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• Sync video only streaming using pts

  26 février 2014, par user2846108

  I am using ffmpeg for streaming video alone (no audio) and SDL 2.0 for display. So far, I have decoded the packets as soon as they arrive and present it to the renderer. But I would like to display the video frames by syncing with PTS value so that the receiver does not go out of sync with the sender (Since I am streaming real time video over RTSP). I have read dranger tutorial but I cannot understand it. My pseudo code looks like this :

  //Create SDL window
  
  SDL_Window * window = SDL_CreateWindow("SDL", 
  
  SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, w, h, 0); 
  
  //Create renderer for the window
  
  SDL_Renderer * renderer = SDL_CreateRenderer(window, -1, 0); 
  
  
  
  //Allocate frame
  
  frame = avcodec_alloc_frame(); 
  
  
  
  //Read frame 
  
  while (av_read_frame(format_context, &avpacket) >= 0) { 
  
  if (avpacket.stream_index == videostream) { 
  
  //Decode the frame
  
  avcodec_decode_video2(codec_context, frame, &frame_finished, 
  
  &avpacket); 
  
  if (frame_finished) {
  
    //update the YUV texture with the decoded frame (SDL_UpdateYUVTexture)
  
    //Copy the texture to the renderer (SDL_RendererCopy)
  
    //Present the rederer (SDL_RenderPresent)
  
   }
  
  
  
  //Handle SDL event
  
  SDL_PollEvent(&event)
  
  }

  Can one help me how and where I can use PTS in the above code (a pseudo code is much better) and implement the synchronization between sender and receiver (such that if more packets are accumulated in the buffer, I should drop some packets so that latency between sender and receiver does not grow up as the time goes) ?

  Thanks in advance.

• Recalculate cropdetect parameters from initial values

  26 août 2020, par steviem1986

  I have a video that is 1920x1080, and cropdetect works great for this static size. My problem is that I am developing for the web, and I want to be able to re-calculate the best crop parameters when the window/video is resized.

  


  Cropping the video, and running cropdetect each time the window is resized seems like overkill. Is there a way to do it from the initial cropdetect values and the resized video width+height ?

  


• change output order of FFprobe

  28 avril 2023, par summerrain

  How can I change the output order of FFprobe ?

  


  ffprobe -hide_banner -show_streams -show_format space.mkv -of json=c=0 -o output.json creates a json output file with the streams sections first and the format section last.

  


  I need the reverse order (format section first, streams section last).

  


  But reordering the parameters (i.e. -show_format -show_streams) has no effect unfortunately.

  


  This is the output of the command above :

  


  {
    "streams": [
        {
            "index": 0,
            "codec_name": "h264",
            "codec_long_name": "H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10",
            "profile": "Main",
            "codec_type": "video",
            "codec_tag_string": "[0][0][0][0]",
            "codec_tag": "0x0000",
            "width": 256,
            "height": 144,
            "coded_width": 256,
            "coded_height": 144,
            "closed_captions": 0,
            "film_grain": 0,
            "has_b_frames": 1,
            "sample_aspect_ratio": "1:1",
            "display_aspect_ratio": "16:9",
            "pix_fmt": "yuv420p",
            "level": 11,
            "color_range": "tv",
            "color_space": "bt709",
            "color_transfer": "bt709",
            "color_primaries": "bt709",
            "chroma_location": "left",
            "field_order": "progressive",
            "refs": 1,
            "is_avc": "true",
            "nal_length_size": "4",
            "r_frame_rate": "3737/250",
            "avg_frame_rate": "3737/250",
            "time_base": "1/1000",
            "start_pts": 0,
            "start_time": "0.000000",
            "bits_per_raw_sample": "8",
            "extradata_size": 41,
            "disposition": {
                "default": 1,
                "dub": 0,
                "original": 0,
                "comment": 0,
                "lyrics": 0,
                "karaoke": 0,
                "forced": 0,
                "hearing_impaired": 0,
                "visual_impaired": 0,
                "clean_effects": 0,
                "attached_pic": 0,
                "timed_thumbnails": 0,
                "captions": 0,
                "descriptions": 0,
                "metadata": 0,
                "dependent": 0,
                "still_image": 0
            },
            "tags": {
                "HANDLER_NAME": "ISO Media file produced by Google Inc.",
                "VENDOR_ID": "[0][0][0][0]",
                "DURATION": "00:10:53.276000000"
            }
        },
        {
            "index": 1,
            "codec_name": "aac",
            "codec_long_name": "AAC (Advanced Audio Coding)",
            "profile": "HE-AAC",
            "codec_type": "audio",
            "codec_tag_string": "[0][0][0][0]",
            "codec_tag": "0x0000",
            "sample_fmt": "fltp",
            "sample_rate": "44100",
            "channels": 2,
            "channel_layout": "stereo",
            "bits_per_sample": 0,
            "initial_padding": 0,
            "r_frame_rate": "0/0",
            "avg_frame_rate": "0/0",
            "time_base": "1/1000",
            "start_pts": 0,
            "start_time": "0.000000",
            "extradata_size": 25,
            "disposition": {
                "default": 1,
                "dub": 0,
                "original": 0,
                "comment": 0,
                "lyrics": 0,
                "karaoke": 0,
                "forced": 0,
                "hearing_impaired": 0,
                "visual_impaired": 0,
                "clean_effects": 0,
                "attached_pic": 0,
                "timed_thumbnails": 0,
                "captions": 0,
                "descriptions": 0,
                "metadata": 0,
                "dependent": 0,
                "still_image": 0
            },
            "tags": {
                "HANDLER_NAME": "ISO Media file produced by Google Inc.",
                "VENDOR_ID": "[0][0][0][0]",
                "DURATION": "00:10:53.409000000"
            }
        }
    ],
    "format": {
        "filename": "space.mkv",
        "nb_streams": 2,
        "nb_programs": 0,
        "format_name": "matroska,webm",
        "format_long_name": "Matroska / WebM",
        "start_time": "0.000000",
        "duration": "653.409000",
        "size": "5252652",
        "bit_rate": "64310",
        "probe_score": 100,
        "tags": {
            "title": "SpaceX Starship explodes on first launch attempt",
            "COMMENT": "https://www.youtube.com/watch?v=gk1BViilFFk",
            "COMPATIBLE_BRANDS": "iso6avc1mp41",
            "MAJOR_BRAND": "dash",
            "MINOR_VERSION": "0",
            "ARTIST": "CNN",
            "DATE": "20230420",
            "DESCRIPTION": "SpaceX’s Starship, the most powerful rocket ever built, took off from a launch pad on the coast of South Texas, but exploded midair before stage separation. #CNN #News",
            "SYNOPSIS": "SpaceX’s Starship, the most powerful rocket ever built, took off from a launch pad on the coast of South Texas, but exploded midair before stage separation. #CNN #News",
            "PURL": "https://www.youtube.com/watch?v=gk1BViilFFk",
            "ENCODER": "Lavf60.4.101"
        }
    }
}