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      Variable frame rate conversion

      What is variable frame rate?

      Variable frame rate (VFR) is a way of encoding video in which the number of frames, or images, displayed per second can vary. In contrast, a constant frame rate (CFR) means that the number of frames displayed per second is fixed.

      Variable frame rate can be used to encode video in a more efficient way since it allows the number of frames to be adjusted based on the complexity of the scene being depicted. This can result in smaller file sizes compared to constant frame rate videos. However, it can also cause problems when used in video editing software, on certain platforms, including WorkCast, and when played back on some devices. 

      Many platforms which support video playback, such as WorkCast, and most video editing software, are designed to work with constant frame rate videos. Due to this, when a video with a VFR is added, they will try to stabilise the frame rate, which can cause the audio and visuals to become out of sync.

      Another problem with variable frame rate video is that it can cause playback issues, such as choppy or uneven video, when viewed on devices that do not support VFR. Some devices, such as TVs and older computers, may not be able to handle VFR and may experience playback issues as a result

      How to tell if a video has a variable frame rate

      • Download the video file to your device, if it's not already stored locally

      • Once the media has downloaded, go to your ‘Downloads’ folder and right-click the MP4 file, then click ‘Properties’:

      • In the ‘Properties’ section, click the ‘Details’ tab, and scroll down until you see the ‘Video’ and ‘Audio’ details:

      • The frame rate should be a whole number (e.g. 30.00 FPS). If the frame rate number is not a whole number (e.g. 30.303 FPS), this is generally an indication that the media is variable frame rate. 

      Many video files include metadata that contains information about the frame rate of the video. This can be checked with a third-party tool such as MediaInfo to view the metadata for a video file and see if it has a variable or constant frame rate. For more information on how to install and use MediaInfo, please click here.

      How to convert variable frame rate to constant frame rate using HandBrake

      1. Download and install HandBrake to your device via the Handbrake website (https://handbrake.fr/)

      2. Open HandBrake and click on the "File" button within Source Selection to select the MP4 you have created in PowerPoint, or you can drag and drop the file into HandBrake.

      3. When your file loads, the “Output Settings" section will be presented on screen, and you will be in the "Summary" tab by default.

      4. Go to the "Video" tab.

      5. Set the “Video Encoder” to “H.264 (x264).

      6. Choose a frame rate value in the "Framerate" field. Set the frame rate to 30 frames per second (30 FPS is the correct frame rate to use for the WorkCast platform, but for other purposes, this may differ)

      7. Below the "Framerate (FPS)" dropdown, ensure that "Constant" is selected.

      8. Set the "Quality" to "Average Bitrate (kbps) and set a value of 1500kbps. (1500kbps is the correct frame rate to use for a WorkCast Interactive event, but for other purposes, this may differ)

      9. You can select the location you would like to save the file to by clicking the “Browse” button at the bottom right of the window, select the desired location and choose a name for your output file and click “Save”.

      10. Click on the "Start Encode" button to begin the conversion process.

      11. When the conversion is complete, upload your Constant Frame Rate media to your WorkCast account.