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• Manipulate wave data from an audio file and write it to a new audio file

  13 avril 2021, par Dr-Zee

  For this question I'm looking less for specific code and more for pointers and recommendations. What I'm doing is custom enough that asking for code samples seems unfair.

  


  I want to take the amplitude data from an audio track and use it to modulate the frequency of a tone. I'd like to record that modulated tone to a separate audio track.

  


  At the moment I'm looking into pyaudio and pydub to run these tasks via a script.

  


  I took this task for granted having used audio programs that allow you to easily link track properties together. Or by manipulating data in real-time with an Arduino. Now that I'm looking into the scripting process I'm realizing how specialized what I'm trying to do is.

  


  Any guidance would be appreciated.

  


• Read/Manipulate data from an audio file and write it to a new audio file

  13 avril 2021, par Dr-Zee

  For this question I'm looking less for specific code and more for pointers and recommendations. What I'm doing is custom enough that asking for code samples seems unfair.

  


  I want to take the amplitude data from an audio track and use it to modulate the frequency of a tone. I'd like to record that modulated tone to a separate audio track.

  


  At the moment I'm looking into pyaudio and pydub to run these tasks via a script.

  


  I took this task for granted having used software that allows you to easily link track properties together. Or by manipulating data in real-time with an Arduino. Now that I'm looking into the scripting process I'm realizing how specialized what I'm trying to do is.

  


  Any guidance would be appreciated.

  


• FFmpeg API example (encode_video.c) does not work correctly

  30 janvier 2023, par NewbieCoder

  I am using the official encode_video.c example to test if FFmpeg works correctly for me. 
I got the pre-built windows edition from ffmpeg.zeranoe.com/builds. It is built already with libx264 and other external libraries. I got both dev and shared editions and added the DLLs, header files and libs accordingly in Visual Studio.

  



  Now the encode_video.c example does not work correctly.

  



  



  What I tried :

  



  I compiled the example and run it on many different file formats and codecs such as the following.

  



  First I tried all of these file formats (.mp4, .m4v, .h264, .x264, .avi, .flv) with codec name as libx264. The code executed without errors but the output video file did not play in VLC or Windows 10 default player.

  



  Next, I tried all of those above file formats but with codec name as mpeg4. The code executed without errors but the output video file played only for .m4v in VLC.

  



  



  What is expected :

  



  All of those combinations should have produced a video file which could be played in VLC. None of them worked except for .m4v as file format and mpeg4 as codec name.

  



  



  Please tell me how to make this work for h264. I mainly want it to work for h264 as that is only important for now.

  



  I am running the code like ./encode_video.exe test.mp4 libx264 where first argument is output filename and second argument is codec name.

  



  This is the output for test.mp4 and libx264 as command line arguments https://imgur.com/a/AHLQwuK

  



  It seems that in the encode function, it goes over the below code and returns because of AVERROR(EAGAIN) or AVERROR_EOF. Please tell me what is happening.

  



  while (ret >= 0) {
        ret = avcodec_receive_packet(enc_ctx, pkt);
        if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
            return;
        else if (ret < 0) {
            fprintf(stderr, "Error during encoding\n");
            exit(1);
        }

        printf("Write packet %3"PRId64" (size=%5d)\n", pkt->pts, pkt->size);
        fwrite(pkt->data, 1, pkt->size, outfile);
        av_packet_unref(pkt);
    }


  



  I used DepenciesGUI to find out the DLLs linked and it shows that the DLLs are correctly linked. Please help me figure out what the problem is now !!