Variable Frame Rate content playback using a standard web browser

Accurate Video
Jan 18, 2021

With work being done from remote locations, as a result of the global Covid pandemic, workflows are being pushed to the cloud, for users to access and collaborate on rich media content. This “cloud first” video strategy is accelerating, and the ever increasing demands for web-based video playback requires more sophisticated players and tools, built specifically for B2B use cases, designed around media workflows and broadcast challenges.

Uncompromising content playback frame accuracy is crucial for these use cases, for example to line up time based metadata with video, such as subtitles, to set ad breaks, mark title sequences or flag end credits. Being able to do this on a web-based proxy file, while retaining timecode accuracy of the high resolution original media is paramount.


There are two main pillars in the frame rate world, Variable Frame Rate (VFR) and Constant Frame Rate (CFR). As the name suggests, Constant Frame Rate video is recorded at a fixed frame rate (such as 24FPS for cinematic feature release), while VFR allows for the frame rate to vary actively during recording and playback. VFR can range from 2FPS (typically CCTV footage) to many thousands of FPS, for example when shooting action sequences, or to create other slomo effects, using specialist high speed cameras. So while not exactly a mainstream format, VFR footage continues to pose challenges (including the syncing of audio and video), as any editor who’s worked with mixed frame rate media can attest!

In fact, Variable Frame Rate footage presents a significant technical problem for all current web video players.

Accurate Player VFR

Accurate Player is the most complete web player for broadcast and media professionals, and the goal has always been to support as many different encoding formats, frame rates and timecodes as possible. Accurate Player has always been able to keep video in sync with frame accuracy, given a fixed frame rate.

However, based on a recent customer feature request, our developers looked into whether supporting VFR playback was even possible in a web browser. Well, after some research, a quick Proof Of Concept (POC) and testing, as part of release 3.4.1, we’re pleased to announce that Accurate Player now supports frame accurate playback of video recorded with a variable frame rate, thus solving a significant remote content workflow challenge!

Solving this technical challenge, and then being able to add this as a standard feature to Accurate Player, within just a few weeks, is something we’re quite proud of, and we think this will be useful for many businesses that need frame-accurate, video playback of VFR content in the cloud.

For more information about Accurate Player and this new VFR feature, please get in touch.

vfr variable frame rate