Ce6.0 camera Buffer Management-优快云博客

本文链接：https://blog.youkuaiyun.com/renpine/article/details/6074553

本文介绍了WinCE系统中摄像头缓冲管理的三种模式：CSPROPERTY_BUFFER_DRIVER、CSPROPERTY_BUFFER_CLIENT_LIMITED和CSPROPERTY_BUFFER_CLIENT_UNLIMITED。详细阐述了客户端分配内存和驱动程序分配内存的实现方式，以及在DMA传输中的限制和问题。对于CSPROPERTY_BUFFER_CLIENT模式，由于缓冲区在进程空间分配，不适用于DMA，而CSPROPERTY_BUFFER_DRIVER模式下，尽管能分配连续内存，但使用HalAllocateCommonBuffer或MmMapIoSpace进行DMA操作可能会遇到错误。

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Wince摄像头缓冲管理三种模式：

typedef enum {
    CSPROPERTY_BUFFER_DRIVER = 1,
    CSPROPERTY_BUFFER_CLIENT_LIMITED = 2,
    CSPROPERTY_BUFFER_CLIENT_UNLIMITED = 4
} CSPROPERTY_BUFFER_MODE;

1、CSPROPERTY_BUFFER_CLIENT的两种模式是由CLIENT分配内存，让底层来填充；但并不是如PB帮助所说：

CSPROPERTY_BUFFER_CLIENT_LIMITED

Indicates that the driver's DMA preparation time is slow and that the then the driver needs to know in advance about all of the buffers that it will receive from the client.

CSPROPERTY_BUFFER_CLIENT_UNLIMITED

Indicates that the driver's DMA preparation time is fast and that the client can allocate, initialize, and release buffers as they are needed.

供DMA来传递数据给该缓冲。如果利用提供的测试程序，可看出代码流程：

BOOL CStreamTest::AllocateBuffers()
{
BOOL bReturnValue = TRUE;
ULONG ulBufferIndex;

WaitForSingleObject(m_hMutex, INFINITE);

    if(m_dwAllocationType != CSPROPERTY_BUFFER_CLIENT_LIMITED &&
        m_dwAllocationType != CSPROPERTY_BUFFER_CLIENT_UNLIMITED &&
        m_dwAllocationType != CSPROPERTY_BUFFER_DRIVER)
    {
        ERRFAIL(TEXT("AllocateBuffers : Invalid buffering mode."));
        bReturnValue = FALSE;
        goto cleanup;
    }

PSTREAM_BUFFERNODE pcsCurrentBufferNode = m_pcsBufferNode;

    // get to the end of the list.
    if(pcsCurrentBufferNode)
    {
        while(pcsCurrentBufferNode->pNext)
            pcsCurrentBufferNode = pcsCurrentBuff