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• MP4 video slightly asynchronous - but only on initial play

  3 mai 2012, par TheSHEEEP

  Here is our procedure :

  1. We create live MP4 videos using ffmpeg (H264/AAC), both as API and as command line tool.*
  2. qt-faststart is used to move the metadata to the beginning of the file to enable fast playback in our Flash client.
  3. Video is renamed to *.m4v.
  4. User uses our Flash client to download the video and starts playing immediatly due to the metadata being at the beginning.

  Edit :
  *First, a MPG video is created with the ffmpeg API, this is then copied together with an intro and an outro video (you can simply chain MPG videos). The resulting MPG is then converted to MP4 using the following command :

  ffmpeg -i inputvideo.mpg -sameq -b 3000000 -vcodec libx264 -acodec libvo_aacenc -ac 2 -g 60 -y outputvideo.mp4

  Basically, this does work.

  The problem :

  We noticed that during the initial playback (the user hasn't clicked anything yet, video still downloading or not does not make a difference), the audio is playing asychnronous, noticeable if you look out for it.

  But as soon as you click around in the video (one time is enough, no matter where you click), the audio becomes more synchronous (still not perfect !) for the rest of the video.

  This behaviour is the same, no matter if you view it via our Flash player or Windows Media Player. Is there anything we can do from our side (in ffmpeg or qt-faststart) to make it synchronous from the start ?

• PHP and ffmpeg - Converting to H.264 on the fly for JW Player

  10 mai 2012, par vertigoelectric

  So the project I'm working on has tons of MP4 files already on the server that need to be played in an embedded player. Ideally we'd like to use the JW Player which is already set up for most of the videos. Unfortunately, a lot of the older videos are MPEG-4 encoded and require additional plugins to play in the browser.

  What I'd like to do is be able to transcode these videos on the fly to a format that JW Player supports, such as H.264. Now, I'm part way there because I can get it to convert the old MP4 files, but I'm having difficulty passing the data directly to the player.

  This is my current script doing the converting (this is media_converted.php) :

  <?php
  
      error_reporting(0);
  
      if (!isset($_GET["MediaName"])) {
  
          $_GET["MediaName"] = "GSX238";
  
      }       
  
      require_once("php/media_center_functions.php");
  
      $MediaURL = ConstructVideoURLInternap($_GET["MediaName"]);  
  
      header("Content-Transfer-Encoding: binary");
  
      //header('Content-type: video/mp4');
  
      //$calculatedFileSize = filesize($MediaURL);
  
      //header("Content-Length: {$calculatedFileSize}");
  
  
  
      $cmd = 'ffmpeg -i "'.$MediaURL.'"  -vcodec libx264 -acodec copy -f mp4  -moov_size 32000 "_temp/'.time().'_temp.mp4"  2> _temp/media_converter_output.txt';
  
      passthru($cmd);
  
  
  
  ?>

  I'm trying to take the above file and pass it to the JW Player as the video source : in the JW Player's variable scripting, like so :

  so.addVariable('file','media_converted.php?MediaName=12345');

  While I believe this should work, it's just not.

  Even when the conversion seems to work and be sending to the player, it's hard to tell because I think the browser is trying to download the entire file before playing anything. Obviously I can't make the user wait like that.

  I've looked into qt-faststart, and I was able to use it on my computer to modify the file so that it can start playing while it's being loaded. Unfortunately, this requires two steps. I first have to completely convert the file, then when it's done I have to use qt-faststart.exe on it. Again, this doesn't isn't really an on-the-fly solution. I'm sure there has to be some way to do produce similar results in a single command to be output to the player... right ?

  There is more video data on the server than I currently have space for on my hard drive, so to permanently re-encode each video, even in batches, would be troublesome, because I'd have to download some, convert, reupload, download more, etc. If I have to do that, I will, but I would prefer to leave them as is and be able to transcode on the fly.

  Any ideas ?

• FFMPEG : preset not found in Windows Vista

  12 juin 2012, par StackOverflowNewbie

  I download FFMPEG from http://www.videohelp.com/tools/ffmpeg#download and saved it in my c :\program files\ffmpeg (Windows Vista). My Path's first 2 entries are :

  c:\program files\ffmpeg\bin;c:\program files\ffmpeg\presets;

  I found the following command on the net (http://paulrouget.com/e/converttohtml5video/)

  ffmpeg -i input.avi -acodec libvorbis -ab 96k -vcodec libx264 -vpre main -level 21 -refs 2 -b 345k -bt 345k -threads 0 -s 320x240 output.mp4

  When I run this on command line, I get the following error :

  File for preset main not found

  Any ideas what might be wrong ?