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• How to identify exact type or variation of a .mp4 file

  5 octobre 2017, par Dave502619

  Can anyone tell me if there are different variations of mp4 file and if so, how to identify the exact type or variation of a mp4 file ?

  The reason I need to know this is if I pass an .mp4 through FFMPEG to create an uncompressed grayscale rgb24 avi file, depending on
  where the .mp4 file has been sourced from will produce a different internally structured avi file as output from FFMPEG. Ie, the file header
  and interframe header sizes differ.

  The ffmpeg command i am using is :
  ffmpeg.exe -i source.mp4 -b 1150 -r 20.97 -g 120 -an -vf format=gray -f rawvideo -pixfmt rgb24 -s 384x216 -vcode rawvideo -y fileX.avi

  So far I have identified that .mp4 files generated by my Samsung S5 mobile phone differ from .mp4 files generated by Power Director 14. So I suspect there are different variations of .mp4 files.

  I have written some software which steps into the FFMPEG output .avi file to extract video frames, but it requires fixed offset positions to work so I can only make it work for one variation of .mp4.

• ffmpeg video to opengl texture

  23 avril 2017, par Infiniti Fizz

  I’m trying to render frames grabbed and converted from a video using ffmpeg to an OpenGL texture to be put on a quad. I’ve pretty much exhausted google and not found an answer, well I’ve found answers but none of them seem to have worked.

  Basically, I am using avcodec_decode_video2() to decode the frame and then sws_scale() to convert the frame to RGB and then glTexSubImage2D() to create an openGL texture from it but can’t seem to get anything to work.

  I’ve made sure the "destination" AVFrame has power of 2 dimensions in the SWS Context setup. Here is my code :

  SwsContext *img_convert_ctx = sws_getContext(pCodecCtx->width,
  
                  pCodecCtx->height, pCodecCtx->pix_fmt, 512,
  
                  256, PIX_FMT_RGB24, SWS_BICUBIC, NULL,
  
                  NULL, NULL);
  
  
  
  //While still frames to read
  
  while(av_read_frame(pFormatCtx, &packet)>=0) {
  
      glClear(GL_COLOR_BUFFER_BIT);
  
  
  
      //If the packet is from the video stream
  
      if(packet.stream_index == videoStream) {
  
          //Decode the video
  
          avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, &packet);
  
  
  
          //If we got a frame then convert it and put it into RGB buffer
  
          if(frameFinished) {
  
              printf("frame finished: %i\n", number);
  
              sws_scale(img_convert_ctx, pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pFrameRGB->data, pFrameRGB->linesize);
  
  
  
              glBindTexture(GL_TEXTURE_2D, texture);
  
              //gluBuild2DMipmaps(GL_TEXTURE_2D, 3, pCodecCtx->width, pCodecCtx->height, GL_RGB, GL_UNSIGNED_INT, pFrameRGB->data);
  
              glTexSubImage2D(GL_TEXTURE_2D, 0, 0,0, 512, 256, GL_RGB, GL_UNSIGNED_BYTE, pFrameRGB->data[0]);
  
              SaveFrame(pFrameRGB, pCodecCtx->width, pCodecCtx->height, number);
  
              number++;
  
          }
  
      }
  
  
  
      glColor3f(1,1,1);
  
      glBindTexture(GL_TEXTURE_2D, texture);
  
      glBegin(GL_QUADS);
  
          glTexCoord2f(0,1);
  
          glVertex3f(0,0,0);
  
  
  
          glTexCoord2f(1,1);
  
          glVertex3f(pCodecCtx->width,0,0);
  
  
  
          glTexCoord2f(1,0);
  
          glVertex3f(pCodecCtx->width, pCodecCtx->height,0);
  
  
  
          glTexCoord2f(0,0);
  
          glVertex3f(0,pCodecCtx->height,0);
  
  
  
      glEnd();

  As you can see in that code, I am also saving the frames to .ppm files just to make sure they are actually rendering, which they are.

  The file being used is a .wmv at 854x480, could this be the problem ? The fact I’m just telling it to go 512x256 ?

  P.S. I’ve looked at this Stack Overflow question but it didn’t help.

  Also, I have glEnable(GL_TEXTURE_2D) as well and have tested it by just loading in a normal bmp.

  EDIT

  I’m getting an image on the screen now but it is a garbled mess, I’m guessing something to do with changing things to a power of 2 (in the decode, swscontext and gluBuild2DMipmaps as shown in my code). I’m usually nearly exactly the same code as shown above, only I’ve changed glTexSubImage2D to gluBuild2DMipmaps and changed the types to GL_RGBA.

  Here is what the frame looks like :

  

  EDIT AGAIN

  Just realised I haven’t showed the code for how pFrameRGB is set up :

  //Allocate video frame for 24bit RGB that we convert to.
  
  AVFrame *pFrameRGB;
  
  pFrameRGB = avcodec_alloc_frame();
  
  
  
  if(pFrameRGB == NULL) {
  
      return -1;
  
  }
  
  
  
  //Allocate memory for the raw data we get when converting.
  
  uint8_t *buffer;
  
  int numBytes;
  
  numBytes = avpicture_get_size(PIX_FMT_RGB24, pCodecCtx->width, pCodecCtx->height);
  
  buffer = (uint8_t *) av_malloc(numBytes*sizeof(uint8_t));
  
  
  
  //Associate frame with our buffer
  
  avpicture_fill((AVPicture *) pFrameRGB, buffer, PIX_FMT_RGB24,
  
      pCodecCtx->width, pCodecCtx->height);

  Now that I ahve changed the PixelFormat in avgpicture_get_size to PIX_FMT_RGB24, I’ve done that in SwsContext as well and changed GluBuild2DMipmaps to GL_RGB and I get a slightly better image but it looks like I’m still missing lines and it’s still a bit stretched :

  

  Another Edit

  After following Macke’s advice and passing the actual resolution to OpenGL I get the frames nearly proper but still a bit skewed and in black and white, also it’s only getting 6fps now rather than 110fps :

  

  P.S.

  I’ve got a function to save the frames to image after sws_scale() and they are coming out fine as colour and everything so something in OGL is making it B&W.

  LAST EDIT

  Working ! Okay I have it working now, basically I am not padding out the texture to a power of 2 and just using the resolution the video is.

  I got the texture showing up properly with a lucky guess at the correct glPixelStorei()

  glPixelStorei(GL_UNPACK_ALIGNMENT, 2);

  Also, if anyone else has the subimage() showing blank problem like me, you have to fill the texture at least once with glTexImage2D() and so I use it once in the loop and then use glTexSubImage2D() after that.

  Thanks Macke and datenwolf for all your help.

• vaapi_encode : Check config attributes before creating config

  18 mai 2016, par Mark Thompson

  vaapi_encode : Check config attributes before creating config
  This prevents attempts to use unsupported modes, such as low-power
  
  H.264 mode on non-Skylake targets.  Also fixes a crash on invalid
  
  configuration, when trying to destroy an invalid VA config/context.
  

  • [DBH] libavcodec/vaapi_encode.c