[pulseaudio-discuss] Sound recording/routing issues on Librem5

[Angus Ainslie]

Hi All,

Ok the first issue has been solved by choosing the correct profile and 
port.

I'm still seeing the latency issue.

Thanks
Angus

On 2019-11-28 15:44, Angus Ainslie wrote:
> Hi,
> 
> On the librem5 phone I'm having problems getting the audio routed from
> the modem to the codec.
> 
> The modem source is displaying a couple of odd behaviours. Here are
> the modem sources
> 
>     index: 0
>         name: <alsa_output.platform-sound-wwan.stereo-fallback.monitor>
>         driver: <module-alsa-card.c>
>         flags: DECIBEL_VOLUME LATENCY
>         state: SUSPENDED
>         suspend cause: IDLE
>         priority: 1000
>         volume: front-left: 65536 / 100% / 0.00 dB,   front-right:
> 65536 / 100% / 0.00 dB
>                 balance 0.00
>         base volume: 65536 / 100% / 0.00 dB
>         volume steps: 65537
>         muted: no
>         current latency: 0.00 ms
>         max rewind: 0 KiB
>         sample spec: s16le 2ch 48000Hz
>         channel map: front-left,front-right
>                      Stereo
>         used by: 0
>         linked by: 0
>         fixed latency: 100.00 ms
>         monitor_of: 0
>         card: 0 <alsa_card.platform-sound-wwan>
>         module: 6
>         properties:
>                 device.description = "Monitor of Built-in Audio Stereo"
>                 device.class = "monitor"
>                 alsa.card = "0"
>                 alsa.card_name = "MODEM"
>                 alsa.long_card_name = "MODEM"
>                 device.bus_path = "platform-sound-wwan"
>                 sysfs.path = "/devices/platform/sound-wwan/sound/card0"
>                 device.form_factor = "internal"
>                 device.string = "0"
>                 module-udev-detect.discovered = "1"
>                 device.icon_name = "audio-card"
>     index: 1
>         name: <alsa_input.platform-sound-wwan.stereo-fallback>
>         driver: <module-alsa-card.c>
>         flags: HARDWARE DECIBEL_VOLUME LATENCY
>         state: SUSPENDED
>         suspend cause: IDLE
>         priority: 9000
>         volume: front-left: 65536 / 100% / 0.00 dB,   front-right:
> 65536 / 100% / 0.00 dB
>                 balance 0.00
>         base volume: 65536 / 100% / 0.00 dB
>         volume steps: 65537
>         muted: no
>         current latency: 0.00 ms
>         max rewind: 0 KiB
>         sample spec: s16le 2ch 48000Hz
>         channel map: front-left,front-right
>                      Stereo
>         used by: 0
>         linked by: 1
>         fixed latency: 100.00 ms
>         card: 0 <alsa_card.platform-sound-wwan>
>         module: 6
>         properties:
>                 alsa.resolution_bits = "16"
>                 device.api = "alsa"
>                 device.class = "sound"
>                 alsa.class = "generic"
>                 alsa.subclass = "generic-mix"
>                 alsa.name = ""
>                 alsa.id = "30030000.sai-gtm601 gtm601-0"
>                 alsa.subdevice = "0"
>                 alsa.subdevice_name = "subdevice #0"
>                 alsa.device = "0"
>                 alsa.card = "0"
>                 alsa.card_name = "MODEM"
>                 alsa.long_card_name = "MODEM"
>                 device.bus_path = "platform-sound-wwan"
>                 sysfs.path = "/devices/platform/sound-wwan/sound/card0"
>                 device.form_factor = "internal"
>                 device.string = "hw:0"
>                 device.buffering.buffer_size = "19200"
>                 device.buffering.fragment_size = "4800"
>                 device.access_mode = "mmap"
>                 device.profile.name = "stereo-fallback"
>                 device.profile.description = "Stereo"
>                 device.description = "Built-in Audio Stereo"
>                 module-udev-detect.discovered = "1"
>                 device.icon_name = "audio-card"
>         ports:
>                 analog-input: Analog Input (priority 10000, latency
> offset 0 usec, available: unknown)
>                         properties:
> 
>         active port: <analog-input>
> 
> If I use parecord to record from alsa_card.platform-sound-wwan I get
> the audio from the modem.
> 
> If I use parecord to record from
> alsa_output.platform-sound-wwan.stereo-fallback.monitor I don't get
> any audio from the call until it disconnects.
> 
> Our application is grabbing the first source from alsa.card_name =
> "MODEM" and is showing the same behaviour as parecord.
> 
> Is there a way to disable the monitor source or possibly reorder the 
> sources ?
> 
> I tried remapping the source and sink but I can't record from that 
> either.
> 
> load-module module-remap-source source_name=Modem
> master=alsa_input.platform-sound-wwan.stereo-fallback
> load-module module-remap-sink sink_name=Modem
> master=alsa_output.platform-sound-wwan.stereo-fallback
> 
> The modem sink is passing audio so that's good. The issue with the
> sink is there is about 3 seconds of latency. I can see ~1 second of
> that due to the cellular network.
> 
> How would I check the latency through pulseaudio ?
> 
> Thanks
> Angus