 在api level9時加入了一個方法setPreviewFpsRange (int min, int max) 預覽幀數從min到max，這個值再*1000. 這個方法已經在高版本的sdk中取代了舊的setPreviewFrameRate。
====================2017-05-15 更新 ===================
當初把這個問題複雜化了，其實對預覽幀的回撥做下控制就能達到該目的，程式碼：
private final static int MAX_FPS = 15; //視訊通話控制在15幀是足夠的 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 預覽幀數和視訊通話圖片快取 中提到為什麼預覽幀設定失效的問題，並且也給出了一個控制預覽幀的方式，這裡提供另外一種類似的實現：無鎖佇列的實現。
下面 RingBuffer的定義：
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;
}
};
出隊執行緒：
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 ===================