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使用 Lubuntu 22.04 和 alsa 将音频直接传输到 Raspberry Pi 上的 HDMI

tag-icon • tag-icon sound pulseaudio alsa raspberrypi
使用 Lubuntu 22.04 和 alsa 将音频直接传输到 Raspberry Pi 上的 HDMI

几天前我设置了 Pi4，并能够让它将声音输出到第一个 HDMI 端口。自动更新后，由于 pulseaudio systemd 服务消失，它失去了此功能。

# systemctl status pulseaudio
Unit pulseaudio.service could not be found.

我对此没意见，因为 pulseaudio 似乎是解决简单问题的复杂解决方案。Alsa 更简单、更成熟，所以我运行了

apt remove pulseaudio

很好。遗憾的是，我似乎无法通过 HDMI 播放音频。

# aplay -l

**** List of PLAYBACK Hardware Devices ****
card 0: Headphones [bcm2835 Headphones], device 0: bcm2835 Headphones [bcm2835 Headphones]
  Subdevices: 8/8
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
  Subdevice #4: subdevice #4
  Subdevice #5: subdevice #5
  Subdevice #6: subdevice #6
  Subdevice #7: subdevice #7
card 1: vc4hdmi0 [vc4-hdmi-0], device 0: MAI PCM i2s-hifi-0 [MAI PCM i2s-hifi-0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 2: vc4hdmi1 [vc4-hdmi-1], device 0: MAI PCM i2s-hifi-0 [MAI PCM i2s-hifi-0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

我想使用 hdmi0，它被列为 card1，所以我填充了 /etc/asound.conf，它之前不存在，

defaults.pcm.card 1
defaults.ctl.card 1

扬声器测试程序产生

speaker-test 1.2.6

Playback device is default
Stream parameters are 48000Hz, S16_LE, 1 channels
Using 16 octaves of pink noise
ALSA lib pcm_direct.c:1206:(snd1_pcm_direct_initialize_slave) requested or auto-format is not available
ALSA lib pcm_dmix.c:1044:(snd_pcm_dmix_open) unable to initialize slave
Playback open error: -22,Invalid argument

运行speaker-test的用户属于audio组，所以如果root运行speaker-test也会产生同样的结果。

我相信 /boot/firmware/config.txt 包含正确的行。

hdmi_drive=2
hdmi_group=1

只是为了好玩，这里是“aplay -L”的输出

null
    Discard all samples (playback) or generate zero samples (capture)
default
    Default Audio Device
sysdefault
    Default Audio Device
iec958
    IEC958 (S/PDIF) Digital Audio Output
samplerate
    Rate Converter Plugin Using Samplerate Library
speexrate
    Rate Converter Plugin Using Speex Resampler
jack
    JACK Audio Connection Kit
oss
    Open Sound System
pulse
    PulseAudio Sound Server
upmix
    Plugin for channel upmix (4,6,8)
vdownmix
    Plugin for channel downmix (stereo) with a simple spacialization
hw:CARD=Headphones,DEV=0
    bcm2835 Headphones, bcm2835 Headphones
    Direct hardware device without any conversions
plughw:CARD=Headphones,DEV=0
    bcm2835 Headphones, bcm2835 Headphones
    Hardware device with all software conversions
default:CARD=Headphones
    bcm2835 Headphones, bcm2835 Headphones
    Default Audio Device
sysdefault:CARD=Headphones
    bcm2835 Headphones, bcm2835 Headphones
    Default Audio Device
dmix:CARD=Headphones,DEV=0
    bcm2835 Headphones, bcm2835 Headphones
    Direct sample mixing device
usbstream:CARD=Headphones
    bcm2835 Headphones
    USB Stream Output
hw:CARD=vc4hdmi0,DEV=0
    vc4-hdmi-0, MAI PCM i2s-hifi-0
    Direct hardware device without any conversions
plughw:CARD=vc4hdmi0,DEV=0
    vc4-hdmi-0, MAI PCM i2s-hifi-0
    Hardware device with all software conversions
default:CARD=vc4hdmi0
    vc4-hdmi-0, MAI PCM i2s-hifi-0
    Default Audio Device
sysdefault:CARD=vc4hdmi0
    vc4-hdmi-0, MAI PCM i2s-hifi-0
    Default Audio Device
front:CARD=vc4hdmi0,DEV=0
    vc4-hdmi-0, MAI PCM i2s-hifi-0
    Front output / input
iec958:CARD=vc4hdmi0,DEV=0
    vc4-hdmi-0, MAI PCM i2s-hifi-0
    IEC958 (S/PDIF) Digital Audio Output
dmix:CARD=vc4hdmi0,DEV=0
    vc4-hdmi-0, MAI PCM i2s-hifi-0
    Direct sample mixing device
usbstream:CARD=vc4hdmi0
    vc4-hdmi-0
    USB Stream Output
hw:CARD=vc4hdmi1,DEV=0
    vc4-hdmi-1, MAI PCM i2s-hifi-0
    Direct hardware device without any conversions
plughw:CARD=vc4hdmi1,DEV=0
    vc4-hdmi-1, MAI PCM i2s-hifi-0
    Hardware device with all software conversions
default:CARD=vc4hdmi1
    vc4-hdmi-1, MAI PCM i2s-hifi-0
    Default Audio Device
sysdefault:CARD=vc4hdmi1
    vc4-hdmi-1, MAI PCM i2s-hifi-0
    Default Audio Device
front:CARD=vc4hdmi1,DEV=0
    vc4-hdmi-1, MAI PCM i2s-hifi-0
    Front output / input
iec958:CARD=vc4hdmi1,DEV=0
    vc4-hdmi-1, MAI PCM i2s-hifi-0
    IEC958 (S/PDIF) Digital Audio Output
dmix:CARD=vc4hdmi1,DEV=0
    vc4-hdmi-1, MAI PCM i2s-hifi-0
    Direct sample mixing device
usbstream:CARD=vc4hdmi1
    vc4-hdmi-1
    USB Stream Output

你知道如何让这个 pi 将声音发送到 hdmi0 吗？

注意：raspi-config ->system options->audio 显示耳机是唯一的音频设备。没有 hdmi0 或 hdmi1 的选项。

答案1

发现问题了。Ubuntu 22.04.3 上当前随 Alsa v1.2.6 分发的文件 /usr/share/alsa/cards/vc4-hdmi.conf 不正确。

上述文件应包含以下内容：

#
# Configuration for the VC4-HDMI sound card using software IEC958
# subframe conversion
#

<confdir:pcm/hdmi.conf>
vc4-hdmi.pcm.hdmi.0 {
        @args [ CARD AES0 AES1 AES2 AES3 ]
        @args.CARD {
                type string
        }
        @args.AES0 {
                type integer
        }
        @args.AES1 {
                type integer
        }
        @args.AES2 {
                type integer
        }
        @args.AES3 {
                type integer
        }
        type iec958
        slave {
                format IEC958_SUBFRAME_LE
                pcm {
                        type hooks
                        slave.pcm {
                                type hw
                                card $CARD
                                device 0
                        }
                        hooks.0 {
                                type ctl_elems
                                hook_args [
                                {
                                        name "IEC958 Playback Default"
                                        interface PCM
                                        optional true
                                        lock true
                                        preserve true
                                        value [ $AES0 $AES1 $AES2 $AES3 ]
                                }
                                ]
                        }
                }
        }
        status [ $AES0 $AES1 $AES2 $AES3 ]
}

# default with plug
vc4-hdmi.pcm.default {
        @args [ CARD ]
        @args.CARD {
                type string
        }
        type plug
        slave.pcm {
                type softvol
                slave.pcm {
                        @func concat
                        strings [ "hdmi:" $CARD ]
                }
                control {
                        name "PCM Playback Volume"
                        card $CARD
                }
        }
}

这是在RPi 论坛。尽管发帖者说这个解决方案对他们不起作用，但对我来说却有效。

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