WinUsb_ReadIsochPipe routine

The WinUsb_ReadIsochPipe function reads data from an isochronous OUT endpoint.


BOOL __stdcall WinUsb_ReadIsochPipe(
  _In_     ULONG                       Offset,
  _In_     ULONG                       Length,
  _Inout_  PULONG                      FrameNumber,
  _In_     PULONG                      NumberOfPackets,
  _Out_    PULONG                      IsoPacketDescriptors,
  _In_opt_ LPOVERLAPPED                Overlapped


BufferHandle [in]

An opaque handle to the transfer buffer that was registered by a previous call to WinUsb_RegisterIsochBuffer.

Offset [in]

Offset into the buffer relative to the start the transfer.

Length [in]

Length in bytes of the transfer buffer.

FrameNumber [in, out]

On input, indicates the starting frame number for the transfer. On output, contains the frame number of the frame that follows the last frame used in the transfer.

NumberOfPackets [in]

Total number of isochronous packets required to hold the transfer buffer. Also indicates the number of elements in the array pointed to by IsoPacketDescriptors.

IsoPacketDescriptors [out]

An array of USBD_ISO_PACKET_DESCRIPTOR structures. After the transfer completes, each element contains the status and size of the isochronous packet.

Overlapped [in, optional]

Pointer to an OVERLAPPED structure used for asynchronous operations.

Return value

WinUsb_ReadIsochPipe returns TRUE if the operation succeeds. Otherwise this function returns FALSE, and the caller can retrieve the logged error by calling GetLastError.


WinUsb_ReadIsochPipe packetizes the transfer buffer so that in each interval, the host can receive the maximum bytes allowed per interval. The maximum bytes is as specified by the endpoint descriptor for full and high-speed endpoints, and endpoint companion descriptor for SuperSpeed endpoints. If the caller submits multiple read requests to stream data from the device, the transfer size should be a multiple of the maximum bytes per interval (as returned by WinUsb_QueryPipeEx) * 8 / interval.


Minimum supported client

Windows 8.1

Minimum supported server

Windows Server 2012 R2

Target platform



Winusb.h (include Winusb.h)





See also

WinUSB Functions
Send USB isochronous transfers from a WinUSB desktop app



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