如何用 AVAssetReader 读取视频文件中,多个轨道的音频数据,保存到 AVAudioPCMBuffer 中
要使用 AVAssetReader
读取视频文件中的多个音频轨道,并将音频数据保存到 AVAudioPCMBuffer
中,你可以按照以下步骤进行操作:
创建 AVAssetReader:首先,创建一个 AVAsset
实例并初始化 AVAssetReader
。
获取音频轨道:从 AVAsset
中获取所有音频轨道。
创建 AVAssetReaderTrackOutput:为每个音频轨道创建一个 AVAssetReaderTrackOutput
。
开始读取:启动 AVAssetReader
并读取音频数据,将其保存到 AVAudioPCMBuffer
中。
以下是一个示例代码,展示了如何实现这些步骤:
import AVFoundation
func readAudioTracks(from url: URL) {
// 创建 AVAsset
let asset = AVAsset(url: url)
// 创建 AVAssetReader
guard let assetReader = try? AVAssetReader(asset: asset) else {
print("Failed to create AVAssetReader")
return
}
// 获取所有音频轨道
let audioTracks = asset.tracks(withMediaType: .audio)
// 创建一个数组来保存所有的 AVAssetReaderTrackOutput
var trackOutputs: [AVAssetReaderTrackOutput] = []
for track in audioTracks {
let trackOutput = AVAssetReaderTrackOutput(track: track, outputSettings: [
AVFormatIDKey: kAudioFormatLinearPCM,
AVLinearPCMIsNonInterleaved: true,
AVLinearPCMBitDepthKey: 16,
AVLinearPCMIsFloatKey: false,
AVLinearPCMIsBigEndianKey: false
])
if assetReader.canAdd(trackOutput) {
assetReader.add(trackOutput)
trackOutputs.append(trackOutput)
}
}
// 开始读取
assetReader.startReading()
// 创建一个数组来保存所有的 AVAudioPCMBuffer
var audioBuffers: [AVAudioPCMBuffer] = []
for trackOutput in trackOutputs {
while let sampleBuffer = trackOutput.copyNextSampleBuffer() {
guard let blockBuffer = CMSampleBufferGetDataBuffer(sampleBuffer) else { continue }
var length = 0
var dataPointer: UnsafeMutablePointer<Int8>?
CMBlockBufferGetDataPointer(blockBuffer, atOffset: 0, lengthAtOffsetOut: &length, totalLengthOut: &length, dataPointerOut: &dataPointer)
let formatDescription = CMSampleBufferGetFormatDescription(sampleBuffer)!
let audioStreamBasicDescription = CMAudioFormatDescriptionGetStreamBasicDescription(formatDescription)!.pointee
let audioBuffer = AVAudioPCMBuffer(pcmFormat: AVAudioFormat(streamDescription: &audioStreamBasicDescription)!, frameCapacity: AVAudioFrameCount(length) / audioStreamBasicDescription.mBytesPerFrame)
audioBuffer.frameLength = audioBuffer.frameCapacity
let audioBufferList = audioBuffer.mutableAudioBufferList.pointee
let audioData = audioBufferList.mBuffers.mData!
memcpy(audioData, dataPointer, length)
audioBuffers.append(audioBuffer)
}
}
// 处理读取到的音频数据
for buffer in audioBuffers {
// 在这里处理每个 AVAudioPCMBuffer
print("Read audio buffer with \(buffer.frameLength) frames")
}
}
AVAsset
实例。AVAsset
初始化 AVAssetReader
。AVAsset
中获取所有音频轨道。AVAssetReaderTrackOutput
,并添加到 AVAssetReader
中。AVAssetReader
并读取音频数据,将其保存到 AVAudioPCMBuffer
中。请注意,这个��例代码假设音频