[RWP] Latency, is shorter always better?

[Chris Belle]

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.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> RWP mailing list
>>>>> RWP at reaaccess.com
>>>>> http://reaaccess.com/mailman/listinfo/rwp_reaaccess.com
>>>>>
>>>>
>>>>
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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:
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>> Skype:
>> skypedude1234
>>
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