Qt音視訊開發之利用ffmpeg實現解碼本地攝像頭

void CameraThreadFFmpeg::initCamera()
{
    //https://blog.csdn.net/weixin_37921201/article/details/120357826
    //命令列開啟 ffplay -f dshow -i video="USB Video Device" -s 1280x720 -framerate 30

    //啟動計時
    timer.restart();

    //引數字典
    AVDictionary *options = NULL;

    //設定解析度
    QString size = QString("%1x%2").arg(videoWidth).arg(videoHeight);
    av_dict_set(&options, "video_size", size.toUtf8().constData(), 0);
    //設定影格率
    if (frameRate > 0) {
        av_dict_set(&options, "framerate", QString::number(frameRate).toUtf8().constData(), 0);
    }

    //設定輸入格式(前提是要對應裝置對應平臺支援)
    //av_dict_set(&options, "input_format", "mjpeg", 0);

    //設定影象格式(有些裝置設定了格式後影格率上不去)
    //av_dict_set(&options, "pixel_format", "yuyv422", 0);

    //列印裝置列表
    //FFmpegHelper::showDevice();
    //列印裝置引數
    //FFmpegHelper::showOption(cameraName);

    //範例化格式處理上下文
    formatCtx = avformat_alloc_context();

    AVInputFormatx *ifmt = NULL;
    QByteArray url = cameraName.toUtf8();
#if defined(Q_OS_WIN)
    //ifmt = av_find_input_format("vfwcap");
    ifmt = av_find_input_format("dshow");
    url = QString("video=%1").arg(cameraName).toUtf8();
#elif defined(Q_OS_LINUX)
    //ifmt = av_find_input_format("v4l2");
    ifmt = av_find_input_format("video4linux2");
#elif defined(Q_OS_MAC)
    ifmt = av_find_input_format("avfoundation");
#endif

    int result = avformat_open_input(&formatCtx, url.data(), ifmt, &options);
    av_dict_free(&options);
    if (result < 0) {
        debug("開啟地址", "錯誤: 開啟出錯 " + FFmpegHelper::getError(result));
        return;
    }

    //獲取流資訊
    result = avformat_find_stream_info(formatCtx, NULL);
    if (result < 0) {
        debug("開啟地址", "錯誤: 找流失敗 " + FFmpegHelper::getError(result));
        return;
    }

    //獲取最佳流索引
    AVCodecx *videoCodec;
    videoIndex = av_find_best_stream(formatCtx, AVMEDIA_TYPE_VIDEO, -1, -1, NULL, 0);
    if (videoIndex < 0) {
        debug("開啟地址", "錯誤: 未找到視訊流");
        return;
    }

    //獲取視訊流
    AVStream *videoStream = formatCtx->streams[videoIndex];

    //查詢視訊解碼器(如果上面av_find_best_stream第五個引數傳了則這裡不需要)
    AVCodecID codecID = FFmpegHelper::getCodecID(videoStream);
    videoCodec = avcodec_find_decoder(codecID);
    //videoCodec = avcodec_find_decoder_by_name("h264");
    if (!videoCodec) {
        debug("開啟地址", "錯誤: 查詢視訊解碼器失敗");
        return;
    }

    //建立視訊流解碼器上下文
    videoCodecCtx = avcodec_alloc_context3(videoCodec);
    if (!videoCodecCtx) {
        debug("開啟地址", "錯誤: 建立視訊解碼器上下文失敗");
        return;
    }

    result = FFmpegHelper::copyContext(videoCodecCtx, videoStream, false);
    if (result < 0) {
        debug("開啟地址", "錯誤: 設定視訊解碼器引數失敗");
        return;
    }

    //設定解碼器引數
    videoCodecCtx->flags |= AV_CODEC_FLAG_LOW_DELAY;
    videoCodecCtx->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
    videoCodecCtx->flags2 |= AV_CODEC_FLAG2_FAST;

    //開啟視訊解碼器
    result = avcodec_open2(videoCodecCtx, videoCodec, NULL);
    if (result < 0) {
        debug("開啟地址", "錯誤: 開啟視訊解碼器失敗 " + FFmpegHelper::getError(result));
        return;
    }

    //獲取實際解析度大小
    FFmpegHelper::getResolution(videoStream, videoWidth, videoHeight);
    //如果沒有獲取到寬高則返回
    if (videoWidth <= 0 || videoHeight <= 0) {
        debug("開啟地址", "錯誤: 獲取寬度高度失敗");
        return;
    }

    //獲取最終真實的影格率
    frameRate = av_q2d(videoStream->r_frame_rate);
    QString msg = QString("索引: %1 解碼: %2 影格率: %3 寬高: %4x%5").arg(videoIndex).arg(videoCodec->name).arg(frameRate).arg(videoWidth).arg(videoHeight);
    debug("視訊資訊", msg);
    openCamera();
}

bool CameraThreadFFmpeg::openCamera()
{
    //分配記憶體
    packet = FFmpegHelper::creatPacket(NULL);
    videoFrame = av_frame_alloc();
    yuvFrame = av_frame_alloc();
    imageFrame = av_frame_alloc();

    //設定屬性以便該幀物件正常
    yuvFrame->format = AV_PIX_FMT_YUV420P;
    yuvFrame->width = videoWidth;
    yuvFrame->height = videoHeight;

    //定義及獲取畫素格式
    AVPixelFormat srcFormat = AV_PIX_FMT_YUYV422;
    //通過解碼器獲取解碼格式
    srcFormat = videoCodecCtx->pix_fmt;
    //各種轉換速度比對 https://www.cnblogs.com/xumaojun/p/8541634.html
    int flags = SWS_FAST_BILINEAR;

    //分配視訊幀資料(轉yuv420)
    int yuvSize = av_image_get_buffer_size(AV_PIX_FMT_YUV420P, videoWidth, videoHeight, 1);
    yuvData = (quint8 *)av_malloc(yuvSize * sizeof(quint8));
    av_image_fill_arrays(yuvFrame->data, yuvFrame->linesize, yuvData, AV_PIX_FMT_YUV420P, videoWidth, videoHeight, 1);
    //視訊影象轉換(轉yuv420)
    yuvSwsCtx = sws_getContext(videoWidth, videoHeight, srcFormat, videoWidth, videoHeight, AV_PIX_FMT_YUV420P, flags, NULL, NULL, NULL);

    //分配視訊幀資料(轉rgb)
    int imageSize = av_image_get_buffer_size(AV_PIX_FMT_RGB24, videoWidth, videoHeight, 1);
    imageData = (quint8 *)av_malloc(imageSize * sizeof(quint8));
    av_image_fill_arrays(imageFrame->data, imageFrame->linesize, imageData, AV_PIX_FMT_RGB24, videoWidth, videoHeight, 1);
    //視訊影象轉換(轉rgb)
    imageSwsCtx = sws_getContext(videoWidth, videoHeight, AV_PIX_FMT_YUV420P, videoWidth, videoHeight, AV_PIX_FMT_RGB24, flags, NULL, NULL, NULL);

    //列印媒體資訊
    //av_dump_format(formatCtx, 0, 0, 0);
    QString msg = QString("源頭: %1 目標: %2").arg(srcFormat).arg(videoMode == VideoMode_Painter ? AV_PIX_FMT_RGB24 : AV_PIX_FMT_YUV420P);
    debug("格式資訊", msg);

    //初始化音訊播放
    this->initAudioPlayer();
    //初始化濾鏡
    this->initFilter();

    int time = timer.elapsed();
    debug("開啟成功", QString("用時: %1 毫秒").arg(time));
    emit receivePlayStart(time);
    emit recorderStateChanged(RecorderState_Stopped, fileName);
    isOk = true;
    return isOk;
}