混合16位线性PCM流和避免削波/溢出 [英] Mixing 16 bit linear PCM streams and avoiding clipping/overflow

问题描述

我试图混合2 16bit的线性PCM音频流在一起，我似乎无法克服噪声问题。我想他们是从溢流样品混合在一起的时候来了。

I've trying to mix together 2 16bit linear PCM audio streams and I can't seem to overcome the noise issues. I think they are coming from overflow when mixing samples together.

我有以下功能...

short int mix_sample(short int sample1, short int sample2)
{
    return #mixing_algorithm#;
}

...这里就是我试图为#mixing_algorithm＃

... and here's what I have tried as #mixing_algorithm#

sample1/2 + sample2/2
2*(sample1 + sample2) - 2*(sample1*sample2) - 65535
(sample1 + sample2) - sample1*sample2
(sample1 + sample2) - sample1*sample2 - 65535
(sample1 + sample2) - ((sample1*sample2) >> 0x10) // same as divide by 65535

他们中的一些已经产生比别人更好的结果，但即使是最好的结果，包含了不少噪音。

Some of them have produced better results than others but even the best result contained quite a lot of noise.

任何想法如何解决呢？

推荐答案

下面是一个描述性的实现：

here's a descriptive implementation:

short int mix_sample(short int sample1, short int sample2) {
    const int32_t result(static_cast<int32_t>(sample1) + static_cast<int32_t>(sample2));
    typedef std::numeric_limits<short int> Range;
    if (Range::max() < result)
        return Range::max();
    else if (Range::min() > result)
        return Range::min();
    else
        return result;
}

混合，它只是添加和剪辑！

to mix, it's just add and clip!

要避免削波伪像，你将要使用的饱和或限制器。理想情况下，你将有一个小的 int32_t 与前瞻少量的缓冲。这将引入的延迟。

to avoid clipping artifacts, you will want to use saturation or a limiter. ideally, you will have a small int32_t buffer with a small amount of lookahead. this will introduce latency.

不是限制到处多见，是在你的信号留下几个比特的价值的净空。

more common than limiting everywhere, is to leave a few bits' worth of 'headroom' in your signal.

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