Re: [Jack-Devel] Network Audio Transmission - Quality

Thanks Harry, Ralf for your suggestions.

I agree it's important to check by listening and trust the ears! It can
fool you though, just try to do the 'pepsi' test with a song as original
wave and the same as 256kbit/s mp3. You probably won't hear the difference
but it's there. :)

Another suggestion i got for testing is to route host A -> host B -> host
A, phase-invert signal and see what remains.

I learned jacktrip is lossless so if the network link is ok, the data
should be identical (except for rounding errors if using different bit
depth).

Cheers,
Thomas


> On Sun, 2013-06-23 at 23:36 +0200, Ralf Mardorf wrote:
>> On Sun, 2013-06-23 at 22:14 +0100, Harry van Haaren wrote:
>> > On Sun, Jun 23, 2013 at 2:38 PM, <[hidden]> wrote:
>> > > I'd like to find out the impact on signal quality when using
>> > different
>> > > network tools for jack (netjack, jacktrip).
>> >
>> > I don't think there is *any* impact on sound quality: the audio data
>> > on both sides is binary identical: hence no loss by transmission.
>> >
>> > So perceptually they're identical (netjack uses float as sample
>> > format, at the same samplerate: so just like an normal JACK patchbay
>> > connection, nothing is lost ). For details on encoding etc on netjack
>> > checkout this page
>> > http://trac.jackaudio.org/wiki/WalkThrough/User/NetJack
>> >
>> > Using certain encodings / bit-depths will cause reduction in sound
>> > quality: as defaults I think its binary identical... perhaps don't
>> > quote me though, I'm not an author of any of the implementations...
>> >
>> > > Question that come to mind are,
>> > The questions that will show the difference between netjack, netjack2
>> > and JackTrip are how jitter / packet loss / latency are handled /
>> > compensated for.
>> >
>> > HTH, -Harry
>>
>> Audacity enables to show a spectrum. When I heard something that nobody
>> else was able to hear, for something that should be a 1:1 digital copy,
>> I could show that the spectrum did differ. It must be somewhere in the
>> Qtractor devel archive. It was a Jack connection from Qtractor out to
>> Qtractor in to mix down the recordings. However, I always wonder that
>> people want to measure things, when they don't hear a difference. Why?
>> If we can't hear it, than it's not an issue. Some time ago I read that
>> somebody wanted to verify by _watching_, if his music has the Katz
>> dynamic and not a loudness war dynamic. It's irrelevant what a meter
>> does tell us, important is what we're able to hear.
>>
>> My advice is to use the ears. If the OP can't hear a difference there's
>> no need to check it with a tool. If a difference is audible where no
>> difference should be, than tools are needed for troubleshooting.
>>
>> 2 Cents,
>> Ralf
>
> PS: Sending the signal several times from A to B and B to A or just from
> A to B and than a recording done with B again from A to B, would
> increase eventually existing loss by rounding errors, jitter, bad cables
> or what ever in what ever analog or digital signal chain might be
> possible.
>
>
> 
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