Convert to Edit-Friendly MP4 CRF value

WingsFromHeaven · May 6, 2021, 12:00am

Could we get some additional details on the default codec option in the ‘Convert to Edit-Friendly’ dialog? Specifically the CRF value (assuming ‘Quality-based VBR’ in x264)? The ‘Lossy: I-frame only H.264/AC-3 MP4’ info is helpful but insufficient to determine if this will serve as an appropriate intermediate codec. We can examine the output to ascertain most input parameters, but things like Rate Control are not discernable. Ultimately, we would need the following additional information (or manual control akin to the Export > Advanced tabs):
Codec > CRF:
Video > Interpolation
Audio > Rate Control
Audio > bitrate or quality AQ

We’re also seeing major blurring (double vision) issues with the Blend method for Overriding the frame rate. But that’s another topic.

brian · May 6, 2021, 1:21am

This is not documented formally anywhere. If you can muddle through the code, you can infer the options here:

github.com

mltframework/shotcut/blob/master/src/widgets/avformatproducerwidget.cpp#L912


      
              nameFilter = tr("MOV (*.mov);;All Files (*)");
              break;
          case 2:
              ffmpegArgs << "-codec:v" << "utvideo" << "-pix_fmt" << "yuv422p";
              if (!ui->scanComboBox->currentIndex()) { // interlaced
                  meltArgs << "field_order=" + QString::fromLatin1(ui->fieldOrderComboBox->currentIndex() ? "tt" :
                                                                   "bb");
              }
              meltArgs << "acodec=pcm_f32le" << "vcodec=utvideo" << "mlt_audio_format=f32le" << "pix_fmt=yuv422p";
              path.append("/%1 - %2.mkv");
              nameFilter = tr("MKV (*.mkv);;All Files (*)");
              break;
          }
          QFileInfo fi(resource);
          path = path.arg(fi.completeBaseName()).arg(tr("Reversed"));
          QString filename = QmlApplication::getNextProjectFile(path);
          if (filename.isEmpty()) {
              filename = QFileDialog::getSaveFileName(this, dialog.windowTitle(), path, nameFilter,
                                                      nullptr, Util::getFileDialogOptions());
          }
          if (!filename.isEmpty()) {

    args << "-f" << "mp4" << "-codec:a" << "ac3" << "-b:a" << "512k" << "-codec:v" << "libx264";
    args << "-preset" << "medium" << "-g" << "1" << "-crf" << "15";

Basically, it uses the “medium” preset for libx264 with crf=15

system · August 4, 2021, 12:00am

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