Introduction; Latency; Dmd Display Device; Image Display - Barco F70 Series User Manual

Image settings and adjustments for optimal latency
B.1 Introduction

Introduction

For projectors used in simulation, latency is always an important component. Barco strives to make latency as
small as possible together with optimal image quality.
There are however some parameters of the installation and setup that affects latency. This white paper
describes these conditions and gives guidance for how to optimize setup of the projector.
B.2 Latency

Latency

Latency is a measurement of the added time the projector needs to display an image. This is measured from
when the first pixel (not v-sync) of an image arrives at the projector until the first light of the same image is
being displayed by the projector. This time is measured in milliseconds. The latency is also referred to as
transport delay.
Different projector settings affect latency. For example, the amount of warp applied to the image might affect
latency since the projector has to wait longer for the required pixels to arrive at the input. As will be shown
later, warping can in certain special settings reduce latency compared to a non-warped image.
In a multi projector setup, different projectors most often have different warp settings and thereby different
latencies. To keep a full system at the same latency and in sync, each projector has the possibility to add to
the latency (transport delay). In a multi-projector setup, all projectors should be set to the same latency as the
projector with the highest transport delay.
B.3 DMD display device

DMD display device

Barco projectors uses a DMD device from Texas Instruments to display the image. A DMD device displays the
intensity of a pixel by time multiplexing the time it is on over the frame time. If one pixel is 50% grey, it is on for
50% of the time for that frame. Since we also change the color of the light during the same frame period, all
the DMD mirrors (pixels) must be displayed synchronously. This is done by dividing the image into bitplanes
and sending the bitplanes one by one to all the mirrors simultaneously. As a simplistic explanation, consider
an 8-bit pr. pixel image. First the LSB bitplane is loaded. All the pixels that has the LSB bit set, has the
corresponding DMD mirror turned on for a short time. Next, the second to last bitplane is loaded, and all the
DMD mirrors where this bit is set are displayed for twice as long. This continues until the MSB (bitiplane 8) is
loaded and displayed.
Because of dividing the image into bitplanes, all pixels of an image must be loaded to the DMD before it can
start to display any of the pixels.
B.4 Image display
Native image
Consider the following setup, where the incoming image has the same resolution as the DMD device.
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