为什么 MCI_OPEN 失败并返回无效的设备 ID？

发布于 2024-08-20 10:25:01 字数 220 浏览 4 评论 0原文

dwReturn = mciSendCommand(0, MCI_OPEN, MCI_OPEN_ELEMENT | MCI_OPEN_TYPE
                         , (DWORD_PTR)(LPVOID) &mciOpenParms);

错误消息是“设备名称已被此应用程序用作别名。请使用唯一的别名。”

为什么会出错？

原文

dwReturn = mciSendCommand(0, MCI_OPEN, MCI_OPEN_ELEMENT | MCI_OPEN_TYPE
                         , (DWORD_PTR)(LPVOID) &mciOpenParms);

error -message is "The device name is already being used as an alias by this application. Use a unique alias."

Why is it giving an error ?

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栀子花开つ 2024-08-27 10:25:01

虽然从技术上讲是正确的，但这个答案对我没有多大帮助。

“如果在最初打开设备或文件时未指定 MCI_OPEN_SHAREABLE 标志，则对该设备或文件的所有后续 MCI_OPEN 命令都将失败。”

我发现我必须在任何 MCI_OPEN 之前执行 MCI_CLOSE，如下所示：

MciClose(void)
{
 int Result;
 MCI_GENERIC_PARMS mciGenericParams;
 DWORD dwFlags;

 mciGenericParams.dwCallback = (long)TestSoundForm->Handle;

 dwFlags = MCI_NOTIFY | MCI_WAIT;
 Result = mciSendCommand(MciDeviceID, MCI_CLOSE, dwFlags, (long)&mciGenericParams);

 // MCIERR_INVALID_DEVICE_ID occurs if the device is already closed.
 if(Result == 0 || Result == MCIERR_INVALID_DEVICE_ID)return;
 else MciError(Result, "MCI_CLOSE  Error"); // display the error
}

另外，这里有一篇关于对这些音频设备进行编程的非常好的文章。

http:// www.c-sharpcorner.com/uploadfile/GemingLeader/creating-a-sound-recorder-in-c-and-C-Sharp/

While technically correct, this answer didn't help me much.

"If the MCI_OPEN_SHAREABLE flag is not specified when a device or file is initially opened, all subsequent MCI_OPEN commands to the device or file will fail."

I found I had to do an MCI_CLOSE before any MCI_OPEN, like this:

MciClose(void)
{
 int Result;
 MCI_GENERIC_PARMS mciGenericParams;
 DWORD dwFlags;

 mciGenericParams.dwCallback = (long)TestSoundForm->Handle;

 dwFlags = MCI_NOTIFY | MCI_WAIT;
 Result = mciSendCommand(MciDeviceID, MCI_CLOSE, dwFlags, (long)&mciGenericParams);

 // MCIERR_INVALID_DEVICE_ID occurs if the device is already closed.
 if(Result == 0 || Result == MCIERR_INVALID_DEVICE_ID)return;
 else MciError(Result, "MCI_CLOSE  Error"); // display the error
}

Also, here is a very nice article on programming these audio devices.

http://www.c-sharpcorner.com/uploadfile/GemingLeader/creating-a-sound-recorder-in-c-and-C-Sharp/

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