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• how to set nVidia video bitrate in a system service ?

  12 septembre 2021, par qycx

  I use an nvidia card for compression and decompression in a video conferencing software. The program uses ffmpeg. The program is a system service. Need to control the bit rate. But I found that I didn't control it. The setting code rate was 700k, and the actual value was 10M. What went wrong ?

  


  /* put sample parameters */
    pUnit->encV_var.c->bit_rate = bitrate;//400000;
    /* resolution must be a multiple of two */
    pUnit->encV_var.c->width = in_w;//352;
    pUnit->encV_var.c->height = in_h;//288;
    pUnit->encV_var.c->qmin=10;
    pUnit->encV_var.c->qmax=30;
    /* frames per second */
    AVRational t1={1,25};
    t1.den=fps;
    pUnit->encV_var.c->time_base = t1;//(AVRational){1, 25};
    AVRational t2={25,1};
    t2.num=fps;
    pUnit->encV_var.c->framerate = t2;//(AVRational){25, 1};

    /* emit one intra frame every ten frames
     * check frame pict_type before passing frame
     * to encoder, if frame->pict_type is AV_PICTURE_TYPE_I
     * then gop_size is ignored and the output of encoder
     * will always be I frame irrespective to gop_size
     */
    pUnit->encV_var.c->gop_size = 256;//10;
    pUnit->encV_var.c->max_b_frames = 0;//1;
    pUnit->encV_var.c->pix_fmt = AV_PIX_FMT_YUV420P;


  


• how to improve image quality when I write c++ using ffmpeg( avcodec)

  6 septembre 2021, par qycx

  I am writing a c++ program, using ffmpeg to encode video.
but the image quality is very bad.
can you help me to improve the video quality ?

  


  following is my code :

  


      pUnit->encV_var.pkt = av_packet_alloc();
    if (!pUnit->encV_var.pkt) {
        goto errLabel;
    }

    /* put sample parameters */
    pUnit->encV_var.c->bit_rate = bitrate;//400000;
    pUnit->encV_var.c->rc_max_rate=bitrate;
    pUnit->encV_var.c->rc_min_rate=bitrate;
    AVCodecContext *c=pUnit->encV_var.c;
    int br = bitrate;
    c->bit_rate_tolerance = br;
c->rc_buffer_size=br;
c->rc_initial_buffer_occupancy = c->rc_buffer_size*3/4;
//c->rc_buffer_aggressivity= (float)1.0;
//c->rc_initial_cplx= 0.5; 



    /* resolution must be a multiple of two */
    pUnit->encV_var.c->width = in_w;//352;
    pUnit->encV_var.c->height = in_h;//288;
    /* frames per second */
    AVRational t1={1,25};
    t1.den=fps;
    pUnit->encV_var.c->time_base = t1;//(AVRational){1, 25};
    AVRational t2={25,1};
    t2.num=fps;
    pUnit->encV_var.c->framerate = t2;//(AVRational){25, 1};

    /* emit one intra frame every ten frames
     * check frame pict_type before passing frame
     * to encoder, if frame->pict_type is AV_PICTURE_TYPE_I
     * then gop_size is ignored and the output of encoder
     * will always be I frame irrespective to gop_size
     */
    pUnit->encV_var.c->gop_size = 256;//10;
    pUnit->encV_var.c->max_b_frames = 0;//1;
    pUnit->encV_var.c->pix_fmt = AV_PIX_FMT_YUV420P;

    //
    pUnit->encV_var.c->flags|=AV_CODEC_FLAG_GLOBAL_HEADER;

    //
    if (codec_id == AV_CODEC_ID_H264) {
        int ret;
        ret = av_opt_set(pUnit->encV_var.c->priv_data, "preset", "fast", 0);
        //ret = av_opt_set(pUnit->encV_var.c->priv_data, "preset", "slow", 0);
        //ret = av_opt_set(pUnit->encV_var.c->priv_data, "preset", "medium", 0);

        //
        ret = av_opt_set(pUnit->encV_var.c->priv_data, "tune","zerolatency",0);

        //
        ret = av_opt_set(pUnit->encV_var.c->priv_data, "profile","main",0);

    }

    /* open it */
    ret = avcodec_open2(pUnit->encV_var.c, pUnit->encV_var.codec, NULL);
   


  


  please help me to improve image quality

  


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• FFMPEG/C++ How to simply write out/passthrough h264 stream ?

  11 août 2021, par Schuerta

  Im trying to learn the basics of ffmpeg writing (reading already works), so im just trying to take in an input .ts file and write out/passthrough the exact same h264 stream to a new output file. I dont get any compilation errors, but for some reason i cant figure out why my output file's framerate is very wrong. Also when i read in my output file, i get printouts saying "Packet corrupt (stream = 0, dts = #)"

  


  I followed the instructions in the ffmpeg library comments so im not sure what im missing. I call initOutStream(), then initH264encoder(), then during the reading/decoding readH264Packet() is called repeatedly. (Removed code for readability sake, left relevant sections below) ;

  


  Edit : If i put my output file through the actuall ffmpeg cmd app, the framerate issue seems to get fixed. Wonder where im messing up

  


  void test::initOutStream() {

//create muxing context
outstreamContext = avformat_alloc_context();

//oformat
AVOutputFormat *guessFormat; //Populate oformat
guessFormat = av_guess_format(NULL, inputVideoUrl.c_str(), NULL);
outstreamContext->oformat = guessFormat; 
outstreamContext->oformat->video_codec = AV_CODEC_ID_H264; 
//outstreamContext->bit_rate = 400000; //No affect; 

//pb
AVIOContext *outAVIOContext = nullptr;
//int result = avio_open(&outAVIOContext, outputVideoUrl.c_str(), AVIO_FLAG_WRITE);
int result = avio_open2(&outAVIOContext, outputVideoUrl.c_str(), AVIO_FLAG_WRITE, NULL, NULL); //Documentain said to use this method
outstreamContext->pb = outAVIOContext;
}


  


  .

  


  void test::initH264encoder() { //Frame -> packet&#xA;int result;&#xA;&#xA;h264OutCodec = avcodec_find_encoder(AV_CODEC_ID_H264);&#xA;&#xA;h264OutStream = avformat_new_stream(outstreamContext, h264OutCodec);&#xA;h264OutStream->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;&#xA;h264OutStream->codecpar->codec_id = AV_CODEC_ID_H264;&#xA;h264OutStream->codecpar->width = 640;&#xA;h264OutStream->codecpar->height = 480;&#xA;h264OutStream->id = H264_STREAM_ID;&#xA;h264OutStream->codecpar->color_range = AVCOL_RANGE_MPEG;&#xA;//h264OutStream->codecpar->bit_rate = 400000;&#xA;&#xA;h264OutContext = avcodec_alloc_context3(h264OutCodec);&#xA;&#xA;h264OutContext->width = 640;&#xA;h264OutContext->height = 480;&#xA;h264OutContext->time_base = (AVRational){1,static_cast<int>(29.97)};&#xA;h264OutContext->pix_fmt = AV_PIX_FMT_YUV420P;&#xA;&#xA;result = avcodec_open2(h264OutContext, h264OutCodec, nullptr);&#xA;&#xA;//Alloc packet &#x2B; finish&#xA;outPacket = av_packet_alloc();&#xA;&#xA;//Write header&#xA;result = avformat_write_header(outstreamContext, NULL);&#xA;}&#xA;</int>

  


  Assume that reading was set up correctly

  


  void test::readH264Packet(__unused uint64_t tick) {
//...av_read_frame(streamContext, inPacket);
//...avcodec_send_packet(h264Context, inPacket);
//...avcodec_receive_frame(h264Context, yuvFrame)
//My passthrough:
if(shouldOutputH264Stream){
        result = avcodec_send_frame(h264OutContext, yuvFrame); //1. Encode frame to packet
        result = avcodec_receive_packet(h264OutContext, outPacket2); //2. get encoded packet
        result = av_interleaved_write_frame(outstreamContext, outPacket2); //3. write packet
        //Write trailer and free happens later
    }
}