Is the Wii U GamePad faster than the TV?
Put simply, the Wii U hardware is capable of rendering and transmitting two different frames, one for the console and the other for the controller in order to offer different images. Alternatively, many video games such as New Super Mario Bros. U, Batman: Arkham City, and Call of Duty: Black Ops 2 can replicate what happens on the home screen, allowing players to continue playing away from the TV. Actual distance may vary, but we were impressed with the ability to play in other rooms, up to 10 meters away and with no direct line of sight to the console.
This feature allowed us to accurately measure the time required to encode and transmit the image from the console to the pad. We had done a similar analysis in the past only to find that the end result was too good to be true: with the pads connected to the console by cable (a feature of the debug console), the tablet was 116 thousandths faster. second to LG's high-definition TV brought by Nintendo to the event. When the final version of the retail hardware arrived in our hands, it was time to take a more precise measurement.
Measuring the delay of the image display on the pad screen is a two-step process: all modern HDTVs have a certain latency value, so to perform the test we had to choose one with a known value . This is where the PlayStation 3D monitor comes into play. In our test, we found that all inputs on it had a latency of two frames (33 milliseconds) regardless of resolution. To be doubly sure of the validity of the test, we re-measured the display using a latency monitor developed by Ben Heck. Previously, we had verified that Forza Motorsport 4 has a response time of 4 frames or 66 milliseconds. The PlayStation 3D screen generated a latency of six frames, confirming our initial result of two frames of latency.
The next step was to connect the Wii U to the same screen, place the gamepad directly in front of it. and film the two screens using a high-speed video camera. We chose New Super Mario Bros. U as our test game due to its 60 frames per second with vertical sync, producing a unique frame with every single screen refresh. With confirmed baseline tests and such a stable game, any difference in updating the two screens would have been helpful in getting a reliable result.
"Even when computing encoding, transmitting and decoding, the GamePad possesses almost identical to the PlayStation 3D screen connected to the Wii U via HDMI. "
The result testifies to the excellent transmission technology used by Nintendo, with no visible difference between the update of the main screen and that of the GamePad. We have slowed down the camera recording to better show the test results. The quality is not excellent but the sequences speak for themselves: the two screens update simultaneously at a distance of one frame, confirming an average latency of about 33 milliseconds. A very remarkable result.
How have such performances been achieved? A recent Polygon article suggests that Nintendo worked closely with Broadcom (responsible for the Raspberry PI core chip among other things) to adapt an existing technology called Miracast to the Wii U whose principles are similar to Apple's AirPlay. . The video is encoded using the h.264 compression system, then transmitted via WiFi with 802.11n protocol to the receiver, where it is decoded and displayed. The difference is that the connection is established directly rather than through a router, which significantly reduces latency times allowing Nintendo to standardize and optimize the connection.
Compression is a fundamental factor due to high volume of data. An uncompressed 24-bit RGB stream with a resolution of 854x480 and 60 frames per second would require a transfer rate of 72MB per second, which is far too much for a WiFi connection. Significantly reducing the color space of the image reduces the value by up to 36 MB per second. A compression technology such as h.264 could reduce this value by ten times with a barely noticeable loss of quality. The direct connection between the two devices could also open the doors to the use of MPEG compression, which is less expensive from a computational point of view and often used for those applications where latency is a fundamental factor. Using it, the 802.11n wireless standard should be able to support the transfer of a 480p video stream at 60Hz.
Beyond the technical subtleties, our tests have shown that the Nintendo-developed GamePad offers video playback at very stable low latency. Bearing in mind that many HDTVs operate at much higher lag levels, this is a significant achievement. For many users, the GamePad screen will even transmit a video stream marginally faster than that of the main display.
