Guides
CCTV Storage Proposals: Compare Recording Hours, Bitrate and Usable Capacity
Check a CCTV storage proposal with a worked recording-volume calculation, clear capacity assumptions and evidence for the required retention period.
DETIAN ICT · Tanzania & East Africa
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Compare the recording requirement before the disk size
A CCTV storage proposal should state which streams are recorded, when they are recorded, the intended retention period and the bitrate assumptions used to estimate their volume. Compare that requirement with the capacity actually available to the recording application. A disk label or a retention setting alone does not demonstrate that the requested footage will remain available.
Start with the observation tasks already agreed for the site. Then ask a separate procurement question: what recording arrangement and storage evidence support those tasks over the required period? DETIAN’s solutions include video surveillance, while its services cover project design, supply, installation and maintenance. The calculation below helps an owner or purchasing team prepare that discussion.
All camera counts, rates, durations and capacities in the worked example are fictional. They are not recommended recording settings, a DETIAN quotation or evidence from a customer installation. The owner must establish the permitted recording scope and retention requirement through the organisation’s applicable privacy and operational review; this guide does not choose a legal retention period.
Give each recorded stream its own assumptions
Use one row per camera group only when its members share the same recording assumptions. Record the camera or scene IDs, number of streams, recording profile, bitrate basis, recording method, daily schedule, requested days, and evidence reference. Split the row when any of those differ. Identify additional recorded streams separately so that a viewing stream is not mistaken for the stored stream.
Copyable row: Group / scene IDs | Stream count | Profile reference | Assumed average recorded Mb/s per stream | Continuous, scheduled or event recording | Recorded hours per day | Required days | Basis and unresolved question.
A profile reference should identify the proposed settings sufficiently for the technical reviewer to reproduce the estimate. Ask whether the bitrate is a design assumption, a manufacturer sizing result or a measurement, and which conditions it represents. Keep an instantaneous reading separate from an average over the period used for storage planning.
Axis’s bitrate-control paper explains that scene activity and encoding settings affect bitrate, and that limiting bitrate can affect image detail. Use representative evidence for the proposed recording profile. A quiet sample or an unspecified compression claim should remain an assumption until reviewed. Any proposed change to settings also needs review against the original scene task.
Calculate a transparent mixed-schedule example
Assume a fictional owner has already approved two recording groups and a 14-day requirement. Group R1 contains four streams, each averaging an assumed 3 Mb/s while recording continuously for 24 hours per day. Group R2 contains two streams, each averaging an assumed 5 Mb/s while recording continuously within a daily 12-hour schedule. R2 intentionally has no recording outside that schedule in this example.
For decimal units, estimated video GB = stream count × average Mb/s × recorded hours per day × 3,600 × days ÷ 8 ÷ 1,000. The factor converts seconds and bits to gigabytes: one Mb/s for one hour produces 0.45 GB. Here MB means megabytes, Mb means megabits, one GB is 1,000,000,000 bytes and one TB is 1,000 GB.
R1 produces 4 × 3 × 24 × 0.45 = 129.6 GB per day. Over 14 days, that is 1,814.4 GB. R2 produces 2 × 5 × 12 × 0.45 = 54 GB per day, or 756 GB over 14 days. The combined video estimate is 183.6 GB per day and 2,570.4 GB, or 2.5704 TB, over the example period.
This is a video-volume calculation under stated average-rate assumptions. It excludes audio, metadata, application overhead and any separate retained copies. Those require explicit treatment in the actual sizing review. If a supplier reports capacity in TiB rather than decimal TB, request a conversion to the same byte basis before comparing the figures.
Now change only R2 to 24-hour recording. Its estimate doubles from 756 GB to 1,512 GB, and the combined 14-day estimate becomes 3,326.4 GB, or 3.3264 TB. The extra 12 hours add 0.756 TB. This makes the scope decision visible: extending coverage cannot be treated as the same recording requirement at the old storage estimate.
Reconcile the quotation with usable recording capacity
Ask the supplier to show the path from installed drive capacity to the amount allocated for recordings. The reply should identify the proposed storage arrangement, any redundancy-related capacity reduction, application allocation, reserved space and other stored material. Axis’s storage overview distinguishes capacity from the performance needed to record and retrieve video; a capacity comparison does not establish recorder throughput or system compatibility.
Suppose a fictional quote says “4 TB storage, 14 days” but gives no usable allocation or recording assumptions. The 4 TB label cannot yet be compared with the calculated 2.5704 TB video requirement. Request the missing allocation and the exact group assumptions before treating the stated days as supported.
Suppose the supplier then documents 3.0 TB available to the recording application after the stated storage arrangement and reserved space. Against the original example, 3.0 − 2.5704 = 0.4296 TB remains for any requirements not already deducted. List each remaining allowance and its basis; do not count a reserve twice. That remainder is a question for the sizing review, not a universal safety margin or an approval.
If R2 is extended to 24 hours, the same allocation is already 3.3264 − 3.0 = 0.3264 TB below the example’s video-only estimate. Resolve that mismatch by revising the proposal or obtaining an explicit change to the requirement. Reducing recording hours without the owner’s agreement would change what footage is available.
Keep capacity, supported recording load and playback/export requirements as separate response fields. Ask the technical team to assess the proposed camera, recorder, software and storage combination. The arithmetic does not select a disk, certify an installation or establish that all streams can be recorded and reviewed concurrently.
Do not turn an event percentage into a retention promise
If a proposal substitutes event recording for continuous recording, show it as an alternative with its own scope. Request the trigger definition, included time before and after events, assumed recorded duration and the evidence behind that duration. A fixed percentage without that basis leaves both the volume and the captured intervals unresolved.
For example, applying a fictional 25% recorded-time assumption to 2.5704 TB gives 0.6426 TB. This is only a proportional arithmetic scenario, assuming the same average bitrate during recorded time. It neither predicts actual activity nor proves that the required moments will be captured. Do not present the smaller result as a saving delivered by the proposed system.
Have the authorised owner compare the proposed recorded intervals with the actual review task before accepting a recording-method change. Keep the original scope and revised alternative side by side. A storage estimate should expose that choice instead of silently changing the requirement to make a smaller disk appear sufficient.
Separate configured days, forecasts and observed recordings
The AXIS Camera Station Pro manual provides a useful product-specific example: its limited retention setting is a maximum age, and the manual warns that full allocated storage can lead to earlier deletion. It also distinguishes configured retention from the oldest recording. Check the selected product’s own documentation; do not assume another recorder uses identical controls.
Use three evidence labels in the proposal record: required period approved by the owner; forecast period supported by stated assumptions and sizing evidence; and observed recording availability over a named interval. A new installation cannot already demonstrate a full 14-day history on its first day. Leave that observation pending while recording what has actually been checked.
Agree a verification record with the authorised operator and supplier. Include the camera IDs, recording profile and schedule, observation dates, measured usage, oldest relevant recordings, any gaps, and results of the agreed playback or export checks. Use authorised material and the site’s normal procedures; this article does not instruct anyone to delete footage or alter a live recorder.
Finding one old clip demonstrates that clip’s availability. Record the scope of any wider checks before describing the required recording intervals as available. If the measured volume or profile changes, update the forecast and outstanding capacity questions rather than retaining a result based on superseded assumptions.
Send DETIAN the requirement and the unresolved comparison
Prepare the project country and town, facility type, camera or scene groups, existing equipment, approved recording schedules and retention requirement. Attach the calculation with its bitrate basis, the supplier’s usable-capacity breakdown and any proposed alternatives. State which requirements are agreed and which need a site-specific assessment.
Use DETIAN’s official contact page, email [email protected] or call +255 723 666 959 to discuss the design, supply, installation and support scope. Ask what evidence and verification work can be included for the proposed arrangement. Model compatibility, equipment availability, actual retention performance, costs and delivery arrangements require confirmation for the project.
