Application-Level SD Card Space Management for DVR Fragmentation

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Solution Overview

Problem

Digital video recorders (DVRs) experience significant fragmentation when saving multiple streams to a secure digital media (SD) card, leading to reduced writing speed and potential data loss due to frequent file creation, deletion, and resizing, which worsens fragmentation.

Innovation Solution

An application-level SD card space management scheme is implemented using a processor and removable media interface circuit to manage file operations, minimizing fragmentation by creating, removing, and resizing files in file block units, and providing user-space APIs for allocating and freeing space, which can work with both vFAT and exFAT file systems.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If multiple streams are saved to SD card simultaneously, then recording functionality is improved, but file fragmentation increases and writing speed decreases

Engineering Contradiction:

Improvemulti-stream recording capabilityVSAvoidwriting speed

Core Design Contradiction:

Adaptability or versatilityVSSpeed

Solution Approach 1:

The patent segments the SD card storage into dedicated pools for different stream types (e.g., front camera, rear camera, audio). Each stream is assigned to specific file pools rather than allowing arbitrary file creation. This segmentation prevents file fragmentation by ensuring that each stream's data is written to predetermined, non-overlapping storage regions, thereby maintaining high writing speeds while supporting multi-stream recording.

Inventive Principle:

Principle #1Segmentation

2Ease of operation

If files are frequently created and deleted, then recording management is improved, but fragmentation increases and writing speed decreases

Engineering Contradiction:

Improverecording management flexibilityVSAvoidwriting speed

Core Design Contradiction:

Ease of operationVSSpeed

Solution Approach 1:

The patent performs preliminary actions by pre-allocating storage pools and file templates before recording begins. File structures are prepared in advance with predetermined paths and formats. This preliminary setup eliminates the need for frequent file creation and deletion operations during recording, as the system simply writes data to pre-configured locations, thereby maintaining writing speed while providing recording management flexibility.

Inventive Principle:

Principle #10Preliminary action

3Extent of automation

If file operations are increased to manage recording, then recording control is improved, but fragmentation increases and writing speed decreases

Engineering Contradiction:

Improverecording control automationVSAvoidwriting speed

Core Design Contradiction:

Extent of automationVSSpeed

Solution Approach 1:

The patent introduces an intermediary layer (file management system) between the recording control logic and the actual file operations on the SD card. This intermediary handles all file creation, deletion, and resizing operations centrally, directing them to predetermined pools rather than allowing direct file operations. This mediation reduces fragmentation by consolidating file operations and maintaining a structured storage layout, thereby preserving writing speed while enabling automated recording control.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS11726682B2Application level SD card space management

Publication Date: 2023.08.15 AMBARELLA INT LP

AI summary

An apparatus includes a removable media interface circuit and a processor. The removable media interface may be configured to read and write files to a non-volatile storage medium. The processor may be configured to generate encoded data and manage file operations involving storing the encoded data on the non-volatile storage medium to minimize a number of file fragments.