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247 lines
6.7 KiB
ReStructuredText
:mod:`wave` --- Read and write WAV files
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========================================
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.. module:: wave
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:synopsis: Provide an interface to the WAV sound format.
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.. sectionauthor:: Moshe Zadka <moshez@zadka.site.co.il>
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.. Documentations stolen from comments in file.
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**Source code:** :source:`Lib/wave.py`
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--------------
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The :mod:`wave` module provides a convenient interface to the WAV sound format.
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It does not support compression/decompression, but it does support mono/stereo.
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The :mod:`wave` module defines the following function and exception:
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.. function:: open(file, mode=None)
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If *file* is a string, open the file by that name, otherwise treat it as a
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file-like object. *mode* can be:
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``'rb'``
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Read only mode.
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``'wb'``
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Write only mode.
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Note that it does not allow read/write WAV files.
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A *mode* of ``'rb'`` returns a :class:`Wave_read` object, while a *mode* of
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``'wb'`` returns a :class:`Wave_write` object. If *mode* is omitted and a
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file-like object is passed as *file*, ``file.mode`` is used as the default
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value for *mode*.
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If you pass in a file-like object, the wave object will not close it when its
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:meth:`close` method is called; it is the caller's responsibility to close
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the file object.
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The :func:`.open` function may be used in a :keyword:`with` statement. When
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the :keyword:`with` block completes, the :meth:`Wave_read.close()
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<wave.Wave_read.close>` or :meth:`Wave_write.close()
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<wave.Wave_write.close()>` method is called.
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.. versionchanged:: 3.4
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Added support for unseekable files.
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.. function:: openfp(file, mode)
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A synonym for :func:`.open`, maintained for backwards compatibility.
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.. exception:: Error
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An error raised when something is impossible because it violates the WAV
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specification or hits an implementation deficiency.
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.. _wave-read-objects:
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Wave_read Objects
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-----------------
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Wave_read objects, as returned by :func:`.open`, have the following methods:
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.. method:: Wave_read.close()
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Close the stream if it was opened by :mod:`wave`, and make the instance
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unusable. This is called automatically on object collection.
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.. method:: Wave_read.getnchannels()
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Returns number of audio channels (``1`` for mono, ``2`` for stereo).
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.. method:: Wave_read.getsampwidth()
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Returns sample width in bytes.
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.. method:: Wave_read.getframerate()
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Returns sampling frequency.
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.. method:: Wave_read.getnframes()
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Returns number of audio frames.
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.. method:: Wave_read.getcomptype()
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Returns compression type (``'NONE'`` is the only supported type).
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.. method:: Wave_read.getcompname()
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Human-readable version of :meth:`getcomptype`. Usually ``'not compressed'``
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parallels ``'NONE'``.
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.. method:: Wave_read.getparams()
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Returns a :func:`~collections.namedtuple` ``(nchannels, sampwidth,
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framerate, nframes, comptype, compname)``, equivalent to output of the
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:meth:`get\*` methods.
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.. method:: Wave_read.readframes(n)
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Reads and returns at most *n* frames of audio, as a string of bytes.
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.. method:: Wave_read.rewind()
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Rewind the file pointer to the beginning of the audio stream.
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The following two methods are defined for compatibility with the :mod:`aifc`
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module, and don't do anything interesting.
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.. method:: Wave_read.getmarkers()
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Returns ``None``.
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.. method:: Wave_read.getmark(id)
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Raise an error.
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The following two methods define a term "position" which is compatible between
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them, and is otherwise implementation dependent.
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.. method:: Wave_read.setpos(pos)
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Set the file pointer to the specified position.
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.. method:: Wave_read.tell()
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Return current file pointer position.
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.. _wave-write-objects:
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Wave_write Objects
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------------------
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For seekable output streams, the ``wave`` header will automatically be updated
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to reflect the number of frames actually written. For unseekable streams, the
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*nframes* value must be accurate when the first frame data is written. An
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accurate *nframes* value can be achieved either by calling
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:meth:`~Wave_write.setnframes` or :meth:`~Wave_write.setparams` with the number
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of frames that will be written before :meth:`~Wave_write.close` is called and
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then using :meth:`~Wave_write.writeframesraw` to write the frame data, or by
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calling :meth:`~Wave_write.writeframes` with all of the frame data to be
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written. In the latter case :meth:`~Wave_write.writeframes` will calculate
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the number of frames in the data and set *nframes* accordingly before writing
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the frame data.
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Wave_write objects, as returned by :func:`.open`, have the following methods:
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.. versionchanged:: 3.4
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Added support for unseekable files.
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.. method:: Wave_write.close()
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Make sure *nframes* is correct, and close the file if it was opened by
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:mod:`wave`. This method is called upon object collection. It will raise
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an exception if the output stream is not seekable and *nframes* does not
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match the number of frames actually written.
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.. method:: Wave_write.setnchannels(n)
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Set the number of channels.
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.. method:: Wave_write.setsampwidth(n)
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Set the sample width to *n* bytes.
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.. method:: Wave_write.setframerate(n)
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Set the frame rate to *n*.
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.. versionchanged:: 3.2
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A non-integral input to this method is rounded to the nearest
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integer.
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.. method:: Wave_write.setnframes(n)
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Set the number of frames to *n*. This will be changed later if the number
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of frames actually written is different (this update attempt will
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raise an error if the output stream is not seekable).
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.. method:: Wave_write.setcomptype(type, name)
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Set the compression type and description. At the moment, only compression type
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``NONE`` is supported, meaning no compression.
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.. method:: Wave_write.setparams(tuple)
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The *tuple* should be ``(nchannels, sampwidth, framerate, nframes, comptype,
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compname)``, with values valid for the :meth:`set\*` methods. Sets all
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parameters.
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.. method:: Wave_write.tell()
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Return current position in the file, with the same disclaimer for the
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:meth:`Wave_read.tell` and :meth:`Wave_read.setpos` methods.
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.. method:: Wave_write.writeframesraw(data)
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Write audio frames, without correcting *nframes*.
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.. versionchanged:: 3.4
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Any :term:`bytes-like object` is now accepted.
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.. method:: Wave_write.writeframes(data)
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Write audio frames and make sure *nframes* is correct. It will raise an
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error if the output stream is not seekable and the total number of frames
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that have been written after *data* has been written does not match the
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previously set value for *nframes*.
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.. versionchanged:: 3.4
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Any :term:`bytes-like object` is now accepted.
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Note that it is invalid to set any parameters after calling :meth:`writeframes`
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or :meth:`writeframesraw`, and any attempt to do so will raise
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:exc:`wave.Error`.
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