Comments on: ADC Processing Delay Compensation For Audio Recording

By: encryptio

encryptio — Thu, 29 May 2008 03:17:00 +0000

Human response times are irrelevant for this discussion. If I *start* playing music, you’ll be able to respond in some time around 180ms. However, the brain doesn’t do that for every single beat, it anticipates the beats. That’s why we dance on time. That’s why a singer with music in their headphones (usually) sings in time. Remember, at 120bpm, 180ms is almost a third of a beat - something anyone can notice.

By: Laribum

Laribum — Sat, 17 May 2008 12:16:51 +0000

I learned, that the brain can already pick up a delay between two audio waves of 30ms. It is part of recognizing audio source directions. You can test it with every delay device.
(e.g. The short delay of ProTools)

I agree, that differences in sample playback are creating harmonic changes. I do not think, that this is directly connected to the audio perception mechanics of the human ear and brain. I’d rather say, that at DA converting, this delay is mixed in and appears as the new harmonic element as the brain just recognizes harmonics while ‘listening to music’. It is not connected directly to human ability to detect noises in the surrounding environment. It just appears to be much more complicated.

So I Agree. It will be a useful feature.

By: huguesbc

huguesbc — Tue, 13 Nov 2007 20:07:17 +0000

good article, but I doubt one could calculatte delay by hand. Let’s say you have a digital hardware synth and digital hardware effects along with your digital sound card, one would had the delay value for the sound card + keyboard + effect. That doesn’t make sense to me, although adc are a big part of that delay it isn’t the only one, and sound card doesn’t always respect the specs so tightly. So one would have to measure delay by hear to get accurate, but then our ear isn’t accurate enough to really notice, so it might be an unsolvable problem. If it really is a problem in the first place.

By: Bantai

Bantai — Sat, 27 Oct 2007 11:48:05 +0000

…mean auditory reaction times being 140-160 msec and visual reaction times being 180-200 msec (Galton, 1899; Woodworth and Schlosberg, 1954; Fieandt et al., 1956; Welford, 1980; Brebner and Welford, 1980). Perhaps this is because an auditory stimulus only takes 8-10 msec to reach the brain (Kemp et al., 1973), but a visual stimulus takes 20-40 msec (Marshall et al., 1943).

Recording a live played instrument, for example one’s voice, in sync with the music, is very much a physical response. Someone presses the record button, the vocalist starts singing after 140-160 ms has passed since the music reached his ears.

Being able to hear that two audio tracks are out of sync by only a few ms is a different trait. One could compensate for the human reaction time, and still notice an offset due to other delays including ADC processing delay afterwards.

Another issue is that Mr Mark Dollin applied the ADC processing delay compensation to a song from Sewen, who cut up his live recordings on MiniDisc into samples! I assume he did the cutting with ‘close enough for rock ‘n’ roll’ accuracy, meaning anyone can but speculate about any delays remaining in those samples.

By: dan

dan — Sat, 27 Oct 2007 06:20:54 +0000

to bantai “human audio reflex time (about 170 ms on average)”.
where did you get that information from?
i think what you mean is physically responding to an audio signal. for instance, moving your hand as soon as you hear a sound. perhaps that could take 170ms, but this has absolutely nothing to do with what they’re talking about in here.

when i am playing a VSTi with 20ms latency on my midi keyboard i VERY WELL feel the difference from 2 ms latency. and there’s even a difference between 5 and 2 ms, altough harder to remark.

the audio delay compensation of the ADC group delay is hearable on sounds with a high amount of transients at the start. for example putting a “clicking” bassdrum on a clap playing together exactly and playing together but the clap being played only 44 samples later (=1 ms @ 44.1kHz) sounds different. if you don’t believe it, do the test yourself in an audio editor.

that said, on most occasions one will not really hear the difference.