Motion Vector Interpolation for Smooth Video Playback Speed Variation
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Solution Overview
Problem
Current video playback technologies struggle to smoothly vary playback speed without introducing stuttering effects, especially when reducing frame rates below 18-20 frames per second, and increasing speed can result in missing frames or visual stutter, due to limitations in existing video encoding and compression standards.
Innovation Solution
The system encodes and plays back video at adjustable speeds by interpolating frames using motion vectors, which describe the movement of pixels between frames, allowing for smooth playback by generating new frames as needed to maintain a desired frame rate, even at reduced frame rates, and storing these vectors to facilitate interpolation during playback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If video playback speed is reduced below 18-20 frames per second, then bandwidth consumption is reduced, but stuttering effect occurs and motion smoothness deteriorates
Solution Approach 1:
The system pre-calculates and stores motion vectors between keyframes during encoding, enabling the playback device to generate intermediate frames in real-time without requiring additional bandwidth. The motion vectors are prepared in advance and embedded in the encoded video stream, allowing smooth playback at reduced frame rates.
Solution Approach 2:
Motion vectors serve as an intermediary data structure that bridges keyframes, enabling the generation of intermediate frames through interpolation. These vectors contain displacement information that acts as a mediator between reference frames and target frames, allowing smooth motion representation without transmitting every frame.
2Reliability
If video is encoded at higher frame rates (e.g., 60 fps), then motion smoothness is improved, but bandwidth requirements increase significantly
Solution Approach 1:
The system extracts only the essential motion information (motion vectors) from between frames and stores this compact representation separately from the full frame data. By taking out only the necessary displacement information rather than transmitting complete intermediate frames, bandwidth consumption is dramatically reduced while preserving motion smoothness.
Solution Approach 2:
The system changes the representation parameters of video data by using motion vectors (displacement fields) instead of full frame pixel data. This parameter transformation allows the same motion information to be represented with far fewer bits, enabling high frame rate playback quality at lower bandwidth costs.
3Quantity of substance
If frames are decimated to reduce video size, then storage and transmission requirements are reduced, but interpolation quality may deteriorate without proper motion data
Solution Approach 1:
The encoding process performs preliminary computation of motion vectors between keyframes and embeds this motion data in the compressed video stream. This pre-prepared motion information ensures that when frames are decimated and need to be interpolated during playback, high-quality reconstruction is possible without requiring additional data.
4Productivity
If playback speed is increased, then viewing efficiency is improved, but frames may be missing causing visual stutter
Solution Approach 1:
Motion vectors act as intermediaries that enable the generation of additional frames during playback. When playback speed is increased, these vectors allow the system to create missing intermediate frames through interpolation, ensuring visual continuity is maintained even when the playback timeline is compressed.
Data Source
AI summary
Systems and methods for encoding and playing back video at adjustable playback speeds by interpolating frames to achieve smooth playback in accordance with embodiments of the invention are described. One embodiment includes a source encoder that includes a processor, memory including an encoder application, where the encoder application directs the processor to: select a subset of frames from a first video sequence; generate motion vectors describing frames from the first video sequence that are not part of the selected subset of frames, where each motion vector describes movement between a frame in the subset of frames and a frame not included in the subset of frames; store the motion vectors; decimate frames not included in the subset of frames from the first video sequence to generate a second video sequence having a nominal frame rate less than the frame rate of the first video sequence; and encode the second video sequence at the nominal frame rate.