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我目前正在为 Mac OS 构建一个游戏音乐播放器，使用GME生成声音缓冲区和SDL用于音频播放。我以前（并且成功地）使用SDL_QueueAudio进行播放，但我需要对缓冲区处理进行更精细的控制，以确定歌曲进度、歌曲结束等。所以，这让我在SDL_AudioSpec API 中使用了 SDL_AudioCallback。

我可以听到歌曲播放，但伴随着噪音和失真（有时会根据我的尝试而回声）。

设置

var desiredSpec = SDL_AudioSpec()
desiredSpec.freq = Int32(44100)
desiredSpec.format = SDL_AudioFormat(AUDIO_U8)
desiredSpec.samples = 512
desiredSpec.channels = 2
desiredSpec.callback = { callback(userData: $0, stream: $1, length: $2) }

SDL_OpenAudio(&desiredSpec, nil)

打回来

func callback(userData: UnsafeMutableRawPointer?, stream: UnsafeMutablePointer<UInt8>?, length: Int32) {
    // Half sample length to compensate for double byte Int16.
    var output = Array<Int16>.init(repeating: 0, count: Int(length / 2))

    // Generates stereo signed Int16 audio samples.
    gme_play(emulator, Int32(output.count), &output)

    // Converts Int16 samples to UInt8 samples expected by the mixer below. Then adds to buffer.
    var buffer = [UInt8]()
    for i in 0 ..< (output.count) {
        let uIntVal = UInt16(bitPattern: output[i])
        buffer.append(UInt8(uIntVal & 0xff))
        buffer.append(UInt8((uIntVal >> 8) & 0xff))
    }

    SDL_MixAudio(stream, buffer, Uint32(length), SDL_MIX_MAXVOLUME)
}
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1 回答 1

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解决了！最后，这足以让它发挥作用：

desiredSpec.format = SDL_AudioFormat(AUDIO_S16)

var buffer = Array<Int16>(repeating: 0, count: Int(length / 2))
gme_play(emulator, Int32(output.count), &output)
SDL_memcpy(stream, buffer, Int(length))
于 2020-07-20T11:23:06.033 回答