Video Compression for Low-Power Always-On Camera Systems
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Solution Overview
Problem
Existing image sensing systems face challenges in recording and preserving pre-event video data while maintaining low power consumption, especially in battery-powered devices, due to high bit error rates at extreme low voltages and the need for efficient video compression and error handling.
Innovation Solution
An always-on image sensing system with an extreme low-power domain that captures and stores pre- and post-event video using a low-power semiconductor memory, employing video compression techniques like colorspace reduction and resynchronization codes to manage bit errors, and transfers data to nonvolatile memory or digital radio for further processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If video data is stored in extreme low-power semiconductor memory, then power consumption is reduced, but bit error rate increases
Solution Approach 1:
Resynchronization codes are injected into the video stream before storage in low-power memory. These codes serve as advance markers that enable the decoder to recover from bit errors without propagating corruption throughout the entire stream, thus preparing the system in advance to handle the high bit error rates inherent in low-voltage memory operation.
Solution Approach 2:
The patent converts the harmful effect of high bit error rates in low-power memory into a manageable issue by implementing error recovery mechanisms. The resynchronization codes transform the potential catastrophic failure mode (complete stream corruption) into a localized error that can be recovered from, effectively turning the harm of low-voltage operation into a controlled challenge with known solutions.
2Quantity of substance
If video compression is applied to reduce data size, then storage requirements are reduced, but decompression complexity and error propagation risk increase
Solution Approach 1:
The video stream is segmented into blocks with resynchronization codes injected at regular intervals. This segmentation divides the continuous video stream into manageable segments that can be independently decoded and error-checked, reducing the complexity of error handling while maintaining compression efficiency.
3Reliability
If resynchronization codes are injected into video stream, then error recovery is improved, but data transmission volume increases
Solution Approach 1:
Rather than implementing comprehensive error correction codes that would significantly increase data volume, the patent applies a partial action approach by injecting resynchronization codes at strategic intervals. This provides sufficient error recovery capability without the overhead of full error correction, achieving a balance between reliability and data efficiency.
Data Source
AI summary
A method of compressing and storing preview video includes performing colorspace-reduction image compression on a reference frame of a video to generate a colorspace-reduced reference frame; determining difference blocks representing areas of a subsequent image frame that differ from the reference frame and generating a difference frame comprising colorspace-reduced image data of the difference blocks; generating a video stream comprising a color palette, the colorspace-reduced reference frame, and the difference frame, and storing the video stream in an extreme low-voltage memory; and injecting, into the video stream prior to storing the video stream in the extreme low-voltage memory, a plurality of resynchronization codes for each reference frame and a plurality of resynchronization codes for each difference frame, the resynchronization codes comprising a byte sequence unique to resynchronization codes. Embodiments continue with decompressing the compressed video and using the resynchronization codes to recover from bit errors in the memory.