上一集，有读者吐槽这个系列更新太慢了，其实实现代码一直都有，只能每天花一点时间整理一些，慢慢整理出来。
前文利用 FFmpeg 分别实现了对 Android Camera2 采集的预览帧进行编码生成 mp4 文件，以及对 Android AudioRecorder 采集 PCM 音频进行编码生成 aac 文件。
本文将实现对采集的预览帧（添加滤镜）和 PCM 音频同时编码复用生成一个 mp4 文件，即实现一个仿微信小视频录制功能。
音视频录制编码流程
音视频编码流程图
本文采用的是软件编码（CPU）实现，所以针对高分辨率的预览帧时，就需要考虑 CPU 能不能吃得消，在骁龙 8250 上使用软件编码分辨率超过 1080P 的图像就会导致 CPU 比较吃力，这个时候帧率就跟不上了。
音视频录制代码实现
Java 层视频帧来自 Android Camera2 API 回调接口。
代码语言：javascript复制private ImageReader.OnImageAvailableListener mOnPreviewImageAvailableListener = new ImageReader.OnImageAvailableListener() {
@Override
public void onImageAvailable(ImageReader reader) {
Image image = reader.acquireLatestImage();
if (image != null) {
if (mCamera2FrameCallback != null) {
mCamera2FrameCallback.onPreviewFrame(CameraUtil.YUV_420_888_data(image), image.getWidth(), image.getHeight());
}
image.close();
}
}
};
Java 层音频使用的是 Android AudioRecorder API 录制的，将 AudioRecoder 封装到线程里，通过接口回调的方式将 PCM 数据传出来，默认采样率为 44.1kHz，双通道立体声，采样格式为 PCM 16 bit 。
JNI 实现主要是，在开始录制时传入输出文件路径、视频码率、帧率、视频宽高等参数，然后不断将音频帧和视频帧传入 Native 层的编码队列中，供编码器编码。
代码语言：javascript复制//开始录制，输出文件路径、视频码率、帧率、视频宽高等参数
extern "C"
JNIEXPORT jint JNICALL
Java_com_byteflow_learnffmpeg_media_MediaRecorderContext_native_1StartRecord(JNIEnv *env,
jobject thiz,
jint recorder_type,
jstring out_url,
jint frame_width,
jint frame_height,
jlong video_bit_rate,
jint fps) {
const char* url = env->GetStringUTFChars(out_url, nullptr);
MediaRecorderContext *pContext = MediaRecorderContext::GetContext(env, thiz);
env->ReleaseStringUTFChars(out_url, url);
if(pContext) return pContext->StartRecord(recorder_type, url, frame_width, frame_height, video_bit_rate, fps);
return 0;
}
//传入音频帧到编码队列
extern "C"
JNIEXPORT void JNICALL
Java_com_byteflow_learnffmpeg_media_MediaRecorderContext_native_1OnAudioData(JNIEnv *env,
jobject thiz,
jbyteArray data,
jint size) {
int len = env->GetArrayLength (data);
unsigned char* buf = new unsigned char[len];
env->GetByteArrayRegion(data, 0, len, reinterpret_cast<jbyte*>(buf));
MediaRecorderContext *pContext = MediaRecorderContext::GetContext(env, thiz);
if(pContext) pContext->OnAudioData(buf, len);
delete[] buf;
}
//传入视频帧到编码队列
extern "C"
JNIEXPORT void JNICALL
Java_com_byteflow_learnffmpeg_media_MediaRecorderContext_native_1OnPreviewFrame(JNIEnv *env,
jobject thiz,
jint format,
jbyteArray data,
jint width,
jint height) {
int len = env->GetArrayLength (data);
unsigned char* buf = new unsigned char[len];
env->GetByteArrayRegion(data, 0, len, reinterpret_cast<jbyte*>(buf));
MediaRecorderContext *pContext = MediaRecorderContext::GetContext(env, thiz);
if(pContext) pContext->OnPreviewFrame(format, buf, width, height);
delete[] buf;
}
//停止录制
extern "C"
JNIEXPORT jint JNICALL
Java_com_byteflow_learnffmpeg_media_MediaRecorderContext_native_1StopRecord(JNIEnv *env,
jobject thiz) {
MediaRecorderContext *pContext = MediaRecorderContext::GetContext(env, thiz);
if(pContext) return pContext->StopRecord();
return 0;
}
将音视频编码的实现流程封装到一个类中，代码基本上就是照着上面的流程图实现的。
代码语言：javascript复制//音视频录制的封装类
class MediaRecorder {
public:
MediaRecorder(const char *url, RecorderParam *param);
~MediaRecorder();
//开始录制
int StartRecord();
//添加音频数据到音频队列
int OnFrame2Encode(AudioFrame *inputFrame);
//添加视频数据到视频队列
int OnFrame2Encode(VideoFrame *inputFrame);
//停止录制
int StopRecord();
private:
//启动音频编码线程
static void StartAudioEncodeThread(MediaRecorder *recorder);
//启动视频编码线程
static void StartVideoEncodeThread(MediaRecorder *recorder);
static void StartMediaEncodeThread(MediaRecorder *recorder);
//分配音频缓冲帧
AVFrame *AllocAudioFrame(AVSampleFormat sample_fmt, uint64_t channel_layout, int sample_rate, int nb_samples);
//分配视频缓冲帧
AVFrame *AllocVideoFrame(AVPixelFormat pix_fmt, int width, int height);
//写编码包到媒体文件
int WritePacket(AVFormatContext *fmt_ctx, AVRational *time_base, AVStream *st, AVPacket *pkt);
//添加媒体流程
void AddStream(AVOutputStream *ost, AVFormatContext *oc, AVCodec **codec, AVCodecID codec_id);
//打印 packet 信息
void PrintfPacket(AVFormatContext *fmt_ctx, AVPacket *pkt);
//打开音频编码器
int OpenAudio(AVFormatContext *oc, AVCodec *codec, AVOutputStream *ost);
//打开视频编码器
int OpenVideo(AVFormatContext *oc, AVCodec *codec, AVOutputStream *ost);
//编码一帧音频
int EncodeAudioFrame(AVOutputStream *ost);
//编码一帧视频
int EncodeVideoFrame(AVOutputStream *ost);
//释放编码器上下文
void CloseStream(AVOutputStream *ost);
private:
RecorderParam m_RecorderParam = {0};
AVOutputStream m_VideoStream;
AVOutputStream m_AudioStream;
char m_OutUrl[1024] = {0};
AVOutputFormat *m_OutputFormat = nullptr;
AVFormatContext *m_FormatCtx = nullptr;
AVCodec *m_AudioCodec = nullptr;
AVCodec *m_VideoCodec = nullptr;
//视频帧队列
ThreadSafeQueue<VideoFrame *>
m_VideoFrameQueue;
//音频帧队列
ThreadSafeQueue<AudioFrame *>
m_AudioFrameQueue;
int m_EnableVideo = 0;
int m_EnableAudio = 0;
volatile bool m_Exit = false;
//音频编码线程
thread *m_pAudioThread = nullptr;
//视频编码线程
thread *m_pVideoThread = nullptr;
};
其中编码一帧视频和编码一帧音频的实现基本上一致，都是先将格式转换为目标格式，然后 avcodec_send_frameavcodec_receive_packet ，最后编码一个空帧作为结束标志。
代码语言：javascript复制int MediaRecorder::EncodeVideoFrame(AVOutputStream *ost) {
LOGCATE("MediaRecorder::EncodeVideoFrame");
int result = 0;
int ret;
AVCodecContext *c;
AVFrame *frame;
AVPacket pkt = { 0 };
c = ost->m_pCodecCtx;
av_init_packet(&pkt);
while (m_VideoFrameQueue.Empty() && !m_Exit) {
usleep(10* 1000);
}
frame = ost->m_pTmpFrame;
AVPixelFormat srcPixFmt = AV_PIX_FMT_YUV420P;
VideoFrame *videoFrame = m_VideoFrameQueue.Pop();
if(videoFrame) {
frame->data[0] = videoFrame->ppPlane[0];
frame->data[1] = videoFrame->ppPlane[1];
frame->data[2] = videoFrame->ppPlane[2];
frame->linesize[0] = videoFrame->pLineSize[0];
frame->linesize[1] = videoFrame->pLineSize[1];
frame->linesize[2] = videoFrame->pLineSize[2];
frame->width = videoFrame->width;
frame->height = videoFrame->height;
switch (videoFrame->format) {
case IMAGE_FORMAT_RGBA:
srcPixFmt = AV_PIX_FMT_RGBA;
break;
case IMAGE_FORMAT_NV21:
srcPixFmt = AV_PIX_FMT_NV21;
break;
case IMAGE_FORMAT_NV12:
srcPixFmt = AV_PIX_FMT_NV12;
break;
case IMAGE_FORMAT_I420:
srcPixFmt = AV_PIX_FMT_YUV420P;
break;
default:
LOGCATE("MediaRecorder::EncodeVideoFrame unSupport format pImage->format=%d", videoFrame->format);
break;
}
}
if((m_VideoFrameQueue.Empty() && m_Exit) || ost->m_EncodeEnd) frame = nullptr;
if(frame != nullptr) {
/* when we pass a frame to the encoder, it may keep a reference to it
* internally; make sure we do not overwrite it here */
if (av_frame_make_writable(ost->m_pFrame) < 0) {
result = 1;
goto EXIT;
}
if (srcPixFmt != AV_PIX_FMT_YUV420P) {
/* as we only generate a YUV420P picture, we must convert it
* to the codec pixel format if needed */
if (!ost->m_pSwsCtx) {
ost->m_pSwsCtx = sws_getContext(c->width, c->height,
srcPixFmt,
c->width, c->height,
c->pix_fmt,
SWS_FAST_BILINEAR, nullptr, nullptr, nullptr);
if (!ost->m_pSwsCtx) {
LOGCATE("MediaRecorder::EncodeVideoFrame Could not initialize the conversion contextn");
result = 1;
goto EXIT;
}
}
sws_scale(ost->m_pSwsCtx, (const uint8_t * const *) frame->data,
frame->linesize, 0, c->height, ost->m_pFrame->data,
ost->m_pFrame->linesize);
}
ost->m_pFrame->pts = ost->m_NextPts ;
frame = ost->m_pFrame;
}
/* encode the image */
ret = avcodec_send_frame(c, frame);
if(ret == AVERROR_EOF) {
result = 1;
goto EXIT;
} else if(ret < 0) {
LOGCATE("MediaRecorder::EncodeVideoFrame video avcodec_send_frame fail. ret=%s", av_err2str(ret));
result = 0;
goto EXIT;
}
while(!ret) {
ret = avcodec_receive_packet(c, &pkt);
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
result = 0;
goto EXIT;
} else if (ret < 0) {
LOGCATE("MediaRecorder::EncodeVideoFrame video avcodec_receive_packet fail. ret=%s", av_err2str(ret));
result = 0;
goto EXIT;
}
LOGCATE("MediaRecorder::EncodeVideoFrame video pkt pts=%ld, size=%d", pkt.pts, pkt.size);
int result = WritePacket(m_FormatCtx, &c->time_base, ost->m_pStream, &pkt);
if (result < 0) {
LOGCATE("MediaRecorder::EncodeVideoFrame video Error while writing audio frame: %s",
av_err2str(ret));
result = 0;
goto EXIT;
}
}
EXIT:
NativeImageUtil::FreeNativeImage(videoFrame);
if(videoFrame) delete videoFrame;
return result;
}
最后注意编码过程中，音视频时间戳对齐，防止出现视频声音播放结束画面还没结束的情况。
代码语言：javascript复制void MediaRecorder::StartVideoEncodeThread(MediaRecorder *recorder) {
AVOutputStream *vOs = &recorder->m_VideoStream;
AVOutputStream *aOs = &recorder->m_AudioStream;
while (!vOs->m_EncodeEnd) {
double videoTimestamp = vOs->m_NextPts * av_q2d(vOs->m_pCodecCtx->time_base);
double audioTimestamp = aOs->m_NextPts * av_q2d(aOs->m_pCodecCtx->time_base);
LOGCATE("MediaRecorder::StartVideoEncodeThread [videoTimestamp, audioTimestamp]=[%lf, %lf]", videoTimestamp, audioTimestamp);
if (av_compare_ts(vOs->m_NextPts, vOs->m_pCodecCtx->time_base,
aOs->m_NextPts, aOs->m_pCodecCtx->time_base) <= 0 || aOs->m_EncodeEnd) {
LOGCATE("MediaRecorder::StartVideoEncodeThread start queueSize=%d", recorder->m_VideoFrameQueue.Size());
//视频和音频时间戳对齐，人对于声音比较敏感，防止出现视频声音播放结束画面还没结束的情况
if(audioTimestamp <= videoTimestamp && aOs->m_EncodeEnd) vOs->m_EncodeEnd = aOs->m_EncodeEnd;
vOs->m_EncodeEnd = recorder->EncodeVideoFrame(vOs);
} else {
LOGCATE("MediaRecorder::StartVideoEncodeThread start usleep");
//视频时间戳大于音频时间戳时，视频编码进行休眠等待对齐
usleep(5 * 1000);
}
}
}
至此，一个小视频录制功能实现了，限于篇幅，代码没有全部贴出来，完整实现代码可以参考项目：
代码语言：javascript复制https://github.com/githubhaohao/LearnFFmpeg
带滤镜的小视频录制
基于上节的代码我们已经实现了类似于微信的小视频录制功能，但是简单的视频录制显然不是本文的目的，关于讲 FFmpeg 视频录制的文章实在是太多了，所以本文就做一些差异化。
我们基于上一节的功能做一个带滤镜的小视频录制功能。
带滤镜的小视频录制
参考上图，我们在 GL 线程里首先创建 FBO ，先将预览帧渲染到 FBO 绑定的纹理上添加滤镜，之后使用 glreadpixels 读取添加完滤镜之后的视频帧放入编码线程编码，最后绑定到 FBO 的纹理再做屏幕渲染，这一点我们已经在添加滤镜的 FFmpeg 视频播放器一文中做了详细介绍。
这里我们定义一个类 GLCameraRender 负责完成离屏渲染（添加滤镜）和屏幕渲染展示预览帧，这部分代码可以参考 FFmpeg 视频播放器的渲染优化一文。
代码语言：javascript复制class GLCameraRender: public VideoRender, public BaseGLRender{
public:
//初始化预览帧的宽高
virtual void Init(int videoWidth, int videoHeight, int *dstSize);
//渲染一帧视频
virtual void RenderVideoFrame(NativeImage *pImage);
virtual void UnInit();
//GLSurfaceView 的三个回调
virtual void OnSurfaceCreated();
virtual void OnSurfaceChanged(int w, int h);
virtual void OnDrawFrame();
static GLCameraRender *GetInstance();
static void ReleaseInstance();
//更新变换矩阵，Camera预览帧需要进行旋转
virtual void UpdateMVPMatrix(int angleX, int angleY, float scaleX, float scaleY);
virtual void UpdateMVPMatrix(TransformMatrix * pTransformMatrix);
//添加好滤镜之后，视频帧的回调，然后将带有滤镜的视频帧放入编码队列
void SetRenderCallback(void *ctx, OnRenderFrameCallback callback) {
m_CallbackContext = ctx;
m_RenderFrameCallback = callback;
}
//加载滤镜素材图像
void SetLUTImage(int index, NativeImage *pLUTImg);
//加载 Java 层着色器脚本
void SetFragShaderStr(int index, char *pShaderStr, int strSize);
private:
GLCameraRender();
virtual ~GLCameraRender();
//创建 FBO
bool CreateFrameBufferObj();
void GetRenderFrameFromFBO();
//创建或更新滤镜素材纹理
void UpdateExtTexture();
static std::mutex m_Mutex;
static GLCameraRender* s_Instance;
GLuint m_ProgramObj = GL_NONE;
GLuint m_FboProgramObj = GL_NONE;
GLuint m_TextureIds[TEXTURE_NUM];
GLuint m_VaoId = GL_NONE;
GLuint m_VboIds[3];
GLuint m_DstFboTextureId = GL_NONE;
GLuint m_DstFboId = GL_NONE;
NativeImage m_RenderImage;
glm::mat4 m_MVPMatrix;
TransformMatrix m_transformMatrix;
int m_FrameIndex;
vec2 m_ScreenSize;
OnRenderFrameCallback m_RenderFrameCallback = nullptr;
void *m_CallbackContext = nullptr;
//支持滑动选择滤镜功能
volatile bool m_IsShaderChanged = false;
volatile bool m_ExtImageChanged = false;
char * m_pFragShaderBuffer = nullptr;
NativeImage m_ExtImage;
GLuint m_ExtTextureId = GL_NONE;
int m_ShaderIndex = 0;
mutex m_ShaderMutex;
};
JNI 层我们需要传入不同滤镜的 shader 脚本和一些 LUT 滤镜的 LUT 图，这样我们在 Java 层可以实现通过左右滑动屏幕来切换不同的滤镜。
代码语言：javascript复制extern "C"
JNIEXPORT void JNICALL
Java_com_byteflow_learnffmpeg_media_MediaRecorderContext_native_1SetFilterData(JNIEnv *env,
jobject thiz,
jint index,
jint format,
jint width,
jint height,
jbyteArray bytes) {
int len = env->GetArrayLength (bytes);
uint8_t* buf = new uint8_t[len];
env->GetByteArrayRegion(bytes, 0, len, reinterpret_cast<jbyte*>(buf));
MediaRecorderContext *pContext = MediaRecorderContext::GetContext(env, thiz);
if(pContext) pContext->SetLUTImage(index, format, width, height, buf);
delete[] buf;
env->DeleteLocalRef(bytes);
}
extern "C"
JNIEXPORT void JNICALL
Java_com_byteflow_learnffmpeg_media_MediaRecorderContext_native_1SetFragShader(JNIEnv *env,
jobject thiz,
jint index,
jstring str) {
int length = env->GetStringUTFLength(str);
const char* cStr = env->GetStringUTFChars(str, JNI_FALSE);
char *buf = static_cast<char *>(malloc(length 1));
memcpy(buf, cStr, length 1);
MediaRecorderContext *pContext = MediaRecorderContext::GetContext(env, thiz);
if(pContext) pContext->SetFragShader(index, buf, length 1);
free(buf);
env->ReleaseStringUTFChars(str, cStr);
}
同样，完整的实现代码可以参考项目：
代码语言：javascript复制https://github.com/githubhaohao/LearnFFmpeg
另外，如果你想要更多的滤镜，可以参考项目 OpenGLCamera2 ，该项目实现 30 种相机滤镜和特效。
代码语言：javascript复制https://github.com/githubhaohao/OpenGLCamera2
-- END --
