Qt音視訊開發之視訊檔儲存功能的實現

bool FFmpegSave::initVideoH264()
{
    //查詢視訊編碼器(如果源頭是H265則採用HEVC作為編碼器)
    AVCodecID codecID = FFmpegHelper::getCodecID(videoStreamIn);
    if (codecID == AV_CODEC_ID_HEVC) {
        videoCodec = avcodec_find_encoder(AV_CODEC_ID_HEVC);
    } else {
        videoCodec = avcodec_find_encoder(AV_CODEC_ID_H264);
    }

    if (!videoCodec) {
        debug("編碼失敗", QString("錯誤: 查詢視訊編碼器失敗"));
        return false;
    }

    //建立視訊編碼器上下文
    videoCodecCtx = avcodec_alloc_context3(videoCodec);
    if (!videoCodecCtx) {
        debug("編碼失敗", QString("錯誤: 建立視訊編碼器上下文失敗"));
        return false;
    }

    //為了相容低版本的編譯器推薦選擇第一種方式
#if 1
    //放大係數是為了小數位能夠正確放大到整型
    int ratio = 10000;
    videoCodecCtx->time_base.num = 1 * ratio;
    videoCodecCtx->time_base.den = frameRate * ratio;
    videoCodecCtx->framerate.num = frameRate * ratio;
    videoCodecCtx->framerate.den = 1 * ratio;
#elif 0
    videoCodecCtx->time_base = {1, frameRate};
    videoCodecCtx->framerate = {frameRate, 1};
#else
    videoCodecCtx->time_base = videoStreamIn->codec->time_base;
    videoCodecCtx->framerate = videoStreamIn->codec->framerate;
#endif

#if 0
    videoCodecCtx->qmin = 10;
    videoCodecCtx->qmax = 51;
    videoCodecCtx->me_range = 16;
    videoCodecCtx->max_qdiff = 4;
    videoCodecCtx->qcompress = 0.6;
#endif

    //初始化視訊編碼器引數(如果要檔案體積小一些畫質差一些可以調整位元速率)
    //引數說明 https://blog.csdn.net/qq_40179458/article/details/110449653
    videoCodecCtx->bit_rate = FFmpegHelper::getBitRate(videoWidth, videoHeight);
    videoCodecCtx->width = videoWidth;
    videoCodecCtx->height = videoHeight;
    videoCodecCtx->gop_size = 25;
    videoCodecCtx->max_b_frames = 3;
    videoCodecCtx->pix_fmt = AV_PIX_FMT_YUV420P;
    videoCodecCtx->level = 50;
    videoCodecCtx->profile = FF_PROFILE_H264_MAIN;

    //加上下面這個才能在檔案屬性中看到解析度等資訊 https://www.cnblogs.com/lidabo/p/15754031.html
    if (saveVideoType == SaveVideoType_Mp4) {
        videoCodecCtx->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
    }

    //載入預設 https://blog.csdn.net/JineD/article/details/125304570
    if (videoCodecCtx->codec_id == AV_CODEC_ID_H264) {
        av_opt_set(videoCodecCtx->priv_data, "preset", "slow", 0);
        //設定零延遲(本地攝像頭視訊流儲存如果不設定則播放的時候會越來越模糊)
        av_opt_set(videoCodecCtx->priv_data, "tune", "zerolatency", 0);
    } else if (videoCodecCtx->codec_id == AV_CODEC_ID_HEVC) {
        av_opt_set(videoCodecCtx->priv_data, "x265-params", "qp=20", 0);
        av_opt_set(videoCodecCtx->priv_data, "preset", "ultrafast", 0);
        av_opt_set(videoCodecCtx->priv_data, "tune", "zero-latency", 0);
    }

    //開啟視訊編碼器
    int result = avcodec_open2(videoCodecCtx, videoCodec, NULL);
    if (result < 0) {
        debug("開啟編碼", QString("錯誤: 開啟視訊編碼器失敗 %1").arg(FFmpegHelper::getError(result)));
        return false;
    }

    videoPacket = FFmpegHelper::creatPacket(NULL);
    return true;
}

bool FFmpegSave::initVideoMp4()
{
    //必須先設定過輸入視訊流
    if (!videoStreamIn || fileName.isEmpty()) {
        return false;
    }

    //有部分視訊引數不正確儲存不了 http://tv.netxt.cc:1998/live/y.flv
    if (videoStreamIn->time_base.num == 0) {
        return false;
    }

    QByteArray fileData = fileName.toUtf8();
    const char *filename = fileData.data();

    //開闢一個格式上下文用來處理視訊流輸出
    int result = avformat_alloc_output_context2(&formatCtx, NULL, "mp4", filename);
    if (result < 0) {
        debug("建立格式", QString("錯誤: %1").arg(FFmpegHelper::getError(result)));
        return false;
    }

    //建立視訊流用來輸出視訊資料到檔案
    videoStreamOut = avformat_new_stream(formatCtx, NULL);
    result = FFmpegHelper::copyContext(videoCodecCtx, videoStreamOut, true);
    if (result < 0) {
        debug("建立視訊", QString("錯誤: %1").arg(FFmpegHelper::getError(result)));
        goto end;
    }

    //開啟輸出檔案
    result = avio_open(&formatCtx->pb, filename, AVIO_FLAG_WRITE);
    if (result < 0) {
        debug("開啟輸出", QString("錯誤: %1").arg(FFmpegHelper::getError(result)));
        goto end;
    }

    //寫入檔案開始符
    result = avformat_write_header(formatCtx, NULL);
    if (result < 0) {
        debug("寫入失敗", QString("錯誤: %1").arg(FFmpegHelper::getError(result)));
        goto end;
    }

    return true;

end:
    //關閉釋放並清理檔案
    this->close();
    this->deleteFile(fileName);
    return false;
}

void FFmpegSave::writePacket(AVPacket *packet)
{
    packetCount++;
    if (saveVideoType == SaveVideoType_H264) {
        file.write((char *)packet->data, packet->size);
    } else if (saveVideoType == SaveVideoType_Mp4) {
        AVRational timeBaseIn = videoStreamIn->time_base;
        AVRational timeBaseOut = videoStreamOut->time_base;

        //沒有下面這段判斷在遇到不連續的幀的時候就會錯位(相當於每次重新計算時間基準保證時間正確)
        //不連續幀的情況有暫停錄製以及切換播放進度導致中間有些幀不需要錄製
        double fps = frameRate;//av_q2d(videoStreamIn->r_frame_rate);
        double duration = AV_TIME_BASE / fps;
        packet->pts = (packetCount * duration) / (av_q2d(timeBaseIn) * AV_TIME_BASE);
        packet->dts = packet->pts;
        packet->duration = duration / (av_q2d(timeBaseIn) * AV_TIME_BASE);

        //重新調整時間基準
        packet->pts = av_rescale_q_rnd(packet->pts, timeBaseIn, timeBaseOut, (AVRounding)(AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));
        packet->dts = packet->pts;
        //packet->dts = av_rescale_q_rnd(packet->dts, timeBaseIn, timeBaseOut, (AVRounding)(AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));
        packet->duration = av_rescale_q(packet->duration, timeBaseIn, timeBaseOut);
        packet->pos = -1;

        //寫入一幀資料
        int result = av_interleaved_write_frame(formatCtx, packet);
        if (result < 0) {
            debug("寫入失敗", QString("錯誤: %1").arg(FFmpegHelper::getError(result)));
        }
    }

    av_packet_unref(packet);
}