Hello @Engineer, I am trying to convert PCM to AAC Format, the sample rate, channel is same to PCM. I use the code modified upon, but when finish, the sound played was very rapid, What's the problem? let bufferLength = buffer.frameLength var offset: UInt32 = 0 var done = false var data = Data() while !done { let aacBuffer = AVAudioCompressedBuffer(format: outputFormat, packetCapacity: 1, maximumPacketSize: converter.maximumOutputPacketSize) converter.convert(to: aacBuffer, error: nil) { packetCount, inputStatus in let count = min(packetCount, buffer.frameLength - offset) if count == 0 { inputStatus.pointee = .noDataNow return nil } let buffer1 = self.getOffsetBuffer(buffer: buffer, offset: offset, count: count) offset += count inputStatus.pointee = .haveData return buffer1 } data.append(Data(bytes: aacBuffer.data, count: Int(aacBuffer.byteLength))) if offset >= bufferLength { done = true } } return data // To add AAC Header

Have you solved this problem?