M-Track 8オーディオデバイス（8 I / O）があります。再生は素晴らしいです。しかし、マイク（48V XLRマイク）では音がほとんど出ませんでした。録音時のすべてのアプリケーションの音量制限は15％に制限されます。
- ミキサースペクトラムアナライザによると、非常にうまく機能します。
- mトラック入力をアナログ出力にリダイレクトし、内蔵マイクで録音すると正常に動作します。
- macOSやWindowsで録音するとうまく動作します。
したがって、問題はALSAまたはドライバのどこかにあります。これは一般的なUSBオーディオクラスデバイスなので、ドライバが問題になる可能性はありません（Gentoo、Ubuntu 20.04、およびUbuntu 18.04 live-usbで再現されます）。
alsamixerすべての入力を100％で表示します。pavucontrolすべての入力を100％で表示- 私は96kHzを強制的に適用するためにいくつかの設定を追加しようとしましたが、
.asoundrc何の効果もありませんでした。 - この問題はマイクの増幅とは関係ありません。非常に弱い信号
ミキサー-c2:
Simple mixer control 'Mic',0
Capabilities: cvolume cswitch
Capture channels: Front Left - Front Right - Rear Left - Rear Right - Front Center - Woofer - Side Left - Side Right
Limits: Capture 0 - 127
Front Left: Capture 127 [100%] [0.00dB] [on]
Front Right: Capture 127 [100%] [0.00dB] [on]
Rear Left: Capture 127 [100%] [0.00dB] [on]
Rear Right: Capture 127 [100%] [0.00dB] [on]
Front Center: Capture 127 [100%] [0.00dB] [on]
Woofer: Capture 127 [100%] [0.00dB] [on]
Side Left: Capture 127 [100%] [0.00dB] [on]
Side Right: Capture 127 [100%] [0.00dB] [on]
Simple mixer control 'Mic',1
Capabilities: cvolume cvolume-joined cswitch cswitch-joined
Capture channels: Mono
Limits: Capture 0 - 127
Mono: Capture 127 [100%] [0.00dB] [on]
Simple mixer control 'M-Audio M-Track Eight',0
Capabilities: pvolume pswitch
Playback channels: Front Left - Front Right - Rear Left - Rear Right - Front Center - Woofer - Side Left - Side Right
Limits: Playback 0 - 127
Mono:
Front Left: Playback 121 [95%] [-6.00dB] [on]
Front Right: Playback 121 [95%] [-6.00dB] [on]
Rear Left: Playback 127 [100%] [0.00dB] [on]
Rear Right: Playback 127 [100%] [0.00dB] [on]
Front Center: Playback 127 [100%] [0.00dB] [on]
Woofer: Playback 127 [100%] [0.00dB] [on]
Side Left: Playback 127 [100%] [0.00dB] [on]
Side Right: Playback 127 [100%] [0.00dB] [on]
Simple mixer control 'M-Audio M-Track Eight',1
Capabilities: pvolume pvolume-joined pswitch pswitch-joined
Playback channels: Mono
Limits: Playback 0 - 127
Mono: Playback 127 [100%] [0.00dB] [on]
lsusb -vv -d 0763:4003
Bus 001 Device 049: ID 0763:4003 M-Audio
Couldn't open device, some information will be missing
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 2.00
bDeviceClass 239 Miscellaneous Device
bDeviceSubClass 2
bDeviceProtocol 1 Interface Association
bMaxPacketSize0 64
idVendor 0x0763 M-Audio
idProduct 0x4003
bcdDevice 1.05
iManufacturer 1
iProduct 3
iSerial 0
bNumConfigurations 2
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 0x0148
bNumInterfaces 4
bConfigurationValue 1
iConfiguration 0
bmAttributes 0x80
(Bus Powered)
MaxPower 500mA
Interface Association:
bLength 8
bDescriptorType 11
bFirstInterface 0
bInterfaceCount 3
bFunctionClass 1 Audio
bFunctionSubClass 0
bFunctionProtocol 32
iFunction 0
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 0
bInterfaceClass 1 Audio
bInterfaceSubClass 1 Control Device
bInterfaceProtocol 32
iInterface 3
AudioControl Interface Descriptor:
bLength 9
bDescriptorType 36
bDescriptorSubtype 1 (HEADER)
bcdADC 2.00
bCategory 8
wTotalLength 0x00a7
bmControls 0x00
AudioControl Interface Descriptor:
bLength 8
bDescriptorType 36
bDescriptorSubtype 10 (CLOCK_SOURCE)
bClockID 41
bmAttributes 3 Internal programmable clock
bmControls 0x07
Clock Frequency Control (read/write)
Clock Validity Control (read-only)
bAssocTerminal 0
iClockSource 9
AudioControl Interface Descriptor:
bLength 8
bDescriptorType 36
bDescriptorSubtype 11 (CLOCK_SELECTOR)
bClockID 40
bNrInPins 1
baCSourceID(0) 41
bmControls 0x03
Clock Selector Control (read/write)
iClockSelector 8
AudioControl Interface Descriptor:
bLength 17
bDescriptorType 36
bDescriptorSubtype 2 (INPUT_TERMINAL)
bTerminalID 2
wTerminalType 0x0101 USB Streaming
bAssocTerminal 0
bCSourceID 40
bNrChannels 8
bmChannelConfig 0x00000000
iChannelNames 19
bmControls 0x0000
iTerminal 6
AudioControl Interface Descriptor:
bLength 42
bDescriptorType 36
bDescriptorSubtype 6 (FEATURE_UNIT)
bUnitID 10
bSourceID 2
bmaControls(0) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(1) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(2) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(3) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(4) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(5) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(6) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(7) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(8) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
iFeature 0
AudioControl Interface Descriptor:
bLength 12
bDescriptorType 36
bDescriptorSubtype 3 (OUTPUT_TERMINAL)
bTerminalID 20
wTerminalType 0x0301 Speaker
bAssocTerminal 0
bSourceID 10
bCSourceID 40
bmControls 0x0000
iTerminal 0
AudioControl Interface Descriptor:
bLength 17
bDescriptorType 36
bDescriptorSubtype 2 (INPUT_TERMINAL)
bTerminalID 1
wTerminalType 0x0201 Microphone
bAssocTerminal 0
bCSourceID 40
bNrChannels 8
bmChannelConfig 0x00000000
iChannelNames 19
bmControls 0x0000
iTerminal 0
AudioControl Interface Descriptor:
bLength 42
bDescriptorType 36
bDescriptorSubtype 6 (FEATURE_UNIT)
bUnitID 11
bSourceID 1
bmaControls(0) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(1) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(2) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(3) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(4) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(5) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(6) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(7) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(8) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
iFeature 0
AudioControl Interface Descriptor:
bLength 12
bDescriptorType 36
bDescriptorSubtype 3 (OUTPUT_TERMINAL)
bTerminalID 22
wTerminalType 0x0101 USB Streaming
bAssocTerminal 0
bSourceID 11
bCSourceID 40
bmControls 0x0000
iTerminal 7
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 1
bAlternateSetting 0
bNumEndpoints 0
bInterfaceClass 1 Audio
bInterfaceSubClass 2 Streaming
bInterfaceProtocol 32
iInterface 4
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 1
bAlternateSetting 1
bNumEndpoints 2
bInterfaceClass 1 Audio
bInterfaceSubClass 2 Streaming
bInterfaceProtocol 32
iInterface 4
AudioStreaming Interface Descriptor:
bLength 16
bDescriptorType 36
bDescriptorSubtype 1 (AS_GENERAL)
bTerminalLink 2
bmControls 0x00
bFormatType 1
bmFormats 0x00000001
PCM
bNrChannels 8
bmChannelConfig 0x00000000
iChannelNames 11
AudioStreaming Interface Descriptor:
bLength 6
bDescriptorType 36
bDescriptorSubtype 2 (FORMAT_TYPE)
bFormatType 1 (FORMAT_TYPE_I)
bSubslotSize 4
bBitResolution 24
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x01 EP 1 OUT
bmAttributes 5
Transfer Type Isochronous
Synch Type Asynchronous
Usage Type Data
wMaxPacketSize 0x0400 1x 1024 bytes
bInterval 1
AudioStreaming Endpoint Descriptor:
bLength 8
bDescriptorType 37
bDescriptorSubtype 1 (EP_GENERAL)
bmAttributes 0x00
bmControls 0x00
bLockDelayUnits 2 Decoded PCM samples
wLockDelay 0x0008
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x81 EP 1 IN
bmAttributes 17
Transfer Type Isochronous
Synch Type None
Usage Type Feedback
wMaxPacketSize 0x0004 1x 4 bytes
bInterval 4
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 2
bAlternateSetting 0
bNumEndpoints 0
bInterfaceClass 1 Audio
bInterfaceSubClass 2 Streaming
bInterfaceProtocol 32
iInterface 5
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 2
bAlternateSetting 1
bNumEndpoints 1
bInterfaceClass 1 Audio
bInterfaceSubClass 2 Streaming
bInterfaceProtocol 32
iInterface 5
AudioStreaming Interface Descriptor:
bLength 16
bDescriptorType 36
bDescriptorSubtype 1 (AS_GENERAL)
bTerminalLink 22
bmControls 0x00
bFormatType 1
bmFormats 0x00000001
PCM
bNrChannels 8
bmChannelConfig 0x00000000
iChannelNames 19
AudioStreaming Interface Descriptor:
bLength 6
bDescriptorType 36
bDescriptorSubtype 2 (FORMAT_TYPE)
bFormatType 1 (FORMAT_TYPE_I)
bSubslotSize 4
bBitResolution 24
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x82 EP 2 IN
bmAttributes 5
Transfer Type Isochronous
Synch Type Asynchronous
Usage Type Data
wMaxPacketSize 0x0400 1x 1024 bytes
bInterval 1
AudioStreaming Endpoint Descriptor:
bLength 8
bDescriptorType 37
bDescriptorSubtype 1 (EP_GENERAL)
bmAttributes 0x00
bmControls 0x00
bLockDelayUnits 2 Decoded PCM samples
wLockDelay 0x0008
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 3
bAlternateSetting 0
bNumEndpoints 0
bInterfaceClass 254 Application Specific Interface
bInterfaceSubClass 1 Device Firmware Update
bInterfaceProtocol 1
iInterface 10
Device Firmware Upgrade Interface Descriptor:
bLength 9
bDescriptorType 33
bmAttributes 7
Will Not Detach
Manifestation Tolerant
Upload Supported
Download Supported
wDetachTimeout 250 milliseconds
wTransferSize 64 bytes
bcdDFUVersion 1.10
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 0x0148
bNumInterfaces 4
bConfigurationValue 1
iConfiguration 0
bmAttributes 0x80
(Bus Powered)
MaxPower 500mA
Interface Association:
bLength 8
bDescriptorType 11
bFirstInterface 0
bInterfaceCount 3
bFunctionClass 1 Audio
bFunctionSubClass 0
bFunctionProtocol 32
iFunction 0
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 0
bInterfaceClass 1 Audio
bInterfaceSubClass 1 Control Device
bInterfaceProtocol 32
iInterface 3
AudioControl Interface Descriptor:
bLength 9
bDescriptorType 36
bDescriptorSubtype 1 (HEADER)
bcdADC 2.00
bCategory 8
wTotalLength 0x00a7
bmControls 0x00
AudioControl Interface Descriptor:
bLength 8
bDescriptorType 36
bDescriptorSubtype 10 (CLOCK_SOURCE)
bClockID 41
bmAttributes 3 Internal programmable clock
bmControls 0x07
Clock Frequency Control (read/write)
Clock Validity Control (read-only)
bAssocTerminal 0
iClockSource 9
AudioControl Interface Descriptor:
bLength 8
bDescriptorType 36
bDescriptorSubtype 11 (CLOCK_SELECTOR)
bClockID 40
bNrInPins 1
baCSourceID(0) 41
bmControls 0x03
Clock Selector Control (read/write)
iClockSelector 8
AudioControl Interface Descriptor:
bLength 17
bDescriptorType 36
bDescriptorSubtype 2 (INPUT_TERMINAL)
bTerminalID 2
wTerminalType 0x0101 USB Streaming
bAssocTerminal 0
bCSourceID 40
bNrChannels 8
bmChannelConfig 0x00000000
iChannelNames 19
bmControls 0x0000
iTerminal 6
AudioControl Interface Descriptor:
bLength 42
bDescriptorType 36
bDescriptorSubtype 6 (FEATURE_UNIT)
bUnitID 10
bSourceID 2
bmaControls(0) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(1) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(2) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(3) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(4) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(5) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(6) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(7) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(8) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
iFeature 0
AudioControl Interface Descriptor:
bLength 12
bDescriptorType 36
bDescriptorSubtype 3 (OUTPUT_TERMINAL)
bTerminalID 20
wTerminalType 0x0301 Speaker
bAssocTerminal 0
bSourceID 10
bCSourceID 40
bmControls 0x0000
iTerminal 0
AudioControl Interface Descriptor:
bLength 17
bDescriptorType 36
bDescriptorSubtype 2 (INPUT_TERMINAL)
bTerminalID 1
wTerminalType 0x0201 Microphone
bAssocTerminal 0
bCSourceID 40
bNrChannels 8
bmChannelConfig 0x00000000
iChannelNames 19
bmControls 0x0000
iTerminal 0
AudioControl Interface Descriptor:
bLength 42
bDescriptorType 36
bDescriptorSubtype 6 (FEATURE_UNIT)
bUnitID 11
bSourceID 1
bmaControls(0) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(1) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(2) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(3) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(4) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(5) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(6) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(7) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
bmaControls(8) 0x0000000f
Mute Control (read/write)
Volume Control (read/write)
iFeature 0
AudioControl Interface Descriptor:
bLength 12
bDescriptorType 36
bDescriptorSubtype 3 (OUTPUT_TERMINAL)
bTerminalID 22
wTerminalType 0x0101 USB Streaming
bAssocTerminal 0
bSourceID 11
bCSourceID 40
bmControls 0x0000
iTerminal 7
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 1
bAlternateSetting 0
bNumEndpoints 0
bInterfaceClass 1 Audio
bInterfaceSubClass 2 Streaming
bInterfaceProtocol 32
iInterface 4
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 1
bAlternateSetting 1
bNumEndpoints 2
bInterfaceClass 1 Audio
bInterfaceSubClass 2 Streaming
bInterfaceProtocol 32
iInterface 4
AudioStreaming Interface Descriptor:
bLength 16
bDescriptorType 36
bDescriptorSubtype 1 (AS_GENERAL)
bTerminalLink 2
bmControls 0x00
bFormatType 1
bmFormats 0x00000001
PCM
bNrChannels 8
bmChannelConfig 0x00000000
iChannelNames 11
AudioStreaming Interface Descriptor:
bLength 6
bDescriptorType 36
bDescriptorSubtype 2 (FORMAT_TYPE)
bFormatType 1 (FORMAT_TYPE_I)
bSubslotSize 4
bBitResolution 24
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x01 EP 1 OUT
bmAttributes 5
Transfer Type Isochronous
Synch Type Asynchronous
Usage Type Data
wMaxPacketSize 0x0400 1x 1024 bytes
bInterval 1
AudioStreaming Endpoint Descriptor:
bLength 8
bDescriptorType 37
bDescriptorSubtype 1 (EP_GENERAL)
bmAttributes 0x00
bmControls 0x00
bLockDelayUnits 2 Decoded PCM samples
wLockDelay 0x0008
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x81 EP 1 IN
bmAttributes 17
Transfer Type Isochronous
Synch Type None
Usage Type Feedback
wMaxPacketSize 0x0004 1x 4 bytes
bInterval 4
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 2
bAlternateSetting 0
bNumEndpoints 0
bInterfaceClass 1 Audio
bInterfaceSubClass 2 Streaming
bInterfaceProtocol 32
iInterface 5
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 2
bAlternateSetting 1
bNumEndpoints 1
bInterfaceClass 1 Audio
bInterfaceSubClass 2 Streaming
bInterfaceProtocol 32
iInterface 5
AudioStreaming Interface Descriptor:
bLength 16
bDescriptorType 36
bDescriptorSubtype 1 (AS_GENERAL)
bTerminalLink 22
bmControls 0x00
bFormatType 1
bmFormats 0x00000001
PCM
bNrChannels 8
bmChannelConfig 0x00000000
iChannelNames 19
AudioStreaming Interface Descriptor:
bLength 6
bDescriptorType 36
bDescriptorSubtype 2 (FORMAT_TYPE)
bFormatType 1 (FORMAT_TYPE_I)
bSubslotSize 4
bBitResolution 24
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x82 EP 2 IN
bmAttributes 5
Transfer Type Isochronous
Synch Type Asynchronous
Usage Type Data
wMaxPacketSize 0x0400 1x 1024 bytes
bInterval 1
AudioStreaming Endpoint Descriptor:
bLength 8
bDescriptorType 37
bDescriptorSubtype 1 (EP_GENERAL)
bmAttributes 0x00
bmControls 0x00
bLockDelayUnits 2 Decoded PCM samples
wLockDelay 0x0008
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 3
bAlternateSetting 0
bNumEndpoints 0
bInterfaceClass 254 Application Specific Interface
bInterfaceSubClass 1 Device Firmware Update
bInterfaceProtocol 1
iInterface 10
Device Firmware Upgrade Interface Descriptor:
bLength 9
bDescriptorType 33
bmAttributes 7
Will Not Detach
Manifestation Tolerant
Upload Supported
Download Supported
wDetachTimeout 250 milliseconds
wTransferSize 64 bytes
bcdDFUVersion 1.10
pacmd list-sources inputs:
index: 16
name: <alsa_output.usb-M-Audio_M-Track_Eight-00.analog-surround-71.monitor>
driver: <module-alsa-card.c>
flags: DECIBEL_VOLUME LATENCY DYNAMIC_LATENCY
state: RUNNING
suspend cause: (none)
priority: 1040
volume: front-left: 65536 / 100% / 0.00 dB, front-right: 65536 / 100% / 0.00 dB, rear-left: 65536 / 100% / 0.00 dB, rear-right: 65536 / 100% / 0.00 dB, front-center: 65536 / 100% / 0.00 dB, lfe: 65536 / 100% / 0.00 dB, side-left: 65536 / 100% / 0.00 dB, side-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: 11 KiB
sample spec: s32le 8ch 44100Hz
channel map: front-left,front-right,rear-left,rear-right,front-center,lfe,side-left,side-right
Surround 7.1
used by: 5
linked by: 5
configured latency: 40.00 ms; range is 8.00 .. 743.04 ms
monitor_of: 7
card: 5 <alsa_card.usb-M-Audio_M-Track_Eight-00>
module: 27
properties:
device.description = "Monitor of M-Track Eight Analog Surround 7.1"
device.class = "monitor"
alsa.card = "2"
alsa.card_name = "M-Track Eight"
alsa.long_card_name = "M-Audio M-Track Eight at usb-0000:00:14.0-5.4, high speed"
alsa.driver_name = "snd_usb_audio"
device.bus_path = "pci-0000:00:14.0-usb-0:5.4:1.0"
sysfs.path = "/devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.4/1-5.4:1.0/sound/card2"
udev.id = "usb-M-Audio_M-Track_Eight-00"
device.bus = "usb"
device.vendor.id = "0763"
device.vendor.name = "M-Audio"
device.product.id = "4003"
device.product.name = "M-Track Eight"
device.serial = "M-Audio_M-Track_Eight"
device.string = "2"
module-udev-detect.discovered = "1"
device.icon_name = "audio-card-usb"
これは録音です：
parecord -r --format=s24le --file-format=wav ./foo.wav
file ./foo.wav
./foo.wav: RIFF (little-endian) data, WAVE audio, Microsoft PCM, 24 bit, stereo 44100 Hz
音はマイクから出てデバイスに切り取られます（Vuメーターを表示する赤いバー）。
答え1
私は明らかなことを見ていませんが、2つの考えがあります。
USBデバイスには2つの構成がありますが、表示されている情報によれば同じように見えます。だから私はそれらが何のためであるかわかりません。別のものに切り替えて（
usb_modeswitch最初にカーネルモジュールを削除する）、変更があるかどうかを確認できます。ディスクリプタを正しく読み取ると、4バイトに24ビットが送信されます。通常のUSBオーディオドライバが間違った3バイトを選択した場合、最上位バイトは0になり、レベルは12.5％に制限されます（観察された15％に一致）。
parecordたとえば、一部のファイル（WAVまたはRAW）に24ビット形式で録音し、16進エディタで確認して確認できます。すべてのサンプルのMSBが0の場合、作成したボリュームがMacまたはWindowsで切り捨てられた場合でも同じことがあります。また、USBパケットをキャプチャするために使用できるため、記録された
wiresharkデータに含まれていないサンプルに追加の3番目のバイトがあるかどうかを比較できます。
このような場合はドライバのバグなので、ALSAカーネルリストにバグレポートを提出してください。
ユースケースの概要：一般に、人々はM-track 8などの製品を購入して、各メンバーが1つまたは2つのマイク（ボーカル+楽器）を使用するバンドなど、複数のマイクを使用して録音します。この場合、Pulseaudioから8つのチャンネルをすべてインポートすると（ダウンミキシングを無効にする）、DAWは実際に録音したチャンネルを選択します。
レイテンシだけを追加してALSAに直接移動するか、Pulseaudioの代わりにJackを使用するため、これを行うためにPulseaudioを完全に無効にすることがよくあります。
「私はノートパソコンを7.1サラウンドスピーカーやステレオヘッドフォンで再生できるようにしたいと思います。
いいですね。マイクが1つだけ必要です。ユースケースではそれはすべてです。また、待ち時間の問題がなく、主に出力に8チャンネルを使用するので、Pulseaudioを維持しようとします。
だから一度見てくださいモジュール再マッピングソースそして次のことをしてください
load-module module-remap-source master=alsa_input.usb-MTRACK.analog-stereo channels=1 master_channel_map=front-left channel_map=mono
front-leftマイクがオンになっているチャンネルは、M MTRACK-Trackソースの実際の名前に置き換えられます（例：使用pactl list short）。次に、新しいソースから録音します。
唯一の実際の問題は、Pulseaudioが8チャンネルすべてをステレオにダウンミックスしてレベルを下げることであれば、これで問題ありません。
他の問題がある場合は、説明の説明に従って、PulseaudioなしでALSAのみを使用して8つのチャネルをすべてテストしてPulseaudioを除外し、問題がALSAドライバにあることを確認できます。