Ubuntu 20.04使用OpenAL-Soft无法打开音频设备问题求助

• 运行环境：Ubuntu 20.04，音频编程入门场景，选用OpenAL-Soft作为音频开发库
• 测试代码核心逻辑为打开默认音频设备，代码如下：

ALCdevice* p_ALCDevice = alcOpenDevice( nullptr ); //nullptr = gets default device
    if( !p_ALCDevice )
        throw( "failed to get sound device" );

• 运行代码直接触发异常，错误输出如下：

[ALSOFT] (WW) Failed to open playback device: Could not open /dev/dsp: No 
such file or directory
[ALSOFT] (WW) Error generated on device (nil), code 0xa004
terminate called after throwing an instance of 'char const*'
Aborted (core dumped)

• 初步排查：调用设备枚举接口打印可用设备列表，代码如下：

const ALCchar * devices = alcGetString( NULL, ALC_DEVICE_SPECIFIER );
printf( "%s", devices );

打印结果仅输出OpenAL Soft，无法识别到系统真实音频设备。

• 后续尝试自行通过cmake编译安装OpenAL-Soft，配置阶段日志显示存在大量依赖缺失，编译安装完成后故障依旧，cmake配置日志核心片段如下：

- Checking for module 'dbus-1'
--   No package 'dbus-1' found
-- Could NOT find DBus1 (missing: DBus1_INCLUDE_DIRS DBus1_LIBRARIES)
-- Checking for module 'libpipewire-0.3>=0.3.23'
--   No package 'libpipewire-0.3' found
-- Could NOT find AudioIO (missing: AUDIOIO_INCLUDE_DIR) 
-- Could NOT find OpenSL (missing: OPENSL_LIBRARY OPENSL_INCLUDE_DIR OPENSL_ANDROID_INCLUDE_DIR) 
-- Could NOT find SDL2 (missing: SDL2_LIBRARY SDL2_INCLUDE_DIR) 
-- Could NOT find MySOFA (missing: MYSOFA_LIBRARY MYSOFA_INCLUDE_DIR) 
-- Could NOT find Qt5Widgets
-- Could NOT find SndFile (missing: SNDFILE_LIBRARY SNDFILE_INCLUDE_DIR) 
-- Could NOT find SDL2 (missing: SDL2_LIBRARY SDL2_INCLUDE_DIR) 
-- 
-- Building OpenAL with support for the following backends:
--     ALSA, OSS, SndIO (linked), PortAudio, PulseAudio, JACK, WaveFile, Null
-- 
-- Building with support for CPU extensions:
--     Default, SSE, SSE2, SSE3, SSE4.1
-- 
-- Embedding HRTF datasets
-- 
-- Installing library and headers
-- Installing sample configuration
-- Installing HRTF data files
-- Installing AmbDec presets
-- 
-- Building utility programs
-- 
-- Building example programs
-- 
-- Configuring done
-- Generating done
-- Build files have been written to: /home/brian/openal-soft/build

1. 报错里提到的/dev/dsp是老旧OSS音频框架的设备节点，Ubuntu 20.04默认已不再启用OSS框架，该节点默认不存在。自行编译的OpenAL-Soft默认后端优先级配置把OSS排在靠前位置，探测时尝试打开该节点失败直接抛出错误。
2. 编译时大量音频后端依赖缺失，虽然配置日志显示标记了支持ALSA、PulseAudio等适配Ubuntu 20.04的音频后端，但实际运行时无法正常加载对应后端模块，无法识别到系统真实音频设备，枚举设备时仅能返回内置的虚拟后端标识OpenAL Soft。

按优先级从高到低尝试：

• 优先使用Ubuntu官方源预编译的OpenAL-Soft包，无需自行编译。执行以下命令安装适配当前系统版本的库文件：

  sudo apt update
  sudo apt install libopenal1 libopenal-dev
  

  官方源的包已经提前适配Ubuntu 20.04的PulseAudio音频栈，后端优先级配置正确，不会优先探测OSS设备。
• 如果必须保留自行编译的版本，先装全所有音频后端的开发依赖，再重新编译：

  sudo apt install libasound2-dev libpulse-dev libdbus-1-dev libsndfile1-dev
  

  装完依赖后重新执行cmake，确认ALSA、PulseAudio后端的依赖探测无缺失，再完成编译安装流程。
• 临时绕过问题可在运行程序前指定OpenAL加载的音频后端，跳过OSS探测：

  export ALSOFT_DRIVERS=pulse,alsa
  ./your_test_program
  

  该环境变量会强制OpenAL优先加载PulseAudio、ALSA后端，不会尝试访问/dev/dsp节点。
• 排查系统音频服务状态，执行pactl info确认PulseAudio服务正常运行，如果返回错误，执行以下命令重启用户级音频服务：

  systemctl --user restart pulseaudio
  

  确保当前用户有权限访问音频设备节点。

内容的提问来源于stack exchange，提问作者Brian