1 :mod:`aifc` --- Read and write AIFF and AIFC files 2 ================================================== 3 4 .. module:: aifc 5 :synopsis: Read and write audio files in AIFF or AIFC format. 6 7 **Source code:** :source:`Lib/aifc.py` 8 9 .. index:: 10 single: Audio Interchange File Format 11 single: AIFF 12 single: AIFF-C 13 14 -------------- 15 16 This module provides support for reading and writing AIFF and AIFF-C files. 17 AIFF is Audio Interchange File Format, a format for storing digital audio 18 samples in a file. AIFF-C is a newer version of the format that includes the 19 ability to compress the audio data. 20 21 Audio files have a number of parameters that describe the audio data. The 22 sampling rate or frame rate is the number of times per second the sound is 23 sampled. The number of channels indicate if the audio is mono, stereo, or 24 quadro. Each frame consists of one sample per channel. The sample size is the 25 size in bytes of each sample. Thus a frame consists of 26 ``nchannels * samplesize`` bytes, and a second's worth of audio consists of 27 ``nchannels * samplesize * framerate`` bytes. 28 29 For example, CD quality audio has a sample size of two bytes (16 bits), uses two 30 channels (stereo) and has a frame rate of 44,100 frames/second. This gives a 31 frame size of 4 bytes (2\*2), and a second's worth occupies 2\*2\*44100 bytes 32 (176,400 bytes). 33 34 Module :mod:`aifc` defines the following function: 35 36 37 .. function:: open(file, mode=None) 38 39 Open an AIFF or AIFF-C file and return an object instance with methods that are 40 described below. The argument *file* is either a string naming a file or a 41 :term:`file object`. *mode* must be ``'r'`` or ``'rb'`` when the file must be 42 opened for reading, or ``'w'`` or ``'wb'`` when the file must be opened for writing. 43 If omitted, ``file.mode`` is used if it exists, otherwise ``'rb'`` is used. When 44 used for writing, the file object should be seekable, unless you know ahead of 45 time how many samples you are going to write in total and use 46 :meth:`writeframesraw` and :meth:`setnframes`. 47 The :func:`.open` function may be used in a :keyword:`with` statement. When 48 the :keyword:`!with` block completes, the :meth:`~aifc.close` method is called. 49 50 .. versionchanged:: 3.4 51 Support for the :keyword:`with` statement was added. 52 53 Objects returned by :func:`.open` when a file is opened for reading have the 54 following methods: 55 56 57 .. method:: aifc.getnchannels() 58 59 Return the number of audio channels (1 for mono, 2 for stereo). 60 61 62 .. method:: aifc.getsampwidth() 63 64 Return the size in bytes of individual samples. 65 66 67 .. method:: aifc.getframerate() 68 69 Return the sampling rate (number of audio frames per second). 70 71 72 .. method:: aifc.getnframes() 73 74 Return the number of audio frames in the file. 75 76 77 .. method:: aifc.getcomptype() 78 79 Return a bytes array of length 4 describing the type of compression 80 used in the audio file. For AIFF files, the returned value is 81 ``b'NONE'``. 82 83 84 .. method:: aifc.getcompname() 85 86 Return a bytes array convertible to a human-readable description 87 of the type of compression used in the audio file. For AIFF files, 88 the returned value is ``b'not compressed'``. 89 90 91 .. method:: aifc.getparams() 92 93 Returns a :func:`~collections.namedtuple` ``(nchannels, sampwidth, 94 framerate, nframes, comptype, compname)``, equivalent to output of the 95 :meth:`get\*` methods. 96 97 98 .. method:: aifc.getmarkers() 99 100 Return a list of markers in the audio file. A marker consists of a tuple of 101 three elements. The first is the mark ID (an integer), the second is the mark 102 position in frames from the beginning of the data (an integer), the third is the 103 name of the mark (a string). 104 105 106 .. method:: aifc.getmark(id) 107 108 Return the tuple as described in :meth:`getmarkers` for the mark with the given 109 *id*. 110 111 112 .. method:: aifc.readframes(nframes) 113 114 Read and return the next *nframes* frames from the audio file. The returned 115 data is a string containing for each frame the uncompressed samples of all 116 channels. 117 118 119 .. method:: aifc.rewind() 120 121 Rewind the read pointer. The next :meth:`readframes` will start from the 122 beginning. 123 124 125 .. method:: aifc.setpos(pos) 126 127 Seek to the specified frame number. 128 129 130 .. method:: aifc.tell() 131 132 Return the current frame number. 133 134 135 .. method:: aifc.close() 136 137 Close the AIFF file. After calling this method, the object can no longer be 138 used. 139 140 Objects returned by :func:`.open` when a file is opened for writing have all the 141 above methods, except for :meth:`readframes` and :meth:`setpos`. In addition 142 the following methods exist. The :meth:`get\*` methods can only be called after 143 the corresponding :meth:`set\*` methods have been called. Before the first 144 :meth:`writeframes` or :meth:`writeframesraw`, all parameters except for the 145 number of frames must be filled in. 146 147 148 .. method:: aifc.aiff() 149 150 Create an AIFF file. The default is that an AIFF-C file is created, unless the 151 name of the file ends in ``'.aiff'`` in which case the default is an AIFF file. 152 153 154 .. method:: aifc.aifc() 155 156 Create an AIFF-C file. The default is that an AIFF-C file is created, unless 157 the name of the file ends in ``'.aiff'`` in which case the default is an AIFF 158 file. 159 160 161 .. method:: aifc.setnchannels(nchannels) 162 163 Specify the number of channels in the audio file. 164 165 166 .. method:: aifc.setsampwidth(width) 167 168 Specify the size in bytes of audio samples. 169 170 171 .. method:: aifc.setframerate(rate) 172 173 Specify the sampling frequency in frames per second. 174 175 176 .. method:: aifc.setnframes(nframes) 177 178 Specify the number of frames that are to be written to the audio file. If this 179 parameter is not set, or not set correctly, the file needs to support seeking. 180 181 182 .. method:: aifc.setcomptype(type, name) 183 184 .. index:: 185 single: u-LAW 186 single: A-LAW 187 single: G.722 188 189 Specify the compression type. If not specified, the audio data will 190 not be compressed. In AIFF files, compression is not possible. 191 The name parameter should be a human-readable description of the 192 compression type as a bytes array, the type parameter should be a 193 bytes array of length 4. Currently the following compression types 194 are supported: ``b'NONE'``, ``b'ULAW'``, ``b'ALAW'``, ``b'G722'``. 195 196 197 .. method:: aifc.setparams(nchannels, sampwidth, framerate, comptype, compname) 198 199 Set all the above parameters at once. The argument is a tuple consisting of the 200 various parameters. This means that it is possible to use the result of a 201 :meth:`getparams` call as argument to :meth:`setparams`. 202 203 204 .. method:: aifc.setmark(id, pos, name) 205 206 Add a mark with the given id (larger than 0), and the given name at the given 207 position. This method can be called at any time before :meth:`close`. 208 209 210 .. method:: aifc.tell() 211 212 Return the current write position in the output file. Useful in combination 213 with :meth:`setmark`. 214 215 216 .. method:: aifc.writeframes(data) 217 218 Write data to the output file. This method can only be called after the audio 219 file parameters have been set. 220 221 .. versionchanged:: 3.4 222 Any :term:`bytes-like object` is now accepted. 223 224 225 .. method:: aifc.writeframesraw(data) 226 227 Like :meth:`writeframes`, except that the header of the audio file is not 228 updated. 229 230 .. versionchanged:: 3.4 231 Any :term:`bytes-like object` is now accepted. 232 233 234 .. method:: aifc.close() 235 236 Close the AIFF file. The header of the file is updated to reflect the actual 237 size of the audio data. After calling this method, the object can no longer be 238 used. 239 240
