Video Codecs Explained: Bitrate, Bit Depth and Chroma Subsampling

Codec specifications sound like jargon and each one maps to something you will feel in the edit. Long-GOP versus all-intra decides whether footage scrubs. Bit depth decides whether a gradient bands when you grade it. Chroma subsampling decides whether a key pulls cleanly. And all three decide how many 512 GB cards a shoot day needs, which is the cost that keeps arriving after the camera is paid for.

Long-GOP and all-intra

A long-GOP codec stores occasional complete frames and describes the frames between them as differences from their neighbours. This is extremely efficient, because most of a frame is usually similar to the one before it, and it is how a 100 Mbps file can look as good as a 400 Mbps one on simple footage.

The cost is that no in-between frame exists as an independent picture. To display frame 37, the software must decode a complete frame and then apply every difference up to that point. That is why scrubbing long-GOP footage is sluggish, why it strains a processor, and why complex or noisy scenes fall apart: the codec runs out of bits to describe how much changed.

An all-intra codec stores every frame complete, like a sequence of stills. Files are several times larger and everything about editing is faster, because any frame can be decoded on its own. On a set where the edit starts the same day, that difference is the whole argument.

Bit depth, and where banding comes from

Bit depth is how many distinct values each colour channel can take. Eight bit gives 256 levels per channel, ten bit gives 1,024, and twelve bit gives 4,096. That sounds like more than enough in every case, and it is, until you grade.

Grading stretches parts of the tonal range. Lifting shadows takes a narrow band of values and spreads it across a wider range, so gaps appear between the levels that were recorded. In 8-bit those gaps become visible steps, which is banding, and it shows up first in gradients like a sky or a wall lit unevenly. In 10-bit there are four times as many levels, so the same stretch usually stays smooth.

This matters most on log footage, because log deliberately compresses a wide dynamic range into the available levels and the grade then expands it again. Eight bit log is the worst combination available and should be avoided: if your camera only offers 8-bit, a standard profile is often the better choice.

Chroma subsampling, in plain terms

The reason 4:2:0 works at all is that human vision resolves brightness far better than colour, so throwing away three quarters of the colour information is nearly invisible on normal footage. It becomes visible when you pull a key, because the edge of a green screen subject is defined by colour, and it becomes visible when you push saturation hard in a grade. For ordinary work, 4:2:0 10-bit is a better use of bitrate than 4:2:2 8-bit.

RAW, and what it actually is

A RAW file stores the sensor data before debayering and before a colour profile is applied. White balance and ISO become adjustable in the edit rather than baked in, which is a genuinely different capability from a very good compressed file.

BRAW and ProRes RAW both compress that sensor data, so they are not uncompressed in the strict sense, and both remain far more flexible than any conventional codec. BRAW is recorded internally on Blackmagic bodies, which is why a Blackmagic Pocket Cinema Camera 6K G2 gives a RAW workflow with no external recorder, and ProRes RAW usually requires a device like the Atomos Ninja RAW.

The costs are real: larger files, a more demanding pipeline, and files that will not simply play for a client. RAW is worth it when grading is a substantial part of the work and unnecessary when it is not. Shooting RAW and then applying a standard look is spending storage on flexibility you did not use.

What a codec choice actually costs

The card that holds the day, the drive it offloads to, and the reader that makes the transfer bearable.

Best value $279.99

Delkin Devices

Delkin 512GB CFexpress Type B 4.0

512 GB of CFexpress 4.0 at the lowest sane price per gigabyte, which matters because RAW eats cards faster than any other format decision.

Capacity

512 GB

Spec

CFexpress 4.0 Type B

The value card for most cine bodies.

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Best value $237

Samsung

Samsung T9 1TB Portable SSD

The same 2000 MB/s class in a smaller shell that holds speed better under a long sustained copy.

Capacity

1 TB

The value pick for daily offloads.

Check price

Offload $104.99

ProGrade Digital

ProGrade CFexpress Type B Reader (USB4)

A fast reader is not optional with CFexpress: a slow one turns a 512 GB card into a lunch break.

Interface

USB4

Buy this with your first CFexpress card.

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Bitrate and storage, with real numbers

The jump from long-GOP to all-intra roughly doubles your storage. The jump to ProRes or RAW multiplies it again. That cost is ongoing rather than one-off, because it lands on every card, every drive and every archive, and it is the part of a codec decision people account for least.

Choosing a codec for a job

1. Delivering fast, simple grade, long recordings: long-GOP 10-bit. Efficient, and the grade will not stress it.
2. Normal client work with a proper grade: all-intra 10-bit 4:2:2 if the camera has it, otherwise 10-bit 4:2:0.
3. Green screen or compositing: 4:2:2 minimum, 10-bit, and all-intra so every frame is independent.
4. Narrative with a real grade: RAW if the camera writes it internally, all-intra if not.
5. Multi-camera events with hours of runtime: long-GOP, because storage and offload time dominate everything else.
6. Anything where the camera only offers 8-bit: a standard profile rather than log, since 8-bit log grades badly.

That last one is the counterintuitive rule that saves the most footage. Log exists to preserve dynamic range for grading, and 8-bit does not have the levels to survive the grade that log requires. An 8-bit standard profile that looks close to finished in camera is a better starting point than 8-bit log.