14.11.2 Mixer Device Objects

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14.11.2 Mixer Device Objects

The mixer object provides two file-like methods:

`close`( | )

  This method closes the open mixer device file. Any further attempts to use the mixer after this file is closed will raise an IOError.

`fileno`( | )

  Returns the file handle number of the open mixer device file.

The remaining methods are specific to audio mixing:

`controls`( | )

  This method returns a bitmask specifying the available mixer controls (``Control'' being a specific mixable ``channel'', such as `SOUND_MIXER_PCM` or `SOUND_MIXER_SYNTH`). This bitmask indicates a subset of all available mixer controls--the `SOUND_MIXER_*` constants defined at module level. To determine if, for example, the current mixer object supports a PCM mixer, use the following Python code:

      mixer=ossaudiodev.openmixer()
      if mixer.controls() & (1 << ossaudiodev.SOUND_MIXER_PCM):
          # PCM is supported
          ... code ...

  For most purposes, the `SOUND_MIXER_VOLUME` (master volume) and `SOUND_MIXER_PCM` controls should suffice--but code that uses the mixer should be flexible when it comes to choosing mixer controls. On the Gravis Ultrasound, for example, `SOUND_MIXER_VOLUME` does not exist.

`stereocontrols`( | )

  Returns a bitmask indicating stereo mixer controls. If a bit is set, the corresponding control is stereo; if it is unset, the control is either monophonic or not supported by the mixer (use in combination with `controls()` to determine which).

  See the code example for the `controls()` function for an example of getting data from a bitmask.

`reccontrols`( | )

  Returns a bitmask specifying the mixer controls that may be used to record. See the code example for `controls()` for an example of reading from a bitmask.

`get`( | control)

  Returns the volume of a given mixer control. The returned volume is a 2-tuple `(left_volume,right_volume)`. Volumes are specified as numbers from 0 (silent) to 100 (full volume). If the control is monophonic, a 2-tuple is still returned, but both volumes are the same.

  Raises `OSSAudioError` if an invalid control was is specified, or `IOError` if an unsupported control is specified.

`set`( | control, (left, right))

  Sets the volume for a given mixer control to `(left,right)`. `left` and `right` must be ints and between 0 (silent) and 100 (full volume). On success, the new volume is returned as a 2-tuple. Note that this may not be exactly the same as the volume specified, because of the limited resolution of some soundcard's mixers.

  Raises `OSSAudioError` if an invalid mixer control was specified, or if the specified volumes were out-of-range.

`get_recsrc`( | )

  This method returns a bitmask indicating which control(s) are currently being used as a recording source.

`set_recsrc`( | bitmask)

  Call this function to specify a recording source. Returns a bitmask indicating the new recording source (or sources) if successful; raises `IOError` if an invalid source was specified. To set the current recording source to the microphone input:

      mixer.setrecsrc (1 << ossaudiodev.SOUND_MIXER_MIC)