How Much Space Does an Hour of 1080p Video Take?
Imagining you want to size a drive or hosting plan for video work, it's a question everyone needs in easily verified numbers.
In this article
The key is bitrate multiplied by duration, one formula states “size = (bitrate x time) / 8,” another has, and a third identifies the “basic formula” as “bit rate x length = file size.”
Now, those are interesting figures, but they mask a deeper truth: video storage is unpredictable until you know the details of bitrate, codec and frame-rate, since these all vary hugely.
This guide maps out in detail:
- How the arithmetic works
- Why bitrate changes
- Real-world reference points
- Storage planning for a project
- Where single-number advice breaks
The Arithmetic
Video efficiency boils down to bitrate - the number of bits it needs to convey each second of screen action.
The industry standard is megabits per second (Mbps), equivalent to 1,000,000 bits per second.
Audio must be factored in separately, although audio bitrates are much lower, typically 160 kbps or 256 kbps.
Storage capacity is measured in bytes, and a byte is 8 bits. So any bitrate's storage needs are exactly one-eighth of the data rate in Mbps.
Multiply your video bit rate by the audio bit rate and by the duration in seconds for your total requirement, then divide by 8.
Why Bitrate Changes
Bitrate changes depending on footage complexity.
Image resolution is the first factor. H.264 (AVC) 1080p at 30 frames per second (fps) is typically 5-10 Mbps, for example, and inches up to 15-17 Mbps at 60 fps.
4K settings rise to 20-30 Mbps at 30 fps and 25-40 Mbps at 60 fps.
VBR variants can vary a bit, with more for more detail or complex, fluid scenes.
Data rate is really controlled by a very large range of factors, including codec efficiency, client settings, coding delay, data packetisation, fielded/non-fielded settings and key framing.
Changing one or more of those could easily double the storage need. And all that varies between segments of footage.
Video production also always generates a second tier of proxy material, which is the working version. This resolves a lot of the original fine detail and can often sit at 3-5 Mbps.
Finally, final exports for delivery are the last dataset. Here, codec choice, target platform and device come into play - the same material to HDTV can be 5-8 Mbps, but down to < 2 Mbps for an online stream or heavily compressed mobile download.
Real-World Reference Points
The industry guidance is that you really need to consult the manufacturer's recommendations for common settings.
For instance, Hikvision specifies 1.6-3.0 Mbps for 720p at 25/30 fps, doubling that to 3.2-6.0 Mbps for 1080p and beyond, rising further at higher fps.
They authoritatively detail for each camera the H.264 and H.265 settings, with a strong recommendation that for best results, you should set different resolutions and frame rates for different locations, times, and lighting.
IC Realtime advises the same. For 1.3 megapixel (1280 by 960 pixel) at 25/30 fps, 1.2-2.4 Mbps. For 4 megapixel at 25/30 fps, 3.5-7.5 Mbps. And while you might think that's all you need to know, in reality, it depends heavily on the activity in the field of view, since handheld shot material with a lot of movement, noise, and fast changes in lighting behaves very differently from static screens.
Storage Planning for a Project
Adding everything together gives a complicated picture.
Per hour, tonight's 10-20 Mbps HD camcorder original could be 10-20 gigabytes. Its 5-8 Mbps HD proxy and its online stream at 1-4 Mbps just add to the storage need.
And since live television commonly runs two recording streams - senior video engineers prefer two copies from the outset in different long-term media every time - storage is a big number.
It falls to managers to know the real distribution of resolutions, frame rates, codecs and desired use cases across all the material, to plan the most efficient project processing and delivery in this context.
Where Single-Number Advice Breaks
Sometimes, such massive differences in storage can arise for what looks like a single detail, as we've seen.
For instance, handheld vs. static screen, or noisy grainy footage vs. high key, are both much more computationally expensive for encoders, because they have to do more work to preserve the essence of the scene.
[TO VERIFY: Some encoders handle such material at higher rates than the same scene taken in a more ideal studio lighting setup, preserving the integrity of the dynamic information.]
Complexity also affects every project, because there is a fundamental difference between footage where the motion is central to meaning, and where the motion mainly amplified the core visual meaning.
High-motion footage, fast moving actors, vehicles, crowd scenes and the like all need different bitrates to display the action clearly, whereas scenes where motion is primarily adding to the main visual point can be compressed further. It isn't a rule, but common sense would suggest the motion in a fashion shoot and a dance competition does completely different things, suggesting a high ratio from both engineering and marketing perspectives.
In that sense, framing alone can encourage very different material planning from the outset, such as deciding when to use stabilized handheld, using studio lighting to control motion and grain, structuring an editorial model in parts, or incorporating friction in the creation workflow.
Your Bitrate Planning
One last note, though: your size calculation needs at least this much, none less. In fact, your planner should complement this advice with a review of your entire storage pipeline for a large media project. There will always be tapes drying in the store room or on IDEV kept for operational emergencies, for instance, and this material is often never deleted.
Building a plan with those considerations can set up systems that at least recognize the difference between raw image data storage, distributed backup, on-line processing, encrypted archival medium, and DAM.
When all that is in place, then it will be easier to practise the principle of making sure files are never lost, deleted, used or overwritten, and an accidental situation never interrupts an institutional possibility.
Then your story can keep coming, without a hiccup.
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