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• FFMPEG - Recursive mp3 bitrate-conversion (Windows)

  3 avril 2018, par ShroomPow

  I am looking for a way to convert every mp3-file in a directory (including sub-directories) to 128kbps using ffmpeg and preferably batch on windows.
  Either by replacing the original files or "cloning" the whole directory-structure.

  I am trying to cut down the size of my musiclibrary for my phone. Is this easily achievable ?

• Surfaceview/TextureView for subtitles alpha does not work

  27 mai 2018, par user654628

  Goal : trying to build video player with subtitles for android. Video can be low resolution but the subtitles should be resolution of phone (such that if video is 720p, the subtitles should render to screen size say 1080p).

  Issue : Render on Textureview or Surfaceview is not see through where you could get it to blend with the background views. I am using FFMPEG to render a frame at say 720p but phone device is 1080p. I need to display subtitles that are different resolution than the subtitles resolution so pixel blending is difficult.

  I first tried to scale the frame (AVFrame) with sws_convert but each frame took 80ms so that is not an option (since it is running software).

  Then I tried two surface views, one for the video and one for subtitles where video would be 720p and subtitles SurfaceView is 1080p, then the video scales up to the phone size. The issue here is that the subtitles are not translucent. Black opacity 0 would be transparent but white with alpha 0 is still white. Why is this ?

  //Code from Java, the view that extends FrameLayout
  
  public VideoView(@NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
  
      super(context, attrs, defStyleAttr);
  
      mVideoSurface = new SurfaceView(context);
  
      mSubtitlesSurface = new SurfaceView(context);
  
      addView(mVideoSurface);
  
      addView(mSubtitlesSurface);
  
      mVideoSurface.getHolder().addCallback(mSurfaceCallback);
  
      mSubtitlesSurface.getHolder().addCallback(mSurfaceCallback);
  
      mSubtitlesSurface.setZOrderMediaOverlay(true);
  
      mSubtitlesSurface.getHolder().setFormat(PixelFormat.TRANSLUCENT);
  
      //etc
  
  }

  Eventually I tried as a test to render a square to the subtitle surface view (C++)

  // Render the video frame, now render the subtitle frame
  
  ANativeWindow_Buffer buffer;
  
  ANativeWindow_setBuffersGeometry(subWindow, width, height, WINDOW_FORMAT_RGBA_8888);
  
  if ((ret = ANativeWindow_lock(subWindow, &buffer, NULL)) < 0) {
  
      return ret;
  
  }
  
  for (int j = height/2; j < height/2 + 100; j++) {
  
      for (int i = width/2; i < width/2 + 100; i++) {
  
          uint8_t * d =  (uint8_t*)buffer.bits + j * (buffer.stride * 4) + i * 4;
  
          d[0] = 0xff;
  
          d[1] = 0xff;
  
          d[2] = 0xFF;
  
          d[3] = 0;           /* alpha */
  
  
  
      }
  
  }
  
  ANativeWindow_unlockAndPost(subWindow);

  So above code should render a white square in the image with 0 alpha (so should be invisible), but it is shown. If I change it to yellow with alpha 0 it will be visible but not the correct color. If I change to white with 1 alpha, it is white and opaque. If I use black with alpha 0xCC, it is invisible, only if alpha is 0xFF then it is visible as black. Seems to have no translucency even though I added it to the SurfaceHolder. Why is it like this ? I can add more code if needed.

  Is my only option to do what I want to render frame as a texture in OpenGL and (GLSurfaceView), resize the image to phone resolution and blend the alpha subtitles onto the frame as a texture ?

  Thanks in advance.

• How to convert/mux/encapsulate AAC-ADTS into M4A on Xamarin Android 4.1+ ?

  27 août 2014, par Ingolmo

  I’m making an Android 4.1+ app with Xamarin, which is mixing two audio files in a resulting AAC-ADTS file, using the MediaCodec API.
  The problem is that this file is not readable by most audio players, or on the iOS version of the app...

  I’m now trying to encapsulate the AAC-ADTS data inside a MP4/M4A container. I found many possible solutions, but I’m not able to implement properly one of them.

  • Android provides the "MediaMuxer" API, which seems capable of doing that... But this is only available on Android 4.3, which is not acceptable for me.

  • https://github.com/sannies/mp4parser this Java library seems to do the work, but I cannot manage to build the Java binding for it (details here), and I did not find any equivalent C# library.

  • I tried to build ffmpeg for Android, but did not manage to make it work (ffmpeg does not find the file on the phone). I don’t really understand the underlying problems, but I mainly don’t know how to build and use ffmpeg so it is compatible on every Android phone, since the architectures may differ.

  Is one of these solutions the "good one", and if so, can you provide me links or help to do it properly, or am I missing a more consistent solution ?