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• C# library for audio resampling that has the same abilities as FFmpeg

  21 avril 2013, par Designation

  I have to use a pure C# solution for resampling audio, which can produce me the exact same results as FFmpeg's audio sampling can.

  FFmpeg first builds some kind of polyphase filter bank, and then uses that for the sampling process (sorry for the vague phrasing, but I'm not too familiar with this topic). According to this brief documentation, the initialization can be customized this way :

  AVResampleContext* av_resample_init(
  
      int     out_rate,
  
      int     in_rate,
  
      int     filter_length,
  
      int     log2_phase_count,
  
      int     linear,
  
      double  cutoff   
  
      )

  The parameters are :

  • out_rate : output sample rate
  • in_rate : input sample rate
  • filter_length : length of each FIR filter in the filterbank relative to the cutoff freq
  • log2_phase_count : log2 of the number of entries in the polyphase filterbank
  • linear : if 1 then the used FIR filter will be linearly interpolated between the 2 closest, if 0 the closest will be used
  • cutoff : cutoff frequency, 1.0 corresponds to half the output sampling rate

  I'd need to use a C# library that is configurable in the same depth. I've been trying to use NAudio (more specifically, its WaveFormatConversionStream class), but there, I could only set the input and output sample rates, so I didn't get the expected results.

  So, is there a C# lib that could resample with the same settings as FFmpeg can ? Or one that has almost all of these settings or similar ones ? Note : I need a C# solution, not a wrapper !

• Dealing with long conversion times on nginx, ffmpeg and Ruby on Rails

  19 avril 2013, par Graeme

  I have developed a Ruby on Rails-based app which allows users to upload videos to one of our local servers (Ubunto 10.04 LTS). The server uses nginx.

  Through the paperclip-ffmpeg gem, videos are converted to mp4 format using the ffmpeg library.

  Everything appears to be working fine in production, except Rails' own 500 page (not the customised version I have provided - but that's a different issue) is displayed whenever certain videos are uploaded. Otherwise, videos are being converted as expected.

  Having done a bit of investigation, I think the default 500 page is being displayed because a 502 error has occurred. I think what is happening, having uploaded the videos locally, is that some videos are taking an extensive amount of time to convert, and that an interruption is occurring on the server (I'm not a server expert by any means).

  Using the excellent Railscasts episode on deployment, I use Capistrano to deploy the app. Here's the unicorn.rb file :

  root = "XXXXXXX"
  
  working_directory root
  
  pid "#{root}/tmp/pids/unicorn.pid"
  
  stderr_path "#{root}/log/unicorn.log"
  
  stdout_path "#{root}/log/unicorn.log"
  
  
  
  listen "/tmp/unicorn.XXXXXXXXX.sock"
  
  worker_processes 2
  
  timeout 200

  And here's the nginx.conf file. Note that client_max_body_size has been set to a fairly hefty 4Gb ! :

  upstream unicorn {
  
    server unix:/tmp/unicorn.XXXXXXXXX.sock fail_timeout=0;
  
  }
  
  
  
  server {
  
    listen 80 default deferred;
  
    root XXXXXXXXX;
  
  
  
  
  
    location ^~ /assets/ {
  
      gzip_static on;
  
      expires max;
  
      add_header Cache-Control public;
  
    }
  
  
  
    try_files $uri/index.html $uri @unicorn;
  
    location @unicorn {
  
      proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
  
      proxy_set_header Host $http_host;
  
      proxy_read_timeout 600; 
  
      proxy_redirect off;
  
      proxy_pass http://unicorn;
  
    }
  
  
  
    error_page 500 502 503 504 /500.html;
  
    client_max_body_size 4G;
  
    keepalive_timeout 10;
  
  
  
  }

  So, my question is...how could I edit (either of) the above two files to deal with the extensive time that certain videos take to convert through ffmpeg - possibly up to an hour, 2 hours or even more ?

  Should I extend timeout in the former and/or keepalive_timeout in the latter - or is there a more efficient way (given that I've no idea how long certain videos will take to convert) ?

  Or, is there possibly a more significant issue I should consider - e.g. the amount of memory in the server ?

  I'm not an nginx/server expert, so any advice would be useful (particularly where to put extra lines of code) - however, as the rest of the app just "works", I'm not keen to make a huge amount of changes !

• ffmpeg and php using ajax javascript

  16 juillet 2014, par user3789242

  I want to make use of ffmpeg for converting an audio file from wav to pcm.upon searching I know that there is a command line to be executed in the php form,and that I need an ajax to execute that command line.but I don’t know what to write in the ajax form nor in the php page.I only know that this is the command line used to convert from wav to pcm

  ffmpeg -i file.wav -f s16be -ar 8000 -acodec pcm_s16be file.raw

  can please somebody help me build my ffmpeg php file and its ajax.thank you in advance.note that i’m very new in ffmpeg