Channel Order Confusion

[directmusic]

Hey! I'm having a bit of confusion around the expected order of channels on Linux when recording using the ALSA backend. My audio interface has 4 channels in and 4 channels out.

When using miniaudio.h on Windows or macOS the order in which the callback receives its data is interleaved like this: 1, 2, 3, 4, but on Linux (using ALSA) it receives its data 1, 3, 2, 4. This happens when using any of the "Monitor Of [device name]" loopback devices or when using the inputs on my interface directly.

This is how I am initializing it.

    ma_device_config device_config = ma_device_config_init(ma_device_type_capture);
    device_config.capture.format = ma_format_f32;
    device_config.capture.channelMixMode = ma_channel_mix_mode_simple;
    device_config.dataCallback = miniaudio_callback;
    device_config.pUserData = this;
    device_config.periodSizeInFrames = 256;
    device_config.resampling.algorithm = ma_resample_algorithm_linear;

    ma_result init_result = ma_device_init_ex(nullptr, 0, nullptr, &device_config, &m_device);
    if (init_result != MA_SUCCESS) {
        return;
    }

    auto result = ma_device_start(&m_device);
    while (result != MA_SUCCESS) {
        result = ma_device_start(&m_device);
    }

Audacity and Bitwig seem to receive the audio in the order I expect as well. I tested with the current dev and dev 0.12 branches and they have the same behavior.

Is there something I have missed?

Thank you for your time.