Qt音视频开发37-USB摄像头解码ffmpeg方案

void FFmpegThread::initOption()
{
    //在打开码流前指定各种参数比如:探测时间/超时时间/最大延时等
    //设置缓存大小,1080p可将值调大
    av_dict_set(&options, "buffer_size", "8192000", 0);
    //以tcp方式打开,如果以udp方式打开将tcp替换为udp
    av_dict_set(&options, "rtsp_transport", transport.toUtf8().constData(), 0);
    //设置超时断开连接时间,单位微秒,3000000表示3秒
    av_dict_set(&options, "stimeout", "3000000", 0);
    //设置最大时延,单位微秒,1000000表示1秒
    av_dict_set(&options, "max_delay", "1000000", 0);
    //自动开启线程数
    av_dict_set(&options, "threads", "auto", 0);

    //单独对USB摄像机设置参数
    if (isUsbCamera) {
        //设置输入格式
        //av_dict_set(&options, "input_format", "mjpeg", 0);
        //设置分辨率
        QString size = QString("%1x%2").arg(videoWidth).arg(videoHeight);
        av_dict_set(&options, "video_size", size.toUtf8().constData(), 0);
        //设置帧率
        av_dict_set(&options, "framerate", "25", 0);
    }

    //本地USB摄像机不需要硬解码,强制改成回调运行和无硬解码
    //视频流编码类型为 AV_CODEC_ID_RAWVIDEO 像素格式为 AV_PIX_FMT_YUYV422 不经过解码操作直接就可显示
    if (isUsbCamera) {
        callback = true;
        hardware = "none";
    }

    //没有启用opengl则强制改为回调
#ifndef opengl
    callback = true;
#endif

    //rtmp视频流强制改成存储成h264裸流,目前存储成mp4还有问题
    if (url.startsWith("rtmp", Qt::CaseInsensitive)) {
        saveMp4 = false;
    }
}

bool FFmpegThread::initInput()
{
    //实例化格式处理上下文
    formatCtx = avformat_alloc_context();
    //设置超时回调,有些不存在的地址或者网络不好的情况下要卡很久
    formatCtx->interrupt_callback.callback = AVInterruptCallBackFun;
    formatCtx->interrupt_callback.opaque = this;

    //必须要有tryOpen标志位来控制超时回调,由他来控制是否继续阻塞等待打开
    tryOpen = false;

    //先判断是否是本地设备(video=设备名字符串),打开的方式不一样
    QByteArray urlData = url.toUtf8();
    AVInputFormat *ifmt = NULL;
    if (isUsbCamera) {
#if defined(Q_OS_WIN)
        ifmt = av_find_input_format("dshow");
#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, urlData.data(), ifmt, &options);
    tryOpen = true;
    if (result < 0) {
        qDebug() << TIMEMS << "open input error" << url;
        return false;
    }

    //释放设置参数
    if (options != NULL) {
        av_dict_free(&options);
    }

    //获取流信息
    result = avformat_find_stream_info(formatCtx, NULL);
    if (result < 0) {
        qDebug() << TIMEMS << "find stream info error";
        return false;
    }

    return true;
}