1. mkrelli's Avatar

    I want to play audio from my Nexus 7 2013 (Razor) in a fixed install environment on a Mutli Channel USB Audio DAC. It is a 7.1 Channel device and has a CMedia CM6206 chip. I currently use the stock Android 5.1.1 build LMY47V.
    From what I've read a multi channel source, e.g. a movie, should play fine, but the difficult part seems to be the spreading of stereo sound onto multiple channels. After reading through different articles related to ALSA I finally found an example configuration which does exactly what I need:

    # for 5.1 speakers
    pcm.ch51dup {
             slave.pcm surround51
             slave.channels 6
             type route
             ttable.0.0 1
             ttable.1.1 1
             ttable.0.2 1
             ttable.1.3 1
             ttable.0.4 0.5
             ttable.1.4 0.5
             ttable.0.5 0.5
             ttable.1.5 0.5
    # for 4.1 speakers
    pcm.ch41dup {
             type route
             slave.pcm surround41
             slave.channels 5
             ttable.0.0 1
             ttable.1.1 1
             ttable.0.2 1
             ttable.1.3 1
             ttable.0.4 0.5
             ttable.1.4 0.5
    Sadly it is for Linux Desktop Editions and Android seems to be quite different (Driver Layer, Configuration ...). After figuring that out I came across a thread on XDA Developers where they want to use all built-in speakers for audio.
    Thus, I finaly found the place the mixer configuration would probably go to (mixer_paths.xml). But now I'm stuck on translating the .asoundrc file into the right XML Syntax. This is where I need help... I already read through my configuration file, but the syntax is not fully clear to me.
    Is there any document which describes the XML Elements valid in the mixer_paths.xml?

    What I got so far:
    - Device is rooted
    - Alsa Mixer is installed
    - Example .asoundrc
    - The USB DAC enumerats (with alsa_aplay -L) as "default:CARD=Device" or as (with alsa_aplay -l) "card 1".

    What I need to know:
    - What is the relevant source elment?
    - How do I route the audio to the actual device?
    - What is the equivalent for "ttable" in .asoundrc?

    Thanks and best regards,
    07-24-2015 06:38 AM

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