translte video_player.c into English

translte video_player.c into English

app/src/main/cpp/video_player.c

@@ -14,30 +14,23 @@
 
 #define TAG "VideoPlayer"
 
-//播放倍率
 float play_rate = 1;
-//视频总时长
 long duration = 0;
 
 VIDEO_PLAYER_FUNC(jint, play, jstring filePath, jobject surface) {
 
     const char *file_name = (*env)->GetStringUTFChars(env, filePath, JNI_FALSE);
     LOGE(TAG, "open file:%s\n", file_name);
-    //注册所有组件
     av_register_all();
-    //分配上下文
     AVFormatContext *pFormatCtx = avformat_alloc_context();
-    //打开视频文件
     if (avformat_open_input(&pFormatCtx, file_name, NULL, NULL) != 0) {
         LOGE(TAG, "Couldn't open file:%s\n", file_name);
         return -1;
     }
-    //检索多媒体流信息
     if (avformat_find_stream_info(pFormatCtx, NULL) < 0) {
         LOGE(TAG, "Couldn't find stream information.");
         return -1;
     }
-    //寻找视频流的第一帧
     int videoStream = -1, i;
     for (i = 0; i < pFormatCtx->nb_streams; i++) {
         if (pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO
@@ -50,15 +43,13 @@ VIDEO_PLAYER_FUNC(jint, play, jstring filePath, jobject surface){
         return -1;
     }
 
-    //获取视频总时长
+    //get duration of video
     if (pFormatCtx->duration != AV_NOPTS_VALUE) {
         duration = (long) (pFormatCtx->duration / AV_TIME_BASE);
         LOGE(TAG, "duration==%ld", duration);
     }
 
-    //获取codec上下文指针
     AVCodecContext *pCodecCtx = pFormatCtx->streams[videoStream]->codec;
-    //寻找视频流的解码器
     AVCodec *pCodec = avcodec_find_decoder(pCodecCtx->codec_id);
     if (pCodec == NULL) {
         LOGE(TAG, "couldn't find Codec.");
@@ -68,33 +59,30 @@ VIDEO_PLAYER_FUNC(jint, play, jstring filePath, jobject surface){
         LOGE(TAG, "Couldn't open codec.");
         return -1;
     }
-    // 获取native window
+
     ANativeWindow *nativeWindow = ANativeWindow_fromSurface(env, surface);
-    // 获取视频宽高
     int videoWidth = pCodecCtx->width;
     int videoHeight = pCodecCtx->height;
-    // 设置native window的buffer大小,可自动拉伸
-    ANativeWindow_setBuffersGeometry(nativeWindow,  videoWidth, videoHeight, WINDOW_FORMAT_RGBA_8888);
+    ANativeWindow_setBuffersGeometry(nativeWindow, videoWidth, videoHeight,
+                                     WINDOW_FORMAT_RGBA_8888);
     ANativeWindow_Buffer windowBuffer;
     if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0) {
         LOGE(TAG, "Couldn't open codec.");
         return -1;
     }
-    //申请内存
     AVFrame *pFrame = av_frame_alloc();
     AVFrame *pFrameRGBA = av_frame_alloc();
     if (pFrameRGBA == NULL || pFrame == NULL) {
         LOGE(TAG, "Couldn't allocate video frame.");
         return -1;
     }
-    // buffer中数据用于渲染,且格式为RGBA
-    int numBytes=av_image_get_buffer_size(AV_PIX_FMT_RGBA, pCodecCtx->width, pCodecCtx->height, 1);
+    int numBytes = av_image_get_buffer_size(AV_PIX_FMT_RGBA, pCodecCtx->width, pCodecCtx->height,
+                                            1);
 
     uint8_t *buffer = (uint8_t *) av_malloc(numBytes * sizeof(uint8_t));
     av_image_fill_arrays(pFrameRGBA->data, pFrameRGBA->linesize, buffer, AV_PIX_FMT_RGBA,
                          pCodecCtx->width, pCodecCtx->height, 1);
 
-    // 由于解码出来的帧格式不是RGBA的,在渲染之前需要进行格式转换
     struct SwsContext *sws_ctx = sws_getContext(pCodecCtx->width,
                                                 pCodecCtx->height,
                                                 pCodecCtx->pix_fmt,
@@ -110,35 +98,28 @@ VIDEO_PLAYER_FUNC(jint, play, jstring filePath, jobject surface){
     AVPacket packet;
 
     while (av_read_frame(pFormatCtx, &packet) >= 0) {
-        //判断是否为视频流
         if (packet.stream_index == videoStream) {
-            //对该帧进行解码
             avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, &packet);
             if (frameFinished) {
                 // lock native window
                 ANativeWindow_lock(nativeWindow, &windowBuffer, 0);
-                // 格式转换
                 sws_scale(sws_ctx, (uint8_t const *const *) pFrame->data,
                           pFrame->linesize, 0, pCodecCtx->height,
                           pFrameRGBA->data, pFrameRGBA->linesize);
-                // 获取stride
                 uint8_t *dst = windowBuffer.bits;
                 int dstStride = windowBuffer.stride * 4;
                 uint8_t *src = pFrameRGBA->data[0];
                 int srcStride = pFrameRGBA->linesize[0];
-                // 由于window的stride和帧的stride不同,因此需要逐行复制
                 int h;
                 for (h = 0; h < videoHeight; h++) {
                     memcpy(dst + h * dstStride, src + h * srcStride, (size_t) srcStride);
                 }
                 ANativeWindow_unlockAndPost(nativeWindow);
             }
-            //延迟等待
             usleep((unsigned long) (1000 * 40 * play_rate));
         }
         av_packet_unref(&packet);
     }
-    //释放内存以及关闭文件
     av_free(buffer);
     av_free(pFrameRGBA);
     av_free(pFrame);
@@ -147,12 +128,10 @@ VIDEO_PLAYER_FUNC(jint, play, jstring filePath, jobject surface){
     return 0;
 }
 
-//设置播放速率
 VIDEO_PLAYER_FUNC(void, setPlayRate, jfloat playRate) {
     play_rate = playRate;
 }
 
-//获取视频总时长
 VIDEO_PLAYER_FUNC(jint, getDuration) {
     return duration;
 }