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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 !

• Configuring install path : prefix=[PREFIX] not fully understood

  3 mai 2016, par whatshisface

  I think this is simply a general c++ question :

  I’m attempting to compile a local version of ffmpeg on Linux Fedora using the gnu c++ compiler. I have source code in a bunch of folders under :

  ~/<username>/Downloads/Code/ffmpeg_sources/
  
  </username>

  which is where I’m attempting to set the config flags to install the build to a target not under this tree but at a root level directory with local shared libraries :

  /usr/local/

  There is this following section near the beginning of the configuration file :

  Standard options:
  
  
  
   --prefix=PREFIX          install in PREFIX []
  
   --bindir=DIR             install binaries in DIR [PREFIX/bin]
  
   --datadir=DIR            install data files in DIR [PREFIX/share/ffmpeg]
  
   --docdir=DIR             install documentation in DIR [PREFIX/share/doc/ffmpeg]
  
   --libdir=DIR             install libs in DIR [PREFIX/lib]
  
   --shlibdir=DIR           install shared libs in DIR [PREFIX/lib]
  
   --incdir=DIR             install includes in DIR [PREFIX/include]
  
   --mandir=DIR             install man page in DIR [PREFIX/share/man]
  
   --enable-rpath           use rpath to allow installing libraries in paths
  
                            not part of the dynamic linker search path

  I may have completely misunderstood this, but I thought that setting a value like

  --prefix=/usr/local

  or

  --prefix=[/usr/local]

  might work, but it appears not to, as once the ./config, make&&make install is complete, it has done a bunch of stuff but there’s nothing installed at the target. There are a LOT of new executable files built in the source directory, so presumably the build is working but I’m simply specifying the paths incorrectly ? A part of the same problem is that it’s unclear whether, once I’ve set the

  --prefix=[PREFIX]

  correctly, I need to set all of the further

  --datadir, --libdir

  etc. or whether the first —prefix value is enough ?

  What is the above configuration syntax trying to show me ?

• Configuring install path : prefix=[PREFIX] not fully understood

  29 septembre 2019, par whatshisface

  I think this is simply a general c++ question :

  I’m attempting to compile a local version of ffmpeg on Linux Fedora using the gnu c++ compiler. I have source code in a bunch of folders under :

  ~/<username>/Downloads/Code/ffmpeg_sources/
  
  </username>

  which is where I’m attempting to set the config flags to install the build to a target not under this tree but at a root level directory with local shared libraries :

  /usr/local/

  There is this following section near the beginning of the configuration file :

  Standard options:
  
  
  
   --prefix=PREFIX          install in PREFIX []
  
   --bindir=DIR             install binaries in DIR [PREFIX/bin]
  
   --datadir=DIR            install data files in DIR [PREFIX/share/ffmpeg]
  
   --docdir=DIR             install documentation in DIR [PREFIX/share/doc/ffmpeg]
  
   --libdir=DIR             install libs in DIR [PREFIX/lib]
  
   --shlibdir=DIR           install shared libs in DIR [PREFIX/lib]
  
   --incdir=DIR             install includes in DIR [PREFIX/include]
  
   --mandir=DIR             install man page in DIR [PREFIX/share/man]
  
   --enable-rpath           use rpath to allow installing libraries in paths
  
                            not part of the dynamic linker search path

  I may have completely misunderstood this, but I thought that setting a value like

  --prefix=/usr/local

  or

  --prefix=[/usr/local]

  might work, but it appears not to, as once the ./config, make&&make install is complete, it has done a bunch of stuff but there’s nothing installed at the target. There are a LOT of new executable files built in the source directory, so presumably the build is working but I’m simply specifying the paths incorrectly ? A part of the same problem is that it’s unclear whether, once I’ve set the

  --prefix=[PREFIX]

  correctly, I need to set all of the further

  --datadir, --libdir

  etc. or whether the first —prefix value is enough ?

  What is the above configuration syntax trying to show me ?