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• How to split audio file into equal-length segments with ffmpeg ?

  11 mars, par GPWR

  I want to split an audio file into several equal-length segments using FFmpeg. I want to specify the general segment duration (no overlap), and I want FFmpeg to render as many segments as it takes to go over the whole audio file (in other words, the number of segments to be rendered is unspecified).
Also, since I am not very experienced with FFmpeg (I only use it to make simple file conversions with few arguments), I would like a description of the code you should use to do this, rather than just a piece of code that I won't necessarily understand, if possible.
Thank you in advance.

  


  P.S. Here's the context for why I'm trying to do this :
I would like to sample a song into single-bar loops automatically, instead of having to chop them manually using a DAW. All I want to do is align the first beat of the song to the beat grid in my DAW, and then export that audio file and use it to generate one-bar loops in FFmpeg.

  


  In the future, I will try to do something like a batch command in which one can specify the tempo and key signature, and it will generate the loops using FFmpeg automatically (as long as the loop is aligned to the beat grid, as I've mentioned earlier). 😀

  


• FFMPEG libav gdigrab capturing with wrong colors

  7 mars 2018, par user1496491

  I’m capturing screen with code below, and it gets me the picture with wrong colors.

  

  The picture on left is raw data which I assumed in ARGB the picture in right is encoded as YUV. I’ve tried different formats, the pictures slighly changing, but it’s never looks ow it should be. In what format gdigrab gives its output ? What’s the right way to encode it ?

  #include "MainWindow.h"
  
  
  
  #include <qguiapplication>
  
  #include <qlabel>
  
  #include <qscreen>
  
  #include <qtimer>
  
  #include <qlayout>
  
  #include <qimage>
  
  #include <qtconcurrent></qtconcurrent>QtConcurrent>
  
  #include <qthreadpool>
  
  
  
  #include "ScreenCapture.h"
  
  
  
  MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent)
  
  {
  
      resize(800, 600);
  
  
  
      label = new QLabel();
  
      label->setAlignment(Qt::AlignHCenter | Qt::AlignVCenter);
  
  
  
      auto layout = new QHBoxLayout();
  
      layout->addWidget(label);
  
  
  
      auto widget = new QWidget();
  
      widget->setLayout(layout);
  
      setCentralWidget(widget);
  
  
  
      init();
  
      initOutFile();
  
      collectFrame();
  
  }
  
  
  
  MainWindow::~MainWindow()
  
  {
  
      avformat_close_input(&amp;inputFormatContext);
  
      avformat_free_context(inputFormatContext);
  
  
  
      QThreadPool::globalInstance()->waitForDone();
  
  }
  
  
  
  void MainWindow::init()
  
  {
  
  
  
      av_register_all();
  
      avcodec_register_all();
  
      avdevice_register_all();
  
  
  
      auto screen = QGuiApplication::screens()[1];
  
      QRect geometry = screen->geometry();
  
  
  
      inputFormatContext = avformat_alloc_context();
  
  
  
      AVDictionary* options = NULL;
  
      av_dict_set(&amp;options, "framerate", "30", NULL);
  
      av_dict_set(&amp;options, "offset_x", QString::number(geometry.x()).toLatin1().data(), NULL);
  
      av_dict_set(&amp;options, "offset_y", QString::number(geometry.y()).toLatin1().data(), NULL);
  
      av_dict_set(&amp;options, "preset", "ultrafast", NULL);
  
      av_dict_set(&amp;options, "probesize", "10MB", NULL);
  
      av_dict_set(&amp;options, "pix_fmt", "yuv420p", NULL);
  
      av_dict_set(&amp;options, "video_size", QString(QString::number(geometry.width()) + "x" + QString::number(geometry.height())).toLatin1().data(), NULL);
  
  
  
      AVInputFormat* inputFormat = av_find_input_format("gdigrab");
  
      avformat_open_input(&amp;inputFormatContext, "desktop", inputFormat, &amp;options);
  
  
  
  //    AVDictionary* options = NULL;
  
  //    av_dict_set(&amp;options, "framerate", "30", NULL);
  
  //    av_dict_set(&amp;options, "preset", "ultrafast", NULL);
  
  //    av_dict_set(&amp;options, "vcodec", "h264", NULL);
  
  //    av_dict_set(&amp;options, "s", "1280x720", NULL);
  
  //    av_dict_set(&amp;options, "crf", "0", NULL);
  
  //    av_dict_set(&amp;options, "rtbufsize", "100M", NULL);
  
  
  
  //    AVInputFormat *format = av_find_input_format("dshow");
  
  //    avformat_open_input(&amp;inputFormatContext, "video=screen-capture-recorder", format, &amp;options);
  
  
  
      av_dict_free(&amp;options);
  
      avformat_find_stream_info(inputFormatContext, NULL);
  
  
  
      videoStreamIndex = av_find_best_stream(inputFormatContext, AVMEDIA_TYPE_VIDEO, -1, -1, NULL, 0);
  
  
  
      inputCodec = avcodec_find_decoder(inputFormatContext->streams[videoStreamIndex]->codecpar->codec_id);
  
      if(!inputCodec) qDebug() &lt;&lt; "Не найден кодек входящего потока!";
  
  
  
      inputCodecContext = avcodec_alloc_context3(inputCodec);
  
      inputCodecContext->codec_id = inputCodec->id;
  
  
  
      avcodec_parameters_to_context(inputCodecContext, inputFormatContext->streams[videoStreamIndex]->codecpar);
  
  
  
      if(avcodec_open2(inputCodecContext, inputCodec, NULL)) qDebug() &lt;&lt; "Не удалось открыть входной кодек!";
  
  }
  
  
  
  void MainWindow::initOutFile()
  
  {
  
      const char* filename = "C:/Temp/output.mp4";
  
  
  
      if(avformat_alloc_output_context2(&amp;outFormatContext, NULL, NULL, filename) &lt; 0) qDebug() &lt;&lt; "Не удалось создать выходной контекст!";
  
  
  
      outCodec = avcodec_find_encoder(AV_CODEC_ID_MPEG4);
  
      if(!outCodec) qDebug() &lt;&lt; "Не удалось найти кодек!";
  
  
  
      videoStream = avformat_new_stream(outFormatContext, outCodec);
  
      videoStream->time_base = {1, 30};
  
  
  
      const AVPixelFormat* pixelFormat = outCodec->pix_fmts;
  
      while (*pixelFormat != AV_PIX_FMT_NONE)
  
      {
  
          qDebug() &lt;&lt; "OUT_FORMAT" &lt;&lt; av_get_pix_fmt_name(*pixelFormat);
  
          ++pixelFormat;
  
      }
  
  
  
      outCodecContext = videoStream->codec;
  
      outCodecContext->bit_rate = 400000;
  
      outCodecContext->width = inputCodecContext->width;
  
      outCodecContext->height = inputCodecContext->height;
  
      outCodecContext->time_base = videoStream->time_base;
  
      outCodecContext->gop_size = 10;
  
      outCodecContext->max_b_frames = 1;
  
      outCodecContext->pix_fmt = AV_PIX_FMT_YUV420P;
  
  
  
      if (outFormatContext->oformat->flags &amp; AVFMT_GLOBALHEADER) outCodecContext->flags |= CODEC_FLAG_GLOBAL_HEADER;
  
  
  
      if(avcodec_open2(outCodecContext, outCodec, NULL)) qDebug() &lt;&lt; "Не удалось открыть выходной кодек!";
  
  
  
      swsContext = sws_getContext(inputCodecContext->width,
  
                                  inputCodecContext->height,
  
  //                                inputCodecContext->pix_fmt,
  
                                  AV_PIX_FMT_ABGR,
  
                                  outCodecContext->width,
  
                                  outCodecContext->height,
  
                                  outCodecContext->pix_fmt,
  
                                  SWS_BICUBIC, NULL, NULL, NULL);
  
  
  
      if(avio_open(&amp;outFormatContext->pb, filename, AVIO_FLAG_WRITE) &lt; 0) qDebug() &lt;&lt; "Не удалось открыть файл!";
  
      if(avformat_write_header(outFormatContext, NULL) &lt; 0) qDebug() &lt;&lt; "Не удалось записать заголовок!";
  
  }
  
  
  
  void MainWindow::collectFrame()
  
  {
  
      AVFrame* inFrame = av_frame_alloc();
  
      inFrame->format = inputCodecContext->pix_fmt;
  
      inFrame->width = inputCodecContext->width;
  
      inFrame->height = inputCodecContext->height;
  
  
  
      int size = av_image_alloc(inFrame->data, inFrame->linesize, inFrame->width, inFrame->height, inputCodecContext->pix_fmt, 1);
  
      qDebug() &lt;&lt; size;
  
  
  
      AVFrame* outFrame = av_frame_alloc();
  
      outFrame->format = outCodecContext->pix_fmt;
  
      outFrame->width = outCodecContext->width;
  
      outFrame->height = outCodecContext->height;
  
  
  
      qDebug() &lt;&lt; av_image_alloc(outFrame->data, outFrame->linesize, outFrame->width, outFrame->height, outCodecContext->pix_fmt, 1);
  
  
  
      AVPacket packet;
  
      av_init_packet(&amp;packet);
  
  
  
      av_read_frame(inputFormatContext, &amp;packet);
  
  //    while(av_read_frame(inputFormatContext, &amp;packet) >= 0)
  
  //    {
  
          if(packet.stream_index == videoStream->index)
  
          {
  
  
  
              memcpy(inFrame->data[0], packet.data, size);
  
  
  
              sws_scale(swsContext, inFrame->data, inFrame->linesize, 0, inputCodecContext->height, outFrame->data, outFrame->linesize);
  
  
  
              QImage image(inFrame->data[0], inFrame->width, inFrame->height, QImage::Format_ARGB32);
  
              label->setPixmap(QPixmap::fromImage(image).scaled(label->size(), Qt::KeepAspectRatio));
  
  
  
              AVPacket outPacket;
  
              av_init_packet(&amp;outPacket);
  
  
  
              int encodeResult = avcodec_receive_packet(outCodecContext, &amp;outPacket);
  
              while(encodeResult == AVERROR(EAGAIN))
  
              {
  
                  if(avcodec_send_frame(outCodecContext, outFrame)) qDebug() &lt;&lt; "Ошибка отправки фрейма на кодирование!";
  
  
  
                  encodeResult = avcodec_receive_packet(outCodecContext, &amp;outPacket);
  
              }
  
              if(encodeResult != 0) qDebug() &lt;&lt; "Ошибка во время кодирования!" &lt;&lt; encodeResult;
  
  
  
              if(outPacket.pts != AV_NOPTS_VALUE) outPacket.pts = av_rescale_q(outPacket.pts, videoStream->codec->time_base, videoStream->time_base);
  
              if(outPacket.dts != AV_NOPTS_VALUE) outPacket.dts = av_rescale_q(outPacket.dts, videoStream->codec->time_base, videoStream->time_base);
  
  
  
              av_write_frame(outFormatContext, &amp;outPacket);
  
  
  
              av_packet_unref(&amp;outPacket);
  
          }
  
  //    }
  
  
  
      av_packet_unref(&amp;packet);
  
  
  
      av_write_trailer(outFormatContext);
  
      avio_close(outFormatContext->pb);
  
  }
  
  </qthreadpool></qimage></qlayout></qtimer></qscreen></qlabel></qguiapplication>

• Revision 32594 : plugins en minuscules, et alias pour les noms de sites

  1er novembre 2009, par fil@… — Log

  plugins en minuscules, et alias pour les noms de sites