sunau | |||
# Stuff to parse Sun and NeXT audio files.
#
# An audio consists of a header followed by the data. The structure
# of the header is as follows.
#
# +---------------+
# | magic word |
# +---------------+
# | header size |
# +---------------+
# | data size |
# +---------------+
# | encoding |
# +---------------+
# | sample rate |
# +---------------+
# | # of channels |
# +---------------+
# | info |
# | |
# +---------------+
#
# The magic word consists of the 4 characters '.snd'. Apart from the
# info field, all header fields are 4 bytes in size. They are all
# 32-bit unsigned integers encoded in big-endian byte order.
#
# The header size really gives the start of the data.
# The data size is the physical size of the data. From the other
# parameter the number of frames can be calculated.
# The encoding gives the way in which audio samples are encoded.
# Possible values are listed below.
# The info field currently consists of an ASCII string giving a
# human-readable description of the audio file. The info field is
# padded with NUL bytes to the header size.
#
# Usage.
#
# Reading audio files:
# f = sunau.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().
# When the setpos() and rewind() methods are 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' or 'ULAW')
# getcompname() -- returns human-readable version of
# compression type ('not compressed' matches 'NONE')
# getparams() -- returns a tuple consisting of all of the
# above in the above order
# getmarkers() -- returns None (for compatibility with the
# aifc module)
# getmark(id) -- raises an error since the mark does not
# exist (for compatibility with the aifc module)
# 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() and the position given to setpos()
# are 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 audio files:
# f = sunau.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:
# 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
# tell() -- return current position in output file
# 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.
# The close() method is called automatically when the class instance
# is destroyed.
Functions | ||
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