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• flv reencode to mp4 for iphone/ipod via ffmpeg and x264 (quality issue)

  3 octobre 2011, par zeroasterisk

  There are a lot of questions on this topic, and I've read most of them and most of the google search results I could come up with.

  When I use FFMPEG to convert a FLV to a iphone3 compatble MP4 file, it just doesn't preserver enough of the quality. Yes, I've worked the hell out of -sameq and -b and -bt settings, text just isn't readable.

  Next I tried to split the video out and process it directly, using these instructions :
  https://sites.google.com/site/linuxencoding/x264-encoding-guide

  The problem is myplayer (via ffmpeg) was not able to determine the duration of the FLV (even though the metadata was set).

  (I assume) Because of that unknown duration, when I create the MP4 file, the resulting x264 file plays through super-fast while the audio plays at the normal rate.

  user@server:/tmp# mplayer -nosound -benchmark -sws 9 -vf dsize=640:480:0,scale=0:0,expand=640:480 -vo yuv4mpeg:file=>(x264 --demuxer y4m --crf 0 --preset slow --threads auto --output output.264 - 2>x264.log) 'input.flv'
  
  MPlayer 1.0rc4-4.4.5 (C) 2000-2010 MPlayer Team
  
  mplayer: could not connect to socket
  
  mplayer: No such file or directory
  
  Failed to open LIRC support. You will not be able to use your remote control.
  
  
  
  Playing input.flv.
  
  libavformat file format detected.
  
  [flv @ 0x1202460]Estimating duration from bitrate, this may be inaccurate
  
  [lavf] stream 0: video (vp6f), -vid 0
  
  [lavf] stream 1: audio (nellymoser), -aid 0
  
  VIDEO:  [VP6F]  1680x992  0bpp  1000.000 fps   33.4 kbps ( 4.1 kbyte/s)
  
  Clip info:
  
   audiocodecid: 6
  
   audiodatarate: 86
  
   audiosamplerate: 44100
  
   audiosamplesize: 16
  
   audiosize: 6097005
  
   canSeekToEnd: true
  
   datasize: 8609138
  
   duration: 567
  
   framerate: 2
  
   hasAudio: true
  
   hasCuePoints: false
  
   hasKeyframes: true
  
   hasMetadata: true
  
   hasVideo: true
  
   height: 992
  
   lasttimestamp: 567
  
   metadatacreator: flvtool++ (Facebook, Motion project, dweatherford)
  
   stereo: false
  
   totalframes: 1043
  
   videocodecid: 4
  
   videodatarate: 33
  
   videosize: 2316256
  
   width: 1680
  
  Using (default) progressive frame mode.Opening video filter: [expand w=640 h=480]
  
  Expand: 640 x 480, -1 ; -1, osd: 0, aspect: 0.000000, round: 1
  
  Opening video filter: [scale w=0 h=0]
  
  Opening video filter: [dsize=640:480:0]
  
  ==========================================================================
  
  Opening video decoder: [ffmpeg] FFmpeg's libavcodec codec family
  
  Selected video codec: [ffvp6f] vfm: ffmpeg (FFmpeg VP6 Flash)
  
  ==========================================================================
  
  Audio: no sound
  
  Starting playback...
  
  Movie-Aspect is undefined - no prescaling applied.
  
  [swscaler @ 0x7f0c738b9620]Lanczos scaler, from yuv420p to yuv420p using MMX2
  
  VO: [yuv4mpeg] 640x480 => 641x480 Planar YV12

  I have also tried specifying FPS, but no change in results

  user@server:/tmp# mplayer -nosound -fps 25-benchmark -sws 9 -vf dsize=640:480:0,scale=0:0,expand=640:480 -vo yuv4mpeg:file=>(x264 --demuxer y4m --fps 25 --crf 0 --preset slow --threads auto --output output.264 - 2>x264.log) 'input.flv'

  Can someone tell me how to either :

  1. fix my split A/V processing/timing/duration issues ?
  2. improve the
     quality of the FFMPEG conversion of FLV to iphone3 compatible
     format ?

• A .NET P/Invoke to convert with ffmpeg ?

  31 août 2011, par Shimmy

  I need to create a program that should convert audio and video files to supported types.

  I've found ffmpeg to be a great tool. However I donno C (which ffmpeg was written with), and I was wondering if there is a way (besides command-line which I donnu if I would use since I'm not sure if you can control the conversion process and get info about its percentage) that I can interact with ffmpeg and build a conversion program on it's API.

  Basically I'm looking for a single .NET-compatible method :

  void Convert(sourceFile, targetFile, string targetExtension);

  It shouldn't ask for bitrate etc., but only should it try to make a 1 to 1 conversion.

  I don't know how to write the underlying P/Invoke, and since I donno ffmpeg from inside, I can't tell what dll it uses, so even I'd want to write the PI myself, I don't know what among the zillion functions of the ffmpeg libraries the conversion functions are.

  So any guidance or approach will be really appreciated.

• Interact with ffmpeg from a .NET program ?

  18 septembre 2011, par Shimmy

  I'm trying to create a .NET wrapper for media-file conversion using ffmepg, here is what I've tried :

  static void Main(string[] args)
  
  {
  
    if (File.Exists("sample.mp3")) File.Delete("sample.mp3");
  
  
  
    string result;
  
  
  
    using (Process p = new Process())
  
    {
  
      p.StartInfo.FileName = "ffmpeg";
  
      p.StartInfo.Arguments = "-i sample.wma sample.mp3";
  
  
  
      p.StartInfo.UseShellExecute = false;
  
      p.StartInfo.RedirectStandardOutput = true;
  
  
  
      p.Start();
  
  
  
      //result is assigned with an empty string!
  
      result = p.StandardOutput.ReadToEnd();
  
  
  
      p.WaitForExit();
  
    }
  
  }

  What actually happens is the content of the ffmpeg program is printed out to the Console app, but the result variable is an empty string. I want to control the conversion progress interactively, so the user doesn't even have to know I'm using ffmpeg, but he still knows the conversion progress' details and what percentage etc. the app is up to.

  Basically I would also be happy with a .NET wrapper for a P/Invoke to conversion function ONLY (I am not interested in a whole external library, unless I can extract the PI function from it).

  Anyone with experience in ffmpeg & .NET ?

  Update
  Please view my further question, how to write input to a running ffmpeg process.