If you've ever poked around your encoder settings, you've probably seen an option for B-frames and left it alone, because it sounds technical and the defaults usually work fine. For on-demand video, that's true. For livestreaming, it's worth a second look.
What a B-Frame Actually Is
Video compression works by not redrawing every pixel in every frame. Instead, encoders describe how a frame differs from the frames around it. There are three types of frames involved:
- I-frames are full images, standing on their own.
- P-frames reference the frame before them.
- B-frames reference frames both before and after them.
That's what makes B-frames good at compression. By looking in both directions, a B-frame can describe a scene using less data than a P-frame would need.
Why That's More Work Than It's Worth for Live
Referencing both backward and forward frames is exactly the kind of work involved in scrubbing back through a video, and that's a clue to why B-frames matter less for live streaming than people assume. When a viewer rewinds or scrubs through a livestream, that DVR functionality is handled by the platform you're streaming to, not by B-frames in your encoder.
So your encoder is doing extra work, and asking the decoder on the other end to do extra work too, to support a kind of frame referencing that the platform is already handling on its own. You're paying an encoding cost for something you don't actually need supported at that layer.
Yes, B-frames help with compression and can nudge quality up slightly. But that benefit is marginal, and it comes at the cost of putting more strain on your encoder for every second of the broadcast.
The Practical Takeaway
For live streaming, turn B-frames off. Your encoder does less work, your stream runs a little leaner, and you're not losing anything meaningful. Any rewind or scrub-back functionality your viewers use is already being handled by the streaming platform itself, not by the frame structure coming out of your encoder.
Look for a "zero latency" or similar tuning preset in your encoder software, or set your B-frame count to zero manually. It's a small setting with a real payoff for anyone running a live broadcast.
FAQ
Do B-frames reduce video quality if I turn them off?
Only minimally. B-frames offer a modest compression benefit, but for live streaming that benefit isn't worth the added encoder and decoder workload.
Are B-frames ever useful?
Yes, for recorded or on-demand video where file size matters more than encoder efficiency in the moment, B-frames are genuinely helpful.
Doesn't turning off B-frames affect DVR or rewind features?
No. DVR and scrub-back functionality on a livestream is handled by the platform you're streaming to, not by B-frames in your encoder, so you don't lose that functionality by turning them off.
How do I turn off B-frames?
Most encoders have a low-latency or zero-latency preset that disables them automatically, or you can set the B-frame count manually to zero in your encoder settings.
