[RWP] Latency, is shorter always better?

[Jim Snowbarger]

well said.

----- Original Message ----- 
From: "Chris Belle" <cb1963 at sbcglobal.net>
To: "Reapers Without Peepers" <rwp at reaaccess.com>
Sent: Tuesday, July 22, 2014 9:02 PM
Subject: Re: [RWP] Latency, is shorter always better?


> Plus, there are very few coders left who know how to think in machine 
> language, they just glue modules together now.
>
> NO wonder everything sucks so bad.
>
>
> On 7/22/2014 12:10 PM, Jim Snowbarger wrote:
>> Would a 30 billion gigahertz processor talk fast?
>> I think we have almost reached the physical limit on processor speed.  It 
>> has to do with the speed of light, and the distances of the connecting 
>> lines that connect up your various components, plus the inevitable 
>> capacitence that such lines represent, and how that interacts with 
>> frequency.   And yes, Keith is right, more power is required to drive 
>> such attempts.
>> Basically, we're going to have to go lazar now in order to get any 
>> significant increase in speed.
>> Either that, or stop writing such crappy, bloated software. Hmmm. 
>> Imagine that possibility.
>> Nope, that won't happen.  Time to market would suffer, and we would all 
>> fall asleep from bordom.
>> Can't have that!
>>
>>
>> ----- Original Message ----- From: "Keith Hinton" 
>> <keithint1234 at gmail.com>
>> To: "Reapers Without Peepers" <rwp at reaaccess.com>
>> Sent: Tuesday, July 22, 2014 10:48 AM
>> Subject: Re: [RWP] Latency, is shorter always better?
>>
>>
>>> We expect a little baby toy  computer to become a huge, furry kitty
>>> cat with paws waving around and a tail that swishes and a meow to
>>> escape the voicebox of the CPU. LOL just kidding.
>>> Couldn't resist.
>>> Fun thread for sure, I'm liking reading all about this stuff.
>>> I didn't know digital audio was so latency-crazy.
>>> But apparently it is.
>>> As for 30 Gigahurts?
>>> Why not 1 billion gigahurt processors? LOL!
>>> Could you imagine how high your electrical bill would be?
>>> one billion gigahurts with a quadrillion cores.
>>> Bet you couldn't even run something like that. LOL.
>>> Not realistically.
>>>
>>>
>>> On 7/22/14, Jim Snowbarger <Snowman at snowmanradio.com> wrote:
>>>> Tape decks with a moveable playback head?  Very nice.  I didn't know 
>>>> about
>>>> that.  But, that would have been great for adjusting the rate of
>>>> regenerative feedback to match the tempo of a song.
>>>> Another way to do that was to vary the speed, except that it had 
>>>> frequency
>>>> response implications as well.
>>>>
>>>> An interesting experiment with DAWs, record a series of clicks into 
>>>> track 1.
>>>>
>>>> Arm track 2, and route the playback of track 1 into the input for track 
>>>> 2.
>>>> Do it externally, rather than inside the computer, so you get the 
>>>> benefit of
>>>>
>>>> the entire chain of processing.
>>>>
>>>> Now, play tracks 1 and 2 back together.  Listen for the time delay 
>>>> between
>>>> the clicks on the two tracks.  Ideally, they will be coincident.
>>>> On reaper here, it isn't quite perfect, but it is pretty darned good.
>>>> Last time I tried Audacity, they arrived in different time zones.
>>>>
>>>> ----- Original Message -----
>>>> From: "Chris Belle" <cb1963 at sbcglobal.net>
>>>> To: "Reapers Without Peepers" <rwp at reaaccess.com>
>>>> Sent: Tuesday, July 22, 2014 12:46 AM
>>>> Subject: Re: [RWP] Latency, is shorter always better?
>>>>
>>>>
>>>>> One more thought  about this latency thing.
>>>>>
>>>>> And us old farts who used to play with tape decks will remember this.
>>>>>
>>>>> How about those 3 head decks where you could listen to play-back while
>>>>> recording?
>>>>>
>>>>> YOU could hear the input while it was going down, and listen to your
>>>>> playback head, and some of those were moveable.
>>>>>
>>>>> So you could change the latency between when something got recorded 
>>>>> and
>>>>> played back by moving the head closer or further away from the 
>>>>> recording
>>>>> head.
>>>>>
>>>>> That was on the commercial machines.
>>>>>
>>>>> I never had one of those, but i did have a very nice 3 head cassette
>>>>> deck.
>>>>>
>>>>> This is, in fact, somewhat similar to what hapens in your daw,
>>>>> even if your not recording but just listening to the signal comming 
>>>>> back
>>>>> from your daw once it goes through the internal processing, and any
>>>>> plug-ins you might have,
>>>>> and they add their own latency you can bet, and most modern daws
>>>>> compensate for that under the hood.
>>>>>
>>>>> Sonar had automatic plug in delay compensation
>>>>> way before many daws, including protools ever had it.
>>>>>
>>>>> Yes, you go back and listen to first episodes of the home recording 
>>>>> show
>>>>> on protools 9 and 10,
>>>>> and you can hear them talking about lining up tracks manually after 
>>>>> the
>>>>> fact, to make the audio come out right, after going through all the
>>>>> processing plugs.
>>>>>
>>>>> Boy howdy, now, isn't that a real pain in the posterior?
>>>>>
>>>>> INteligently keeping up with when in the time line a recording starts, 
>>>>> and
>>>>>
>>>>> how to play it precisely in the right way to account for plug-ins
>>>>> latencies, and then play it properly again when you take plugs of is 
>>>>> not
>>>>> an easy task, but your daw does that all for you under the hood, if 
>>>>> it's
>>>>> worth a squat.
>>>>>
>>>>> People sometimes get in real trouble even with this automatic
>>>>> stuff going on by not routing their monitoring right,
>>>>> because there are certain ways of routing and recording which makes it
>>>>> impossible for your daw to implement delay compensation properly.
>>>>>
>>>>> So this is why I tend to like to not do plugs until after I've laid my
>>>>> audio.
>>>>>
>>>>> Not always possible, you can't lay that heavy rock guitar track easily
>>>>> only hearing plink, plunk, twang,
>>>>> but you can believe your daw is doing the latency shuffle dance when 
>>>>> you
>>>>> have many tracks playing and you are laying guitar amp simms which has
>>>>> latency going both ways, because remember, you are going audio in, and
>>>>> audio back out,
>>>>> and this is why with mastering plugs which cause a lot of latency,
>>>>> especially multi-band compressors with look ahead and back in my early
>>>>> early days of learning this stuff it used to drive me nuts, why are my
>>>>> midi tracks being delayed so much when I press a note but they play 
>>>>> just
>>>>> fine on playback?
>>>>>
>>>>> Well, it's that delay compensation working for you.
>>>>>
>>>>> Imagine having to figure out how much delay you had and fixing all 
>>>>> that
>>>>> manually?
>>>>>
>>>>> You can get interesting things happening when using reverb in projects 
>>>>> by
>>>>>
>>>>> turning off delay compensation,
>>>>> you get a built in pre-delay, which is a setting on high quality 
>>>>> reverb
>>>>> units, the reverb doesn't start right away, and
>>>>> this helps make room in the mix when you don't wan the verb in the 
>>>>> way,
>>>>> and it kicks in after the initial atack of your audio.
>>>>>
>>>>> Or do we remember real world latency,
>>>>> and the days when distructive editing was the only kind you did, if 
>>>>> you
>>>>> wanted to process an equalizer, or chorus fx, you hit the button, and 
>>>>> then
>>>>>
>>>>> go have a sandwich and waited for your 486 to process that track, and
>>>>> you'd come back 10 minutes later and maybe have a wet and dry track.
>>>>> and you could do interesting things with that by time delaying the wet
>>>>> track 'grin'.
>>>>>
>>>>> When I do drum replacement by generating midi tracks from transient 
>>>>> points
>>>>>
>>>>> of an audio drum track and then feeding it to a audio bus with 
>>>>> samples, I
>>>>>
>>>>> have to time align the new track to match the old one,
>>>>> at least in the old days we had to do more of that before delay
>>>>> compensation was automatic.
>>>>> in most daws.
>>>>>
>>>>> Still, most daws will only do this in a certain range, see above, 
>>>>> where I
>>>>>
>>>>> mention mastering plugs,
>>>>> linear phase equalizers are also notorious for introducing way too 
>>>>> much
>>>>> delay to use them in real time.
>>>>>
>>>>> So are transient  processors, shapers.
>>>>>
>>>>> Maybe when we get processors running at 30 gigahertz
>>>>> we'll be able to do that stuff in real time, and did I hear silly 
>>>>> people
>>>>> want to make a daw out of an ipad?
>>>>>
>>>>> Right now in 2014, an ipad will just barely run a guitar simm with low
>>>>> enough latency
>>>>> \to be playable.
>>>>>
>>>>> Well, what do you expect from a little baby toy computer?
>>>>>
>>>>>
>>>>> On 7/21/2014 9:33 PM, Jim Snowbarger wrote:
>>>>>> Now and then, I feel like a slight departure from topic..  And, this 
>>>>>> is
>>>>>> one of them.  So, stand bye with your delete key ready as I carry on.
>>>>>>
>>>>>> This probably belongs over on MidiMag.  But, I don't feel like 
>>>>>> joining
>>>>>> just so I can post this once in a blue mooner.
>>>>>>
>>>>>> One of the great things that digital audio processing has brought to 
>>>>>> us
>>>>>> is so-called latency.  You might just call it delay.  but, in the 
>>>>>> 21st
>>>>>> century, we like to use clever names.  It makes us feel smarter.  So,
>>>>>> let's co-opt the term latency, which had a totally different meaning
>>>>>> before the techno-gods got hold of it. And, let's now define latency 
>>>>>> as
>>>>>> the act of being late.  But, however you slice it, it comes down to
>>>>>> delay.
>>>>>>
>>>>>> Digital devices impose delay mostly because data consumers, like 
>>>>>> sound
>>>>>> cards, or recording devices, have learned to be defensive, knowing 
>>>>>> full
>>>>>> good and well that data providers, such as input sound cards, or 
>>>>>> other
>>>>>> streaming devices, can not be counted on to keep up a steady stream 
>>>>>> of
>>>>>> data.  Internet congestion, or scheduling congestion inside your own
>>>>>> machine, can temporarily block the normal flow of things. Sound 
>>>>>> playback
>>>>>>
>>>>>> requires a rock-solid comsumption rate of the data. The sampels need 
>>>>>> to
>>>>>> keep flowing. You might not get that next buffer load of data in 
>>>>>> time.
>>>>>> so, it pays to keep a backlog.  The more backlog, the safer you are.
>>>>>> But, if the backlog is too great, you get, latency, that annoying 
>>>>>> delay.
>>>>>>
>>>>>> I recently picked up one of those fine Computers Chris is always 
>>>>>> talking
>>>>>>
>>>>>> about from StudioCat.com.  That is one very fine box. And, now that I
>>>>>> also own Chris's Delta 1010, I was enjoying fine-tuning my latency 
>>>>>> down
>>>>>> to acceptable levels,  not carefully measured, but clearly less than 
>>>>>> 10
>>>>>> milliseconds.
>>>>>>
>>>>>> Most of the recording work I do involves a microphone and headphones. 
>>>>>> I
>>>>>>
>>>>>> am quite typically listening to my own voice as I speak. If you have
>>>>>> listened to the Snowman Radio Broadcasts, you know the kind of
>>>>>> multi-track microphone work I'm guilty of.
>>>>>> When living on machines where such short delays were not possible, my
>>>>>> habit was to listen to my own foice direct out of the mixer, and not
>>>>>> going through Reaper.  So, I kept the reaper monitor off. What was
>>>>>> annoying about that is that, if I panned my various character voices 
>>>>>> in
>>>>>> the stereo  mix, then, my direct microphone sound would not be panned 
>>>>>> the
>>>>>>
>>>>>> same as the character voice track I was recording into. So, when it
>>>>>> played back, it came from elsewhere, and was more than a little bit
>>>>>> confusing.
>>>>>>
>>>>>> But, with delay this short, I find that I switch off the direct 
>>>>>> sound,
>>>>>> and now can monitor the signal coming back from reaper with the 
>>>>>> monitor
>>>>>> turned on.  So, I'm now listening to a delayed version of my voice, 
>>>>>> and
>>>>>> it is panned to the same place where that character voice sits, which
>>>>>> helps me keep track of who I am supposed to be right now. And, I can
>>>>>> more easily tell now whetehr a track is armed, and even if one is 
>>>>>> armed
>>>>>> that should not be. It's nice to be able to work like that, just
>>>>>> listening to reaper's output.
>>>>>>
>>>>>> But, here is the cool thing.  The exact amount of latency you provide
>>>>>> affects the quality of what you hear in your headphones.
>>>>>>
>>>>>> No matter how good your phones, the sound that you hear when you are
>>>>>> listening to yourself speaking live into a microphone, is actually 
>>>>>> the
>>>>>> composite of at least two signal paths, and maybe more. Yes, there is
>>>>>> the direct signal coming through Reaper. Then, there is bone
>>>>>> conductivity, the sound of your own voice coming through the 
>>>>>> structure of
>>>>>>
>>>>>> your head, which will very somewhat with density.  If you don't get 
>>>>>> any
>>>>>> of that, you might wonder about that density stuff.
>>>>>> And maybe even, there is leakage around the ear muffs.  In all, it is 
>>>>>> a
>>>>>> complex sond that actually reaches your ears.  And, the phase
>>>>>> relationship between all of the various contributors will affect the
>>>>>> frequency response of the final signal that you hear.
>>>>>>
>>>>>> In the old days, we knew about the affect that phase would have on 
>>>>>> such
>>>>>> things.  Having your head phones out of phase with your microphone 
>>>>>> left
>>>>>> you feeling empty headed, due to the phase cancellation that took 
>>>>>> place.
>>>>>> But, since delay was in the nanoseconds, we didn't get to know so 
>>>>>> much
>>>>>> about the effect that delay would have, despite our compulsive
>>>>>> preoccupation with tape delay.
>>>>>>
>>>>>> Phase is mostly a frequency independent phenomenon.  Yes, we know 
>>>>>> that
>>>>>> some systems, especially mechanical transducers, or even cheap
>>>>>> equalizers, which will have a reactive component to their impedance,
>>>>>> introduce a variable amound of phase shift, depending on frequency. 
>>>>>> But,
>>>>>>
>>>>>> usually those effects are at the far ends of their usable range.
>>>>>> In general, especially in mixer land, where things are nice and 
>>>>>> linear,
>>>>>> and where impedances are strictly non-reactive, if you put something 
>>>>>> 180
>>>>>>
>>>>>> degrees out of phase, you will get perfect cancellation, all across 
>>>>>> the
>>>>>> frequency band.
>>>>>>
>>>>>> Enter the digital age, and the new innovation, latency.
>>>>>> The relationship between signal phase, and a delay is frequency. For
>>>>>> example, a delay of 4 milliseconds is one full cycle of a 250 Hertz 
>>>>>> tone.
>>>>>>
>>>>>> But, it is only half a cycle of a 125 hertz tone.   It is all still a 
>>>>>> 4
>>>>>> millisecond delay.  But, the phase impact depends on the frequency.
>>>>>> Combining the pre and post delays of these two tones with that 4ms 
>>>>>> delay
>>>>>>
>>>>>> will have completely different effects. The 125 hertz tone would be
>>>>>> nulled out.  The 250 hertz tone would actually see a 6 db increase.
>>>>>>
>>>>>>
>>>>>> The result is that, if you put a delay in front of your headphone 
>>>>>> mix,
>>>>>> you will cause what is referred to as a comb filter effect on the
>>>>>> perceived headphone signal.  It is a filter that has a frequency 
>>>>>> response
>>>>>>
>>>>>> curve that looks like a rola coaster, with hills and valleys.  If you
>>>>>> were listening to an audio tone sweep, one that you would actually 
>>>>>> need
>>>>>> to sing, in this case, in order to get that bone conductivity thing
>>>>>> happening as well, As you move steadily up in frequency, the sound 
>>>>>> would
>>>>>>
>>>>>> be much stronger at some frequencies, and much weaker at others.  As 
>>>>>> the
>>>>>>
>>>>>> tone rises, you would hear rising and falling of the net response. 
>>>>>> And,
>>>>>>
>>>>>> changing the amounbt of delay slides that comb up and down the audio
>>>>>> spectrum.
>>>>>> Depending on several things, the frequency range of your voice, 
>>>>>> response
>>>>>>
>>>>>> of your headphones, your ears, the density of your grey matter, your
>>>>>> preferences, and on and on, you might have preferences about the 
>>>>>> optimal
>>>>>>
>>>>>> position of that comb.  What frequencies do you like to accentuate? 
>>>>>> And,
>>>>>>
>>>>>> which to attenuate.
>>>>>>
>>>>>> The cool thing is that, by fine-tuning your headphone latency, you 
>>>>>> can
>>>>>> position that comb how you like, and can optimize your headphone
>>>>>> experience. The latency needs to be short enough to not give you a 
>>>>>> delay
>>>>>>
>>>>>> echo effect. But, beyond that, the shortest possible latency may not 
>>>>>> give
>>>>>>
>>>>>> you the headphone experience you like.  Instead, relax it a little, 
>>>>>> and
>>>>>> see what enriching tones come your way.
>>>>>> Silly you.  And you always thought shorter was better. And now you
>>>>>> know.
>>>>>> TROTS.
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> _______________________________________________
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>>>>>>
>>>>>
>>>>>
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>>>>
>>>>
>>>>
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>>>
>>>
>>> -- 
>>> Sincerely,
>>>
>>> Keith
>>>
>>> Home Phone:
>>> 928-554-3936
>>> Mobile Phone:
>>> 928-713-6370
>>> Primary email:
>>> keithint1234 at gmail.com
>>> Twitter:
>>> @keithint1234
>>> Facebook:
>>> http://facebook.com/keith.hinton1
>>> Skype:
>>> skypedude1234
>>>
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>>
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