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Comment by ksec | Hacker News Reader

I think the first gen AirPod was 200ms, and current AirPod Pro had it down to ~150ms. Which is already the outliner in the industry as most are still 250ms+.

Compared to Wired Headphone of 5ms latency.

At least Apple continues the R&D to lower latency. Hopefully someday it will reach sub 50ms.

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I don't think wired headphones really have latency of their own. A single audio sample takes less than a microsecond. The latency will all come from upstream buffering, which will depend on the application and the OS.

Yup, not sure where the OP got the 5mSec number; perhaps it's about the soundcard buffering but then it's probably sort of high end using ASIO drivers and a rather small buffersize (say 192 samples at 44.1kHz) because I duoubt your everyday buit-in soundcard achieves that. But it cannot be about the speed of the analog signal from the DAC until it reaches your speaker: too lazy too look it up but worst case IIRC is still half the speed of light so not even near mSec range.

5 milliseconds is about what you'll measure for latency if you measure a wired headset, but yes, you're really measuring your sound card.

c ≈ 1ns/ft

Just to be pedant, c is the speed of a photon in a vacuum. Electrons are much heavier and are traveling in a medium, copper.

[0] https://en.wikipedia.org/wiki/Drift_velocity

The signal speed has nothing to do with the electrons’ drift velocity. It is a bit slower than c, but negligibly so.

Tyvm, this is super handy! More precisely, ~1.01670 ns/ft (~0.983571 ft/ns).

1ns = 300mm (or 30cm)

1us = 300m

1ms = 300km

Does the phone adjust for this when playing videos? Because I find even 50ms desync between audio and video to be very jarring.

Yes, phones delay video playback so it matches the reported latency of the audio device. This works via networked audio protocols as well, at least on Apple devices in my experience.

1 frame at 30fps lasts 33.33 ms. I work as a freelance rerecording mixer and can assure you that a shift of one frame can definitly be noticible.

However there are some people who are more sensitive to this than others.

50ms would be two frames at 25fps, which is already quite much indeed. Anything beyond that is just a crime against anybody who worked hard to sync sound and image.

This can be easily seen in action when playing audio over AirPlay where the latency is ~2 seconds. When you press Play the video waits for a moment to compensate for the audio delay and only starts after the two-second delay to sync with audio.

The popular type is from Qualcomm called AptX Low Latency (not the same as 'lossless' AptX HD versions) and you need it on both sides xmt/receive. I have never seen this supported natively before so I got them as a pair of headphone jack to BT dongle adapters. Video works fine on Hotel TVs which was my normal useage.

A normal old school ISM band headphone with transmitter base is better for TV but the dongles travel better.

That is a very good point. I have no idea as I dont use it to watch video. Would not be surprised to see if that was the case.

No need to wait for apple. Low latency was a thing many years ago... Where we are talking about ~40ms over bluetooth.

40ms is not low latency. It's good for Bluetooth, but it's not low. Low latency, as usable for rhythm games or music, is more like 10ms.

My TV already has higher latency than that and I manage on Rock Band just fine - anything that depends on A/V synchronization is generally aware of latency being a problem and has knobs for the users to adjust for it.

That being said, waiting multiple frames for video playback to start while audio buffers fill and transmit is a shitty experience - so it’s always good to reduce it.

What devices support that/

Not sure what the best way to look for it is, but searching for devices that support aptx low latency might be a decent indication.

https://www.aptx.com/product-listing?product_category=7&aptx...

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