To circumvent these limitations, vendors have added proprietary extensions to VfW. Features important to video conferencing, TV viewing, capture of video fields, and ancillary data streams are missing from the VfW architecture. VfW was optimized for capturing movies to disk. Note : This section does not describe the obsolete Video for Windows (VfW) technology. However, the Stream class interface is obsolete, and Microsoft has discontinued its further development. Microsoft provides the Stream class interface for backward compatibility. Microsoft recommends that all new video capture drivers use the AVStream interface.
Vendors can provide additional property sets if needed. Microsoft defines property sets for most standard devices. These data transfers do not require a thread to transition to user mode, thereby avoiding a performance hit.īoth interfaces support a uniform streaming model for standard and custom data types. These interfaces support data transfer between kernel-mode drivers. The AVStream and Stream class interfaces both provide a framework that provide support for integrated devices. With the integration of DVD, MPEG decoders, video decoders and tuners, video port extensions (VPEs), and audio codecs on single adapters, a unified driver model that supports all these devices and handles resource contention simplifies development efforts. For information on creating a minidriver for audio-only devices, the Audio devices Design Guide. It assumes familiarity with concepts discussed in Kernel Streaming. It's dumb.This section describes how to create video capture minidrivers, which follow the Windows Driver Model (WDM) architecture. There are a VERY FEW edge-cases where 1PC capture-carding is needed, but they are exceedingly rare. Game/Window Capture copy the video texture from one spot in the GPU's VRAM to another, staying on-GPU the whole time. And it eats up one of your GPU's output ports (most GPUs only 'get' to run four monitors simultaneously). It's like driving ALL the way across town and back, every time you want to visit your neighbor.Ī capture card in a 1PC has to: Composite the desktop, Output video over the GPU, be intaken by the capture device, (be encoded by the capture device to fit within USB 2.0 bandwidth limitations, on a 2.0 cap device), be transferred over USB into system memory, be decoded by the CPU, be sent over PCIe into the GPU's VRAM.
You only use capture cards for recording other systems. Unless you set up the capture card as an Extended Monitor or Mirrored Display in the OS display settings, your GPU isn't sending any signal, and so color-bars.īut like said, using a capture card will RAISE your overhead in a 1PC setup. Many capture devices will output them when they are not receiving a signal, to show that the capture device is working and outputting captured video to the host system.
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