Recherche avancée

Sur d’autres sites (6266)

• How do I improve the quality of a video produced from still PNG images ?

  9 avril 2012, par cormullion

  I'm trying to create a video from a few hundred PNG images. The PNG images look OK to me, e.g. here are two in MacOS X Preview :

  

  They're about 1200 pixels square, 16 bit RGB, no transparency.

  But my attempt to make a few hundred of these into a video is encountering the following problem - nearly every frame has this yellow corruption (artefacts ?), that sort of blocky flickery stuff you see on poor quality videos :

  

  The ffmpeg command I'm using is something like this :

  ffmpeg -f image2 -i /tmp/image-%07d.png -vcodec mpeg4 -vb 20M -r 20 poincare.mov

  I've tried changing a few parameters, but I probably changed the wrong ones. Any idea which parameters I should be changing, and to what value ?

  Console output is :

   ffmpeg -f image2 -i /tmp/image-%07d.png -vcodec mpeg4 -vb 30M -r 30 poincare.mov
  
      FFmpeg version UNKNOWN, Copyright (c) 2000-2010 the FFmpeg developers
  
      built on Nov  9 2010 12:20:29 with gcc 4.2.1 (Apple Inc. build 5664)
  
      configuration: --prefix=/Users/worth/OtherApps/ffmpeg/ffmpeg/../local/x86_64 --enable-static --enable-shared --enable-gpl --enable-version3 --enable-libmp3lame --enable-pthreads --enable-libvorbis --enable-libx264 --enable-libxvid --enable-libspeex --enable-libopencore_amrwb --enable-libopencore_amrnb --enable-libvpx --enable-memalign-hack --disable-debug --disable-stripping --arch=x86_64
  
    libavutil     50.33. 0 / 50.33. 0
  
    libavcore      0.12. 0 /  0.12. 0
  
    libavcodec    52.94. 3 / 52.94. 3
  
    libavformat   52.84. 0 / 52.84. 0
  
    libavdevice   52. 2. 2 / 52. 2. 2
  
    libavfilter    1.59. 0 /  1.59. 0
  
    libswscale     0.12. 0 /  0.12. 0
  
      Input #0, image2, from '/tmp/image-%07d.png':
  
    Duration: 00:08:55.44, start: 0.000000, bitrate: N/A
  
      Stream #0.0: Video: png, rgb48be, 1200x1198, 25 fps, 25 tbr, 25 tbn, 25 tbc
  
  File 'poincare.mov' already exists. Overwrite ? [y/N] y
  
  [buffer @ 0x101301ae0] w:1200 h:1198 pixfmt:rgb48be
  
  [ffsink @ 0x101301d50] auto-inserting filter 'auto-inserted scaler 0' between the filter 'src' and the filter 'out'
  
  [scale @ 0x101302090] w:1200 h:1198 fmt:rgb48be -> w:1200 h:1198 fmt:yuv420p flags:0xa0000004
  
  Output #0, mov, to 'poincare.mov':
  
    Metadata:
  
      encoder         : Lavf52.84.0
  
      Stream #0.0: Video: mpeg4, yuv420p, 1200x1198, q=2-31, 30000 kb/s, 30 tbn, 30 tbc
  
  Stream mapping:
  
    Stream #0.0 -> #0.0
  
  Press [q] to stop encoding
  
  frame=13386 fps= 27 q=2.0 Lsize=  536132kB time=535.43 bitrate=8202.7kbits/s    
  
  video:535981kB audio:0kB global headers:0kB muxing overhead 0.028261%

• ffmpeg Error when evaluating the expression xxx for y when overlay

  23 mars 2023, par LF00

  I use ffmpeg to add a flip watermark on the wideo with overlay,

  


  This works well with x

  


  ffmpeg -hide_banner -i HLS_540.ts -i out.png -filter_complex "[0:v][1:v]overlay=x='-w+400+100*mod(t\,(W+w-400)/100)':y=250" out.mp4

  


  But when I set y with expression if(eq(mod(t,5),0),rand(0,100),y) it show's error.

  


  ffmpeg -hide_banner -i HLS_540.ts -i out.png -filter_complex "[0:v][1:v]overlay=x='-w+400+100*mod(t\,(W+w-400)/100)':y='if(eq(mod(t\,5)\,0)\,rand(0\,100)\,y)'" out.mp4

  


  [Parsed_overlay_0 @ 000002438ba6d880] [Eval @ 000000cf5a3fe2e0] Unknown function in 'rand(0,100),y)'
[Parsed_overlay_0 @ 000002438ba6d880] Error when evaluating the expression 'if(eq(mod(t,5),0),rand(0,100),y)' for y
[Parsed_overlay_0 @ 000002438ba6d880] Failed to configure input pad on Parsed_overlay_0


  


  While when I do like this ffplay -f lavfi -i "color=color=yellow" -vf "drawtext=text='s':x=if(eq(mod(t\,5)\,0)\,rand(0\,(W-tw))\,x+0.03*mod(t\,5)):y=if(eq(mod(t\,5)\,0)\,rand(0\,(H-th))\,y)" it works well.

  


  How can I set rand y in the failed command ?

  


  Envirionment :
win11, git-bash

  


  ffmpeg -version
ffmpeg version N-104863-g6cf55b9da2-20211213 Copyright (c) 2000-2021 the FFmpeg developers
built with gcc 11.2.0 (crosstool-NG 1.24.0.498_5075e1f)
configuration: --prefix=/ffbuild/prefix --pkg-config-flags=--static --pkg-config=pkg-config --cross-prefix=x86_64-w64-mingw32- --arch=x86_64 --target-os=mingw32 --enable-gpl --enable-version3 --disable-debug --disable-w32threads --enable-pthreads --enable-iconv --enable-libxml2 --enable-zlib --enable-libfreetype --enable-libfribidi --enable-gmp --enable-lzma --enable-fontconfig --enable-libvorbis --enable-opencl --enable-libvmaf --disable-libxcb --disable-xlib --enable-amf --enable-libaom --enable-avisynth --enable-libdav1d --enable-libdavs2 --disable-libfdk-aac --enable-ffnvcodec --enable-cuda-llvm --enable-frei0r --enable-libgme --enable-libass --enable-libbluray --enable-libmp3lame --enable-libopus --enable-librist --enable-libtheora --enable-libvpx --enable-libwebp --enable-lv2 --enable-libmfx --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenh264 --enable-libopenjpeg --enable-libopenmpt --enable-librav1e --enable-librubberband --enable-schannel --enable-sdl2 --enable-libsoxr --enable-libsrt --enable-libsvtav1 --enable-libtwolame --enable-libuavs3d --disable-libdrm --disable-vaapi --enable-libvidstab --enable-vulkan --enable-libshaderc --enable-libplacebo --enable-libx264 --enable-libx265 --enable-libxavs2 --enable-libxvid --enable-libzimg --enable-libzvbi --extra-cflags=-DLIBTWOLAME_STATIC --extra-cxxflags= --extra-ldflags=-pthread --extra-ldexeflags= --extra-libs=-lgomp --extra-version=20211213
libavutil      57. 11.100 / 57. 11.100
libavcodec     59. 14.100 / 59. 14.100
libavformat    59. 10.100 / 59. 10.100
libavdevice    59.  0.101 / 59.  0.101
libavfilter     8. 20.100 /  8. 20.100
libswscale      6.  1.101 /  6.  1.101
libswresample   4.  0.100 /  4.  0.100
libpostproc    56.  0.100 / 56.  0.100


  


• Surfaceview 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 : 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.