On Thu, 10 Aug 2017, at 02:05 AM, Per Gunnarsson wrote:
> Hello!
>
> I bought a microphone (MICO from Trust) and plugged it into the 3.5 jack
> of my computer.
>
> My OS is Debian testing on an old Acer desktop.
>
> To begin, I had a lot of static noise which was removed when I tried:
>
> pactl load-module module-echo-cancel aec_method=webrtc
>
> without really understanding what I did.
>
> I have looked into pactl list and see this:
>
> Source #2
> State: RUNNING
> Name: alsa_input.pci-_00_14.2.analog-stereo
> Description: Built-in Audio Analog Stereo
> Driver: module-alsa-card.c
> Sample Specification: s16le 2ch 48000Hz
> Channel Map: front-left,front-right
> Owner Module: 8
> Mute: no
> Volume: front-left: 21845 / 33% / -28.63 dB, front-right:
> 21845 / 33% / -28.63 dB
> balance 0.00
> Base Volume: 5841 / 9% / -63.00 dB
> Monitor of Sink: n/a
> Latency: 2301 usec, configured 6 usec
> Flags: HARDWARE HW_MUTE_CTRL HW_VOLUME_CTRL DECIBEL_VOLUME
> LATENCY
> Properties:
> alsa.resolution_bits = "16"
> device.api = "alsa"
> device.class = "sound"
> alsa.class = "generic"
> alsa.subclass = "generic-mix"
> alsa.name = "ALC662 rev1 Analog"
> alsa.id = "ALC662 rev1 Analog"
> alsa.subdevice = "0"
> alsa.subdevice_name = "subdevice #0"
> alsa.device = "0"
> alsa.card = "1"
> alsa.card_name = "HDA ATI SB"
> alsa.long_card_name = "HDA ATI SB at 0xfeb4 irq 16"
> alsa.driver_name = "snd_hda_intel"
> device.bus_path = "pci-:00:14.2"
> sysfs.path =
> "/devices/pci:00/:00:14.2/sound/card1"
> device.bus = "pci"
> device.vendor.id = "1002"
> device.vendor.name = "Advanced Micro Devices, Inc.
> [AMD/ATI]"
> device.product.id = "4383"
> device.product.name = "SBx00 Azalia (Intel HDA)"
> device.form_factor = "internal"
> device.string = "front:1"
> device.buffering.buffer_size = "384000"
> device.buffering.fragment_size = "192000"
> device.access_mode = "mmap+timer"
> device.profile.name = "analog-stereo"
> device.profile.description = "Analog Stereo"
> device.description = "Built-in Audio Analog Stereo"
> alsa.mixer_name = "Realtek ALC662 rev1"
> alsa.components = "HDA:10ec0662,10258100,00100101"
> module-udev-detect.discovered = "1"
> device.icon_name = "audio-card-pci"
> Ports:
> analog-input-front-mic: Front Microphone (priority:
> 8500, not available)
> analog-input-rear-mic: Rear Microphone (priority: 8200,
> available)
> analog-input-linein: Line In (priority: 8100, not
> available)
> Active Port: analog-input-rear-mic
> Formats:
> pcm
>
>
>
>
> Source #7
> State: RUNNING
> Name: alsa_input.pci-_00_14.2.analog-stereo.echo-cancel
> Description: Built-in Audio Analog Stereo (echo cancelled with
> Built-in Audio Analog Stereo)
> Driver: module-echo-cancel.c
> Sample Specification: float32le 1ch 32000Hz
> Channel Map: mono
> Owner Module: 31
> Mute: no
> Volume: mono: 21845 / 33%
> balance 0.00
> Base Volume: 65536 / 100%
> Monitor of Sink: n/a
> Latency: 9221 usec, configured 6 usec
> Flags: HW_MUTE_CTRL LATENCY
> Properties:
> device.master_device =
> "alsa_input.pci-_00_14.2.analog-stereo"
> device.class = "filter"
> device.intended_roles = "phone"
> device.description = "Built-in Audio Analog Stereo (echo
> cancelled with Built-in Audio Analog Stereo)"
> device.icon_name = "audio-input-microphone"
> Formats:
> pcm
>
> Now I wonder why there is a difference in sample specification between
> the sources.
>
>
> Without echo cancellation:
>
> Sample Specification: s16le 2ch 48000Hz
>
>
> With echo cancellation:
>
> Sample Specification: float32le 1ch 32000Hz
That's just the default (for voice, higher sample rates aren't really
necessary). You can set the rate as a module argument, or set
use_master_format=true to just use what the source provides.
Cheers,
Arun
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