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• ffmpeg resizing video puts it at wrong resolution

  16 décembre 2015, par agmcleod

  I have a 1080p video that i’m trying to resize for an iOS app upload. So i tried scaling it to the iPhone 6 resolution of 1334x750 :

  ffmpeg -i WrathTrailer.mp4 -strict -2 -vf scale=1334:750 WrathTrailer1334x750.mp4

  The output file comes to 1333x750. iTunes connect won’t accept it. Any ideas ?

• iOS Recorded Video Playback on Android

  1er mars 2015, par Nirav

  I am trying to record video from iPhone device using UIImagePickerController and able to store it in MP4 format. The same video is uploaded on the Amazon S3 cloud.

  When I try to play the same video on Android devices, it fails to play with an error, cannot play.

  I searched forums/google and found that ffmpeg should be used to compress the video before uploading. I want to do the compression on the phone itself rather than on the server. Which is the best way to achieve this ?

  Regards,

  Nirav

• iOS SDK avcodec_decode_video Optimization

  6 août 2013, par Johny Cage

  I've recently started a project that relies on streaming FLV directly to an iOS device. As most famous i went with ffmpeg (and an iOS wrapper - kxmovie). To my surprise iPhone 4 is incapable of playing even SD low-bitrate FLV videos. The current implementation i'm using is decoding the video/audio/sub frames in dispatch_async while loop and copies the YUV frame data to a object, where the object is parsed to 3 textures - Y/U/V (in case of RGB color space - just parse the data) and rendered on screen. After much trial and error, i've decided to kill the whole rendering pipeline and leave only the avcodec_decode_video2 function to run. Surprisingly the FPS did not improve and videos are still unplayable.

  My question is : What can i do to improve the performance of avcodec_decode_video2 ?

  Note :
  I've tried a few commercial apps and they play the same file perfectly fine with no more than 50-60% cpu usage.

  The library is based off the 1.2 branch and this is are the build args :

  '--arch=arm',
  
  '--cpu=cortex-a8',
  
  '--enable-pic',
  
  "--extra-cflags='-arch armv7'",
  
  "--extra-ldflags='-arch armv7'",
  
  "--extra-cflags='-mfpu=neon -mfloat-abi=softfp -mvectorize-with-neon-quad'",
  
  '--enable-neon',
  
  '--enable-optimizations',
  
  '--disable-debug',
  
  '--disable-armv5te',
  
  '--disable-armv6',
  
  '--disable-armv6t2',
  
  '--enable-small',
  
  '--disable-ffmpeg',
  
  '--disable-ffplay',
  
  '--disable-ffserver',
  
  '--disable-ffprobe',
  
  '--disable-doc',
  
  '--disable-bzlib',
  
  '--target-os=darwin',
  
  '--enable-cross-compile',
  
  #'--enable-nonfree',
  
  '--enable-gpl',
  
  '--enable-version3',

  And according to Instruments the following functions take about 30% CPU usage each :

  Running Time    Self        Symbol Name
  
  37023.9ms   32.3%   13874,8                   ff_h264_decode_mb_cabac
  
  34626.2ms   30.2%   9194,7                    loop_filter
  
  29430.0ms   25.6%   173,8                     ff_h264_hl_decode_mb