从WasapiLoopbackCapture捕获音频,然后转换为muLaw [英] Capture audio from WasapiLoopbackCapture, and convert to muLaw
问题描述
我正在使用WasapiLoopbackCapture捕获音频
I'm capturing audio with WasapiLoopbackCapture
- format = IeeeFloat
- SampleRate = 48000
- BitsPerSample = 32
我需要将其转换为muLaw(8Khz,8位,单声道)-最终它将通过SIP中继发送到电话.我已经尝试了100个样本(其中大多数样本都使用NAudio)和解决方案,但仍然不知道如何执行此操作...
I need to convert this to muLaw (8Khz, 8 bit, mono) - eventually it'll be sent to a phone via SIP trunking. I've tried 100s of samples (most of them with NAudio) and solutions but still have no clue how to do this ...
推荐答案
NAudio中的Mu-Law工具受到限制,因此您可能必须自己动手.
The Mu-Law tools in NAudio are limited so you might have to roll your own.
您需要设置一个IWaveProvider
过滤器链,以转换为单声道,更改比特率和更改比特深度.
You'll need to set up a chain of IWaveProvider
filters to convert to mono, change bit-rate, and change bit-depth.
waveBuffer = new BufferedWaveProvider(waveIn.WaveFormat);
waveBuffer.DiscardOnBufferOverflow = true;
waveBuffer.ReadFully = false; // leave a buffer?
sampleStream = new WaveToSampleProvider(waveBuffer);
// Stereo to mono
monoStream = new StereoToMonoSampleProvider(sampleStream)
{
LeftVolume = 1f,
RightVolume = 1f
};
// Downsample to 8000
resamplingProvider = new WdlResamplingSampleProvider(monoStream, 8000);
// Convert to 16-bit in order to use ACM or MuLaw tools.
ieeeToPcm = new SampleToWaveProvider16(resamplingProvider);
然后为下一步创建自定义IWaveProvider.
Then create a custom IWaveProvider for the next step.
// In MuLawConversionProvider
public int Read(byte[] destinationBuffer, int offset, int readingCount)
{
// Source buffer has twice as many items as the output array.
var sizeOfPcmBuffer = readingCount * 2;
_sourceBuffer = BufferHelpers.Ensure(_sourceBuffer, sizeOfPcmBuffer);
var sourceBytesRead = _sourceProvider.Read(_sourceBuffer, offset * 2, sizeOfPcmBuffer);
var samplesRead = sourceBytesRead / 2;
var outIndex = 0;
for (var n = 0; n < sizeOfPcmBuffer; n += 2)
{
destinationBuffer[outIndex++] = MuLawEncoder.LinearToMuLawSample(BitConverter.ToInt16(_sourceBuffer, offset + n));
}
return samplesRead * 2;
}
新的提供程序可以直接发送到WaveOut
The new provider can be sent directly to WaveOut
outputStream = new MuLawConversionProvider(ieeeToPcm);
waveOut.Init(outputStream);
waveOut.Play();
这些过滤器保留在原处,并且BufferedWaveProvider为根".每当您调用BufferedWaveProvider.AddSamples()
时,数据都会通过所有这些过滤器.
These filters remain in place with the BufferedWaveProvider as the "root". Whenever you call BufferedWaveProvider.AddSamples()
, the data will go through all these filters.
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