What is Bitrate? A deep dive.

300 megabits per a second sounds like a lot. But what is bitrate, really? And why does it matter? Let’s learn.

1) What is bitrate?

Bitrate is simply how fast image data is written—the rate at which your camera turns photons into bits and shoves them onto a card. Cameras advertise it in megabits per second (Mb/s). Storage and copy tools think in megabytes per second (MB/s). Those aren’t the same thing.

• The translation is 8 bits = 1 byte.
• So 300 Mb/s ÷ 8 = 37.5 MB/s.
• Multiply by time to get storage: 37.5 MB/s × 60 = 2,250 MB/min ≈ 2.2 GiB/min.

That’s the math behind how fast your cards fill up.

Bitrate is shaped by what you ask the camera to do: resolution, frame rate, color sampling, bit depth, and codec. A 4K/60p, 10-bit, 4:2:2 All-I recording will demand far more bitrate than 4K/24p, 8-bit, 4:2:0 Long-GOP. Why? Because that's more data that needs to be written every single second.

Think of bitrate as the width of the pipe; the more complex the picture (motion, fine detail, noise), the more water trying to go through it.

Two more terms live next door to bitrate:

• CBR (constant bitrate): the camera writes a steady stream regardless of scene complexity. Predictable card math; sometimes inefficient.
• VBR (variable bitrate): the camera writes more bits when the picture gets “busy” (confetti, water spray, backlit hair) and fewer when it’s simple. Efficient—until the chaos hits and your storage plan was too tight.

Bitrate isn’t quality by itself. It’s capacity. Whether that capacity is used wisely depends on the codec (intra-frame vs. inter-frame), chroma subsampling (4:2:2 vs. 4:2:0), and bit depth (10-bit vs. 8-bit). High bitrate with a fragile codec can still bite you; moderate bitrate with a sturdy codec can soar.

2) Why does it matter?

Because every decision you make on set and in post sits on the floor that bitrate builds.

• Image integrity: Too little bitrate for the scene/codec shows up as blocking in skies, banding in gradients, mosquito noise around titles and fine edges, and soft, waxy detail where texture should live.
• Card math and media choice: Bitrate decides whether a 128 GB card holds ~54 minutes at 300 Mb/s or ~27 minutes at 600 Mb/s.
• Copy speed and schedule: Your camera can happily write at 75 MB/s (600 Mb/s). Your assistant’s bus-powered drive and cheap hub might not keep up. That’s how “five minutes to copy” becomes way longer.
• Editorial performance: Long-GOP at a modest bitrate may look fine, then stutter under heavy cutting and color. Intra-frame at a sane bitrate flies in the timeline and tolerates abuse.
• Delivery: YouTube, broadcast, and CTV will re-encode your file. Feeding them a clean mezzanine with smart bitrate/codec choices often beats “as big as possible.”

3) What is the impact of bitrate on filmmaking in production?

Bitrate is basically what builds your logistics on set. It touches camera choice, card strategy, heat, power, and how many “let’s just grab one more” takes you can afford.

Card math you can trust (examples):

• 300 Mb/s (≈37.5 MB/s): ~2.2 GiB/min. On a “128 GB” card (~119 GiB real) ≈ 54 minutes of record time.
• 600 Mb/s (≈75 MB/s): ~4.4 GiB/min. Same card ≈ 27 minutes.

CBR vs. VBR on set:

CBR makes planning simple: minutes per card are stable. VBR can be a gift or a trap. It will cruise on interviews and spike on texture and motion—music videos with glitter, product pours, dance, anything with backlit hair. If you’re betting the day on VBR, bring extra cards and treat high-detail moments as bitrate storms.

Codec family:

• All-I (intra-frame): each frame is self-contained. It costs more bitrate but edits quickly and grades well. Good for fast turnarounds, heavy color, or agency village that wants instant playback scrubbing.
• Long-GOP (inter-frame): packs more time into the same storage by predicting between frames. Efficient, but harder on the CPU and touchier when pushing grades or doing VFX.

Heat and power: Higher data rates can raise sensor/processor load. Some bodies throttle or misbehave when you shoot hot (4K/60, high bitrates, warm day). If you’re living at the top of the spec, test the actual camera you’ll take to set. Ten-minute rolls. Real ambient temps. Real media.

DIT and copy pipe:

A camera writing 75 MB/s is fine. Two cameras dumping simultaneously can exceed 150–200 MB/s sustained. If your target drive tops out at ~120 MB/s (many bus-powered HDDs do), you’ve built a bottleneck. Bring NVMe storage and a reader/hub that publishes honest throughput. Copy speed is part of the image—treat it like lighting.

Quick field test for image stress:

Point the camera at a clean gradient (sky, painted wall) and at a high-detail torture test (fabric with fine weave, hair in backlight). Roll a ten-second clip at your actual settings (fps, shutter, ISO, codec). If the monitor shows crawling noise or blocky skies, your bitrate/codec pair is undersized—or your exposure is too stingy for that codec.

4) What is the impact of bitrate in post-production?

Post is where bitrate rewards or punishes the whole team.

Ingest and storage:

High bitrate footage eats ingest time and space. Plan storage by show total minutes × GiB/min (don’t guess). Keep 20–30% overhead on working volumes; drives near full crawl and fail. If two editors will pull from the same media, don’t strand them on a single USB bus.

Transcode strategy:

If editorial needs speed, transcode to a mezzanine that matches the job: ProRes 422/444 or DNxHR HQ/HQX. Yes, that can increase bitrate—but it gives you predictable performance and headroom to grade. For long-GOP originals, proxies are often the cheapest sanity.

Color latitude vs. numbers on the box:

A fat number on the spec sheet doesn’t guarantee latitude; codec structure and bit depth do. A 10-bit, intra-frame 300 Mb/s file will generally grade cleaner than an 8-bit, long-GOP 400 Mb/s file. Judge with scopes and pushes, not just the brochure.

Artifact hunting (do this before the client arrives):

Zoom to 200% on a reference monitor and scrub midtones. Look for banding in skies, blocking in gradients, mosquito noise around logos and fine edges, and chroma crawl in saturated fabrics. If you see it in the mezzanine, it will get worse after platform transcodes.

Delivery realities (YouTube, broadcast, OTT):

Platforms re-encode. A clean, stable mezzanine (say, 200–400 Mb/s intra for web delivery; higher for HDR/broadcast) can survive the transcode better than a louder, noisier long-GOP master. Ask deliverables for target bitrates and profiles; pushing 1–2 Gb/s at an uploader doesn’t guarantee a better result if your source is noisy or blocky.

Archival footprint:

High bitrate across a campaign balloons archive. If the client wants every take forever, standardize on a mezzanine and archive that, not fifteen flavors. Put a data retention note in your wrap email: how big the project is, what format the archive is in, and what it will cost to keep alive.

A few house rules that save months:

• Pick the fattest codec your team can actually move. If assistant machines wheeze, you picked wrong.
• Normalize mixed-camera shoots before creative cutting. A little prep (transcodes/mezzanine) beats a lot of pain.
• Keep one QC pass purely for artifacts that smell like bitrate/codec weakness. Fix upstream if possible; don’t paint the whole timeline with denoise out of panic.