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• Converting any video to iPhone - transcoding logic/algorithm ?

  28 septembre 2012, par cajwine

  I have many-many video files in different formats (mostly avi). For example, some relevant lines from ffprobe :

    Duration: 02:27:14.70, start: 0.000000, bitrate: 664 kb/s
  
      Stream #0.0: Video: mpeg4, yuv420p, 608x256 [PAR 1:1 DAR 19:8], 23.98 tbr, 23.98 tbn, 23.98 tbc
  
      Stream #0.1: Audio: mp3, 44100 Hz, stereo, s16, 96 kb/s
  
  
  
    Duration: 00:20:51.84, start: 0.000000, bitrate: 3286 kb/s
  
      Stream #0.0: Video: mpeg4, yuv420p, 640x480 [PAR 1:1 DAR 4:3], 25 tbr, 25 tbn, 25 tbc
  
      Stream #0.1: Audio: mp3, 48000 Hz, stereo, s16, 128 kb/s
  
  
  
    Duration: 01:26:01.84, start: 0.000000, bitrate: 845 kb/s
  
      Stream #0.0: Video: mpeg4, yuv420p, 704x544 [PAR 1:1 DAR 22:17], 25 fps, 25 tbr, 25 tbn, 30k tbc
  
      Stream #0.1: Audio: mp3, 44100 Hz, stereo, s16, 128 kb/s
  
  
  
    Duration: 01:42:25.68, start: 0.000000, bitrate: 952 kb/s
  
      Stream #0.0: Video: h264 (High), yuv420p, 600x244 [PAR 1:1 DAR 150:61], 25 fps, 25 tbr, 25 tbn, 50 tbc
  
      Stream #0.1: Audio: mp3, 48000 Hz, stereo, s16, 112 kb/s

  As you can see, the bitrates, video-sizes, codecs are vary. Want write a script (bash, perl) what will convert them for iPhone with ffmpeg.

  With googling i found many different ffmpeg profiles, but all profiles are "static", e.g. converts video to same resolution and this is probably not the right way, because i have many different video resolutions with many different bitrates. (this applies for the audio too).

  I'm able write the script - but need help with one basic question.

  I need help with the algorithm how to calculate the values for ffmpeg arguments from the above ffprobe results. E.g. when have video 704x544 and 845kb/s and another video with smaller size 640x480 but 3200kb/s bitrate - how to calculate the "right values" for ffmpeg in the script ?

  What is right algorithm/logic for transcoding video for the desired device ? (in my case iPhone)

  If someone care, I have ffmpeg recompiled with "nonfree" codecs, and have mencoder (from mplayer package) too.

  Second : In the avi containers are many videos already in the mpeg4 format. How to determine the "fastest" converting profile ? Mean a profile, where ffmpeg will only do the less-possible calculations, so probably will leave as-is : the format mpeg4, the size, the bitrate and "only" will change the container format. Is this possible ?

  I was read many ffmpeg SO questions, but not find answers - maybe I missed something. Can somebody point me to some good documents ?

• What are the encoding techniques to be used while creating 3gp videos on iPhone

  23 avril 2013, par Mahesh

  Some converted 3gp video using ffmpeg library, played on iphone and some not played and that all video played on android,blackberry and J2ME without issues.

  1. please suggest to what type of encoding to be used while creating 3gp videos which is play in iphone without issues.

• iPhone - FFMPEG/VLC audio stream for iOS

  24 avril 2013, par Siriss

  I am trying to write an app for a school project that will play a video stream of the lab. They use Foscam cameras, and from what I understand they only stream audio in FFMPEG and VLC (a wrapper of FFMPEG and others, correct ?). I can play the video stream in a UIWebView just fine, but I can't figure out how to get audio to work. I have read a bunch of post on here about the different audio stream options, but none support this format. I have also looked into VLCKit, but that seems to only work in OS X, not iOS.

  Is there a Framework, or Kit that can stream audio from a VLC/FFMPEG file, or does someone know of a better way to get audio from a Foscam ?