Why a range, not one number
A camera's bit rate depends on what it sees. The same 4MP H.265 camera can record under 2 Mbps on a quiet night and several times that in a busy lobby with trees moving outside. Smart codecs widen the spread further: one vendor's own measurements of its smart codec run from 25% savings to over 99%. IPVM, the industry's main independent tester, says getting within ±30% is "generally infeasible" for any calculator. So this one shows the range that published measurements support, and plans with its upper end unless you choose the middle.
When you have the real number from the camera's web page or your VMS, enter it as the actual bit rate. That replaces the estimate for that stream.
How the estimate is built
bit rate = published bit rate for the resolution and codec × frame-rate factor × scene motion × scene detail × quality × (1 − smart codec saving)
Motion in the scene: low is a hallway or office with people now and then; moderate a lobby, store or parking lot; high a busy entrance, checkout or street. Scene detail: detailed means trees, water, crowds or busy signage.
Each factor is a low–high pair taken from a published source. Multiplying the lows gives a quiet, simple scene where a smart codec does its best. Multiplying the highs gives a busy, detailed scene where it does its least.
| Factor | Low–high | Source |
|---|---|---|
| Resolution and codec | Hikvision's published figure; between its rows, interpolated by pixel count | Hikvision, H.264(5) & H.264(5)+ Recommended Bit Rate at General Resolutions (e.g. 4MP: 8,192 kbps H.264, 4,096 kbps H.265) |
| Frame rate (vs 30 fps) | 15 fps: 0.71–0.80; 10 fps: 0.53–0.68 | Bosch DINION IP starlight 8000 MP datasheet, typical bit rates; IPVM Frame Rate Guide measurements |
| Motion: low | 0.23–0.85 | Hikvision H.265+ white paper, café scene, night and day, measured |
| Motion: moderate | 0.39–1.00 | Bosch typical 1080p bit rate; Hikvision recommended figure |
| Motion: high | 0.65–1.07 | Hikvision H.265+ white paper, intersection, night and day, measured |
| Detailed scene | 1.2–1.3 | Hikvision recommended bit rate table, note 1: "increase the bit rate 20%~30%" |
| H.265 vs H.264 | about 0.5 | Ohm et al., IEEE TCSVT 2012; Hikvision's table |
| MJPEG vs H.264 | 5–6× | Axis, H.264 video compression standard white paper |
| MPEG-4 Part 2 vs H.264 | 1–2× | Same Axis white paper |
| Quality: lower / higher | 0.7–1.0 / 1.0–1.5 | Not sourced. A labelled planning range; it never lowers the upper end. |
Smart codecs, whoever makes the camera
Every major manufacturer has a smart codec, and each manufacturer's calculator only knows its own. This one takes each vendor's published figure and uses the smallest credible saving for the upper end of the range. Where a vendor publishes only an "up to" figure, the least saving is 12%, the lowest measured result for any smart codec that we found published.
| Smart codec | Saving | Basis |
|---|
Multi-sensor cameras
Multi-sensor cameras are where most calculators go wrong. What matters is how the camera sends its video.
- A stream per head, as most multi-directional cameras do: a four-head camera is four video streams and usually four VMS channels. Storage and bandwidth count all four.
- One stitched stream, as a stitched panoramic does: one stream and one channel at the stitched resolution. Counting it four times overstates storage three to four times.
- Either way, it is one device on one switch port. For PoE, see the PoE budget calculator.
Heads do not have to match. Tick "Set each head separately" for, say, three fixed heads and a PTZ.
Storage, RAID and drives
storage = recorded bit rate ÷ 8 × 86,400 s × days × (1 + headroom)
Storage is in decimal terabytes, as drives are labelled: 1 TB is 1012 bytes (Seagate). Your operating system counts in binary units, so a 5 TB drive shows as about 4.5 TB. The extra figures give both. RAID capacity follows Synology's published rules: RAID 5 keeps one drive's worth for parity, RAID 6 two, and RAID 10 half.
Network bandwidth counts every stream the cameras send, all the time, including a substream used for live view. Recording on motion or on a schedule lowers storage but not bandwidth, because most cameras stream continuously either way.
VMS channels
Most video management software licenses per video channel, so a four-head camera sending four streams usually needs four licenses. Some license per device (per IP address) instead. The channel count here is per stream; check how your VMS counts.
What this does not account for
- Night-time noise. Low light can raise the bit rate sharply on some cameras: Axis's design tool, as reported by IPVM, puts a detailed night scene at four times a simple day scene. Other measurements show night lower, not higher. If your cameras face dark, busy scenes, enter a measured bit rate.
- Constant bit rate (CBR). A camera set to CBR records at its configured bit rate all the time; enter that number as the actual bit rate.
- Motion recording: the percentage of time you enter should include pre- and post-event recording. The bit rate during motion is higher than the camera's average; plan with the upper end.
- Frame rates above 30 fps. No published scaling was found, so they are scaled in proportion, which overstates rather than understates.
- Resolutions above 12MP or below CIF are extrapolated beyond the published table, and the calculator flags them.
- Recorder overheads beyond the file system reserve, such as databases, thumbnails and analytics metadata.
Common questions
- How much storage does a 4MP camera need for 30 days?
- At 15 fps, H.265, a moderately busy scene and continuous recording, about 0.6 to 1.3 TB. With a smart codec on, less; see the range above for your settings.
- I have 24 TB. How many days is that?
- Choose "Days my storage holds" and enter 24 TB, or the number of drives and the RAID level. The answer is a range too.
- Does H.265 really halve storage?
- On average, roughly: the reference comparison of the codecs found about 50% at equal quality, and vendor surveillance tests measured H.265 at 33% to 73% of H.264's bit rate depending on the scene.
- Should I trust a smart codec's "up to 90%"?
- Treat it as a best case. Savings are largest in quiet, still scenes and fall as motion increases, which Hikvision states in its own white paper. That is why the upper end of the range here uses the smallest published saving.
Sources
- Hikvision, H.264(5) & H.264(5)+ Recommended Bit Rate at General Resolutions (FAQ document).
- Hikvision, H.265+ Encoding Technology: Halve Your Bandwidth and Storage (white paper). Measured 1080p at 25 fps.
- Bosch, DINION IP starlight 8000 MP datasheet (2016), "Bitrate optimized profile" table.
- IPVM, Frame Rate Guide for Video Surveillance; IPVM, Bandwidth Guide for Video Networks (2020); IPVM, Axis Zipstream (2015); IPVM discussions on calculator accuracy (2014, 2015).
- J.-R. Ohm, G. J. Sullivan, H. Schwarz, T. K. Tan, T. Wiegand, "Comparison of the Coding Efficiency of Video Coding Standards—Including HEVC", IEEE Trans. Circuits Syst. Video Technol. 22(12), 2012.
- Axis Communications, H.264 video compression standard (white paper, 2008); Axis Zipstream technology (white paper).
- Vendor smart-codec figures: Dahua datasheet DH-IPC-HDBWD5A1R-AZ; Hanwha Vision WiseStream II and III pages; Uniview technology page; Bosch iDNR white paper (2013); Avigilon HDSM SmartCodec flyer; i-PRO Smart Coding page.
- Seagate, Why does my hard drive report less capacity than indicated on the drive's label?; Synology, Choose a RAID Type; Synology RAID Calculator notes.