Recherche avancée

Sur d’autres sites (9658)

• What is the structure of AVPacket::data ?

  17 mai 2017, par Sanduni Wickramasinghe

  I’m extracting data of an MPEG data packet using data member variable which is inside AVPacket structure.

  AVDictionary *options = NULL;
  
  AVFormatContext *s = avformat_alloc_context();
  
  AVPacket *pkt = new AVPacket();

  Now I can read data as a bit stream. But I want to know the structure of data that I am reading. I mean, by separating it in to I,P and B frames.

  int ret = avformat_open_input(&s, url_ref, NULL, NULL);
  
  
  
  data = pkt->data;

• avutil/hwcontext_vulkan : Improve type-safety

  14 septembre 2023, par Andreas Rheinhardt

  avutil/hwcontext_vulkan : Improve type-safety
  The AVBuffer API uses uint8_t as base type for buffers
  
  and therefore its free callbacks need to abide by this.
  
  Therefore vulkan_frame_free() used an inappropriate signature
  
  which caused casts whenever this function has been called
  
  manually.
  This commit changes this by making vulkan_frame_free()
  
  use the proper type and a vulkan_frame_free_cb() that
  
  is used as free callback for the AVBuffer API.
  Reviewed-by : Lynne <dev@lynne.ee>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavutil/hwcontext_vulkan.c

• Identification of Frame Type using Xuggle

  1er décembre 2012, par Samveen

  I'm trying to extract just the I-Frames from a video using the Xuggle API. I took the first example from the Xuggle source from here and removing the display code, added the following code snippet to identify the frame type of the current frame :

  //    Decode loop {
  
            if (picture.isComplete()) {
  
                com.xuggle.xuggler.IVideoPicture.PictType type = picture.getPictureType()
  
                if(type == com.xuggle.xuggler.IVideoPicture.PictType.I_TYPE)
  
                    System.out.println("(I-Frame)\n");
  
                else if(type == com.xuggle.xuggler.IVideoPicture.PictType.B_TYPE)
  
                    System.out.println("(B-Frame)\n");
  
                else if(type == com.xuggle.xuggler.IVideoPicture.PictType.P_TYPE)
  
                    System.out.println("(P-Frame)\n");
  
                else if(type == com.xuggle.xuggler.IVideoPicture.PictType.S_TYPE)
  
                    System.out.println("(S-Frame)\n");
  
                else if(type ==com.xuggle.xuggler.IVideoPicture.PictType.DEFAULT_TYPE)
  
                    System.out.println("(Default)\n");
  
                else
  
                    System.out.println("(Other)\n");
  
            }
  
  //    }

  Using this code, I never get an I-Frame in my test video, which by definition of being it being a video is impossible (every video's first frame MUST be an I-Frame) and every frame is identified as

  When I use mplayer to extract the I-Frames from the same video using :

  mplayer video20.mp4 -benchmark -nosound -noaspect -noframedrop -ao null \
  
          -vo png:z=6 -vf framestep=I

  I correctly get a set of I-Frames.

  The number of frames displayed by my code is identical to that extracted by mplayer without the framestep filter

  mplayer video20.mp4 -benchmark -nosound -noaspect -noframedrop -ao null \
  
          -vo png:z=6

  The input video in question is an H264 encoded video.

  My question is that what can I do to correctly get the I-Frames from the video using xuggle

  I picked up the method from Java - Keyframe extraction from a video