主页 / unix / 问题 / 687534
Accepted
Emmanuel Lepage Vallee
Asked: 2022-01-24 00:30:35 +0800 CST

我的 USB 音频输入通道最大输出/剪辑约为 15%

  • 772

我有一个 M-track 8 音频设备（8 个 I/O）。它适用于播放。但是，麦克风（48 伏 XLR 麦克风）几乎没有发出任何声音。录制时，它们在任何应用程序中的音量上限为 15%。

  • 根据混频器频谱分析仪，它们工作得很好。
  • 如果我将 m-track 输入重定向到模拟输出并使用内置麦克风进行录制，那么它可以正常工作
  • 如果我在 macOS 或 Windows 中录制，它可以正常工作。

所以问题出在 ALSA 或驱动程序的某个地方。这是一个普通的 USB 音频类设备，因此驱动程序不太可能出现问题（在 Gentoo、Ubuntu 20.04 和 Ubuntu 18.04 live-usb 中重现）。

  • alsamixer显示所有输入为 100%
  • pavucontrol以 100% 显示所有输入
  • 我尝试添加一些.asoundrc配置来强制 96kHz，但它什么也没做
  • 该问题与麦克风增强无关。信号超弱

混音器-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"

这是一段录音：

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

声音来自麦克风并被夹在设备上（显示了 vu-meter 红色条）。

enter image description here

enter image description here

pulseaudio alsa

1 个回答

  1. Best Answer

    我没有看到任何明显的东西，但有两个想法：

    1. USB 设备有两种配置，但从显示的有关它们的信息来看，它们似乎是相同的。所以我不知道它们是干什么用的。您可以尝试切换到另一个（使用usb_modeswitch，首先卸载内核模块），看看是否有任何改变

    2. 如果我正确读取描述符，您将在 4 个字节中传输 24 位。如果通用 USB 音频驱动程序选择了错误的 3 个字节，您最终可能会得到一个最高有效字节为零，这会将级别限制为 12.5%（与您观察到的 15% 匹配）。

      You can verify this by recording (e.g. parecord) to some file (WAV or raw) in 24-bit format, and examining it with a hex editor. If the MSB of all samples is zero, even when you produce a volume that clips on Mac or Windows, that would make this very likely.

      In addition, you can use wireshark to capture the USB packets, so you can compare if they do have an additional third byte in the samples that doesn't make it into the recorded data.

    In that case, it's a bug in the driver, so please file a bug report on the ALSA kernel list.

    Quick excurse on use cases: Normally people buy something like the M-track 8 to record with multiple mics, e.g. a band where ever member has one or two mics (vocals + instrument). In that case, you'd just get all 8 channels from Pulseaudio (disabling downmixing), and your DAW would select which channels you'd actually record.

    Often you'd even completely disable Pulseaudio for that, as it only adds latency, and go directly to ALSA, or use Jack instead of Pulseaudio.

    "I want my laptop to play into my 7.1 surround speakers or my stereo headphone. Then if I make a conference call, I just want people to hear me.

    Ok, so you have a single mic, and that's all you have in the use case. You also want to keep Pulseaudio, as you don't have latency issues, and you are using the 8 channels mainly for output.

    So have a look at the module-remap-source and do something like

    load-module module-remap-source master=alsa_input.usb-MTRACK.analog-stereo channels=1 master_channel_map=front-left channel_map=mono

    where front-left is the channel you have your mic on, and MTRACK is replaced with the actual name of your M-Track source (use e.g. pactl list short). Then record from the new source.

    If the only actual problem was that Pulseaudio was downmixing all 8 channels to stereo and reducing the level with that, the you should be good now.

    If there's still another problem, please test recording all 8 channels without Pulseaudio and only with ALSA as described in the comments, so we can rule out Pulseaudio and see if the problem is in the ALSA drivers.

    • 1

相关问题