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61 lines
2.2 KiB
Lua
61 lines
2.2 KiB
Lua
;
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; module to parse the header data of a .wav file
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;
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; note: the sample rate in hz can be converted to a vera rate via:
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; const float vera_freq_factor = 25e6 / 65536.0
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; vera_rate = (wavfile.sample_rate as float / vera_freq_factor) + 1.0 as ubyte
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; vera_rate_hz = (vera_rate as float) * vera_freq_factor as uword
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;
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wavfile {
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const ubyte WAVE_FORMAT_PCM = $1
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const ubyte WAVE_FORMAT_ADPCM = $2
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const ubyte WAVE_FORMAT_IEEE_FLOAT = $3
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const ubyte WAVE_FORMAT_ALAW = $6
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const ubyte WAVE_FORMAT_MULAW = $7
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const ubyte WAVE_FORMAT_DVI_ADPCM = $11
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uword sample_rate
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ubyte bits_per_sample
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uword data_offset
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ubyte wavefmt
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ubyte nchannels
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uword block_align
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uword data_size_hi
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uword data_size_lo
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sub parse_header(uword wav_data) -> bool {
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; "RIFF" , filesize (int32) , "WAVE", "fmt ", fmtsize (int32)
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uword @zp header = wav_data
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if header[0]!=iso:'R' or header[1]!=iso:'I' or header[2]!=iso:'F' or header[3]!=iso:'F'
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or header[8]!=iso:'W' or header[9]!=iso:'A' or header[10]!=iso:'V' or header[11]!=iso:'E'
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or header[12]!=iso:'f' or header[13]!=iso:'m' or header[14]!=iso:'t' or header[15]!=iso:' ' {
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return false
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}
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; uword filesize = peekw(header+4)
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uword chunksize = peekw(header+16)
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wavefmt = peek(header+20)
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nchannels = peek(header+22)
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sample_rate = peekw(header+24) ; we assume sample rate <= 65535 so we can ignore the upper word
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block_align = peekw(header+32)
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bits_per_sample = peek(header+34)
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if wavefmt==WAVE_FORMAT_DVI_ADPCM or wavefmt==WAVE_FORMAT_ADPCM
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bits_per_sample *= 4
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; skip chunks until we reach the 'data' chunk
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header += chunksize + 20
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repeat {
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chunksize = peekw(header+4) ; assume chunk size never exceeds 64kb so ignore upper word
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if header[0]==iso:'d' and header[1]==iso:'a' and header[2]==iso:'t' and header[3]==iso:'a'
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break
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header += 8 + chunksize
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}
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data_size_lo = chunksize
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data_size_hi = peekw(header+6)
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data_offset = header + 8 - wav_data
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return true
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}
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}
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