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• Is there iOS HLS player that can read #EXT-X-PROGRAM-DATETIME tag in manifest

  12 juillet 2017, par ukits

  about HLS streaming in iOS,

  for calculating the delay between streaming server and iOS client, it need to read #EXT-X-PROGRAM-DATETIME tag in HLS chunk’s manifest.

  iOS AVPlayer object doesn’t support to read tags of incoming streaming.

  Because iOS AVPlayer object doesn’t support to read tags of incoming streaming, we have to look for open source or commercial HLS player library that can read tag using ffmpeg or the other.

  If you have a library you know, recommend it please.

• Can not set the number of channels in VideoCapture in OpenCV

  30 septembre 2016, par vkubicki

  I am trying to use OpenCV to apply treatments on an mj2 file encoded as grayscale uint16 per pixel. Unfortunately, a non disclosure agreement covers this file (which I did not generate myself) and I can not post a sample mj2 file.

  The description of my .mj2 file as provided by ffmpeg is :

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'data/DEVISSAGE_181.mj2':
  
    Metadata:
  
      major_brand     : mjp2
  
      minor_version   : 0
  
      compatible_brands: mjp2
  
      creation_time   : 2015-10-09 08:07:43
  
    Duration: 00:01:03.45, start: 0.000000, bitrate: 14933 kb/s
  
      Stream #0:0: Video: jpeg2000 (mjp2 / 0x32706A6D), gray16le, 1152x288, lossless, 14933 kb/s, SAR 1:4 DAR 1:1, 5.50 fps, 5.50 tbr, 55 tbn, 55 tbc (default)
  
      Metadata:
  
        creation_time   : 2015-10-09 08:07:43
  
        handler_name    : Video
  
        encoder         : Motion JPEG2000

  I take it that gray16le confirms the uint16 encoding somehow.

  Here is my C++ code :

  #include<iostream>
  
  
  
  #include "opencv2/opencv.hpp"
  
  
  
  int main(int, char**) {
  
      cv::VideoCapture cap("data/DEVISSAGE_181.mj2"); // open the video file
  
      cap.set(CV_CAP_PROP_FORMAT, CV_16UC1);
  
  
  
      cv::Mat frame;
  
      cap.read(frame); // get a new frame from file
  
  
  
      std::cout &lt;&lt; "frame.rows: " &lt;&lt; frame.rows &lt;&lt; ", frame.cols: " &lt;&lt; frame.cols &lt;&lt; ", frame.channels(): " &lt;&lt; frame.channels() &lt;&lt; std::endl;
  
  
  
      return 0;
  
  }
  
  </iostream>

  The result of running this code is :

  frame.rows: 288, frame.cols: 1152, frame.channels(): 3, frame.depth(): 0

  Which indicates a 3 channels, CV_8U pixel encoding. Why does the cap.set instruction appear to be ignored ? What should I do to get the correct encoding ?

• Get "Delay relative to video" value using ffmpeg

  22 avril 2023, par user3449922

  I like to known if is possible detect via ffmpeg the value of property "Delay relative to video" showed here :

  


  Audio #2
ID                                       : 3
Format                                   : AC-3
Format/Info                              : Audio Coding 3
Commercial name                          : Dolby Digital
Codec ID                                 : A_AC3
Duration                                 : 10 min 0 s
Bit rate mode                            : Constant
Bit rate                                 : 320 kb/s
Channel(s)                               : 2 channels
Channel layout                           : L R
Sampling rate                            : 48.0 kHz
Frame rate                               : 31.250 FPS (1536 SPF)
Bit depth                                : 32 bits
Compression mode                         : Lossy
Delay relative to video                  : 1 s 78 ms
Stream size                              : 22.8 MiB (1%)
Language                                 : rom
Service kind                             : Complete Main
Default                                  : No
Forced                                   : No


  


  Thank you !