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Linux 2.6 - man page for pvanal (linux section 1)

PVANAL(1)			  The Canonical Csound Reference			PVANAL(1)

       pvanal - Converts a soundfile into a series of short-time Fourier transform frames. .

       Fourier analysis for the Csound pvoc generator

	   csound -U pvanal [flags] infilename outfilename

	   pvanal [flags] infilename outfilename

       The standard Csound utility program pvanal has been extended to enable a PVOC-EX format
       file to be created, using the existing interface. To create a PVOC-EX file, the file name
       must be given the required extension, ".pvx", e.g "test.pvx". The requirement for the FFT
       size to be a power of two is here relaxed, and any positive value is accepted; odd numbers
       are rounded up internally. However, power-of-two sizes are still to be preferred for all
       normal applications.

       The channel select flags are ignored, and all source channels will be analysed and written
       to the output file, up to a compiler-set limit of eight channels. The analysis window size
       (iwinsize) is set internally to double the FFT size.

       pvanal converts a soundfile into a series of short-time Fourier transform (STFT) frames at
       regular timepoints (a frequency-domain representation). The output file can be used by
       pvoc to generate audio fragments based on the original sample, with timescales and pitches
       arbitrarily and dynamically modified. Analysis is conditioned by the flags below. A space
       is optional between the flag and its argument.

       -s srate -- sampling rate of the audio input file. This will over-ride the srate of the
       soundfile header, which otherwise applies. If neither is present, the default is 10000.

       -c channel -- channel number sought. The default is 1.

       -b begin -- beginning time (in seconds) of the audio segment to be analyzed. The default
       is 0.0

       -d duration -- duration (in seconds) of the audio segment to be analyzed. The default of
       0.0 means to the end of the file.

       -n frmsiz -- STFT frame size, the number of samples in each Fourier analysis frame. Must
       be a power of two, in the range 16 to 16384. For clean results, a frame must be larger
       than the longest pitch period of the sample. However, very long frames result in temporal
       "smearing" or reverberation. The bandwidth of each STFT bin is determined by sampling rate
       / frame size. The default framesize is the smallest power of two that corresponds to more
       than 20 milliseconds of the source (e.g. 256 points at 10 kHz sampling, giving a 25.6 ms

       -w windfact -- Window overlap factor. This controls the number of Fourier transform frames
       per second. Csound's pvoc will interpolate between frames, but too few frames will
       generate audible distortion; too many frames will result in a huge analysis file. A good
       compromise for windfact is 4, meaning that each input point occurs in 4 output windows, or
       conversely that the offset between successive STFT frames is framesize/4. The default
       value is 4. Do not use this flag with -h.

       -h hopsize -- STFT frame offset. Converse of above, specifying the increment in samples
       between successive frames of analysis (see also lpanal). Do not use with -w.

       -H -- Use a Hamming window instead of the default von Hann window.

       -K -- Use a Kaiser window instead of the default von Hann window. The Kaiser parameter
       default is 6.8, but can be set with the -B option.

       -B beta -- Set the beta parameter for any Kaiser window used to the floating point value

	   pvanal asound pvfile

       will analyze the soundfile "asound" using the default frmsiz and windfact to produce the
       file "pvfile" suitable for use with pvoc.

       The output file has a special pvoc header containing details of the source audio file, the
       analysis frame rate and overlap. Frames of analysis data are stored as float, with the
       magnitude and "frequency" (in Hz) for the first N/2 + 1 Fourier bins of each frame in
       turn.  "Frequency" encodes the phase increment in such a way that for strong harmonics it
       gives a good indication of the true frequency. For low amplitude or rapidly moving
       harmonics it is less meaningful.

       Prints total number of frames, and frames completed every 20th frame.

       Author: Dan Ellis

       MIT Media Lab

       Cambridge, Massachussetts


       Barry Vercoe
       MIT Media Lab


       Dan Ellis
       MIT Media Lab,


5.07					    06/23/2009					PVANAL(1)

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