aifc | |||
# Stuff to parse AIFF-C and AIFF files.
#
# Unless explicitly stated otherwise, the description below is true
# both for AIFF-C files and AIFF files.
#
# An AIFF-C file has the following structure.
#
# +-----------------+
# | FORM |
# +-----------------+
# | <size> |
# +----+------------+
# | | AIFC |
# | +------------+
# | | <chunks> |
# | | . |
# | | . |
# | | . |
# +----+------------+
#
# An AIFF file has the string "AIFF" instead of "AIFC".
#
# A chunk consists of an identifier (4 bytes) followed by a size (4 bytes,
# big endian order), followed by the data. The size field does not include
# the size of the 8 byte header.
#
# The following chunk types are recognized.
#
# FVER
# <version number of AIFF-C defining document> (AIFF-C only).
# MARK
# <# of markers> (2 bytes)
# list of markers:
# <marker ID> (2 bytes, must be > 0)
# <position> (4 bytes)
# <marker name> ("pstring")
# COMM
# <# of channels> (2 bytes)
# <# of sound frames> (4 bytes)
# <size of the samples> (2 bytes)
# <sampling frequency> (10 bytes, IEEE 80-bit extended
# floating point)
# in AIFF-C files only:
# <compression type> (4 bytes)
# <human-readable version of compression type> ("pstring")
# SSND
# <offset> (4 bytes, not used by this program)
# <blocksize> (4 bytes, not used by this program)
# <sound data>
#
# A pstring consists of 1 byte length, a string of characters, and 0 or 1
# byte pad to make the total length even.
#
# Usage.
#
# Reading AIFF files:
# f = aifc.open(file, 'r')
# where file is either the name of a file or an open file pointer.
# The open file pointer must have methods read(), seek(), and close().
# In some types of audio files, if the setpos() method is not used,
# the seek() method is not necessary.
#
# This returns an instance of a class with the following public methods:
# getnchannels() -- returns number of audio channels (1 for
# mono, 2 for stereo)
# getsampwidth() -- returns sample width in bytes
# getframerate() -- returns sampling frequency
# getnframes() -- returns number of audio frames
# getcomptype() -- returns compression type ('NONE' for AIFF files)
# getcompname() -- returns human-readable version of
# compression type ('not compressed' for AIFF files)
# getparams() -- returns a tuple consisting of all of the
# above in the above order
# getmarkers() -- get the list of marks in the audio file or None
# if there are no marks
# getmark(id) -- get mark with the specified id (raises an error
# if the mark does not exist)
# readframes(n) -- returns at most n frames of audio
# rewind() -- rewind to the beginning of the audio stream
# setpos(pos) -- seek to the specified position
# tell() -- return the current position
# close() -- close the instance (make it unusable)
# The position returned by tell(), the position given to setpos() and
# the position of marks are all compatible and have nothing to do with
# the actual postion in the file.
# The close() method is called automatically when the class instance
# is destroyed.
#
# Writing AIFF files:
# f = aifc.open(file, 'w')
# where file is either the name of a file or an open file pointer.
# The open file pointer must have methods write(), tell(), seek(), and
# close().
#
# This returns an instance of a class with the following public methods:
# aiff() -- create an AIFF file (AIFF-C default)
# aifc() -- create an AIFF-C file
# setnchannels(n) -- set the number of channels
# setsampwidth(n) -- set the sample width
# setframerate(n) -- set the frame rate
# setnframes(n) -- set the number of frames
# setcomptype(type, name)
# -- set the compression type and the
# human-readable compression type
# setparams(tuple)
# -- set all parameters at once
# setmark(id, pos, name)
# -- add specified mark to the list of marks
# tell() -- return current position in output file (useful
# in combination with setmark())
# writeframesraw(data)
# -- write audio frames without pathing up the
# file header
# writeframes(data)
# -- write audio frames and patch up the file header
# close() -- patch up the file header and close the
# output file
# You should set the parameters before the first writeframesraw or
# writeframes. The total number of frames does not need to be set,
# but when it is set to the correct value, the header does not have to
# be patched up.
# It is best to first set all parameters, perhaps possibly the
# compression type, and then write audio frames using writeframesraw.
# When all frames have been written, either call writeframes('') or
# close() to patch up the sizes in the header.
# Marks can be added anytime. If there are any marks, ypu must call
# close() after all frames have been written.
# The close() method is called automatically when the class instance
# is destroyed.
#
# When a file is opened with the extension '.aiff', an AIFF file is
# written, otherwise an AIFF-C file is written. This default can be
# changed by calling aiff() or aifc() before the first writeframes or
# writeframesraw.
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