在媒体编解码方面，我有点新手，如果我说错了什么，请纠正我。
我想使用VLC/ffplay播放MediaCodec的原始h264输出。我需要这样做是因为我的最终目标是将一些实时视频流传输到计算机上，并且MediaMuxer只能产生一个文件，而不能像我想要的那样低延迟地流式传输到桌面。（我也可以接受其他解决方案，但我还没有找到符合延迟要求的其他东西）
以下是我用于编码视频并将其写入文件的代码：（它基于此处找到的MediaCodec示例，只是删除了MediaMuxer部分）
package com.jackos2500.droidtop;
import android.media.MediaCodec;
import android.media.MediaCodecInfo;
import android.media.MediaFormat;
import android.opengl.EGL14;
import android.opengl.EGLConfig;
import android.opengl.EGLContext;
import android.opengl.EGLDisplay;
import android.opengl.EGLExt;
import android.opengl.EGLSurface;
import android.opengl.GLES20;
import android.os.Environment;
import android.util.Log;
import android.view.Surface;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
public class StreamH264 {
private static final String TAG = "StreamH264";
private static final boolean VERBOSE = true; // lots of logging
// where to put the output file (note: /sdcard requires WRITE_EXTERNAL_STORAGE permission)
private static final File OUTPUT_DIR = Environment.getExternalStorageDirectory();
public static int MEGABIT = 1000 * 1000;
private static final int IFRAME_INTERVAL = 10;
private static final int TEST_R0 = 0;
private static final int TEST_G0 = 136;
private static final int TEST_B0 = 0;
private static final int TEST_R1 = 236;
private static final int TEST_G1 = 50;
private static final int TEST_B1 = 186;
private MediaCodec codec;
private CodecInputSurface inputSurface;
private BufferedOutputStream out;
private MediaCodec.BufferInfo bufferInfo;
public StreamH264() {
}
private void prepareEncoder() throws IOException {
bufferInfo = new MediaCodec.BufferInfo();
MediaFormat format = MediaFormat.createVideoFormat("video/avc", 1280, 720);
format.setInteger(MediaFormat.KEY_BIT_RATE, 2 * MEGABIT);
format.setInteger(MediaFormat.KEY_FRAME_RATE, 30);
format.setInteger(MediaFormat.KEY_COLOR_FORMAT, MediaCodecInfo.CodecCapabilities.COLOR_FormatSurface);
format.setInteger(MediaFormat.KEY_I_FRAME_INTERVAL, IFRAME_INTERVAL);
codec = MediaCodec.createEncoderByType("video/avc");
codec.configure(format, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);
inputSurface = new CodecInputSurface(codec.createInputSurface());
codec.start();
File dst = new File(OUTPUT_DIR, "test.264");
out = new BufferedOutputStream(new FileOutputStream(dst));
}
private void releaseEncoder() throws IOException {
if (VERBOSE) Log.d(TAG, "releasing encoder objects");
if (codec != null) {
codec.stop();
codec.release();
codec = null;
}
if (inputSurface != null) {
inputSurface.release();
inputSurface = null;
}
if (out != null) {
out.flush();
out.close();
out = null;
}
}
public void stream() throws IOException {
try {
prepareEncoder();
inputSurface.makeCurrent();
for (int i = 0; i < (30 * 5); i++) {
// Feed any pending encoder output into the file.
drainEncoder(false);
// Generate a new frame of input.
generateSurfaceFrame(i);
inputSurface.setPresentationTime(computePresentationTimeNsec(i, 30));
// Submit it to the encoder. The eglSwapBuffers call will block if the input
// is full, which would be bad if it stayed full until we dequeued an output
// buffer (which we can't do, since we're stuck here). So long as we fully drain
// the encoder before supplying additional input, the system guarantees that we
// can supply another frame without blocking.
if (VERBOSE) Log.d(TAG, "sending frame " + i + " to encoder");
inputSurface.swapBuffers();
}
// send end-of-stream to encoder, and drain remaining output
drainEncoder(true);
} finally {
// release encoder, muxer, and input Surface
releaseEncoder();
}
}
private void drainEncoder(boolean endOfStream) throws IOException {
final int TIMEOUT_USEC = 10000;
if (VERBOSE) Log.d(TAG, "drainEncoder(" + endOfStream + ")");
if (endOfStream) {
if (VERBOSE) Log.d(TAG, "sending EOS to encoder");
codec.signalEndOfInputStream();
}
ByteBuffer[] outputBuffers = codec.getOutputBuffers();
while (true) {
int encoderStatus = codec.dequeueOutputBuffer(bufferInfo, TIMEOUT_USEC);
if (encoderStatus == MediaCodec.INFO_TRY_AGAIN_LATER) {
// no output available yet
if (!endOfStream) {
break; // out of while
} else {
if (VERBOSE) Log.d(TAG, "no output available, spinning to await EOS");
}
} else if (encoderStatus == MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED) {
// not expected for an encoder
outputBuffers = codec.getOutputBuffers();
} else if (encoderStatus == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) {
// should happen before receiving buffers, and should only happen once
MediaFormat newFormat = codec.getOutputFormat();
Log.d(TAG, "encoder output format changed: " + newFormat);
} else if (encoderStatus < 0) {
Log.w(TAG, "unexpected result from encoder.dequeueOutputBuffer: " + encoderStatus);
// let's ignore it
} else {
ByteBuffer encodedData = outputBuffers[encoderStatus];
if (encodedData == null) {
throw new RuntimeException("encoderOutputBuffer " + encoderStatus + " was null");
}
if ((bufferInfo.flags & MediaCodec.BUFFER_FLAG_CODEC_CONFIG) != 0) {
// The codec config data was pulled out and fed to the muxer when we got
// the INFO_OUTPUT_FORMAT_CHANGED status. Ignore it.
if (VERBOSE) Log.d(TAG, "ignoring BUFFER_FLAG_CODEC_CONFIG");
bufferInfo.size = 0;
}
if (bufferInfo.size != 0) {
// adjust the ByteBuffer values to match BufferInfo (not needed?)
encodedData.position(bufferInfo.offset);
encodedData.limit(bufferInfo.offset + bufferInfo.size);
byte[] data = new byte[bufferInfo.size];
encodedData.get(data);
out.write(data);
if (VERBOSE) Log.d(TAG, "sent " + bufferInfo.size + " bytes to file");
}
codec.releaseOutputBuffer(encoderStatus, false);
if ((bufferInfo.flags & MediaCodec.BUFFER_FLAG_END_OF_STREAM) != 0) {
if (!endOfStream) {
Log.w(TAG, "reached end of stream unexpectedly");
} else {
if (VERBOSE) Log.d(TAG, "end of stream reached");
}
break; // out of while
}
}
}
}
private void generateSurfaceFrame(int frameIndex) {
frameIndex %= 8;
int startX, startY;
if (frameIndex < 4) {
// (0,0) is bottom-left in GL
startX = frameIndex * (1280 / 4);
startY = 720 / 2;
} else {
startX = (7 - frameIndex) * (1280 / 4);
startY = 0;
}
GLES20.glClearColor(TEST_R0 / 255.0f, TEST_G0 / 255.0f, TEST_B0 / 255.0f, 1.0f);
GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT);
GLES20.glEnable(GLES20.GL_SCISSOR_TEST);
GLES20.glScissor(startX, startY, 1280 / 4, 720 / 2);
GLES20.glClearColor(TEST_R1 / 255.0f, TEST_G1 / 255.0f, TEST_B1 / 255.0f, 1.0f);
GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT);
GLES20.glDisable(GLES20.GL_SCISSOR_TEST);
}
private static long computePresentationTimeNsec(int frameIndex, int frameRate) {
final long ONE_BILLION = 1000000000;
return frameIndex * ONE_BILLION / frameRate;
}
/**
* Holds state associated with a Surface used for MediaCodec encoder input.
* <p>
* The constructor takes a Surface obtained from MediaCodec.createInputSurface(), and uses that
* to create an EGL window surface. Calls to eglSwapBuffers() cause a frame of data to be sent
* to the video encoder.
* <p>
* This object owns the Surface -- releasing this will release the Surface too.
*/
private static class CodecInputSurface {
private static final int EGL_RECORDABLE_ANDROID = 0x3142;
private EGLDisplay mEGLDisplay = EGL14.EGL_NO_DISPLAY;
private EGLContext mEGLContext = EGL14.EGL_NO_CONTEXT;
private EGLSurface mEGLSurface = EGL14.EGL_NO_SURFACE;
private Surface mSurface;
/**
* Creates a CodecInputSurface from a Surface.
*/
public CodecInputSurface(Surface surface) {
if (surface == null) {
throw new NullPointerException();
}
mSurface = surface;
eglSetup();
}
/**
* Prepares EGL. We want a GLES 2.0 context and a surface that supports recording.
*/
private void eglSetup() {
mEGLDisplay = EGL14.eglGetDisplay(EGL14.EGL_DEFAULT_DISPLAY);
if (mEGLDisplay == EGL14.EGL_NO_DISPLAY) {
throw new RuntimeException("unable to get EGL14 display");
}
int[] version = new int[2];
if (!EGL14.eglInitialize(mEGLDisplay, version, 0, version, 1)) {
throw new RuntimeException("unable to initialize EGL14");
}
// Configure EGL for recording and OpenGL ES 2.0.
int[] attribList = {
EGL14.EGL_RED_SIZE, 8,
EGL14.EGL_GREEN_SIZE, 8,
EGL14.EGL_BLUE_SIZE, 8,
EGL14.EGL_ALPHA_SIZE, 8,
EGL14.EGL_RENDERABLE_TYPE, EGL14.EGL_OPENGL_ES2_BIT,
EGL_RECORDABLE_ANDROID, 1,
EGL14.EGL_NONE
};
EGLConfig[] configs = new EGLConfig[1];
int[] numConfigs = new int[1];
EGL14.eglChooseConfig(mEGLDisplay, attribList, 0, configs, 0, configs.length,
numConfigs, 0);
checkEglError("eglCreateContext RGB888+recordable ES2");
// Configure context for OpenGL ES 2.0.
int[] attrib_list = {
EGL14.EGL_CONTEXT_CLIENT_VERSION, 2,
EGL14.EGL_NONE
};
mEGLContext = EGL14.eglCreateContext(mEGLDisplay, configs[0], EGL14.EGL_NO_CONTEXT,
attrib_list, 0);
checkEglError("eglCreateContext");
// Create a window surface, and attach it to the Surface we received.
int[] surfaceAttribs = {
EGL14.EGL_NONE
};
mEGLSurface = EGL14.eglCreateWindowSurface(mEGLDisplay, configs[0], mSurface,
surfaceAttribs, 0);
checkEglError("eglCreateWindowSurface");
}
/**
* Discards all resources held by this class, notably the EGL context. Also releases the
* Surface that was passed to our constructor.
*/
public void release() {
if (mEGLDisplay != EGL14.EGL_NO_DISPLAY) {
EGL14.eglMakeCurrent(mEGLDisplay, EGL14.EGL_NO_SURFACE, EGL14.EGL_NO_SURFACE,
EGL14.EGL_NO_CONTEXT);
EGL14.eglDestroySurface(mEGLDisplay, mEGLSurface);
EGL14.eglDestroyContext(mEGLDisplay, mEGLContext);
EGL14.eglReleaseThread();
EGL14.eglTerminate(mEGLDisplay);
}
mSurface.release();
mEGLDisplay = EGL14.EGL_NO_DISPLAY;
mEGLContext = EGL14.EGL_NO_CONTEXT;
mEGLSurface = EGL14.EGL_NO_SURFACE;
mSurface = null;
}
/**
* Makes our EGL context and surface current.
*/
public void makeCurrent() {
EGL14.eglMakeCurrent(mEGLDisplay, mEGLSurface, mEGLSurface, mEGLContext);
checkEglError("eglMakeCurrent");
}
/**
* Calls eglSwapBuffers. Use this to "publish" the current frame.
*/
public boolean swapBuffers() {
boolean result = EGL14.eglSwapBuffers(mEGLDisplay, mEGLSurface);
checkEglError("eglSwapBuffers");
return result;
}
/**
* Sends the presentation time stamp to EGL. Time is expressed in nanoseconds.
*/
public void setPresentationTime(long nsecs) {
EGLExt.eglPresentationTimeANDROID(mEGLDisplay, mEGLSurface, nsecs);
checkEglError("eglPresentationTimeANDROID");
}
/**
* Checks for EGL errors. Throws an exception if one is found.
*/
private void checkEglError(String msg) {
int error;
if ((error = EGL14.eglGetError()) != EGL14.EGL_SUCCESS) {
throw new RuntimeException(msg + ": EGL error: 0x" + Integer.toHexString(error));
}
}
}
}
然而，从这段代码生成的文件无法在VLC或ffplay中播放。有人能告诉我我做错了什么吗？我认为这是由于播放原始h264所需的标头格式（或完全缺少）不正确导致的，因为我已经成功地使用ffplay播放从互联网下载的.264文件。此外，我不确定如何将此视频流式传输到计算机上，如果有人能给我一些建议，我将非常感激！谢谢！