AptX Bluetooth (TX/RX) and 2.4Ghx Wireless... low latency guitar to low latency Bluetooth Headphones

espiegel123

@McD: what buffer size did you do when you did the test?

McD

@espiegel123 said:
@McD: what buffer size did you do when you did the test?

The iPad default. I have a question posted here about where that might be modified.
You are out of questions until mine is answered. :^)

rs2000

@McD said:
A $10 investment in LatencyMeter could be useful to evaluate the 2.4Ghz TX/RX pair compared to a straight loopback cable and to verify my assumptions about TE Reader's echos. I'll think about it since I have $47.13 in credit and but Black Friday is only 11 days away.
Latency Meter won't help me with the AptX headphones... wait... there might be a way to test that too. If I don't find it useful I could request a refund. And $10 is my impulse limit.

Should I keep testing? or let someone else take the baton? Bueller? Godot? @rs2000?

Yes!! A latency meter cannot be better than this unconventional but simple diy setup!

@espiegel123 said:
...
I wonder if you get double the latency -- I am not sure if the buffers are there on both input and output. If they are, your return trip passes through the buffer on the way to the headphones and then on the way back in.

No, the buffers will affect the audio path but they won't distort the measurement.
If you want to measure the latency between string pick and eardrum then this setup will give you that time. If the distance between microphone and string is as long as the distance between microphone and headphones diaphragm then you can get a very precise measurement, only affected by your "finding the correct peak position" in both the original and the reproduced signal. Be aware that the phase might be inverted.

McD

@rs2000 said:
Be aware that the phase might be inverted.

When that happens, I just click the drum sticks together and quickly stand on my head.
It doesn't seem to change the results so I have discounted the 180% phase change in my computations. I'm still trying to determine the "fundamental" frequency of the drum sticks...
it's tricky since there are 2 of them. I'm going to have to shop for a pair that's aligned ideally
at A=440. Aha! I can use a tuned metallophone for the stimulus. I have a lovely Tibetan Bowl
and I have tuner apps to determine the frequency.

Mad scientist at work.

rs2000

@McD your lab must be the magic cave of joy 😋

McD

@rs2000 said:
@McD your lab must be the magic cave of joy 😋

This work was done on the sofa while binging "The Crown (Season 4)".
The "Magic Cave of Joy" is the bathroom, I think. Long story... (no pun intended).

espiegel123

Which options did you have on in TW Recorder. DId you turn off 'enable iOS' processing? If not, that might contribute to latency.

Since the app doesn't indicate what size buffer 'low latency recording' is, I wonder if it would make sense to use something like AUM to make the recording since you will have a buffer of known size -- and can run the test at a couple of buffer sizes.

McD

@espiegel123 said:
Which options did you have on in TW Recorder.

32-bit temp files OFF

Low Latency recording ON

External Speakers ON (true for headphones)

Bluetooth Recording OFF (the AptX Bluetooth is external to the iPad with a Transmitter and Headphone matched set)

DId you turn off 'enable iOS' processing? If not, that might contribute to latency.

It was ON

Prevent Sleeping OFF

POP-UP options:
Mono and some trials in stereo
48000 Hz sample rate (didn't try other rates but we're talking millisecond measurements)

Since the app doesn't indicate what size buffer 'low latency recording' is, I wonder if it would make sense to use something like AUM to make the recording since you will have a buffer of known size -- and can run the test at a couple of buffer sizes.

I'd love to use AUM and have a GAIN control but I need an app that measures and display Millisecond intervals in the recording. Any recommendations? I have a few that might...
Auditor, Audioshare or ???

espiegel123

@McD said:

@espiegel123 said:
Which options did you have on in TW Recorder.

32-bit temp files OFF

Low Latency recording ON

External Speakers ON (true for headphones)

Bluetooth Recording OFF (the AptX Bluetooth is external to the iPad with a Transmitter and Headphone matched set)

DId you turn off 'enable iOS' processing? If not, that might contribute to latency.

It was ON

Prevent Sleeping OFF

POP-UP options:
Mono and some trials in stereo
48000 Hz sample rate (didn't try other rates but we're talking millisecond measurements)

Since the app doesn't indicate what size buffer 'low latency recording' is, I wonder if it would make sense to use something like AUM to make the recording since you will have a buffer of known size -- and can run the test at a couple of buffer sizes.

I'd love to use AUM and have a GAIN control but I need an app that measures and display Millisecond intervals in the recording. Any recommendations? I have a few that might...
Auditor, Audioshare or ???

Just record in AUM and then open the file in Auditor. Its timeline can be in whatever units you want. Or you could open the file in TW Recorder as you have been.

McD

@espiegel123 said:
Just record in AUM and then open the file in Auditor. Its timeline can be in whatever units you want. Or you could open the file in TW Recorder as you have been.

Facepalm... (ouch). Getting old sucks.

I finished "The Crown" so it might be a while. Twitter and Parler are keeping me busy. May this era be over soon and replace with the age of re-enlightenment... the Re-Renaissance.