Bitmovin developed a new encoding method for its VOD services to optimise chunk lengths and bitrate distribution, improving visual quality and easing the move toward Per-Shot Encoding.

Bitmovin per shot encoding

Per-shot encoding – now in development – is handled in relation to shot boundaries, resulting in better bitrate distribution. By removing unnecessary I-frames, playback becomes visually smoother.

Bitmovin has optimised its VOD Encoder with Smart Chunking to increase the quality and speed of the software’s split and stitch algorithm. The new functionality optimises chunk lengths and bitrate distribution, improving the visual quality throughout the whole asset. The difference is visible to audiences and results are achieved at a faster pace than before. 

Bitmovin’s Smart Chunking is the next evolution of the split and stitch algorithm, which splits a video file is into multiple parallel encoding jobs. The algorithm accelerates encoding but can cause the quality to drop between segments due to sudden, visible changes in bitrate. Smart Chunking quickly and intelligently optimises chunk lengths and bitrate distribution, ensuring smooth visual quality throughout the whole asset.

To achieve this, Bitmovin decoupled the chunk durations, allowing the chunk sizes to vary depending on the type of codec and the complexity of encoding, which made immediate improvements to the visual quality.

“Smart Chunking is a new innovation that makes it possible for users to encode video files more efficiently, at speed and scale and at the highest quality possible, without compromising other aspects of processing,” said Stefan Lederer, CEO and Co-Founder of Bitmovin. “The changes apply to broadcasters with millions of viewers as well as to more nimble streaming services. All users can take advantage of Smart Chunking through optimised split and stitch encoding that enhances the viewing experience for audiences.”

Bitmovin smart chunking

Lowest 1% of frames increased by 6 VMAF points (the difference noticeable to human eyes); lowest 0.1% frames by 22 VMAF points; the worst frame by 60 VMAF points.

Smart Chunking enhances low-quality frames in assets by up to 60 VMAF (Video Multimethod Assessment Fusion} points based on early customer testing. This amount of difference is visible to audiences, resulting in a noticeably higher quality of experience and giving customers a competitive advantage.

VMAF is an objective video quality measuring system that Netflix developed with image laboratories in the US and France. It predicts subjective video quality based on a reference and a distorted video sequence, and can be used to evaluate the quality of different video codecs, encoders and other factors.

The availability of Smart Chunking also marks Bitmovin’s first stage in making Per-Shot Encoding available to its customers. With Per-Shot Encoding, the video file is divided into shots and each shot is encoded separately, further optimising bitrate efficiencies.