aifc —- Read and write AIFF and AIFC files

Source code:Lib/aifc.py

This module provides support for reading and writing AIFF and AIFF-C files.AIFF is Audio Interchange File Format, a format for storing digital audiosamples in a file. AIFF-C is a newer version of the format that includes theability to compress the audio data.

Audio files have a number of parameters that describe the audio data. Thesampling rate or frame rate is the number of times per second the sound issampled. The number of channels indicate if the audio is mono, stereo, orquadro. Each frame consists of one sample per channel. The sample size is thesize in bytes of each sample. Thus a frame consists ofnchannels samplesize bytes, and a second's worth of audio consists ofnchannels samplesize * framerate bytes.

For example, CD quality audio has a sample size of two bytes (16 bits), uses twochannels (stereo) and has a frame rate of 44,100 frames/second. This gives aframe size of 4 bytes (22), and a second's worth occupies 22*44100 bytes(176,400 bytes).

Module aifc defines the following function:

• aifc.open(file, mode=None)
• Open an AIFF or AIFF-C file and return an object instance with methods that aredescribed below. The argument file is either a string naming a file or afile object. mode must be 'r' or 'rb' when the file must beopened for reading, or 'w' or 'wb' when the file must be opened for writing.If omitted, file.mode is used if it exists, otherwise 'rb' is used. Whenused for writing, the file object should be seekable, unless you know ahead oftime how many samples you are going to write in total and usewriteframesraw() and setnframes().The open() function may be used in a with statement. Whenthe with block completes, the close() method is called.

在 3.4 版更改: 支持了 with 语句。

Objects returned by open() when a file is opened for reading have thefollowing methods:

• aifc.getnchannels()

• Return the number of audio channels (1 for mono, 2 for stereo).

• aifc.getsampwidth()

• Return the size in bytes of individual samples.

• aifc.getframerate()

• Return the sampling rate (number of audio frames per second).

• aifc.getnframes()

• Return the number of audio frames in the file.

• aifc.getcomptype()

• Return a bytes array of length 4 describing the type of compressionused in the audio file. For AIFF files, the returned value isb'NONE'.

• aifc.getcompname()

• Return a bytes array convertible to a human-readable descriptionof the type of compression used in the audio file. For AIFF files,the returned value is b'not compressed'.

• aifc.getparams()

• 返回一个 namedtuple() (nchannels, sampwidth, framerate, nframes, comptype, compname)，与 get*() 方法的输出相同。

• aifc.getmarkers()

• Return a list of markers in the audio file. A marker consists of a tuple ofthree elements. The first is the mark ID (an integer), the second is the markposition in frames from the beginning of the data (an integer), the third is thename of the mark (a string).

• aifc.getmark(id)

• Return the tuple as described in getmarkers() for the mark with the givenid.

• aifc.readframes(nframes)

• Read and return the next nframes frames from the audio file. The returneddata is a string containing for each frame the uncompressed samples of allchannels.

• aifc.rewind()

• Rewind the read pointer. The next readframes() will start from thebeginning.

• aifc.setpos(pos)

• Seek to the specified frame number.

• aifc.tell()

• Return the current frame number.

• aifc.close()

• Close the AIFF file. After calling this method, the object can no longer beused.

Objects returned by open() when a file is opened for writing have all theabove methods, except for readframes() and setpos(). In additionthe following methods exist. The get() methods can only be called afterthe corresponding set() methods have been called. Before the firstwriteframes() or writeframesraw(), all parameters except for thenumber of frames must be filled in.

• aifc.aiff()

• Create an AIFF file. The default is that an AIFF-C file is created, unless thename of the file ends in '.aiff' in which case the default is an AIFF file.

• aifc.aifc()

• Create an AIFF-C file. The default is that an AIFF-C file is created, unlessthe name of the file ends in '.aiff' in which case the default is an AIFFfile.

• aifc.setnchannels(nchannels)

• Specify the number of channels in the audio file.

• aifc.setsampwidth(width)

• Specify the size in bytes of audio samples.

• aifc.setframerate(rate)

• Specify the sampling frequency in frames per second.

• aifc.setnframes(nframes)

• Specify the number of frames that are to be written to the audio file. If thisparameter is not set, or not set correctly, the file needs to support seeking.

• aifc.setcomptype(type, name)

• Specify the compression type. If not specified, the audio data willnot be compressed. In AIFF files, compression is not possible.The name parameter should be a human-readable description of thecompression type as a bytes array, the type parameter should be abytes array of length 4. Currently the following compression typesare supported: b'NONE', b'ULAW', b'ALAW', b'G722'.

• aifc.setparams(nchannels, sampwidth, framerate, comptype, compname)

• Set all the above parameters at once. The argument is a tuple consisting of thevarious parameters. This means that it is possible to use the result of agetparams() call as argument to setparams().

• aifc.setmark(id, pos, name)

• Add a mark with the given id (larger than 0), and the given name at the givenposition. This method can be called at any time before close().

• aifc.tell()

• Return the current write position in the output file. Useful in combinationwith setmark().

• aifc.writeframes(data)

• Write data to the output file. This method can only be called after the audiofile parameters have been set.

在 3.4 版更改: 现在可接受任意 bytes-like object。

• aifc.writeframesraw(data)
• Like writeframes(), except that the header of the audio file is notupdated.

在 3.4 版更改: 现在可接受任意 bytes-like object。

• aifc.close()
• Close the AIFF file. The header of the file is updated to reflect the actualsize of the audio data. After calling this method, the object can no longer beused.