Changing speed of a sound file

最新推荐文章于 2022-02-15 16:28:09 发布

转载最新推荐文章于 2022-02-15 16:28:09 发布 · 330 阅读

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本文探讨了声音文件播放速度的两种调整方法：增加采样率和减少单位时间内的采样数。通过调整，可以相应地改变声音的音高。介绍了增加采样率的方法，使其播放速度加快；同时，提出了在保持播放采样率不变的情况下，减少采样数的一种不理想方法，并建议采用平均采样来改善音频质量。最后，分享了一个简单的伪代码实例来演示如何将播放速度加倍。

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原文地址：http://stackoverflow.com/questions/939904/changing-speed-of-a-sound-file

There are two options to speed up the playback of a sound file:

Increase the sample rate
Reduce the number of samples per unit of time.

In either of these methods, the increase in playback speed will have a corresponding change in the pitch of the sound.

Increasing the sample rate

Increasing the sample rate will increase the playback speed of the sound. For example, going from a 22 KHz sampling rate to 44 KHz will make the playback sound twice as fast as the original. In this method, the original sampling data is unaltered -- only the audio playback settings need to be changed.

Reduce the number of samples per unit of time

In this method, the playback sampling rate is kept constant, but the number of samples are reduced -- some of the samples are thrown out.

The naive approach to make the playback of the sound be twice the speed of the original is to remove every other sample, and playback at the original playback sampling rate.

However, with this approach, some of the information will be lost, and I would expect that some artifacts will be introduced to the audio, so it's not the most desirable approach.

Although I haven't tried it myself, the idea of averaging the samples to create a new sample to be a good approach to start with. This would seem to mean that rather than just throwing out audio information, it can be "preserved" to an extent by the averaging process.

As a rough idea of the process, here's a piece of pseudocode to double the speed of playback:

original_samples = [0, 0.1, 0.2, 0.3, 0.4, 0.5]

def faster(samples):
    new_samples = []
    for i = 0 to samples.length:
        if i is even:
            new_samples.add(0.5 * (samples[i] + samples[i+1]))
    return new_samples

faster_samples = faster(original_samples)

I've also posted an answered to the a question "Getting started with programmatic audio" where I went into some details about some basic audio manipulation that can be performed, so maybe that might be of interest as well.