| guysoft42 | hey , is there a way to get a hard realtime kernel on regular ubuntu? | 21:01 |
|---|---|---|
| OvenWerks | guysoft42: pretty much build your own. Take a look through some of the PPAs though. | 21:02 |
| guysoft42 | OvenWerks, did that for raspberrypi, so I can. Just thought there was something that was tested | 21:05 |
| guysoft42 | OvenWerks, which PPAs? | 21:05 |
| OvenWerks | Anything I can find seems to stop with 14.04 | 21:05 |
| OvenWerks | I can see wanting an RT for the R-pi, however I have done quite well with lowlatency so far (down to jackd at 16/2 with my ice1712 based interface) | 21:07 |
| OvenWerks | USB based boxes are over 1ms regardless | 21:08 |
| OvenWerks | In fact USB boxes will have different latency every time they are reconnected varying between 1 ms and 1 ms + buffer size | 21:12 |
| guysoft42 | OvenWerks, you mean its not good? 1ms sounds good | 21:43 |
| guysoft42 | how is the buffer sound? | 21:43 |
| guysoft42 | i mean how much? | 21:46 |
| OvenWerks | guysoft42: 1 ms is ok, but the problem with USB is that it is not constant, One time the latency of the device will be 1ms and the next maybe 1.7ms for example. even with no settings changes | 21:47 |
| guysoft42 | um, so what about something over GPIO? | 21:48 |
| OvenWerks | the buffer at 16/2 and 48khz is .7ms with 32/2 is 1.3ms and 64/2 is 3ish ms. not including interface internal time (mine is 1ms so at 16/2 the total one way time is 1.66ms or 3.3 for round trip | 21:49 |
| OvenWerks | basically anything under 10ms from you hit the note till you hear it is ok. | 21:49 |
| OvenWerks | All (reasonable) DAWs compensate for latency in such a way that it is not a problem so long as you use external monitoring. | 21:51 |
| OvenWerks | for live use (softsynth, guitar effects etc.) latency matters. | 21:51 |
| OvenWerks | As an example, I have found that I have trouble keeping time with the band at even a 30foot distance. I can hear that I am playing late by the time my sound gets to me... this is with no digital conversion, just analog | 21:53 |
| guysoft42 | OvenWerks, 30 feet would me a 27 ms delay | 21:58 |
| guysoft42 | just factoring speed of sound | 21:59 |
| guysoft42 | so I need to get the delay as low as 10ms? | 21:59 |
| OvenWerks | for stage use yes | 21:59 |
| guysoft42 | I am gonna build this and test: https://wiki.linuxaudio.org/wiki/jack_latency_tests | 22:00 |
| guysoft42 | OvenWerks, well i am jamming at the moment, but I wanna try and get to that | 22:00 |
| OvenWerks | It does depend on the instrument being played to some extent | 22:00 |
| guysoft42 | OvenWerks, electric violin, in the process of building that too | 22:00 |
| OvenWerks | piano needs to be fast, pipe organ can be slower | 22:00 |
| guysoft42 | string instrument? | 22:01 |
| OvenWerks | plucked is pretty percusive. | 22:01 |
| guysoft42 | Yes, there seems to be little information about bow instruments. I guess I'll have to build and test really | 22:02 |
| OvenWerks | Just playing around with guitar through guitarix, 128/2 in jack seems to be ok. | 22:02 |
| OvenWerks | even bowed instruments sometimes are played with sharp attack as in fiddle playing. | 22:03 |
| OvenWerks | string pad kind of playing won't show up delay as much | 22:04 |
| guysoft42 | OvenWerks, googling around, there are i2c audio controllers for the Pi. that would remove the USB stack | 22:07 |
| OvenWerks | i2c can use whatever buffering you want I guess | 22:08 |
| OvenWerks | i2c would be interupting the cpu at every sample? | 22:09 |
| guysoft42 | http://shop.audioinjector.net/detail/sound_card/Stereo+Raspberry+pi+sound+card | 22:09 |
| guysoft42 | this one claims to have as low as 0.54 ms latency | 22:09 |
| guysoft42 | bounch here, some other perhaps: https://elinux.org/index.php?title=RPi_Expansion_Boards#Sound | 22:10 |
| OvenWerks | so more than one sample.... .54ms seems an odd number of samples unless that is the interface delay | 22:12 |
| OvenWerks | at 48khz 32 samples is .66ms and at 96k 32 samples is .33ms for example | 22:12 |
| guysoft42 | OvenWerks, perhaps. anyway, i think ill call it a day. I'll start by building the usb testing rigg, and flash a pi and all, see how bad it ias with no optimization | 22:13 |
| OvenWerks | I think the MOD code is open. youmight want to look there | 22:13 |
| guysoft42 | OvenWerks, i see. well, thanks, its really great taking small steps in this area and having someone with answers :) | 22:13 |
| OvenWerks | http://moddevices.com/ | 22:14 |
| guysoft42 | OvenWerks, oh, one question - my device is high Z. should i watch out for anything when it comes to sound cards? | 22:15 |
| OvenWerks | depends on how high. A lot of the usb devices have an "instrument" plug that will handle a guitar. | 22:16 |
| OvenWerks | I don't know about piezo though | 22:16 |
| OvenWerks | I use a fishman loudbox as my preamp for my mandolin | 22:16 |
| guysoft42 | OvenWerks, I heard that name before. | 22:17 |
| guysoft42 | This is the pickup i got: http://www.kksound.com/products/twinspot.php | 22:17 |
| guysoft42 | doesn't really say much beyond "high ohomic" | 22:17 |
| OvenWerks | I have found that a pre designed for piezo pickups sounds much better than plugging into a sound board (mackie c1604 in this case) | 22:18 |
| OvenWerks | Ya, those are piezo pickups and definately hiz. Mine sounds ok in the mixer, but a bit on the dead side. the hiz pre makes a difference for sure | 22:19 |
| OvenWerks | the average electric guitar (also called hiz) is 10 to 20 kohms and so need 50 to 100 kohm input impedance | 22:22 |
| OvenWerks | a piezo needs 10meg input impedance to really sound nice | 22:23 |
| OvenWerks | That is why acousic guitars often have a built in preamp | 22:24 |
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