Cannot open the same soundcard for Output and Vinyl Control when using OSS API

[Phillip Whelan]

When I try to open the same soundcard for Vinyl Control Input as the card I'm using for Output Mixxx hangs.

Apparently it is some kind of deadlock in libportaudio:

Thread 1 (Thread 0x7fcadb9ac7a0 (LWP 24697)):
#0 0x00007fcad63913c1 in sem_wait () from /lib/libpthread.so.0
#1 0x00007fcad65b75bd in ?? () from /usr/lib/libportaudio.so.2
#2 0x0000000000612c98 in SoundDevicePortAudio::open (this=0x7fcac00edd60)
    at src/sounddeviceportaudio.cpp:223
#3 0x0000000000607ea1 in SoundManager::setupDevices (this=0x7fcac009ef60)

Before it hangs I usually get the following error message (dialog box):

  Configuration Error:
        Audio device could not be opened

Steps to Reproduce:

    * Choose the OSS API in Sound Hardware
    * Select a multiple out soundcard for Deck 1 (ch1/ch2)
    * Select the same card for Deck2 (ch3/ch4)
    * Select the same card for Vinyl Control
    * Ignore the Dialog (the drop down does not revert to None anyways)
    * Select the Channels for Vinyl Control on that card

Expected Result:

    No Hang, No error, just plain old good full duplex sound.

Actual Result:

    Dialog Box Error. The Dropdown is *NOT* reset. Hang on selecting the channels.

This may or may not be related to a slew of old bugs.

[Phillip Whelan (pwhelan)]

This part of the mixxx.log might be relevant:

Debug: [Main]: PortAudio: Started stream successfully
Debug: [Main]: iNumDevicesOpenedForOutput: 1
Debug: [Main]: iNumDevicesOpenedForInput: 0
Debug: [Main]: Displaying mixxx
Debug: [Main]: Running Mixxx
Debug: [Main]: select()
Debug: [Main]: select()
Debug: [Main]: select()
Debug: [Main]: select()
Debug: [Main]: Setting vinyl device #2's channels to: ""
Debug: [Main]: SoundManager::setupDevices()
Debug: [Main]: Building timecode lookup tables...
Debug: [Main]: Starting vinyl control xwax thread
Debug: [Main]: Building timecode lookup tables...
Debug: [Main]: Starting vinyl control xwax thread
Debug: [Main]: SoundDevicePortAudio::open() "1, /dev/dsp1"
Debug: [Main]: m_dSampleRate 44100
Debug: [Main]: iLatencyMSec: 5
Debug: [Main]: output channels: 4 | input channels: 2
Debug: [Main]: iFramesPerBuffer 256
Debug: [Main]: iLatencyMSec: 5
Debug: [Main]: Opening stream with id 1
Debug: [Main]: Error opening stream: Invalid number of channels

That's when the Dialog Error shows up.

The Log for the hang is here:

Debug: [Main]: select()
Debug: [Main]: Setting vinyl device #2's channels to: "2"
Debug: [Main]: SoundManager::setupDevices()
Debug: [Main]: Building timecode lookup tables...
Debug: [Main]: Starting vinyl control xwax thread
Debug: [Main]: Building timecode lookup tables...
Debug: [Main]: Starting vinyl control xwax thread
Debug: [Main]: SoundDevicePortAudio::open() "1, /dev/dsp1"
Debug: [Main]: m_dSampleRate 44100
Debug: [Main]: iLatencyMSec: 5
Debug: [Main]: output channels: 4 | input channels: 4
Debug: [Main]: iFramesPerBuffer 256
Debug: [Main]: iLatencyMSec: 5
Debug: [Main]: Opening stream with id 1
Debug: [Main]: Opened PortAudio stream successfully... starting
Debug: [Main]: Dynamically loaded PortAudio library!

[Phillip Whelan (pwhelan)]

I was able to get full duplex working with ALSA.

In case anyone is wondering, I used the a PPA kernel with the new BFS scheduler. With the CPUFREQ set at performance I am able to get 5ms latency with full duplex, using vinyl control.

For now I am marking the bug as wont fix since it seems like the OSS emulation layer does not support full duplex.

[Swiftb0y (swiftb0y)]

Mixxx now uses GitHub for bug tracking. This bug has been migrated to:
https://github.com/mixxxdj/mixxx/issues/5357