ANN: wave.erl

[Ivan Uemlianin]

Dear All

Please find below wave.erl, an erlang script for reading and writing 
.wav audio files.  I am releasing it under the ISC license.

The script exports functions read/1, write/3 and write/2, and the wave 
record:

     -record(wave, {audio_format, sample_rate, data}).

where:
- audio_format is an unsigned integer (currently only 1, i.e. pcm 
encoding, is supported);
- sample_rate is an unsigned integer (i.e., samples per second, in kHz);
- data is a list of lists of signed integers, one list for each channel 
(e.g., stereo will have two lists of integers).

read(FileName) reads a wav file and returns a wave record.

write(WavRecord, FileName, BitsPerSample) writes the wave record 
WavRecord to the file FileName with the sample size BitsPerSample.

write(WavRecord, FileName) just calls write/3 with BitsPerSample = 16.

[identical announcement at 
http://llaisdy.wordpress.com/2010/06/01/wave-erl-an-erlang-script-to-read-and-write-wav-files/]

With thanks and best wishes

Ivan


%% Copyright © 2010 by Ivan Uemlianin (ivan@REDACTED)
%%
%% Permission to use, copy, modify, and/or distribute this software for any
%% purpose with or without fee is hereby granted, provided that the above
%% copyright notice and this permission notice appear in all copies.
%%
%% THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHORS AND COPYRIGHT HOLDERS
%% DISCLAIM ALL WARRANTIES WITH SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
%% MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
%% HOLDERS BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
%% DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
%% PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
%% ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
%% THIS SOFTWARE.

%% * wave.erl --- Erlang functions to read and write .wav files.
%%
%% ** version 1.0:
%% - does not support compression
%% - only pcm encoding (AudioFormat = 1)
%%
%% ** todo
%% - set debug flags to disable io:format in read/1 and write/3
%% - test wav file for well-formed-ness
%% - function to parse and return header (ie without reading whole file)
%% - pread(FileName, Offset, NFrames)
%%
%% ** refs
%%
%% [1] http://www-mmsp.ece.mcgill.ca/Documents/AudioFormats/WAVE/WAVE.html
%% [2] http://ccrma.stanford.edu/courses/422/projects/WaveFormat/
%% [3] http://chlorophil.blogspot.com/2007/06/erlang-binary-map.html

-module(wave).
-export([read/1, write/2, write/3]).

% audio_format = integer (see wav docs for formats)
% sample_rate in kHz
% data is list of lists of integers (one list for each channel)

-record(wave, {audio_format, sample_rate, data}).

read(FileName) -> %% returns wave record
     {ok, Binary} = file:read_file(FileName),

<<ChunkID:4/binary,
      ChunkSize:4/little-unsigned-integer-unit:8,
      Format:4/binary,
      SubChunk1ID:4/binary,
      SubChunk1Size:4/little-unsigned-integer-unit:8,
      AudioFormat:2/little-unsigned-integer-unit:8,   % 1 = pcm
      NumChannels:2/little-unsigned-integer-unit:8,   % 1 = mono
      SampleRate:4/little-unsigned-integer-unit:8,    % 16000, etc
      ByteRate:4/little-unsigned-integer-unit:8,      % SampleRate * 
NumChannels * BitsPerSample/8
      BlockAlign:2/little-unsigned-integer-unit:8,    % NumChannels * 
BitsPerSample/8
      BitsPerSample:2/little-unsigned-integer-unit:8, % 16, etc
      SubChunk2ID:4/binary,
      SubChunk2Size:4/little-unsigned-integer-unit:8,
      Data/binary>> = Binary,

     % TODO: test file for well-formedness, e.g.:
     % ChunkID == "RIFF"
     % ChunkSize == SubChunk2Size + 36
     % Format == "WAVE"
     % AudioFormat = 1  % no other encodings supported in v1.0
     % SubChunk1ID == "fmt "
     % SubChunk1Size == 16
     % SubChunk2ID == "data"
     % SubChunk2Size == NumSamples * NumChannels * BitsPerSample div 8

     Channels = data2channels(Data, NumChannels, BitsPerSample),

     io:format("* ~p~n~n- ChunkID: ~p~n- ChunkSize: ~B~n- Format: ~p~n- 
SubChunk1ID: ~p~n- SubChunk1Size: ~B~n- AudioFormat: ~B~n- NumChannels: 
~B~n- SampleRate: ~B~n- ByteRate: ~B~n- BlockAlign: ~B~n- BitsPerSample: 
~B~n- SubChunk2ID: ~p~n- SubChunk2Size: ~B~n- Data: [...]~n~n",
     [FileName,
     binary_to_list(ChunkID),
     ChunkSize,
     binary_to_list(Format),
     binary_to_list(SubChunk1ID),
     SubChunk1Size,
     AudioFormat,
     NumChannels,
     SampleRate,
     ByteRate,
     BlockAlign,
     BitsPerSample,
     binary_to_list(SubChunk2ID),
     SubChunk2Size
    ]),

     #wave{sample_rate=SampleRate,
       audio_format=AudioFormat,
       data=Channels
      }.

mono(Data, NBytes) ->
     [[ X || <<X:NBytes/little-signed-integer-unit:8>> <= Data ]].

stereo(Data, NBytes) ->
     LP = [ [A,B] || << A:NBytes/little-signed-integer-unit:8, 
B:NBytes/little-signed-integer-unit:8 >> <= Data],
     lp2pl(LP, [], []).

% list of pairs to pair of lists
lp2pl([], Left, Right) ->
     [lists:reverse(Left), lists:reverse(Right)];

lp2pl([[L,R]|T], Left, Right) ->
     lp2pl(T, [L|Left], [R|Right]).

data2channels(Data, NumChannels, BitsPerSample) ->
     NBytes = BitsPerSample div 8,
     case NumChannels of
      1  -> mono(Data, NBytes);
      2  -> stereo(Data, NBytes)
     end.

lt2l([], Acc) ->
     lists:reverse(Acc);

lt2l([H|T], Acc) ->
     lt2l(T, [element(2, H), element(1, H) | Acc]).

pl2l(PL) ->
     X = lists:zip(lists:nth(1, PL), lists:nth(2, PL)),
     lt2l(X, []).

channels2dataBin(Channels, BitsPerSample) ->
     case length(Channels) of
     1 -> Data = lists:nth(1, Channels);
     2 -> Data = pl2l(Channels)
     end,
     Size = length(Data) * (BitsPerSample div 8),
     DataBin = list_to_binary([ <<X:2/little-signed-integer-unit:8>> ||  
X <- Data]),
     {Size, DataBin}.

write(WavRecord, FileName) ->
     write(WavRecord, FileName, 16).

write(WavRecord, FileName, BitsPerSample) ->
     {SubChunk2Size, Data} = channels2dataBin(WavRecord#wave.data, 
BitsPerSample),

     ChunkID = list_to_binary("RIFF"),
     Format = list_to_binary("WAVE"),
     SubChunk1ID = list_to_binary("fmt "),
     SubChunk1Size = 16,
     AudioFormat = 1, % only pcm encoding supported
     NumChannels = length(WavRecord#wave.data),
     SampleRate = WavRecord#wave.sample_rate,
     ByteRate = SampleRate * NumChannels * BitsPerSample div 8,
     BlockAlign = NumChannels * BitsPerSample div 8,
     SubChunk2ID = list_to_binary("data"),
     ChunkSize = SubChunk2Size + 36,

     io:format("* ~p~n~n- ChunkID: ~p~n- ChunkSize: ~B~n- Format: ~p~n- 
SubChunk1ID: ~p~n- SubChunk1Size: ~B~n- AudioFormat: ~B~n- NumChannels: 
~B~n- SampleRate: ~B~n- ByteRate: ~B~n- BlockAlign: ~B~n- BitsPerSample: 
~B~n- SubChunk2ID: ~p~n- SubChunk2Size: ~B~n- Data: [...]~n~n",
     [FileName,
      binary_to_list(ChunkID),
      ChunkSize,
      binary_to_list(Format),
      binary_to_list(SubChunk1ID),
      SubChunk1Size,
      AudioFormat,
      NumChannels,
      SampleRate,
      ByteRate,
      BlockAlign,
      BitsPerSample,
      binary_to_list(SubChunk2ID),
      SubChunk2Size
     ]),

     Binary = <<ChunkID:4/binary,
            ChunkSize:4/little-unsigned-integer-unit:8,  %%
            Format:4/binary,
            SubChunk1ID:4/binary,
            SubChunk1Size:4/little-unsigned-integer-unit:8,
            AudioFormat:2/little-unsigned-integer-unit:8,
            NumChannels:2/little-unsigned-integer-unit:8,
            SampleRate:4/little-unsigned-integer-unit:8,
            ByteRate:4/little-unsigned-integer-unit:8,
            BlockAlign:2/little-unsigned-integer-unit:8,
            BitsPerSample:2/little-unsigned-integer-unit:8,
            SubChunk2ID:4/binary,
            SubChunk2Size:4/little-unsigned-integer-unit:8,  %%
           Data/binary
 >>,

     file:write_file(FileName, Binary),
     {ok, FileName}.



-- 
============================================================
Ivan A. Uemlianin
Speech Technology Research and Development

                     ivan@REDACTED
                      www.llaisdy.com
                          llaisdy.wordpress.com
                      www.linkedin.com/in/ivanuemlianin

     "Froh, froh! Wie seine Sonnen, seine Sonnen fliegen"
                      (Schiller, Beethoven)
============================================================