Software update version 184.108.40.206 to the Amazon Fire TV has added the ability to configure the media player so that it adjusts your TVs refresh rate to match the frame rate of the video content being played. This is a feature that home theater enthusiasts have been wanting for a long time because it eliminates video judder and results in a perfectly smooth one-to-one correlation between the frames of a video and the frames being shown on the TV.
Before getting into how this new Fire TV feature works, lets briefly discuss why it exists in the first place. By default, the Fire TV, as with most media players, sets your TV to a refresh rate of 59.94 Hz. This means that the image being displayed by the Fire TV is updating about 60 times per second. The higher the refresh rate, the smoother moving objects will appear. This allows the animations and movements seen when navigating around the Fire TV user interface or inside an app to appear crisp and responsive.
Most movies and TV shows are recorded at 23.976 frames per second (fps). Why such an odd frame rate is used is not important for this discussion, but it’s the source of the issues that the frame rate matching feature fixes. Since, by default, the Fire TV is updating the TV image 59.94 times per second, it needs to figure out how to display the 23.976 frames per second of most videos within the 59.94 refresh rate. If a 59.94 fps video was being played, it would simply display one frame every time it updated the TV image. But since 23.976 does not divide evenly into 59.94, the Fire TV must show some frames more often than other frames.
When playing a 23.976 fps video on a TV set to a refresh rate of 59.94 Hz, which was the only option prior to the new frame rate matching feature, the Fire TV must constantly switch between showing a frame 3 times and then showing the next frame 2 times. This results in something called video judder, which makes motion and camera pans in videos appear choppy because you are literally seeing half of the frames more often than the other half.
The solution to eliminating video judder is to simply display every frame in a video only once. The way to achieve this is to set the TV’s refresh rate to the same value as the videos frame rate. If a 23.976 fps video is being played, then the TV should be set to 23.976 Hz so that the image on the TV only updates once per video frame.
This is exactly what the new frame rate matching feature of the Amazon Fire TV does. When enabled, it will change your TVs refresh rate to exactly match every video you start to play. If the video you begin playing is shot at 59.94 fps, then the TV does not need to be updated because that is the default frame rate of the Fire TV user interface. But when you play a video with any other frame rate, the Fire TV will adjust your TV’s refresh rate just before the video begins to play when you have frame rate matching enabled.
The new frame rate matching option is currently only available on the 3rd generation Fire TV (Pendant). It will very likely be added to the Amazon Fire TV Cube in a future update, but it is unknown at this time if other Fire TV, Fire TV Stick, or Fire TV Edition television models will also gain this feature. To enable the new feature, change the option under Settings > Display & Sound > Display > Match Original Frame Rate to ON. In order to turn on the feature, you must have your Fire TV’s Video Resolution setting set to Auto.
For the frame rate matching feature to work, the app used to play the video must support it. At this time, all videos through Amazon Prime Video will correctly take advantage of this new feature, but most apps, such as Netflix, have not yet been updated to use the feature. With the frame rate matching feature enabled, videos played in unsupported apps will simply play at a refresh rate of 59.94 Hz, just as they have always played. There’s no need to toggle the feature off when using apps that don’t support the feature. The only other apps that currently support this feature are the media player apps MrMC, Kodi, and Plex.
To use frame rate matching for Amazon Prime Video content, simply enable the feature under settings and play any video as usual. Immediately after pressing play on Amazon content, the Fire TV will display the text “Adjusting Video Frame Rate…” for a split second as it changes your TV’s refresh rate to match the frame rate of the video being played. This message does not appear within 3rd-party apps that support refresh rate matching. Once the video ends, the TV will switch back to a refresh rate of 59.94 Hz just before returning to the user interface.
In addition to enabling the refresh rate matching feature in the Fire TV’s settings, you may also need to enable the option inside the app you use to play video. In MrMC, you’ll need to go into Settings > Video > Playback and set the “Adjust display refresh rate” option. You’ll need to change the settings mode from “Basic” to “Advanced” or “Expert” for this option to appear. In Kodi, the setting is under Settings > Player Settings > Videos. Likewise, Kodi’s settings mode will need to be changed from “Basic” to “Standard” or higher to see the option. In Plex, you’ll need to change the “Refresh Rate Switching” option to “On” under Settings > Advanced.
The biggest downside to this new feature is that most TVs will display a black screen for a few seconds every time the refresh rate is updated. The amount of time it takes for the TV to change to a new refresh rate is completely dependent on the TV and has nothing to do with the Fire TV. Some TVs feature dynamic refresh rates that can change on-the-fly instantaneously without displaying a black screen, but most will take a second or two to switch. Since this will happen every time a video starts and again when it stops, some people don’t find the frame rate matching feature worth the inconvenience of waiting for the TV to adjust. A compromise could be to leave the feature off for regular day-to-day viewing, but flip it on for movie night or highly anticipated movies and shows.
In my testing, the Fire TV correctly switched the TV to a refresh rate of 23.976Hz, 24Hz, 25Hz, 29.97Hz, 30Hz, 50Hz, 59.94Hz, and 60Hz when a video of each matching frame rate was played. I did verify that it does correctly use fractional refresh rates. This means that, for example, it does not use 24Hz for a 23.976fps video. A 23.976fps video uses a 23.976Hz refresh rate. Refresh rate switching occurs both in 4K, 1080p, and lower resolutions.
The only oddity I encountered is that the Fire TV sometimes set the TV to a refresh rate that was double the video frame rate, instead of using the exact refresh rate. This resulted in a 25fps file using a 50Hz refresh rate, a 29.97fps file using 59.94Hz, and a 30fps file using 60Hz. This is fine because it means each frame is displayed exactly twice and achieves the exact same effect as using an exactly matching frame rate. Remember, unwanted video judder occurs when the frames cannot be evenly divided into the refresh rate, so a TV refresh rate that is double the frame rate of the video does not have a negative effect. Interestingly, this doubling behavior did not always occur. For example, playing the first episode of the second season of The Grand Tour, which is a 25fps video because it was shot in the UK, used a 25Hz refresh rate, but playing a 25fps video in MrMC used a 50Hz refresh rate, so it might be dependent on the app being used.
MrMC has informed me that they deliberately use a refresh rate that is double the video frame rate, whenever possible, in order to preserve UI smoothness. Kodi and Plex likely adopted MrMC’s open source code, since MrMC was the first to support frame rate matching. This means that 25fps, 29.97fps, and 30fps videos will use a 50Hz, 59.94Hz, and 60Hz refresh rate, respectively, in all three apps when possible. Additionally, some TVs struggle, and even flicker slightly, when set to low refresh rates, so doubling the frame rate when it has no negative consequences alleviates those issues as well.
If you want to verify that the correct refresh rates are being used, you should enable the “System X-Ray” setting and “Advanced Options” setting in the Fire TV’s hidden Developer Tools Menu. The menu can be opened by holding the SELECT and DOWN button for 5 seconds and then pressing the MENU button on the remote. The System X-Ray setting will display a bar across the top of your screen. The number after the 2160p/1080p/720p resolution value is the current refresh rate of your TV. While in the Fire TV interface it will likely be 59.94 and will change once a video begins playing and your TV’s refresh rate is updated. Note that the value displayed is truncated to 2 decimal places, so when the refresh rate is set to 23.976, it will be listed as 23.97 in the System X-Ray bar.
Enabling the “Advanced Options” setting in the Developer Tools Menu will display a box on the right side of the screen that contains information about the video currently being played. The most important value for this scenario is the one labeled “Frame Rate” under the “VIDEO” section. This value is like a running average of the actual playback frame rate, so it might not exactly match the frame rate you’re expecting at first, but it should eventually level off to list the video’s actual frame rate. Sample files to use for testing various frame rates can be found here.
Additionally, most TVs have a way of displaying information about the current resolution settings of the TV. This sometimes includes information about the current refresh rate. That can also help you determine if your Fire TV is correctly switching and using the refresh rates you’re expecting. However, be aware that some TVs will round decimal refresh rate values to whole numbers, so even though the Fire TV might actually be using a refresh rate of 23.976Hz, the TV might incorrectly display it as 24Hz.
Lastly, the Fire TV will only switch your TV to refresh rates that it detects your TV supports, so the full list of refresh rates listed above may not be available to you with your particular TV. Devices like AV Receivers or HDMI switches connected between the Fire TV and your TV could prevent your Fire TV from correctly detecting your TV’s refresh rate capabilities. If you suspect this is happening, try connecting your Fire TV directly to your TV’s HDMI input.