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• How build ffmpeg optimized for iOS, using hardware decoding probably ?

  9 décembre 2013, par jAckOdE

  I make a FFMPEG-based player for ios. It works fine on simulator, but on real-device (iPhone 4) the frame rate is low and make my audio and video out of sync. the player works fine on iPhone 4s, so I guess it's just problem about device's computing power.

  So, is there anyway to build FFMPEG optimized for iOS device (armv7, arvm7s arch) ? or is there anyway to utilize ios device hardware to decode video stream ?

  My video stream is encode in H264/AAC.

• ffmpeg : How to limit bit rate of video output ?

  27 mars 2017, par Mat

  To a 2GB raw video file taken in front of a greenscreen I want to add the alpha channel.

  My problem is : the output files appear much too large to me (about 20-fold the size of the input), and OpenShot, the video editor, seems unable to handle such huge files. Comparing file properties of input and output shows bitrates of about 15k in the infiles, and 150k-250k in the result files, which seems to pinpoint the problem.

  (By the way, I also want to discard the first part of the clip as well as its audio channel and reduce the frame rate from 30 to 24 fps in the process, which all works fine.)

  This is my command :

  ffmpeg.exe -i  -vf chromakey=0x007d06:0.15:0.0 -ss 40.420 -r 24 -b:v 15840k -maxrate 15840k -bufsize 15840k -an -c:v <encoder> 
  
  </encoder>

  The parameters as I understand them :

  -i  ... infile
  
  -vf chromakey=0x007d06:0.15:0.0 ... chroma, tolerance & blend of greenscreens
  
  -ss 40.420 ... skip before second 40.420 (this works)
  
  -r 24 ... frame rate (this works, too)
  
  -b:v 15804k ... bitrate (seemingly no effect)
  
  -maxrate 15840k ... maximum BitRate (seemingly no effect)
  
  -bufzise 15840k ... Buffer size (can't tell)
  
  -an ... no audio channel (works fine)
  
  -c:v <encoder> ... Video Encoder (ffvhuff, png, qtrle and tiff were tried, all to the same result)
  
   ... outfile
  
  </encoder>

  b, maxrate and bufsize are described as global options. No matter what setting, during the process bitrates of up to some 3000000kbits/s (tiff) are reported.

  (I also added -pixel_format argb, but this, too, seemed to be ignored, ffmpeg always reports to write yuva420p.)

  What am I missing ?

• Execute FFMPEG conversion with php

  17 avril 2016, par Alexis Martin

  I’ve a problem using ffmpeg. From the cmd the command works great but not in php with exec function. (It’s a conversion from RTSP (ip camera) to jpg)

  In cmd : ffmpeg -i rtsp://user:password@192.168.0.4:554/11 -y -f image2 -frames 1 -t 5 -strict -2 C:/image.jpg

  so it works fine, i get image.jpg in c:/ : see here

  code from php :

  <?php
  
  exec('C:/Programmes_meteo/ffmpeg/bin/ffmpeg.exe ffmpeg -i rtsp://user:password@192.168.0.4:554/11 -y -f image2 -frames 1 -t 5 -strict -2 C:/image.jpg 2>&1', $output);
  
  echo "<pre>";
  
  print_r($output);
  
  echo "</pre>";
  
  ?>

  The result is : see here

  We can see that ffmpeg works with php but he doesn’t execute the code completely.

  Does anybody knows the problem ?

  PS : OS is windows server 2012

  Thanks a lot !