python - 解释 WAV 数据

Question

我正在尝试编写一个程序来显示 PCM 数据。我一直很沮丧地试图找到一个具有正确抽象级别的库，但我找到了 python wave 库并一直在使用它。但是，我不确定如何解释这些数据。

wave.getparams 函数返回(2 channel ，2 字节，44100 赫兹，96333 帧，无压缩，无压缩)。这一切看起来很愉快，但后来我尝试打印一个帧:'\xc0\xff\xd0\xff'，它是 4 个字节。我想一个帧可能是 2 个样本，但歧义并没有就此结束。

96333 帧 * 2 个样本/帧 *(1/44.1k 秒/样本)= 4.3688 秒

但是，iTunes 报告的时间接近 2 秒，根据文件大小和比特率计算得出的时间大约为 2.7 秒。这是怎么回事？

此外，我如何知道字节是有符号的还是无符号的？

非常感谢!

Answer 1

感谢您的帮助!我让它工作了，我会在这里发布解决方案供大家使用，以防其他可怜的人需要它:

import wave
import struct

def pcm_channels(wave_file):
    """Given a file-like object or file path representing a wave file,
    decompose it into its constituent PCM data streams.

    Input: A file like object or file path
    Output: A list of lists of integers representing the PCM coded data stream channels
        and the sample rate of the channels (mixed rate channels not supported)
    """
    stream = wave.open(wave_file,"rb")

    num_channels = stream.getnchannels()
    sample_rate = stream.getframerate()
    sample_width = stream.getsampwidth()
    num_frames = stream.getnframes()

    raw_data = stream.readframes( num_frames ) # Returns byte data
    stream.close()

    total_samples = num_frames * num_channels

    if sample_width == 1: 
        fmt = "%iB" % total_samples # read unsigned chars
    elif sample_width == 2:
        fmt = "%ih" % total_samples # read signed 2 byte shorts
    else:
        raise ValueError("Only supports 8 and 16 bit audio formats.")

    integer_data = struct.unpack(fmt, raw_data)
    del raw_data # Keep memory tidy (who knows how big it might be)

    channels = [ [] for time in range(num_channels) ]

    for index, value in enumerate(integer_data):
        bucket = index % num_channels
        channels[bucket].append(value)

    return channels, sample_rate