使用运行Raspbian GNU / Linux 8（jessie）的Raspberry Pi Model B +，其蓝色“ Snowball” USB麦克风和有源扬声器连接到3.5mm插孔输出。尝试运行GassistPi的Google Assistant示例pushtotalk.py。样本运行，但会产生多个下溢错误，并且音频断断续续。 Git搜索显示this similar issue，并指向audio_helpers.py中的缓冲区参数设置（完整代码here）和可能的CPU问题。下面的代码段显示了参数设置以及产生错误消息的代码。浏览了有关python-sounddevice here的更详细的解释，但这超出了我的理解（才刚刚开始学习Python！）。寻找一个简洁（且相对简单）的答案，是什么决定参数设置的值，以及如何修改代码/参数以防止/减少下溢错误？
audio_helpers.py示例中的代码段＃1参数设置：
import sounddevice as sd
DEFAULT_AUDIO_SAMPLE_RATE = 16000
DEFAULT_AUDIO_SAMPLE_WIDTH = 2
DEFAULT_AUDIO_ITER_SIZE = 3200
DEFAULT_AUDIO_DEVICE_BLOCK_SIZE = 6400
DEFAULT_AUDIO_DEVICE_FLUSH_SIZE = 25600
def normalize_audio_buffer(buf, volume_percentage, sample_width=2):
"""Adjusts the loudness of the audio data in the given buffer.
代码段＃2 audio_helpers.py示例中的错误报告代码：
class SoundDeviceStream(object):
"""Audio stream based on an underlying sound device.
It can be used as an audio source (read) and a audio sink (write).
Args:
sample_rate: sample rate in hertz.
sample_width: size of a single sample in bytes.
block_size: size in bytes of each read and write operation.
flush_size: size in bytes of silence data written during flush operation.
"""
def __init__(self, sample_rate, sample_width, block_size, flush_size):
if sample_width == 2:
audio_format = 'int16'
else:
raise Exception('unsupported sample width:', sample_width)
self._audio_stream = sd.RawStream(
samplerate=sample_rate, dtype=audio_format, channels=1,
blocksize=int(block_size/2), # blocksize is in number of frames.
)
self._block_size = block_size
self._flush_size = flush_size
self._sample_rate = sample_rate
def read(self, size):
"""Read bytes from the stream."""
buf, overflow = self._audio_stream.read(size)
if overflow:
logging.warning('SoundDeviceStream read overflow (%d, %d)',
size, len(buf))
return bytes(buf)
def write(self, buf):
"""Write bytes to the stream."""
underflow = self._audio_stream.write(buf)
if underflow:
logging.warning('SoundDeviceStream write underflow (size: %d)',
len(buf))
return len(buf)
最后是运行pushtotalk.py
WARNING:root:SoundDeviceStream write underflow (size: 4000)
WARNING:root:SoundDeviceStream write underflow (size: 4000)
WARNING:root:SoundDeviceStream write underflow (size: 4000)
WARNING:root:SoundDeviceStream write underflow (size: 4000)
WARNING:root:SoundDeviceStream write underflow (size: 4000)
WARNING:root:SoundDeviceStream write underflow (size: 4000)
更新好吧，我做了一些修补，通过注释掉audio_helpers.py中的代码来减少断断续续的音频，该代码针对下溢和上溢情况生成警告消息输出。似乎当检测到下溢/上溢情况时，logging.warning将输出到终端（stdout？），这会导致音频播放短暂中断。您仍然可以在音频输出中检测到轻微的震颤，但它比以前好得多。理想情况下，与其阻止警告消息的输出，不如首先防止下溢/溢出情况发生，那就更好了！
下面的代码段显示了audio_helpers.py中注释的两个logging.warning函数。该文件位于我的设置中的/home/pi/env/lib/python3.5/site-packages/googlesamples/assistant/grpc上。
def read(self, size):
"""Read bytes from the stream."""
buf, overflow = self._audio_stream.read(size)
# if overflow:
# logging.warning('SoundDeviceStream read overflow (%d, %d)',
# size, len(buf))"""
return bytes(buf)
def write(self, buf):
"""Write bytes to the stream."""
underflow = self._audio_stream.write(buf)
# if underflow:
# logging.warning('SoundDeviceStream write underflow (size: %d)',
# len(buf))"""
return len(buf)
更新2
根据@Matthias的建议，详细介绍了pushtotalk.py的启动方式以及使用开关--audio-block-size
pi@raspberrypi:~ $ /home/pi/env/bin/googlesamples-assistant-pushtotalk --project-id 'gassistpi-xxxxx' --device-model-id 'gassistpi-xxxxx-gassistpi-xxxxx' --audio-block-size -77
Traceback (most recent call last):
File "/home/pi/env/bin/googlesamples-assistant-pushtotalk", line 11, in <module>
sys.exit(main())
File "/home/pi/env/lib/python3.5/site-packages/click/core.py", line 722, in __call__
return self.main(*args, **kwargs)
File "/home/pi/env/lib/python3.5/site-packages/click/core.py", line 697, in main
rv = self.invoke(ctx)
File "/home/pi/env/lib/python3.5/site-packages/click/core.py", line 895, in invoke
return ctx.invoke(self.callback, **ctx.params)
File "/home/pi/env/lib/python3.5/site-packages/click/core.py", line 535, in invoke
return callback(*args, **kwargs)
File "/home/pi/env/lib/python3.5/site-packages/googlesamples/assistant/grpc/pushtotalk.py", line 351, in main
flush_size=audio_flush_size
File "/home/pi/env/lib/python3.5/site-packages/googlesamples/assistant/grpc/audio_helpers.py", line 190, in __init__
blocksize=int(block_size/2), # blocksize is in number of frames.
File "/home/pi/env/lib/python3.5/site-packages/sounddevice.py", line 1264, in __init__
**_remove_self(locals()))
File "/home/pi/env/lib/python3.5/site-packages/sounddevice.py", line 779, in __init__
callback_ptr, userdata),
OverflowError: can't convert negative number to unsigned
pi@raspberrypi:~ $
我还尝试了--audio-block-size的（有效二进制）值，范围从1024到65536，并且也很好地设置了0。全部产生相同的原始结果或运行时错误。