gusucode.com > audiovideo工具箱matlab源码程序 > audiovideo/audioread.m
function [y,Fs] = audioread(filename, range, datatype)
%AUDIOREAD Read audio files
% [Y, FS]=AUDIOREAD(FILENAME) reads an audio file specified by the
% string FILE, returning the sampled data in Y and the sample rate
% FS, in Hertz.
%
% [Y, FS]=AUDIOREAD(FILENAME, [START END]) returns only samples START
% through END from each channel in the file.
%
% [Y, FS]=AUDIOREAD(FILENAME, DATATYPE) specifies the data type format of
% Y used to represent samples read from the file.
% If DATATYPE='double', Y contains double-precision normalized samples.
% If DATATYPE='native', Y contains samples in the native data type
% found in the file. Interpretation of DATATYPE is case-insensitive and
% partial matching is supported.
% If omitted, DATATYPE='double'.
%
% [Y, FS]=AUDIOREAD(FILENAME, [START END], DATATYPE);
%
% Output Data Ranges
% Y is returned as an m-by-n matrix, where m is the number of audio
% samples read and n is the number of audio channels in the file.
%
% If you do not specify DATATYPE, or dataType is 'double',
% then Y is of type double, and matrix elements are normalized values
% between -1.0 and 1.0.
%
% If DATATYPE is 'native', then Y may be one of several MATLAB
% data types, depending on the file format and the BitsPerSample
% of the input file:
%
% File Format BitsPerSample Data Type of Y Data Range of Y
% ----------------------------------------------------------------------
% WAVE (.wav) 8 uint8 0 <= Y <= 255
% 16 int16 -32768 <= Y <= 32767
% 24 int32 -2^32 <= Y <= 2^32-1
% 32 int32 -2^32 <= Y <= 2^32-1
% 32 single -1.0 <= Y <= +1.0
% ----------------------------------------------------------------------
% FLAC (.flac) 8 uint8 0 <= Y <= 255
% 16 int16 -32768 <= Y <= 32767
% 24 int32 -2^32 <= Y <= 2^32-1
% ----------------------------------------------------------------------
% MP3 (.mp3) N/A single -1.0 <= Y <= +1.0
% MPEG-4(.m4a,.mp4)
% OGG (.ogg)
% ----------------------------------------------------------------------
%
% Call audioinfo to learn the BitsPerSample of the file.
%
% Note that where Y is single or double and the BitsPerSample is
% 32 or 64, values in Y might exceed +1.0 or -1.0.
%
% See also AUDIOINFO, AUDIOWRITE
% Copyright 2012-2014 The MathWorks, Inc.
% Parse input arguments:
narginchk(1, 3);
if nargin < 2
range = [1 inf];
datatype = 'double';
elseif nargin < 3 && ischar(range)
datatype = range;
range = [1 inf];
elseif nargin < 3
datatype = 'double';
end
% Expand the path, using the matlab path if necessary
filename = audiovideo.internal.absolutePathForReading(...
filename, ...
'MATLAB:audiovideo:audioread:fileNotFound', ...
'MATLAB:audiovideo:audioread:filePermissionDenied');
import multimedia.internal.audio.file.PluginManager;
try
readPlugin = PluginManager.getInstance.getPluginForRead(filename);
catch exception
% The exception has been fully formed. Only the prefix has to be
% replaced.
exception = PluginManager.replacePluginExceptionPrefix(exception, 'MATLAB:audiovideo:audioread');
throw(exception);
end
try
options.Filename = filename;
% Create Channel object
channel = asyncio.Channel( ...
readPlugin,...
PluginManager.getInstance.MLConverter, ...
options, [0, 0]);
channel.InputStream.addFilter( ...
PluginManager.getInstance.TransformFilter, ...
[]);
% Validate the datatype is correctly formed
datatype = validateDataType(datatype, channel);
[startSample, samplesToRead] = validateRange(range, channel.TotalSamples);
options.StartSample = startSample;
options.FrameSize = double(multimedia.internal.audio.file.FrameSize.Optimal);
options.FilterTransformType = 'DeinterleaveTranspose';
options.FilterOutputDataType = datatype;
channel.open(options);
c = onCleanup(@()channel.close()); % close when going out of scope
y = channel.InputStream.read(samplesToRead);
Fs = double(channel.SampleRate);
% Generate a warning if the number of samples read is lesser than the
% number requested.
actNumSamplesRead = size(y, 1);
if actNumSamplesRead < samplesToRead
stopSample = startSample + samplesToRead - 1;
if (startSample+1 ~= 1) || (stopSample+1 ~= channel.TotalSamples)
warning(message('MATLAB:audiovideo:audioread:incompleteRead', actNumSamplesRead));
end
end
catch exception
exception = PluginManager.convertPluginException(exception, ...
'MATLAB:audiovideo:audioread');
throw(exception);
end
end
function datatype = validateDataType(datatype, channel)
datatype = validatestring(datatype, {'double','native'},'audioread','datatype');
if strcmp(datatype,'native')
if ismember('BitsPerSample',properties(channel))
% Channel has a 'BitsPerSample' property and is most likely
% uncompressed or lossless.
% Set the 'native' data type to the underlying channel's
% datatype.
datatype = channel.DataType;
else
% Channel is most likely compressed. 'native' datatype
% should be single
datatype = 'single';
end
else
datatype = 'double';
end
end
function [startSample, samplesToRead] = validateRange(range, totalSamples)
validateattributes( ...
range,{'double'}, ...
{'positive','nonempty','nonnan','ncols',2,'nrows',1}',...
'audioread','range',2);
% replace any Inf values with total samples
range(range == Inf) = totalSamples;
if any(range > totalSamples)
error(message('MATLAB:audiovideo:audioread:endoffile', totalSamples));
end
range = range - 1; % sample ranges are zero based
range = max(range, 0); % bound the range by zero
% Validate that all values are integers
validateattributes( ...
range,{'numeric'}, ...
{'integer'},...
'audioread','range',2);
% Validate that start of range is less than the end of range
if (range(1) > range(2))
error(message('MATLAB:audiovideo:audioread:invalidrange'));
end
startSample = range(1);
samplesToRead = (range(2) - startSample) + 1;
end