[Ardour-Users] OT: jack_iodelay outside jack

Tweed tweed at lollipopfactory.com
Mon Jun 28 16:13:39 PDT 2021

On Sun, 27 Jun 2021 22:07:02 -0500
"Chris Caudle" <6807.chris at pop.powweb.com> wrote:

> On Sun, June 27, 2021 8:09 pm, Matt Keys wrote:
> > I've asked in other forums without success.  
> Have you tried Hydrogen Audio?  Those guys have done a lot of
> listening tests.
> Have you checked the opus information direct from the web site?
> This page has a comparison that shows opus at 96k is high quality, but
> still perceptible:
> https://opus-codec.org/comparison/
> Latency seems to be in the 5ms-20ms range for high bit rate opus.
> > I'm trying to understand which is better for tx/rx of highest
> > quality and lowest latency audio to multple remote peers -
> > uncompressed audio  
> How remote?  If on a LAN you control then multicast uncompressed is
> both highest quality and lowest latency.
> > example jacktrrip 2 channel 48k / 128 frames), or something like
> > opus at 48k 2 channel (for example webrtc using opus)?  
> The network protocol built into jackd can use opus (well, celt, the
> immediate precursor to opus); you could start with that, compare
> uncompressed and compressed using netjack1.
> https://jackaudio.org/faq/netjack.html
> > My focus is within a controlled
> > environment like a flat wired or optical 1g or 10g ethernet.  
> That isn't what I would consider remote.  Just use uncompressed audio,
> anything else is just adding latency and reducing audio quality for no
> reason.
> > Does the use of opus (and a sip stack/webrtc) add latency overall  
> Yes
> > there efficiency gains (for example network bandwidth reduction)
> > through its use?  
> Why do you care about network efficiency on a 10Gb or even 1Gb
> network in a flat?  You can carry something like 500 channels of
> uncompressed audio on a 1Gb network.  At 48k sampling that is
> 48k*4bytes = 192k bytes/second = 1.55-ish Mbits/second per channel.
> Even with overhead of packet headers you can get hundreds of channels
> into 1000Mb/s Ethernet.
> > Could this difference, if any, be measured using jack_iodelay?  
> Yes, as pointed out above you can just use jackd with netjack1 and
> switch between uncompressed and compressed audio.
> But you should only do that for the educational value, if you just
> want to get audio work done just load up zita-j2n and get going,
> messing around with opus on a LAN doesn't make sense.


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