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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 ?

• Errors compiling ffmpeg for iPhone

  20 juillet 2013, par simon.d

  I'm on OS X Lion and I'm trying to compile the armv7 libraries of ffmpeg for the iPhone. I'm using ffmpeg 0.10.

  Here's my configure line :

  ./configure --disable-doc --disable-ffmpeg --disable-ffplay --disable-ffserver --disable-ffprobe --enable-cross-compile --arch=arm --target-os=darwin --cc=/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin/gcc --as='gas-preprocessor/gas-preprocessor.pl /Developer/Platforms/iPhoneOS.platform/Developer/usr/bin/gcc' --sysroot=/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS5.0.sdk --cpu=cortex-a8 --extra-cflags='-arch armv7' --extra-ldflags='-arch armv7 -isysroot /Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS5.0.sdk' --enable-pic --disable-avdevice --disable-avfilter --disable-zlib --disable-bzlib

  Configure runs fine although it ends with : WARNING : Compiler does not indicate floating-point ABI, guessing soft.

  Here are my make results :

  Users-MacBook-Pro:ffmpeg-0.10 user$ make
  
  CC    libavformat/4xm.o
  
  CC    libavformat/a64.o
  
  CC    libavformat/aacdec.o
  
  CC    libavformat/ac3dec.o
  
  CC    libavformat/act.o
  
  CC    libavformat/adtsenc.o
  
  CC    libavformat/adxdec.o
  
  CC    libavformat/aea.o
  
  CC    libavformat/aiffdec.o
  
  CC    libavformat/aiffenc.o
  
  CC    libavformat/allformats.o
  
  CC    libavformat/amr.o
  
  CC    libavformat/anm.o
  
  CC    libavformat/apc.o
  
  CC    libavformat/ape.o
  
  CC    libavformat/apetag.o
  
  CC    libavformat/applehttp.o
  
  CC    libavformat/applehttpproto.o
  
  CC    libavformat/asf.o
  
  CC    libavformat/asfcrypt.o
  
  error: invalid operand in inline asm: 'ldr   ${0:Q}, $1 
  
      ldr   ${0:R}, $2 
  
      '
  
  make: *** [libavformat/asfcrypt.o] Error 1
  
  Users-MacBook-Pro:ffmpeg-0.10 user$

  Any ideas ? Thanks !

• linker error when using FFMPEG library in iphone

  26 novembre 2014, par Anurag Sharma

  I a trying to use FFMPEG library but it gives linker error.I spent three day for this but still not get any answer ?Instead of rejecting my question please focus on what i am trying to ask .
  plz help