If you’re using a rearview mirror dash cam with a Micro SD card—like those bundled with Acumen Rear View Mirror products—you might be curious about how much video you can store. Whether you’re relying on continuous loop recording for your daily commute or time-lapse mode to keep an eye on your parked car, knowing your storage capacity helps you plan ahead. I’ve crunched the numbers for 64GB, 128GB, and 256GB cards to give you a clear, practical guide, including storage times for various recording setups. Let’s dive in together!
Factors Affecting Video Storage
The amount of video a Micro SD card can hold depends on your dash cam’s resolution (e.g., 1080p or 4K), frame rate (typically 30fps), bitrate (data usage per second), and recording mode (loop or time-lapse). For multi-camera systems (e.g., dual, triple, or quad) like those in Acumen Rear View Mirror designs, the total bitrate multiplies based on the number of active channels. After formatting overhead, a card’s usable capacity is about 90-95% of its advertised size. For this analysis, we’ll use 90% usability: 58GB for 64GB, 115GB for 128GB, and 230GB for 256GB. Dash cams use loop recording to overwrite old footage and time-lapse mode to compress footage, both impacting total hours.
Loop Recording: Continuous Video Capture
Loop recording captures video in short segments (1,3,5 minutes), overwriting the oldest files when the card is full. Here’s how long different capacities support this for various recording configurations at medium to high quality:
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Single Camera 1080p (6-8 Mbps)
- At 8 Mbps (a common bitrate for 1080p at 30fps), 1 MB/s translates to 3.6GB/hour.
- 64GB: 58 ÷ 3.6 ≈ 16 hours.
- 128GB: 115 ÷ 3.6 ≈ 32 hours.
- 256GB: 230 ÷ 3.6 ≈ 64 hours.
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Single Camera 4K (15-20 Mbps)
- At 20 Mbps (5.4GB/hour, typical for 4K at 30fps):
- 64GB: 58 ÷ 5.4 ≈ 10-11 hours.
- 128GB: 115 ÷ 5.4 ≈ 21-22 hours.
- 256GB: 230 ÷ 5.4 ≈ 42-43 hours.
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Dual Camera (Front 4K + Rear 1080p, 25-32 Mbps)
- Front 4K at 20 Mbps + Rear 1080p at 12 Mbps = 32 Mbps (7.2GB/hour).
- 64GB: 58 ÷ 7.2 ≈ 8 hours.
- 128GB: 115 ÷ 7.2 ≈ 16 hours.
- 256GB: 230 ÷ 7.2 ≈ 32 hours.
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Three Cameras 1080p (24-36 Mbps)
- Three 1080p cameras at 8-12 Mbps each, totaling 24 Mbps (5.4GB/hour) to 36 Mbps (8.1GB/hour).
- 64GB: 58 ÷ 8.1 ≈ 7.2 hours (at 36 Mbps); 58 ÷ 5.4 ≈ 10.7 hours (at 24 Mbps).
- 128GB: 115 ÷ 8.1 ≈ 14.2 hours (at 36 Mbps); 115 ÷ 5.4 ≈ 21.3 hours (at 24 Mbps).
- 256GB: 230 ÷ 8.1 ≈ 28.4 hours (at 36 Mbps); 230 ÷ 5.4 ≈ 42.6 hours (at 24 Mbps).
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Four Cameras 1080p (32-48 Mbps)
- Four 1080p cameras at 8-12 Mbps each, totaling 32 Mbps (7.2GB/hour) to 48 Mbps (10.8GB/hour).
- 64GB: 58 ÷ 10.8 ≈ 5.4 hours (at 48 Mbps); 58 ÷ 7.2 ≈ 8 hours (at 32 Mbps).
- 128GB: 115 ÷ 10.8 ≈ 10.6 hours (at 48 Mbps); 115 ÷ 7.2 ≈ 16 hours (at 32 Mbps).
- 256GB: 230 ÷ 10.8 ≈ 21.3 hours (at 48 Mbps); 230 ÷ 7.2 ≈ 32 hours (at 32 Mbps).
These estimates reflect industry norms, adjusted for usability and loop efficiency, and account for the increased demand of multi-channel recording in Acumen Rear View Mirror systems.
Time-Lapse Mode: Parked Monitoring
Time-lapse mode compresses 30 minutes of footage into 1 minute (e.g., 1fps vs. 30fps), saving space for parking surveillance. Here’s the breakdown for various setups:
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Standard Time-Lapse (1fps, 1080p or 4K)
- At 0.3 Mbps (0.0375MB/s or 135MB/hour, a midpoint for 1fps compression), applicable to single, dual, triple, or quad setups as time-lapse typically records from one camera or aggregates frames:
- 64GB: 58,000 MB ÷ 135 MB/hour ≈ 430 hours (18 days).
- 128GB: 115,000 MB ÷ 135 MB/hour ≈ 852 hours (35 days).
- 256GB: 230,000 MB ÷ 135 MB/hour ≈ 1,704 hours (71 days).
This efficiency comes from reduced frame rates, a feature noted in dash cam guides for conserving space, and applies across Acumen Rear View Mirror configurations.
Storage Comparison Table
Capacity |
Single 1080p(Hours) |
Single 4K(Hours) |
Dual 4K+1080p(Hours) |
Three 1080p(Hours) |
Four 1080p(Hours) |
|---|---|---|---|---|---|
| 64GB | 16 | 10-11 | 8 | 7.2-10.7 | 5.4-8 |
| 128GB | 32 | 21-22 | 16 | 14.2-21.3 | 10.6-16 |
| 256GB | 64 | 42-43 | 32 | 28.4-42.6 | 21.3-32 |
Note: Times vary based on bitrate and dash cam settings. Test your Acumen Rear View Mirror device for exact results.
Practical Tips for Maximizing Storage
- Format Regularly: Format your card every 2-3 months (via dash cam settings) to prevent corruption and optimize loops.
- Choose High-Endurance Cards: Opt for brands like Lexar or SanDisk, designed for continuous overwriting, lasting 1-2 years with care.
- Adjust Settings: Lower frame rate (e.g., 30fps to 15fps) to extend loop time if needed.
- Monitor G-Sensor: Adjust sensitivity to avoid locking too many emergency files.
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