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• How do I split a M4B file provided I have a CUE file ?

  4 mars 2023, par user6779573

  I have a large M4B file and a CUE file for it. I want to either split it into many M4B files, or split it into many MP3 files (former preferred).

  



  I want to do this in the command line (OS X, but can use Linux if needed) and not install sketchy software. I have ffmpeg and can install other command line audio programs.

  


• FFMPEG trimming video (using select between) doesn't affect overall duration

  5 mai 2022, par srb7

  Completely new to working with FFMPEG, what I'm trying to achieve is applying overlaying graphics at certain positions and times, and cutting out sections of a single input video.

  


  I've worked out the overlaying graphics, so this code is working :

  


  ffmpeg -i /Users/username/projectdir/static/video.mp4 \
  -i overlay.png -i overlay2.png \
  -filter_complex "[0:v][1:v] overlay=192:108:enable='between(t, 0, 5)'[ov0]; 
                   [ov0] overlay=192:108:enable='between(t, 5, 10)'" \
  -pix_fmt yuv420p output_overlayed.mp4


  


  But when I try to cut out sections using this code :

  


  ffmpeg -i /Users/username/projectdir/static/video.mp4 \
  -i overlay.png -i overlay2.png \
  -filter_complex "[0:v][1:v] overlay=192:108:enable='between(t, 0, 5)'[ov0]; \
                   [ov0] overlay=192:108:enable='between(t, 5, 10)', \
                      select='between(t,0,5)+between(t,10,15)', \
                      setpts='N/FRAME_RATE/TB'" \
  -pix_fmt yuv420p output_overlayed_trimmed.mp4


  


  It seems to cut correctly, so the original video starts playing from 0 seconds until 5 seconds and then plays from 10 seconds in until 15 seconds and cuts out. But after the point where the video cuts out it's just a black screen for the duration of the video. I can't seem to get it to work so it affects the overall duration of the video.

  


  (The values being passed in are just examples by the way, eg. I've got it to start an overlay 5 seconds in but also cut 5 seconds in)

  


  I have the timestamps for when the overlays should appear on the non-trimmed video, so the overlaying should happen first and then the trimming. If the video is trimmed first then the overlays will appear at the wrong times.

  


  An alternative way of achieving this that is currently working is by performing the first line of code (which just produces a new video file with the overlay) and then separately take this new file and perform the trimming independently :

  


  ffmpeg -ss 0 -to 5 -i /Users/username/projectdir/static/output_overlayed.mp4 \
  -ss 15 -to 20 -i /Users/username/projectdir/static/output_overlayed.mp4 \
  -filter_complex "[0][1]concat=n=2:v=1:a=1" output_trimmed.mp4


  


  But this means working with 2 separate files and then having to remove the first after the 2nd execution is complete. Ideally I'd combine them into one command which doesn't produce multiple files.

  


  Would appreciate any help - thanks !

  


• select a screen section ffmpeg c++ on macos

  21 avril 2022, par C1ngh10

  I am trying to record the screen on macos, with ffmpeg. I would like to be able to select a section of the screen instead of the whole desktop. I tried to set several options such as vf, with values like "crop=150:150:0:0", or video_size with value "150x150". The result was that the output video had the correct dimensions (150x150) but whole screen has been recorded instead of the specified section. Does anybody know another way to do that ?

  


  int ScreenRecorder::openVideoDevice() {
    value = 0;
    videoOptions = nullptr;
    pAVFormatContext = nullptr;

    pAVFormatContext = avformat_alloc_context();


    string dimension = to_string(width) + "x" + to_string(height);
    av_dict_set(&videoOptions, "video_size", dimension.c_str(), 0);   //option to set the dimension of the screen section to record
    value = av_dict_set(&videoOptions, "framerate", "25", 0);
    if (value < 0) {
        cerr << "Error in setting dictionary value (setting framerate)" << endl;
        exit(-1);
    }

    value = av_dict_set(&videoOptions, "preset", "ultrafast", 0);
    if (value < 0) {
        cerr << "Error in setting dictionary value (setting preset value)" << endl;
        exit(-1);
    }

    //The distance from the left edge of the screen or desktop
    value = av_dict_set(&videoOptions, "vf", ("crop=" + to_string(width) + ":" + to_string(height) + ":" + to_string(x_offset) + ":" +
        to_string(y_offset)).c_str(), 0);

    if (value < 0) {
        cerr << "Error in setting crop" << endl;
        exit(-1);
    }

    value = av_dict_set(&videoOptions, "pixel_format", "yuv420p", 0);
    if (value < 0) {
        cerr << "Error in setting pixel format" << endl;
        exit(-1);
    }
    
    pAVInputFormat = av_find_input_format("avfoundation");

    if (avformat_open_input(&pAVFormatContext, "1:none", pAVInputFormat, &videoOptions) != 0) {
        cerr << "Error in opening input device" << endl;
        exit(-1);
    }
    //get video stream infos from context
    value = avformat_find_stream_info(pAVFormatContext, nullptr);
    if (value < 0) {
        cerr << "Error in retrieving the stream info" << endl;
        exit(-1);
    }

    VideoStreamIndx = -1;
    for (int i = 0; i < pAVFormatContext->nb_streams; i++) {
        if (pAVFormatContext->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
            VideoStreamIndx = i;
            break;
        }
    }
    if (VideoStreamIndx == -1) {
        cerr << "Error: unable to find video stream index" << endl;
        exit(-2);
    }

    pAVCodecContext = pAVFormatContext->streams[VideoStreamIndx]->codec;
    pAVCodec = avcodec_find_decoder(pAVCodecContext->codec_id/*params->codec_id*/);
    if (pAVCodec == nullptr) {
        cerr << "Error: unable to find decoder video" << endl;
        exit(-1);
    }

    return 0;
}