[alsa-devel] RFC: PCM extra attributes

James Courtier-Dutton james.dutton at gmail.com
Wed Jun 24 19:18:48 CEST 2009

2009/6/19 Takashi Iwai <tiwai at suse.de>:
>> Another option could be to stream the gain control values with the PCM stream.
>> I.e. Instead of attributes attached to the PCM, stream those
>> attributes with the PCM stream.
> Hrm how can it be done?  Could you elaborate?
You said that you were adding a method to identify the channel maps.
I.e. Is Front the first of second channel in the stream.
Add extra channels in the stream that can be tagged as non-audio data
and also tag the sort of non audio data they are. They could be gain
values, time stamps, etc.
So, basically just an extra way to capture metadata on a per sample basis.
For example, when capturing this sample, the analog input gain was set to X.
Obviously we don't have the functionality in the driver itself yet,
but making sure the api could permit this would be useful.

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