22.4. wave — Read and write WAV files

Código Fonte: Lib/wave.py

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The wave module provides a convenient interface to the WAV sound format. It does not support compression/decompression, but it does support mono/stereo.

The wave module defines the following function and exception:

wave.open(file, mode=None)

If file is a string, open the file by that name, otherwise treat it as a file-like object. mode can be:

'rb'

Modo somente para leitura

'wb'

Apenas modo de escrita.

Note that it does not allow read/write WAV files.

A mode of 'rb' returns a Wave_read object, while a mode of 'wb' returns a Wave_write object. If mode is omitted and a file-like object is passed as file, file.mode is used as the default value for mode.

If you pass in a file-like object, the wave object will not close it when its close() method is called; it is the caller’s responsibility to close the file object.

The open() function may be used in a with statement. When the with block completes, the Wave_read.close() or Wave_write.close() method is called.

Alterado na versão 3.4: Added support for unseekable files.

wave.openfp(file, mode)

A synonym for open(), maintained for backwards compatibility.

exception wave.Error

An error raised when something is impossible because it violates the WAV specification or hits an implementation deficiency.

22.4.1. Objetos Wave_read

Wave_read objects, as returned by open(), have the following methods:

Wave_read.close()

Close the stream if it was opened by wave, and make the instance unusable. This is called automatically on object collection.

Wave_read.getnchannels()

Returns number of audio channels (1 for mono, 2 for stereo).

Wave_read.getsampwidth()

Retorna a largura da amostra em bytes.

Wave_read.getframerate()

Retorna a frequência de amostragem.

Wave_read.getnframes()

Retorna o número de quadros de áudio.

Wave_read.getcomptype()

Returns compression type ('NONE' is the only supported type).

Wave_read.getcompname()

Human-readable version of getcomptype(). Usually 'not compressed' parallels 'NONE'.

Wave_read.getparams()

Retorna a namedtuple() (nchannels, sampwidth, framerate, nframes, comptype, compname), equivalente à saída dos métodos get*().

Wave_read.readframes(n)

Reads and returns at most n frames of audio, as a bytes object.

Wave_read.rewind()

Retrocede o ponteiro do arquivo para o início do fluxo de áudio.

The following two methods are defined for compatibility with the aifc module, and don’t do anything interesting.

Wave_read.getmarkers()

Retorna None.

Wave_read.getmark(id)

Levanta um erro.

Os dois métodos a seguir definem um termo “posição” que é compatível entre eles e é dependente da implementação.

Wave_read.setpos(pos)

Set the file pointer to the specified position.

Wave_read.tell()

Return current file pointer position.

22.4.2. Objetos Wave_write

For seekable output streams, the wave header will automatically be updated to reflect the number of frames actually written. For unseekable streams, the nframes value must be accurate when the first frame data is written. An accurate nframes value can be achieved either by calling setnframes() or setparams() with the number of frames that will be written before close() is called and then using writeframesraw() to write the frame data, or by calling writeframes() with all of the frame data to be written. In the latter case writeframes() will calculate the number of frames in the data and set nframes accordingly before writing the frame data.

Wave_write objects, as returned by open(), have the following methods:

Alterado na versão 3.4: Added support for unseekable files.

Wave_write.close()

Make sure nframes is correct, and close the file if it was opened by wave. This method is called upon object collection. It will raise an exception if the output stream is not seekable and nframes does not match the number of frames actually written.

Wave_write.setnchannels(n)

Define o número de canais.

Wave_write.setsampwidth(n)

Set the sample width to n bytes.

Wave_write.setframerate(n)

Set the frame rate to n.

Alterado na versão 3.2: A non-integral input to this method is rounded to the nearest integer.

Wave_write.setnframes(n)

Set the number of frames to n. This will be changed later if the number of frames actually written is different (this update attempt will raise an error if the output stream is not seekable).

Wave_write.setcomptype(type, name)

Set the compression type and description. At the moment, only compression type NONE is supported, meaning no compression.

Wave_write.setparams(tuple)

The tuple should be (nchannels, sampwidth, framerate, nframes, comptype, compname), with values valid for the set*() methods. Sets all parameters.

Wave_write.tell()

Return current position in the file, with the same disclaimer for the Wave_read.tell() and Wave_read.setpos() methods.

Wave_write.writeframesraw(data)

Escreve quadros de áudio, sem corrigir nframes.

Alterado na versão 3.4: Todo objeto do tipo byte agora é aceito.

Wave_write.writeframes(data)

Write audio frames and make sure nframes is correct. It will raise an error if the output stream is not seekable and the total number of frames that have been written after data has been written does not match the previously set value for nframes.

Alterado na versão 3.4: Todo objeto do tipo byte agora é aceito.

Note that it is invalid to set any parameters after calling writeframes() or writeframesraw(), and any attempt to do so will raise wave.Error.