树莓派Zero W使用sounddevice播放音频仅生效一次需重启

DevOps 小满

2026-8-29

问题背景

我受旋转电话改造谷歌助手项目启发，计划将Raspberry Pi Zero WH装入老式旋转电话，使用Python开发所需功能，首个基础功能为拿起听筒时播放拨号音。
但使用sounddevice模块播放音频时出现故障：音频仅首次播放正常，之后系统音频功能完全失效，即便使用aplay、speaker-test等系统工具也无法输出音频，必须重启设备才能恢复，初步推测是播放结束后相关资源未正确关闭释放。

硬件配置

Raspberry Pi Zero WH
USB Audio Adapter

我编写了继承Thread的DialTone类，可作为线程被核心应用调用，通过队列消息控制拨号音按需启停，代码末尾编写了main函数用于功能测试。该代码在Windows系统下可反复正常运行，但在树莓派上仅首次运行生效；且未运行Python音频程序时，直接使用aplay播放同一音频文件可反复正常无异常。

核心疑问：

是否是程序锁定了音频资源未释放？
为何进程退出后资源仍处于占用状态？
应当从哪些方向排查定位问题？

问题代码

class DialTone(Thread):

    def __init__(self, input_queue:Queue, device:int_or_str ) -> None:
        """Initialize the dialtone class 

        Args:
            input_queue (Queue): A way to communicate with the thread
        """
        super().__init__()
        global _DIAL_TONE_FILE

        self.input_queue = input_queue
        sd.default.device = device

        # Commit the dial-tone data to memory so we can start/end quickly
        try:
            self.data, self.fs = sf.read(_DIAL_TONE_FILE, always_2d=True)
        except Exception as e:
            logging.debug( type(e).__name__ + ":" + str(e) )
    
    def run(self) -> None:
        """Play a dial tone in a continuous loop until we die
        """
        while( True ):
            cmd = self.input_queue.get(True)
            if( cmd == DialToneComms.DT_START ):
                logging.debug("DT: starting dial tone")
                sd.play(self.data, self.fs, loop=True)
                logging.debug(sd.get_status())
            elif( cmd == DialToneComms.DT_END ):
                logging.debug("DT: stopping dial tone")
                try:
                    sd.stop(ignore_errors=False)
                except Exception as e:
                    logging.error( type(e).__name__ + ":" + str(e) )
                logging.debug(sd.get_status())
            elif( cmd == DialToneComms.DT_KILL ):
                logging.debug("DT: killing self")
                try:
                    sd.stop(ignore_errors=False)
                except Exception as e:
                    logging.error( type(e).__name__ + ":" + str(e) )
                logging.debug(sd.get_status())
                break

# Test this capability
if __name__ == "__main__":
    parser = argparse.ArgumentParser()
    parser.add_argument("--device",type=int_or_str,help="Audio device to use", default=1)
    parser.add_argument("--play_time",type=float,help="how long to play the dial tone",default=10.0)
    parser.add_argument("--num_cycles", type=int, help="Number of play, wait cycles", default=2)
    args = parser.parse_args()

    # Setup logging
    logging.basicConfig(level=logging.DEBUG)

    dial_tone_queue = Queue()
    print( "Instantiating DialTone" )
    dial_tone = DialTone(dial_tone_queue, args.device)
    print( "Starting DialTone Thread" )
    dial_tone.start()

    # Play the dial tone a number of iterations
    for _ in range(args.num_cycles):
        print( "Playing dialtone for {} sec".format(args.play_time))
        dial_tone_queue.put(DialToneComms.DT_START)
        time.sleep(args.play_time)
        dial_tone_queue.put(DialToneComms.DT_END)
        
        print("Waiting 2 seconds")
        time.sleep(2)

    print("Kill the thread")
    dial_tone_queue.put(DialToneComms.DT_KILL)
    print("Joining DialTone")
    dial_tone.join(_JOIN_WAIT_TIME)

    if( dial_tone.is_alive() ):
        logging.warning( "Dial tone thread is still alive! What gives?" )
    else:
        logging.warning( "Dial tone thread is nice and dead")

运行输出对比

树莓派首次运行输出

（底部错误为停止未播放流导致：stop调用已终止流，kill调用再次执行停止触发报错）

Instantiating DialTone
Starting DialTone Thread
Playing dialtone for 3.0 sec
DEBUG:root:DT: starting dial tone
DEBUG:root:
Waiting 2 seconds
DEBUG:root:DT: stopping dial tone
DEBUG:root:
Playing dialtone for 3.0 sec
DEBUG:root:DT: starting dial tone
DEBUG:root:
Waiting 2 seconds
DEBUG:root:DT: stopping dial tone
DEBUG:root:
Playing dialtone for 3.0 sec
DEBUG:root:DT: starting dial tone
DEBUG:root:
Waiting 2 seconds
DEBUG:root:DT: stopping dial tone
DEBUG:root:
Kill the thread
Joining DialTone
DEBUG:root:DT: killing self
ERROR:root:PortAudioError:Error stopping stream: Invalid stream pointer [PaErrorCode -9988]
DEBUG:root:
WARNING:root:Dial tone thread is nice and dead

树莓派第二次运行输出

（注意stop后指令执行顺序错乱，第二次运行无音频输出）

Instantiating DialTone
Starting DialTone Thread
Playing dialtone for 3.0 sec
DEBUG:root:DT: starting dial tone
DEBUG:root:
Waiting 2 seconds
DEBUG:root:DT: stopping dial tone
Playing dialtone for 3.0 sec
Waiting 2 seconds
Playing dialtone for 3.0 sec
Waiting 2 seconds
Kill the thread
Joining DialTone
DEBUG:root:
DEBUG:root:DT: starting dial tone
DEBUG:root:
DEBUG:root:DT: stopping dial tone
WARNING:root:Dial tone thread is still alive! What gives?
DEBUG:root:
DEBUG:root:DT: starting dial tone
DEBUG:root:
DEBUG:root:DT: stopping dial tone
DEBUG:root:
DEBUG:root:DT: killing self
ERROR:root:PortAudioError:Error stopping stream: Invalid stream pointer [PaErrorCode -9988]
DEBUG:root:

Windows环境运行输出（运行正常）

Instantiating DialTone
Starting DialTone Thread
Playing dialtone for 3.0 sec
DEBUG:root:DT: starting dial tone
DEBUG:root:
Waiting 2 seconds
DEBUG:root:DT: stopping dial tone
DEBUG:root:
Playing dialtone for 3.0 sec
DEBUG:root:DT: starting dial tone
DEBUG:root:
DEBUG:root:DT: stopping dial tone
Waiting 2 seconds
DEBUG:root:
Playing dialtone for 3.0 sec
DEBUG:root:DT: starting dial tone
DEBUG:root:
Waiting 2 seconds
DEBUG:root:DT: stopping dial tone
DEBUG:root:
Kill the thread
DEBUG:root:DT: killing self
Joining DialTone
ERROR:root:PortAudioError:Error stopping stream: Invalid stream pointer [PaErrorCode -9988]
DEBUG:root:
WARNING:root:Dial tone thread is nice and dead

问题原因与解决方案

这个问题本质是sounddevice依赖的PortAudio后端在ARM架构Linux系统上，跨线程调用流操作接口时会出现资源锁死、流指针失效的问题。Windows下PortAudio对多线程的容错性更好所以不会触发，而树莓派的ALSA音频子系统一旦被异常持有，就会锁死整个音频栈，哪怕进程退出也不会自动重置USB声卡的占用状态。
具体到现有代码，存在三个核心问题：

在主线程修改sd.default.device全局配置，但实际音频流的创建、播放、停止操作都在子线程执行，PortAudio的上下文在两个线程间没有做同步，第一次调用sd.play创建的流在sd.stop后没有被正确销毁，残留的流指针直接占住了ALSA的音频设备句柄。
没有维护流的状态标记，重复调用sd.play会创建新的流，但旧的流没有被关闭，多次启停后流指针错乱，就会出现命令执行顺序错位、线程无法正常退出的问题。
sd.stop()是全局停止所有流的接口，调用后不会等待流完全关闭就返回，在性能较弱的Pi Zero上，流资源释放的延迟会导致下一次播放调用拿到无效的设备句柄。

修复步骤

所有sounddevice的流操作全部放到同一个线程里执行，不要跨线程调用任何sd.play/sd.stop接口。现有队列传命令的思路是可行的，只要保证所有音频API调用都在DialTone线程内即可，不要在主线程修改任何sounddevice相关配置。

自行维护播放状态和流对象，不要用全局的sd.play/sd.stop，改用显式创建sd.OutputStream的方式，自己持有流实例，启停的时候直接操作这个实例，停止后主动调用close()释放资源，参考修改片段：

def __init__(self, input_queue:Queue, device:int_or_str ) -> None:
    super().__init__()
    self.input_queue = input_queue
    self.device = device
    self.stream = None
    self.data, self.fs = sf.read(_DIAL_TONE_FILE, always_2d=True)
    self.is_playing = False

def run(self) -> None:
    # 所有sounddevice配置都在线程内初始化
    sd.default.device = self.device
    while True:
        cmd = self.input_queue.get(True)
        if cmd == DialToneComms.DT_START and not self.is_playing:
            # 显式创建输出流，循环填充音频数据
            self.stream = sd.OutputStream(
                samplerate=self.fs,
                device=self.device,
                channels=self.data.shape[1],
                callback=lambda outdata, frames, time, status: outdata[:] = self.data[:frames]
            )
            self.stream.start()
            self.is_playing = True
        elif cmd == DialToneComms.DT_END and self.is_playing:
            self.stream.stop()
            self.stream.close() # 主动释放流资源
            self.stream = None
            self.is_playing = False
        elif cmd == DialToneComms.DT_KILL:
            if self.is_playing:
                self.stream.stop()
                self.stream.close()
            break

修复后如果还是出现进程退出后音频占用的问题，可以在程序退出前主动调用sd._terminate()强制关闭PortAudio上下文，释放所有ALSA句柄。
额外排查点：确认树莓派上的PortAudio版本为最新版，19.6以下版本的PortAudio对USB声卡的多线程支持存在已知bug，可执行sudo apt install --reinstall portaudio19-dev python3-sounddevice升级到仓库最新版。

内容的提问来源于stack exchange，提问作者Will

树莓派Zero W使用sounddevice播放音频仅生效一次需重启

硬件配置 #

问题代码 #

运行输出对比 #

树莓派首次运行输出 #

树莓派第二次运行输出 #

Windows环境运行输出（运行正常） #

修复步骤 #