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[英]Convert CMSampleBuffer to AVAudioPCMBuffer to get live audio frequencies
[英]How to create AVAudioPCMBuffer with CMSampleBuffer?
我有一個AVAsset
並且我使用AVAssetReaderAudioMixOutput
來獲取CMSampleBuffer
,我想使用這個CMSampleBuffer
創建AVAudioPlayerNode
來scheduleBuffer
怎么辦,有人幫忙嗎?
extension AVAudioPCMBuffer {
static func create(from sampleBuffer: CMSampleBuffer) -> AVAudioPCMBuffer? {
guard let description: CMFormatDescription = CMSampleBufferGetFormatDescription(sampleBuffer),
let sampleRate: Float64 = description.audioStreamBasicDescription?.mSampleRate,
let channelsPerFrame: UInt32 = description.audioStreamBasicDescription?.mChannelsPerFrame /*,
let numberOfChannels = description.audioChannelLayout?.numberOfChannels */
else { return nil }
guard let blockBuffer: CMBlockBuffer = CMSampleBufferGetDataBuffer(sampleBuffer) else {
return nil
}
let samplesCount = CMSampleBufferGetNumSamples(sampleBuffer)
//let length: Int = CMBlockBufferGetDataLength(blockBuffer)
let audioFormat = AVAudioFormat(commonFormat: .pcmFormatFloat32, sampleRate: sampleRate, channels: AVAudioChannelCount(1), interleaved: false)
let buffer = AVAudioPCMBuffer(pcmFormat: audioFormat!, frameCapacity: AVAudioFrameCount(samplesCount))!
buffer.frameLength = buffer.frameCapacity
// GET BYTES
var dataPointer: UnsafeMutablePointer<Int8>?
CMBlockBufferGetDataPointer(blockBuffer, atOffset: 0, lengthAtOffsetOut: nil, totalLengthOut: nil, dataPointerOut: &dataPointer)
guard var channel: UnsafeMutablePointer<Float> = buffer.floatChannelData?[0],
let data = dataPointer else { return nil }
var data16 = UnsafeRawPointer(data).assumingMemoryBound(to: Int16.self)
for _ in 0...samplesCount - 1 {
channel.pointee = Float32(data16.pointee) / Float32(Int16.max)
channel += 1
for _ in 0...channelsPerFrame - 1 {
data16 += 1
}
}
return buffer
}
}
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