使用gst-launch-1.0从PipeWire源录制音频到WAV文件遇错求助

环境信息 #

• Gentoo Linux，内核版本6.7.6-gentoo
• 桌面环境：Hyprland（基于Wayland）
• GStreamer 1.22.3、PipeWire 1.0.4

核心现象 #

通过pipewiresrc播放音频（pipewiresrc target-object=67 ! autoaudiosink）正常，但录制音频到WAV文件时，执行以下命令：

gst-launch-1.0 --gst-debug-level=3 pipewiresrc target-object=67 ! audioconvert ! audioresample ! wavenc ! filesink location=output.wav

会触发错误：

0:00:00.017102534 110033 0x7fe5dc002500 ERROR             video-info video-info.c:540:gst_video_info_from_caps: wrong name 'audio/x-raw', expected video/ or image/

且录制进程卡在0:00:00.0 / 99:99:99.状态。该问题不仅出现在摄像头音频源，内置音频源也会触发相同错误。

设备信息 #

摄像头音频源（st-device-monitor-1.0 Audio/Source输出） #

Device found:

    name  : HD Pro Webcam C920 Analog Stereo
    class : Audio/Source
    caps  : audio/x-raw, layout=interleaved, format=S16LE, rate=[ 16000, 32000 ], channels=2
    properties:
        alsa.card = 1
        alsa.card_name = HD Pro Webcam C920
        alsa.class = generic
        alsa.device = 0
        alsa.driver_name = snd_usb_audio
        alsa.id = USB Audio
        alsa.long_card_name = HD Pro Webcam C920 at usb-0000:00:14.0-10.2, high speed
        alsa.name = USB Audio
        alsa.resolution_bits = 16
        alsa.subclass = generic-mix
        alsa.subdevice = 0
        alsa.subdevice_name = subdevice #0
        api.alsa.card.longname = HD Pro Webcam C920 at usb-0000:00:14.0-10.2, high speed
        api.alsa.card.name = HD Pro Webcam C920
        api.alsa.path = front:1
        api.alsa.pcm.card = 1
        api.alsa.pcm.stream = capture
        audio.channels = 2
        audio.position = FL,FR
        card.profile.device = 0
        device.api = alsa
        device.class = sound
        device.id = 55
        device.profile.description = Analog Stereo
        device.profile.name = analog-stereo
        device.routes = 1
        factory.name = api.alsa.pcm.source
        media.class = Audio/Source
        node.description = HD Pro Webcam C920 Analog Stereo
        node.name = alsa_input.usb-046d_HD_Pro_Webcam_C920_B71E5BFF-02.analog-stereo
        node.nick = HD Pro Webcam C920
        node.pause-on-idle = false
        object.path = alsa:pcm:1:front:1:capture
        priority.driver = 2009
        priority.session = 2009
        factory.id = 18
        clock.quantum-limit = 8192
        client.id = 32
        node.driver = true
        factory.mode = split
        audio.adapt.follower = 
        library.name = audioconvert/libspa-audioconvert
        object.id = 63
        object.serial = 67
    gst-launch-1.0 pipewiresrc target-object=67 ! ...

内置音频源（st-device-monitor-1.0 Audio/Source输出） #

Device found:

    name  : Built-in Audio Analog Stereo
    class : Audio/Source
    caps  : audio/x-raw, layout=interleaved, format={ (string)S32LE, (string)S16LE }, rate=[ 44100, 192000 ], channels=2
    properties:
        alsa.card = 0
        alsa.card_name = HDA Intel PCH
        alsa.class = generic
        alsa.device = 0
        alsa.driver_name = snd_hda_intel
        alsa.id = ALC897 Analog
        alsa.long_card_name = HDA Intel PCH at 0x4406220000 irq 247
        alsa.name = ALC897 Analog
        alsa.resolution_bits = 16
        alsa.subclass = generic-mix
        alsa.subdevice = 0
        alsa.subdevice_name = subdevice #0
        api.alsa.card.longname = HDA Intel PCH at 0x4406220000 irq 247
        api.alsa.card.name = HDA Intel PCH
        api.alsa.path = front:0
        api.alsa.pcm.card = 0
        api.alsa.pcm.stream = capture
        audio.channels = 2
        audio.position = FL,FR
        card.profile.device = 0
        device.api = alsa
        device.class = sound
        device.id = 56
        device.profile.description = Analog Stereo
        device.profile.name = analog-stereo
        device.routes = 3
        factory.name = api.alsa.pcm.source
        media.class = Audio/Source
        node.description = Built-in Audio Analog Stereo
        node.name = alsa_input.pci-0000_00_1f.3.analog-stereo.3
        node.nick = ALC897 Analog
        node.pause-on-idle = false
        object.path = alsa:pcm:0:front:0:capture
        priority.driver = 2009
        priority.session = 2009
        factory.id = 18
        clock.quantum-limit = 8192
        client.id = 32
        node.driver = true
        factory.mode = split
        audio.adapt.follower = 
        library.name = audioconvert/libspa-audioconvert
        object.id = 91
        object.serial = 1146
    gst-launch-1.0 pipewiresrc target-object=1146 ! ...

该错误是GStreamer的pipewiresrc插件加载了不必要的视频模块，或隐式尝试用视频组件处理音频流导致的，可通过以下方式解决：

1. 显式指定音频Caps，强制音频流处理 #

在pipewiresrc后直接声明音频格式参数，避免GStreamer误判流类型：

gst-launch-1.0 pipewiresrc target-object=67 ! audio/x-raw,format=S16LE,rate=16000,channels=2 ! audioconvert ! audioresample ! wavenc ! filesink location=output.wav

参数需匹配设备实际支持的Caps（比如摄像头支持16000/32000采样率，内置音频支持44100+）。

2. 使用PipeWire原生工具pw-record录制 #

绕开GStreamer的兼容性问题，直接用PipeWire原生命令录制：

pw-record --target 67 output.wav

也可通过设备名称指定：

pw-record --device alsa_input.usb-046d_HD_Pro_Webcam_C920_B71E5BFF-02.analog-stereo output.wav

3. 升级GStreamer或PipeWire版本 #

该错误在GStreamer 1.24+、PipeWire 1.0.5+版本中已修复，Gentoo下可更新相关包：

emerge -av media-libs/gstreamer media-libs/pipewire

4. 调整GStreamer插件依赖（可选） #

若坚持使用GStreamer，可在Gentoo下通过USE flags禁用不必要的视频组件，重新构建GStreamer：

echo "media-libs/gstreamer -X -video" >> /etc/portage/package.use/gstreamer
emerge -av media-libs/gstreamer

内容的提问来源于stack exchange，提问作者ufk