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• 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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• 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;


  


• Sync video and data with ffmpeg

  31 août 2022, par plj

  I join a video and data where I copy the video from the vid1.ts along with the data (klv) from the vid2.ts :

  


  ffmpeg -y -i vid1.ts -i vid2.ts -c copy -map 0:0 -map 1:2 -shortest full_exclude.ts

  


  When I probe the resulting video I see that the packets don't line up :

  


  ffprobe -show_packets full_exclude.ts

  


  The 1st data packet is :

  


  [PACKET]
codec_type=data
stream_index=1
pts=126000
pts_time=1.400000
dts=126000
dts_time=1.400000
duration=N/A
duration_time=N/A
size=324
pos=564
flags=K_
[SIDE_DATA]
side_data_type=MPEGTS Stream ID
id=252
[/SIDE_DATA]
[/PACKET]


  


  The 1st video packet is :

  


  [PACKET]
codec_type=video
stream_index=0
pts=341392
pts_time=3.793244
dts=341392
dts_time=3.793244
duration=N/A
duration_time=N/A
size=9270
pos=28952
flags=K_
[SIDE_DATA]
side_data_type=MPEGTS Stream ID
id=224
[/SIDE_DATA]
[/PACKET]
[PACKET]


  


  How do I get the data and video in sync with each other ?