语境

我在我的计算机（播放器）上使用Windows 7，而在我的大学计算机（流媒体）上使用linux（debian），使用ssh控制。
我试图通过读取波形文件来模拟麦克风的恒定字节速率，就像有人在说话一样。问题在于字节速率低于目标。

选择32KB / s的速率和0.020秒的捕获时间。
我使用time.sleep实现了模拟麦克风，以每0.020秒产生每个数据块。但是获得的速率约为27KB / s，而不是32KB / s

问题

我决定通过阅读此问题，使用一些想法来测试linux机器上time.sleep的精确度。

我做了2种测试。1）繁忙的睡眠2）正常的睡眠

平均而言，从我得到的样本中可以看出，Linux机器的睡眠分辨率为4ms。在Windows上时，其小于/等于1毫秒。

问题

1. 有什么可能会限制linux机器上的睡眠分辨率？
2. （在Linux上）为什么繁忙的睡眠与time.sleep具有相同的分辨率？
3. 如何通过读取波形文件成功模拟麦克风？

码

import time

def busy_sleep(t):
    s=time.time()
    while time.time() - s < t:
        pass
    e=time.time()
    return e-s

def normal_sleep(t):
    s=time.time()
    time.sleep(t)
    e=time.time()
    return e-s

def test(fun):
    f = lambda x: sum(fun(x) for d in range(10))/10
    print("0.100:{}".format(f(0.100)))
    print("0.050:{}".format(f(0.050)))
    print("0.025:{}".format(f(0.025)))
    print("0.010:{}".format(f(0.010)))
    print("0.009:{}".format(f(0.010)))
    print("0.008:{}".format(f(0.008)))
    print("0.007:{}".format(f(0.007)))
    print("0.006:{}".format(f(0.006)))
    print("0.005:{}".format(f(0.005)))
    print("0.004:{}".format(f(0.004)))
    print("0.003:{}".format(f(0.003)))
    print("0.002:{}".format(f(0.002)))
    print("0.001:{}".format(f(0.001)))

if __name__=="__main__":
    print("Testing busy_sleep:")
    test(busy_sleep)
    print("Testing normal_sleep:")
    test(normal_sleep)

结果

"""
Debian
Testing busy_sleep:
0.100:0.10223722934722901
0.050:0.051996989250183104
0.025:0.027996940612792967
0.020:0.02207831859588623
0.010:0.011997451782226562
0.009:0.011997222900390625
0.008:0.009998440742492676
0.007:0.007997279167175292
0.006:0.0079974365234375
0.005:0.007997465133666993
0.004:0.005918483734130859
0.003:0.003997836112976074
0.002:0.0039977550506591795
0.001:0.003997611999511719
Testing normal_sleep:
0.100:0.1020797061920166
0.050:0.051999988555908205
0.025:0.028000001907348634
0.020:0.02192000865936279
0.010:0.011999979019165039
0.009:0.012000055313110351
0.008:0.010639991760253906
0.007:0.008000001907348633
0.006:0.00799997329711914
0.005:0.008000059127807617
0.004:0.006159958839416504
0.003:0.004000000953674317
0.002:0.00399998664855957
0.001:0.004000091552734375

$ uname -a
Linux 3.2.0-4-amd64 #1 SMP Debian 3.2.57-3+deb7u2 x86_64 GNU/Linux
"""

"""
Windows 7

Testing busy_sleep:
0.100:0.10000572204589844
0.050:0.05000288486480713
0.025:0.0250014066696167
0.010:0.010500597953796388
0.009:0.010500597953796388
0.008:0.008000493049621582
0.007:0.00740041732788086
0.006:0.006400299072265625
0.005:0.005400300025939942
0.004:0.004700303077697754
0.003:0.003200197219848633
0.002:0.002700185775756836
0.001:0.0016000032424926759
Testing normal_sleep:
0.100:0.10000579357147217
0.050:0.0500028133392334
0.025:0.02500150203704834
0.010:0.01000049114227295
0.009:0.0100006103515625
0.008:0.008000493049621582
0.007:0.007000398635864257
0.006:0.006000304222106934
0.005:0.00500030517578125
0.004:0.0040001869201660155
0.003:0.0030002117156982424
0.002:0.0020000934600830078
0.001:0.0010000944137573243
"""

实码

导入os导入wave导入sys导入io导入时间

FORMAT = 8 #get_format_from_width(2)
NCHANNELS = 1
FRAMERATE = 16000 # samples per second
SAMPWIDTH = 2 # bytes in a sample
BYTE_RATE = FRAMERATE*SAMPWIDTH
CHUNK_DURATION = 0.020
CHUNK_BYTES = int(CHUNK_DURATION*BYTE_RATE)

class StreamSimulator:
    def __init__(self):
        wf = wave.open("Kalimba.wav","rb")
        buf = io.BytesIO()
        buf.write(wf.readframes(wf.getnframes()))
        wf.close()
        buf.seek(0)
        self.buf = buf
        self.step = time.time()

    def delay(self):
        #delay
        delta = time.time() - self.step 
        self.step=time.time()
        delay = CHUNK_DURATION - delta      
        if delay > 0.001:
            time.sleep(delay)


    def read(self):
        buf = self.buf  
        data = buf.read(CHUNK_BYTES)
        if len(data) == 0:
            buf.seek(0)
            data = buf.read(CHUNK_BYTES)

        self.delay()
        return data

    def close(self):
        self.buf.close()

class DynamicPainter:
    def __init__(self):
        self.l=0

    def paint(self,obj):        
        str1=str(obj)
        l1=len(str1)
        bs="\b"*self.l
        clean=" "*self.l
        total = bs+clean+bs+str1
        sys.stdout.write(total)
        sys.stdout.flush()
        self.l=l1

if __name__=="__main__":
    painter = DynamicPainter()
    stream = StreamSimulator()
    produced = 0
    how_many = 0
    painted = time.time()
    while True:
        while time.time()-painted < 1:
            d = stream.read()
            produced += len(d)
            how_many += 1
        producing_speed = int(produced/(time.time()-painted))       
        painter.paint("Producing speed: {} how many: {}".format(producing_speed,how_many))
        produced=0
        how_many=0
        painted = time.time()

编辑

更改了“实码”，添加了包括睡眠时间在内的时间度量。
但是现在我有了DOUBLE Byte Rate：Producing speed: 63996 how many: 100
这让我非常困惑。我尝试了不同的方法，最终每次都是两倍。

结论

感谢@JFSebastian和他的代码，我了解到：

• 最好使用截止日期作为时间参考，而不是在每个循环中创建新的参考
• 使用截止日期可以使time.sleep的不精确度“摊销”，使比特率在所需的比特率附近振荡，但会得出正确的（并且要更稳定）的平均值。
• 您只需要使用一次time.time（），这意味着更少的计算误差。

结果，我有时会以恒定的32000 B / s振荡到31999，很少会振荡到31745。
现在我可以听到音乐而没有任何滞后或抖动！

最终密码

def read(self):
    buf = self.buf  
    data = buf.read(CHUNK_BYTES)
    if len(data) == 0:
        buf.seek(0)
        data = buf.read(CHUNK_BYTES)

    self.deadline += CHUNK_DURATION 
    delay = self.deadline - time.time()
    if delay > 0:
        time.sleep(delay)
    return data