Unable to play to snd-aloop output device

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mattkhan:
I'm attempting to get MC to play to a loopback device. I see the following in the logs

--- Code: ---1289688: 2166068992: Playback: CALSAPlugin::OpenALSA: Opened audio device plughw:CARD=Loopback,DEV=0
1289688: 2166068992: Playback: CALSAPlugin::OpenALSA: Opened device at bitdepth S16_LE
1289688: 2166068992: Playback: CALSAPlugin::OpenALSA: Failed to get desired sample rate (48000): Invalid argument
1289688: 2166068992: Playback: CALSAPlugin::OpenALSA: Finish (1 ms)

--- End code ---

This log is with the PCM output format explicitly set to S16_LE (hence the 2nd line), I get the same behaviour if I set this to auto.

The error displayed is

--- Code: ---1289689: 2211079936: Playback: CPlayerZone::JRPlaybackEngine_PlaybackError: Start
1289689: 2211079936: Playback: CPlayerZone::JRPlaybackEngine_PlaybackError: Error: Playback could not be started on the output 'ALSA' using the format
'48 kHz 2ch'.

This output format may not be supported by your hardware. You can use DSP Studio to change the output to a compatible format.

Also, make sure that your system has a valid sound playback device and that it is properly configured in playback options.
1289689: 2211079936: Playback: CPlayerZone::JRPlaybackEngine_PlaybackError: Finish (0 ms)

--- End code ---

the same file plays without issue using aplay

--- Code: ---$ aplay -D plughw:CARD=Loopback,DEV=0 MeasSweep_48000_0_24000_LR_refL.wav
Playing WAVE 'MeasSweep_48000_0_24000_LR_refL.wav' : Signed 16 bit Little Endian, Rate 48000 Hz, Stereo

--- End code ---

any ideas how to get MC to play to this device?

bob:

--- Quote from: mattkhan on February 22, 2018, 08:58:35 am ---I'm attempting to get MC to play to a loopback device. I see the following in the logs

--- Code: ---1289688: 2166068992: Playback: CALSAPlugin::OpenALSA: Opened audio device plughw:CARD=Loopback,DEV=0
1289688: 2166068992: Playback: CALSAPlugin::OpenALSA: Opened device at bitdepth S16_LE
1289688: 2166068992: Playback: CALSAPlugin::OpenALSA: Failed to get desired sample rate (48000): Invalid argument
1289688: 2166068992: Playback: CALSAPlugin::OpenALSA: Finish (1 ms)

--- End code ---

This log is with the PCM output format explicitly set to S16_LE (hence the 2nd line), I get the same behaviour if I set this to auto.

The error displayed is

--- Code: ---1289689: 2211079936: Playback: CPlayerZone::JRPlaybackEngine_PlaybackError: Start
1289689: 2211079936: Playback: CPlayerZone::JRPlaybackEngine_PlaybackError: Error: Playback could not be started on the output 'ALSA' using the format
'48 kHz 2ch'.

This output format may not be supported by your hardware. You can use DSP Studio to change the output to a compatible format.

Also, make sure that your system has a valid sound playback device and that it is properly configured in playback options.
1289689: 2211079936: Playback: CPlayerZone::JRPlaybackEngine_PlaybackError: Finish (0 ms)

--- End code ---

the same file plays without issue using aplay

--- Code: ---$ aplay -D plughw:CARD=Loopback,DEV=0 MeasSweep_48000_0_24000_LR_refL.wav
Playing WAVE 'MeasSweep_48000_0_24000_LR_refL.wav' : Signed 16 bit Little Endian, Rate 48000 Hz, Stereo

--- End code ---

any ideas how to get MC to play to this device?

--- End quote ---
The only thing I see here is that you are using a plughw: device. MC will NOT let ALSA do sample rate manipulation using the plughw devices. You might want to check to see what sample rates your loopback device supports then setup DSP studio to use them and not use a plughw device.

Since I really don't know much about loopback devices, it's possible that it won't work at any rate but you could give this a try.

mattkhan:

--- Quote from: bob on February 22, 2018, 09:25:37 am ---The only thing I see here is that you are using a plughw: device. MC will NOT let ALSA do sample rate manipulation using the plughw devices. You might want to check to see what sample rates your loopback device supports then setup DSP studio to use them and not use a plughw device.

Since I really don't know much about loopback devices, it's possible that it won't work at any rate but you could give this a try.

--- End quote ---
it's just another device, as far as I can see it supports

S32_LE:44100,48000,88200,96000,176400,192000

and we can see that 48kHz is ok because aplay can play that file without issue. I have tried with MC set to 48kHz or passthrough to no avail.

Which device should I try instead?

bob:

--- Quote from: mattkhan on February 22, 2018, 10:31:00 am ---it's just another device, as far as I can see it supports

S32_LE:44100,48000,88200,96000,176400,192000

and we can see that 48kHz is ok because aplay can play that file without issue. I have tried with MC set to 48kHz or passthrough to no avail.

Which device should I try instead?

--- End quote ---
What does the output of /usr/lib/jriver/Media\ Center\ 23/alsacap look like?

mattkhan:

--- Quote from: bob on February 22, 2018, 12:07:52 pm ---What does the output of /usr/lib/jriver/Media\ Center\ 23/alsacap look like?

--- End quote ---
it reports 44100 only on that device

--- Code: ---Card 2, ID `Loopback', name `Loopback'
Device 0, ID `Loopback PCM', name `Loopback PCM', 8 subdevices (8 available)
2 channels, sampling rates 44100 Hz
Sample formats: S32_LE
Subdevice 0, name `subdevice #0'
Subdevice 1, name `subdevice #1'
Subdevice 2, name `subdevice #2'
Subdevice 3, name `subdevice #3'
Subdevice 4, name `subdevice #4'
Subdevice 5, name `subdevice #5'
Subdevice 6, name `subdevice #6'
Subdevice 7, name `subdevice #7'
Device 1, ID `Loopback PCM', name `Loopback PCM', 8 subdevices (8 available)
1..32 channels, sampling rates 8000, 11025, 16000, 22050, 32000, 44100, 48000, 88200, 96000, 176400, 192000 Hz
Sample formats: S16_LE, S16_BE, S32_LE, S32_BE, FLOAT_LE, FLOAT_BE
Subdevice 0, name `subdevice #0'
Subdevice 1, name `subdevice #1'
Subdevice 2, name `subdevice #2'
Subdevice 3, name `subdevice #3'
Subdevice 4, name `subdevice #4'
Subdevice 5, name `subdevice #5'
Subdevice 6, name `subdevice #6'
Subdevice 7, name `subdevice #7'

--- End code ---

what is it reading to get that info?

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