用于支持Windows Vista / 7中的回声消除的API

这就是Nick White通过常见问题解答所说的话：

Will echo cancellation work less well for premium content?

We believe that Windows Vista provides applications with access to sufficient information to successfully build high quality echo cancellation functionality.

Windows Vista提供哪些信息以允许应用程序构建高质量的回声消除功能？

Note: Reading that statement,i get the impression that Windows Vista provides sufficient information to allow applications to successfully build high-quality echo cancellation functionality. Presumably the way Windows provides this information is through an API.

回声消除的工作原理是对播放输出进行采样,并从录制的麦克风输入中“减去”.

不幸的是,as MSDN notes,一个不能总是采样播放输出：

Windows Vista provides digital rights
management (DRM). Content providers
rely on DRM to protect their
proprietary music or other content
from unauthorized copying and other
illegal uses. WASAPI does not permit
loopback recording of digital streams
that contain DRM-protected content.
Similarly,a trusted audio driver does
not permit a loopback device to
capture digital streams that contain
protected content. Windows Vista
allows only trusted drivers to play
protected content. For more
information about trusted drivers and
DRM,see the Windows DDK
documentation.

据推测,这意味着使用WASAPI中的Loopback Mode并不是提供回声消除服务的预期方法.

什么是允许实现高质量回声消除的API？

Note: This is related to,but separate from,another question i asked: 07003. This question is specifically looking for an expansion of the response by the Window Vista team that echo-cancellation is possible in Windows. This question is looking for the API; it can be a separate question of how to use it.

谷歌搜索答案,我得到的印象是(在执行回声消除时)允许应用程序对受DRM保护的内容进行采样,但内容将降级(即“足够的信息”).这将使任何回声消除更糟,但仍然可能.

或者Windows团队暗示“足以满足大多数情况,但不是在用户正在收听歌曲或播放电影时” – 并且事实上不可能成功构建高质量的回声消除功能？

更新：应该注意我不是在寻找回声消除API,我正在寻找一个API来对播放输出进行采样 – 这是实现回声消除所需要的.除非Windows Vista提供回声消除API(这是他们继续保护高级内容的方式).但我也没见过回声消除API.