Enabling Render Scaling on Port Encoders without Hardware Scaling

The Intel^® EMGD Render Scaling feature allows the driver to support any one of the standard modes (640x480, 800x600, 1024x768 or 1280x1024) as a drawable framebuffer size output to a native panel and connected via a port encoder that does not hardware scale. To achieve this, the GPU engine repeats all rendering operations twice (from the original OS-targeted back buffer) to a separate front buffer, which is rendered via the 3D engine for scaling. This feature is enabled by turning on the “Panel-Fit” attribute (“0x12”) on a port driver that does not support that attribute. But this only happens if there is a native mode timing (see Upscaling for the Chrontel CH7308 LVDS Transmitters for information about how native mode timing is determined).

Users should be aware that this feature can impact performance and produce scaled output which is inferior in quality to hardware encoder scaling.