如何多次跳转到特定偏移量？

发布于 2024-07-12 03:46:50 字数 578 浏览 9 评论 0原文

想象一下这个函数：

void SoundManager::playSource(ALuint sourceID, float offset)
{
    alSourceStop(sourceID);

    ALint iTotal = 0;
    ALint iCurrent = 0;
    ALint uiBuffer = 0;
    alGetSourcei(sourceID, AL_BUFFER, &uiBuffer);
    alGetBufferi(uiBuffer, AL_SIZE, &iTotal);
    iCurrent = iTotal * offset;

    alSourcei(sourceID, AL_BYTE_OFFSET, iCurrent);
    alSourcePlay(sourceID);
}

这个想法是调用 playSource(x, 0.5f) 会跳转到（大约）缓冲区的一半，等等。

我第一次调用它时它工作正常，但如果我调用它再次在同一源上（无论该源是否正在播放）它开始播放，就好像我用偏移量 0 调用它一样。

有什么想法吗？

原文

Imagine this function:

void SoundManager::playSource(ALuint sourceID, float offset)
{
    alSourceStop(sourceID);

    ALint iTotal = 0;
    ALint iCurrent = 0;
    ALint uiBuffer = 0;
    alGetSourcei(sourceID, AL_BUFFER, &uiBuffer);
    alGetBufferi(uiBuffer, AL_SIZE, &iTotal);
    iCurrent = iTotal * offset;

    alSourcei(sourceID, AL_BYTE_OFFSET, iCurrent);
    alSourcePlay(sourceID);
}

The idea is calling playSource(x, 0.5f) would jump to (roughly) halfway through the buffer, etc.

It works fine the first time I call it, but if I call it again on the same source (whether that source is playing or not) it begins playing as though I'd called it with offset 0.

Any ideas why?

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反差帅 2024-07-19 03:46:50

解决了！

尽管 API 声称设置偏移量适用于任何状态的源，但问题是我应该在开始时调用 alSourceRewind 而不是 alSourceStop。

看来设置偏移量仅适用于处于 AL_INITIAL 状态的源。

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离去的眼神 2024-07-19 03:46:50

你可以先播放音频文件，然后像这样调用setOffset，不需要调用alSourcePlay：

- (BOOL)setOffset:(float)offset
{
  ALint iTotal = 0;
  ALint iCurrent = 0;
  ALint uiBuffer = 0;
  alGetSourcei(_sourceID, AL_BUFFER, &uiBuffer);
  alGetBufferi(uiBuffer, AL_SIZE, &iTotal);
  iCurrent = iTotal * offset;
  alSourcei(_sourceID, AL_BYTE_OFFSET, iCurrent);
  return ((_error = alGetError()) != AL_NO_ERROR);
}

you can play the audio file first,then call setOffset like this,don't need to call alSourcePlay:

- (BOOL)setOffset:(float)offset
{
  ALint iTotal = 0;
  ALint iCurrent = 0;
  ALint uiBuffer = 0;
  alGetSourcei(_sourceID, AL_BUFFER, &uiBuffer);
  alGetBufferi(uiBuffer, AL_SIZE, &iTotal);
  iCurrent = iTotal * offset;
  alSourcei(_sourceID, AL_BYTE_OFFSET, iCurrent);
  return ((_error = alGetError()) != AL_NO_ERROR);
}

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