播放一個視頻，都需要經(jīng)過解封裝衔瓮、視頻解碼浊猾、音頻解碼、音視頻同步热鞍、視頻輸出顯示和音頻輸出播放等過程葫慎。
先簡單介紹下視頻解碼的流程。

image.png

利用FFmpeg進行視頻解碼

ffmpeg視頻解碼.png

具體代碼實現(xiàn)

創(chuàng)建VideoDecoder類搅方，分別實現(xiàn)init比吭、start绽族、release等3個方法。
init為初始化衩藤，對一些重要的結(jié)構(gòu)體進行復(fù)制或者指向吧慢。
start為開始解碼循環(huán)，讀取幀數(shù)據(jù)
release為釋放邏輯慷彤，在代碼結(jié)束時釋放娄蔼。

int videoDecoder::init(const char *url) {
    strcpy(m_url, url);
    int result = -1;
    //1.創(chuàng)建封裝格式上下文
    m_AVFormatContext = avformat_alloc_context();
    //2.打開文件
    if (avformat_open_input(&m_AVFormatContext, m_url, nullptr, nullptr) != 0) {
        LOGE("avformat_open_input fail");
    }
    //3.獲取音視頻流信息
    if (avformat_find_stream_info(m_AVFormatContext, nullptr) < 0) {

    }
    //4.獲取視頻流索引
    m_StreamIndex = av_find_best_stream(m_AVFormatContext, AVMEDIA_TYPE_VIDEO, -1, -1, nullptr, 0);
    if (m_StreamIndex == -1) {

    }
    //5.獲取解碼器參數(shù)
    AVCodecParameters *codecParameters = m_AVFormatContext->streams[m_StreamIndex]->codecpar;
    //6.獲取解碼器
    m_AVCodec = avcodec_find_decoder(codecParameters->codec_id);
    if (m_AVCodec == nullptr) {

    }
    //7.創(chuàng)建解碼器上下文
    m_AVCodecContext = avcodec_alloc_context3(m_AVCodec);
    //將流的參數(shù)（codecParameters）復(fù)制到解碼器中，否則某些流可能無法正常解碼
    if (avcodec_parameters_to_context(m_AVCodecContext, codecParameters) != 0) {

    }
    AVDictionary *pAVDictionary = nullptr;
    av_dict_set(&pAVDictionary, "buffer_size", "1024000", 0);
    av_dict_set(&pAVDictionary, "stimeout", "20000000", 0);
    av_dict_set(&pAVDictionary, "max_delay", "30000000", 0);
    av_dict_set(&pAVDictionary, "rtsp_transport", "tcp", 0);

    //8.打開解碼器
    result = avcodec_open2(m_AVCodecContext, m_AVCodec, &pAVDictionary);
    if (result < 0) {

    }
    m_Duration = m_AVFormatContext->duration / AV_TIME_BASE * 1000;//us to ms
    //創(chuàng)建 AVPacket 存放編碼數(shù)據(jù)
    m_Packet = av_packet_alloc();
    //創(chuàng)建 AVFrame 存放解碼后的數(shù)據(jù)
    m_Frame = av_frame_alloc();
    return result;
}

void videoDecoder::release() {
//釋放資源底哗，解碼完成
    if(m_Frame != nullptr) {
        av_frame_free(&m_Frame);
        m_Frame = nullptr;
    }

    if(m_Packet != nullptr) {
        av_packet_free(&m_Packet);
        m_Packet = nullptr;
    }

    if(m_AVCodecContext != nullptr) {
        avcodec_close(m_AVCodecContext);
        avcodec_free_context(&m_AVCodecContext);
        m_AVCodecContext = nullptr;
        m_AVCodec = nullptr;
    }

    if(m_AVFormatContext != nullptr) {
        avformat_close_input(&m_AVFormatContext);
        avformat_free_context(m_AVFormatContext);
        m_AVFormatContext = nullptr;
    }
}

int videoDecoder::start() {
    int result = av_read_frame(m_AVFormatContext, m_Packet);
    while (result >= 0) {
        //過濾數(shù)據(jù)，找出對應(yīng)流锚沸，符合才進一步解碼
        if (m_Packet->stream_index == m_StreamIndex) {
            //解碼視頻跋选，將packet數(shù)據(jù)交給avcodec去處理
            if (avcodec_send_packet(m_AVCodecContext,m_Packet)!=0){
                return -1;
            }
            while (avcodec_receive_frame(m_AVCodecContext,m_Frame)==0){
                //獲取到 m_Frame 解碼數(shù)據(jù)，在這里進行格式轉(zhuǎn)換哗蜈，然后進行渲染并且顯示
                LOGD("m_Frame pts is %ld",m_Frame->pts);
            }
        }
        av_packet_unref(m_Packet);
        result = av_read_frame(m_AVFormatContext, m_Packet);
    }
}

測試代碼

checkPermission(object : RequestPermissionListener {
            override fun permissionAllGranted() {
                PlayLocalVideo("/sdcard/Download/v1080.mp4")
            }

            override fun permissionDenied(list: MutableList<String>) {
            }

        })

    private external fun PlayLocalVideo(url: String)

videoDecoder *vDecoder = new videoDecoder();
    const char *url = env->GetStringUTFChars(jUrl, nullptr);
    vDecoder->init(url);
    vDecoder->start();
    vDecoder->release();

測試結(jié)果

image.png

首先在布局中增加一個surfaceView

    <SurfaceView
        android:id="@+id/surfaceVideo"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintTop_toBottomOf="@id/sample_text" />

android代碼中綁定窗口和傳遞參數(shù)

    binding.surfaceVideo.holder.addCallback(this)

    override fun surfaceCreated(holder: SurfaceHolder) {
        surface = holder.surface
        PlayLocalVideo("/sdcard/Download/v1080.mp4", surface!!)
    }

    override fun surfaceChanged(holder: SurfaceHolder, format: Int, width: Int, height: Int) {
    }

    override fun surfaceDestroyed(holder: SurfaceHolder) {
    }

接下來需要做的就是洞翩，如何把上面解碼得到的數(shù)據(jù)稽犁，刷到這個SurfaceView中。在實現(xiàn)之前骚亿，需要知道顯示的控件支持什么類型的數(shù)據(jù)已亥。ANativeWindow 僅支持 RGB 類型的圖像數(shù)據(jù)，所以我們還需要利用 libswscale 庫將解碼后的 YUV 數(shù)據(jù)轉(zhuǎn)成 RGB 来屠。

首先在初始化的方法里虑椎，加入ANativeWindow的初始化。

    //1. 利用 Java 層 SurfaceView 傳下來的 Surface 對象俱笛，獲取 ANativeWindow
    m_NativeWindow = ANativeWindow_fromSurface(env, surface);
    //顯示窗口初始化
    ANativeWindow_setBuffersGeometry(m_NativeWindow, m_RenderWidth, m_RenderHeight,
                                     WINDOW_FORMAT_RGBA_8888);


    m_VideoWidth = m_AVCodecContext->width;
    m_VideoHeight = m_AVCodecContext->height;
    m_RGBAFrame = av_frame_alloc();
    //計算 Buffer 的大小
    int bufferSize = av_image_get_buffer_size(AV_PIX_FMT_RGBA, m_VideoWidth, m_VideoHeight, 1);
    //為 m_RGBAFrame 分配空間
    m_FrameBuffer = static_cast<uint8_t *>(av_malloc(bufferSize * sizeof(uint8_t)));
    av_image_fill_arrays(m_RGBAFrame->data, m_RGBAFrame->linesize, m_FrameBuffer, AV_PIX_FMT_RGBA,
                         m_VideoWidth, m_VideoHeight, 1);
    //獲取轉(zhuǎn)換的上下文
    m_SwsContext = sws_getContext(m_VideoWidth, m_VideoHeight, m_AVCodecContext->pix_fmt,
                                  m_VideoWidth, m_VideoHeight, AV_PIX_FMT_RGBA,
                                  SWS_BICUBIC, nullptr, nullptr, nullptr);

然后在上面讀取幀數(shù)據(jù)的地方捆姜，加入轉(zhuǎn)換和顯示刷新的邏輯

sws_scale(m_SwsContext, m_Frame->data, m_Frame->linesize, 0,
              m_VideoHeight, m_RGBAFrame->data, m_RGBAFrame->linesize);
    if(m_NativeWindow == nullptr){
        LOGE("NativeWindow is null");
    return;
    }
    ANativeWindow_lock(m_NativeWindow, &m_NativeWindowBuffer, nullptr);
    uint8_t *dstBuffer = static_cast<uint8_t *>(m_NativeWindowBuffer.bits);

    int srcLineSize = m_RGBAFrame->linesize[0];//RGBA
    int dstLineSize = m_NativeWindowBuffer.stride * 4;

    for (int i = 0; i < m_VideoHeight; ++i) {
        memcpy(dstBuffer + i * dstLineSize,
               m_FrameBuffer + i * srcLineSize,
               srcLineSize);
    }

    ANativeWindow_unlockAndPost(m_NativeWindow);

這樣就可以看到視頻的播放了。但由于是demo代碼嫂粟，很多細節(jié)都沒有處理娇未，例如實際開發(fā)的時候，需要在異線程中進行解碼星虹、還有適當?shù)卦黾覮og提示零抬、指針的處理等镊讼，避免產(chǎn)生bug。