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• YUV to RGB by Shader on iPhone

  27 octobre 2012, par user1333656

  Currently I am developing a video player using FFMPEG.
  I'm trying to convert YUV420P to RGB by Shader to reduce performance hit and I could see it works fine. The problem is caused when I try to change image size.

  Case 1. YUV to RGB is perfect. but the image is not exactly fit to Texture Bounds.
  For example, if i play 640x360 video, right (640-512) part is cropped and bottom (512-360) is filled with green colored rectangle.

  FRAME_X=512; //This is texture size
  
  FRAME_Y=512;
  
  
  
      avpicture_fill((AVPicture *) f, [currentVideoBuffer.data mutableBytes],
  
                 enc->pix_fmt,
  
                 FRAME_X, FRAME_Y);
  
  
  
      av_picture_copy((AVPicture *) f, (AVPicture *) avFrame,
  
                  enc->pix_fmt,
  
                  enc->width, enc->height);

  ....

  int yuvWidth= FRAME_X ;
  
  int  yuvHeight= FRAME_Y;
  
  glBindTexture ( GL_TEXTURE_2D, textureIdY );
  
  glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE, 
  
  yuvWidth, yuvHeight, 0, GL_LUMINANCE, GL_UNSIGNED_BYTE, y_channel);
  
  
  
  
  
  glBindTexture ( GL_TEXTURE_2D, textureIdU );
  
  glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE,
  
  yuvWidth/2, yuvHeight/2, 0, GL_LUMINANCE, GL_UNSIGNED_BYTE, u_channel);
  
  
  
  glBindTexture ( GL_TEXTURE_2D, textureIdV );
  
  glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE, 
  
  yuvWidth/2, yuvHeight/2, 0, GL_LUMINANCE, GL_UNSIGNED_BYTE, v_channel);

  Case 2. If i set actual image size to texture size, then image is exactly fit to texture but the color of image is a little bit strange. It has too much green color.

  Does anybody give me some clues for this ??
  Thanks in advance.

• How to increase performance of bitmap drawing on Android

  20 avril 2012, par vitakot

  I created a movie player based on FFmpeg. It works fine. The decoding is quite fast, on LG P970 (Cortex A8 with Neon) I have an average 70 fps with 640 x 424 resolution video stream including YUV2RGB conversion. However, there is one bottleneck. It is drawing on Canvas.

  I use jnigraphics native library to fill picture data into the bitmap in the native side and then I draw this bitmap on Canvas in SurfaceView. It is quite simple and common approach, but the drawing takes 44 ms for bitmap with 640 x 424 resolution which reduces fps to 23 and makes this technique unusable... It takes a lot more then the whole A/V frame decoding !

  Is there any method how to draw bitmaps significantly faster ? I would prefer to render completely in the native code using OpenGLES 2, but I have read it also could be slow. So what now ?...

  How can I render bitmaps as fast as possible ?

• FFmpeg AVFrame to OpenGL texture without YUV to RGB soft conversion

  23 février 2012, par zebeurton

  I want to decode an encrypted H264 video file on iOS. I already have ported our decryption algorithm and it is working fine. However, we cannot directly use H264 hardware decoder due to lack of API in SDK.

  So I am trying to find an alternative to decode H264 video. I am trying to use FFmpeg to decode these video even if there are some possible LGPL license issues. I decode H264 video without any problems and I render H264 frames thanks to OpenGL ES texture. But there are some performance issues. I instrumented my code and the bottleneck is the ffmpeg rescaling and YUV to RGB conversion.
  I know that I can use OpenGL ES 2.0 shaders to convert YUV to RGB with GPU acceleration (related post Alternative to ffmpeg for iOS).
  I also know how AVFrame structure is composed : data[0] for Y data, data[1] for U data and data[1] for V data. But I do not understand how can I use line size[x] with data[x] to transmit data to OpenGL texture.

  Does anybody have an example of AVFrame YUV to OpenGL texture ?

  Thanks,
  David