| Re: reading wav files [message #23340] |
Tue, 16 January 2001 02:29  |
hahn
Messages: 108
Registered: November 1993
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Senior Member |
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jnettle1@utk.edu (jnettle1) wrote:
> Does anyone have a routine/set of routines to read *.wav files in IDL? And if
> so, do you feel like sharing it?? :)
I process wav files randomly, so I have some read/write routines
written on my own. However, these routines work on stereo encoded
16 bits per sample files only and ignore anything but the data chunk.
I can send you the routines by mail if needed.
The following structe defines the header. It is 44 bytes long. It
assumes that the data chunk follows the format descriptor block.
WAV_HDR = { WAVE_HEADER, $
ID1:'****', LoF:0L, ID2:'********', LoH:0L, $
FMT:0, NChan:0, SpSc:0L, DpSc:0L, $
BypSa:0, BipSa:0, ID3:'****', LoD:0L }
; ID1 the letters "RIFF"
; LOF bytes from here (i.e. from byte 8) to end of file
; ID2 the letters "WAVE" followed by "fmt "
; "fmt " is the beginning of the format descriptor block
; LoH Length of Header (here 16 Bytes format descriptor) that follows
; ---- start of format header ----
; FMT format tag, 1 = PCM, 257 = IBM mu Law, 258 = IBM a Law,
; 259 = IBM Adaptive PCM (adpcm)
; NChan channels (1 = Mono, 2 = Stereo ...)
; SpSc samples per second
; DpSc data bytes per second = samples per second * bytes per sample
; BypSa bytes per sample = channels * (bits per sample / 8)
; BipSa bits per sample
; ---- end of format header ----
; Now watch for "data": Other blocks will be skipped.
; ID3 the letters "data". This is the beginning of the data block
; LoD data length, i.e. the number of bytes of the actual data.
; ---- start of sampled data ----
; for multi-channel samples 1st byte is channel 1, 2nd byte is
; channel 2, 3rd byte channel 3 (or if 2 channels, channel 1 again)
; Amplitude (y-values) from -127 to 127 or -32767 to 32767.
; ---- end of sampled data ----
; Comments may follow. Don't play 'em
;
Norbert
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