PyAudio Input overflowed

Question

I'm trying to make real-time plotting sound in python. I need to get chunks from my microphone.

Using PyAudio, try to use

import pyaudio
import wave
import sys

chunk = 1024
FORMAT = pyaudio.paInt16
CHANNELS = 1
RATE = 44100
RECORD_SECONDS = 5
WAVE_OUTPUT_FILENAME = "output.wav"

p = pyaudio.PyAudio()

stream = p.open(format = FORMAT,
                channels = CHANNELS,
                rate = RATE,
                input = True,
                frames_per_buffer = chunk)

print "* recording"
all = []
for i in range(0, RATE / chunk * RECORD_SECONDS):
    data = stream.read(chunk)
    all.append(data)
print "* done recording"

stream.close()
p.terminate()

After, I getting the followin error:

* recording
Traceback (most recent call last):
  File "gg.py", line 23, in <module>
    data = stream.read(chunk)
  File "/usr/lib64/python2.7/site-packages/pyaudio.py", line 564, in read
    return pa.read_stream(self._stream, num_frames)
IOError: [Errno Input overflowed] -9981

I can't understand this buffer. I want, to use blocking IO mode, so if chunks not available, i want to wait for those chunks. But when I creating try except segment or sleep(0.1), i hear clicks, so this is not what i want.

Please suggest the best solution for my ploblem?

Answer 1

pyaudio.Stream.read() has a keyword parameter exception_on_overflow, set this to False.

For your sample code that would look like:

import pyaudio
import wave
import sys

chunk = 1024
FORMAT = pyaudio.paInt16
CHANNELS = 1
RATE = 44100
RECORD_SECONDS = 5
WAVE_OUTPUT_FILENAME = "output.wav"

p = pyaudio.PyAudio()

stream = p.open(format = FORMAT,
                channels = CHANNELS,
                rate = RATE,
                input = True,
                frames_per_buffer = chunk)

print "* recording"
all = []
for i in range(0, RATE / chunk * RECORD_SECONDS):
    data = stream.read(chunk, exception_on_overflow = False)
    all.append(data)
print "* done recording"

stream.close()
p.terminate()

See the PyAudio documentation for more details.

Answer 2

It seems like a lot of people are encountering this issue. I dug a bit into it and I think it means that between the previous call to stream.read() and this current call, data from the stream was lost (i.e. the buffer filled up faster than you cleared it).

From the doc for Pa_ReadStream() (the PortAudio function that stream.read() eventually ends up calling):

@return On success PaNoError will be returned, or PaInputOverflowed if
input data was discarded by PortAudio after the previous call and
before this call.

(PaInputOverflowed then causes an IOError in the pyaudio wrapper).

If it's OK for you to not capture every single frame, then you may ignore this error. If it's absolutely critical for you to have every frame, then you'll need to find a way to increase the priority of your application. I'm not familiar enough with Python to know a pythonic way to do this, but it's worth trying a simple nice command, or changing the scheduling policy to SCHED_DEADLINE.

Edit:

One issue right now is that when IOError is thrown, you lose all the frames collected in that call. To instead ignore the overflow and just return what we have, you can apply the patch below, which will cause stream.read() to ignore output underrun and input overflow errors from PortAudio (but still throw something if a different error occurred). A better way would be to make this behaviour (throw/no throw) customizable depending on your needs.

diff --git a/src/_portaudiomodule.c b/src/_portaudiomodule.c
index a8f053d..0878e74 100644
--- a/src/_portaudiomodule.c
+++ b/src/_portaudiomodule.c
@@ -2484,15 +2484,15 @@ pa_read_stream(PyObject *self, PyObject *args)
     } else {
       /* clean up */
       _cleanup_Stream_object(streamObject);
+
+      /* free the string buffer */
+      Py_XDECREF(rv);
+
+      PyErr_SetObject(PyExc_IOError,
+                       Py_BuildValue("(s,i)",
+                                     Pa_GetErrorText(err), err));
+      return NULL;
     }
-
-    /* free the string buffer */
-    Py_XDECREF(rv);
-
-    PyErr_SetObject(PyExc_IOError,
-                   Py_BuildValue("(s,i)",
-                                 Pa_GetErrorText(err), err));
-    return NULL;
   }

   return rv;

Answer 3

I got the same error when I ran your code. I looked at the default sample rate of my default audio device, my macbook's internal microphone, it was 48000Hz not 44100Hz.

p.get_device_info_by_index(0)['defaultSampleRate']
Out[12]: 48000.0

When I changed RATE to this value, it worked.