04-27-2020, 12:59 AM
Thank you for the very useful post! This is generally consistent with what I am finding out as I try to reduce latency with a cheap USB audio adapter (driven by tape out from a PA head) with the ASIO4ALL driver on a Windows 10 system. Not the way to go, but almost adequate until I get my hands on a real audio interface. I've been able to beat my hardware latency down to 15 ms as reported by solo session diagnostic, I measure 14.1 ms with a scope looking at analog in/out to the USB audio adapter.
Frame size seems to have the largest impact on latency of any of the knobs I can turn. With the ASIO4ALL driver I was expecting to see a difference in latency as I vary buffer size in the ASIO4ALL settings, but I do not. The Buffer In/Out counts also do not seem to affect latency. I've experimented with power of 2 buffer sizes from 64 to 512, and In/Out counts from 0 to 3.
Changing the USB audio adpater sample rate from 44.1 to 48.0 kHz made a difference. This is about a 9% increase in sample rate, and produced about a 6% reduction in latency. I haven't attempted to change any of the other settings you mention, such as the bitrate settings.
As far as fiber vs. copper, there are so many factors affecting latency that it is difficult to make a broad and correct generalization. More bandwidth does not necessarily mean less latency. It is entirely possible for a 20 Mbps copper internet connection to have lower latency than a 200 Mbps fiber connection. It really depends on your in-home network interface and the equipment your internet service provider deploys in the path between your network interface and the external internet. A large system that aggregates many high bandwidth fiber channels and does a lot of buffering can introduce delay.
Frame size seems to have the largest impact on latency of any of the knobs I can turn. With the ASIO4ALL driver I was expecting to see a difference in latency as I vary buffer size in the ASIO4ALL settings, but I do not. The Buffer In/Out counts also do not seem to affect latency. I've experimented with power of 2 buffer sizes from 64 to 512, and In/Out counts from 0 to 3.
Changing the USB audio adpater sample rate from 44.1 to 48.0 kHz made a difference. This is about a 9% increase in sample rate, and produced about a 6% reduction in latency. I haven't attempted to change any of the other settings you mention, such as the bitrate settings.
As far as fiber vs. copper, there are so many factors affecting latency that it is difficult to make a broad and correct generalization. More bandwidth does not necessarily mean less latency. It is entirely possible for a 20 Mbps copper internet connection to have lower latency than a 200 Mbps fiber connection. It really depends on your in-home network interface and the equipment your internet service provider deploys in the path between your network interface and the external internet. A large system that aggregates many high bandwidth fiber channels and does a lot of buffering can introduce delay.