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• Mixing audio stream into video stream using ffmpeg while retaining original audio from the video stream as background [duplicate]

  18 mars 2020, par Core7s

  I have a live video stream and a live audio stream. The audio stream has to get mixed into the video stream and the resulting stream is pushed to YouTube. I have this working ffmpeg -i videostream -i audiostream -map 0:1 -map 1:0 -shortest -c:a copy -c:v copy -f flv streamout-youtube;
  However I am losing the original audio in the videostream. I want to have the original audio playing at maybe 20% of the original volume.
  I looked around a lot and found maybe I can modify the above command to use -filter_complex to get ffmpeg -i videostream -i audiostream -filter_complex "volume=0.2" -map 0:1 -map 1:0 -shortest -c:a copy -c:v copy -f flv streamout-youtube;

  However, when I add the -filter_complex option, the stream goes dead meaning it doesn’t get pushed to youtube anymore. I have verified the stream keys are correct. This seems to be a rather simple thing but I can’t put my finger on what’s wrong.

  I am using rtmp module of nginx to receive, mix and push out streams.

• what container and stream buffersize for recording a incoming h264 stream using ffmpeg ?

  26 mai 2015, par Nyaruko

  I am saving a incoming h264 stream to a file so that it could be played by vlc player.

  1) what kind of file/container should I use ? I am currently using mpeg in the following way :

     fmt = ffmpeg::av_guess_format(NULL, "test.mpeg", NULL);
  
     oc  = ffmpeg::avformat_alloc_context();
  
     oc->oformat = fmt;
  
     avio_open2(&oc->pb, "test.mpeg", AVIO_FLAG_WRITE, NULL, NULL);

  where fmt is a AVOutputFormat* and oc is a AVFormatContext*
  I have tried using avi, but it doesn’t work...

  2) How to set the proper vbv-buffersize through setting stream->codec->rc_buffer_size here the stream is the output stream.

  If I set this value too small, it gives many buffer underflow warning.
  So what’s the proper value for it ? I am using 720*576 512kbps h264 stream with 20fps.

  3) Since the incoming h264 stream doesn’t come with time information, I used the following code to manually add the time base/pts/dts for the stream, is the code correct ?

        if (stream == NULL){//create stream in file
  
            stream = avformat_new_stream(oc, incomeStream->codec->codec);
  
            avcodec_copy_context(stream->codec, incomeStream->codec);
  
            stream->sample_aspect_ratio = incomeStream->codec->sample_aspect_ratio;
  
  
  
            stream->sample_aspect_ratio.num = incomeStream->codec->sample_aspect_ratio.num;
  
            stream->sample_aspect_ratio.den = incomeStream->codec->sample_aspect_ratio.den;
  
  
  
            // Assume r_frame_rate is accurate
  
            stream->r_frame_rate = incomeStream->r_frame_rate;
  
            stream->avg_frame_rate = stream->r_frame_rate;
  
            stream->time_base = av_inv_q(stream->r_frame_rate);
  
            stream->codec->time_base = stream->time_base;
  
            stream->codec->rc_buffer_size = 1024*500;
  
            avformat_write_header(oc, NULL);
  
        }
  
        ...
  
        //set the packet's dts pts
  
        packet.pts = stream->pts.val;
  
        packet.dts = stream->pts.val;

  Here stream is the output stream.

• how to transfer an audio stream to a video stream ?

  14 janvier 2021, par 12345xw

  enter image description here

  


  PS C:\Users\RI\Desktop\Movie> ffprobe mov002.mpg 
Input #0, mpeg, from 'mov002.mpg':
  Duration: 00:00:00.26, start: 31.949778, bitrate: 2258447 kb/s
    Stream #0:0[0x1e0]: Audio: mp3, 0 channels, fltp
    Stream #0:1[0x1c0]: Audio: mp2, 48000 Hz, stereo, s16p, 192 kb/s


  


  Stream #0:0 should be a video stream, but it is parsed as an audio stream

  


  how to transfer the audio stream to a video stream