Diva features

Input lag

What the built-in lag tester measures

Input lag is a property of your display rather than of your source, and the only honest way to know it is to measure it. The Diva ships with the light sensor that does exactly that.

Input lag is the delay between a frame arriving at a display's input and that frame appearing on the panel. It is not the same as response time, which describes how quickly a pixel changes once it has been told to. Response time is a matter of a few milliseconds and panel chemistry, while input lag is a matter of processing, and on a television doing everything it knows how to do it can run past a hundred milliseconds.

The processing is the whole cause. Scaling, deinterlacing, noise reduction, motion interpolation and local dimming analysis all need frames buffered before anything can be drawn, and each buffered frame at 60Hz costs about 16.7ms. Game mode exists to switch most of that off, which is why the same set can measure over 100ms in a film preset and under 20ms in game mode. Every device in the path adds its own share, although a pass-through device's contribution is usually small: the Diva's own is quoted as a few pixel clocks.

The lag tester on the HDfury Diva

The Diva draws a square on the picture and times how long the supplied sensor takes to see it change. Plug the lag tester cable into the IR sensor input on the back, the same jack the IR RX cable uses, then work in the TOOLS section of the web server.

1. Tick ACTIVATE LAG TEST. A squared window appears on the active video from TX1.
2. Set TARGET to left top, centre, or right bottom.
3. Stick the sensor to the screen so that it sits over the square.
4. Click START TEST and read the result in the top left corner of the screen, reported through the OSD in milliseconds to one decimal place.

Over IP or RS232 the same three controls are set lagtestenable 1, set lagtesttarget 1 and set lagteststart. The measurement works on the TX1 output only, which is what makes testing a 4K HDR signal awkward: TX1 is the 1080p SDR output, so you connect TX1 back into a Diva input, route that input to TX0, and put the display under test on TX0. For the figure to mean anything the scaling must be at defaults, with AUTOSCALING enabled, the presets at AUTOSENSE with UPSCALING enabled, and HDR to SDR conversion for TX0 disabled by selecting Profile 0-OFF.

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