[James Price[_5_]]

What's the best way to compensate for phase shift (due to latency) when bussing things out in digital?

[Scott Dorsey]

James Price wrote:
What's the best way to compensate for phase shift (due to latency) when bussing things out in digital?

Use software that compensates for it. Just about all of the modern DAW systems
deal with this automatically; the total latency of the system is the latency
of the slowest plug-in plus the latency of the DAW application.

The day of having to line everything up or do batch processing to avoid
delays are gone with the days of Session 8.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Mike Rivers[_2_]]

On 9/2/2017 12:32 PM, James Price wrote:
What's the best way to compensate for phase shift (due to latency) when bussing things out in digital?

What program (or programs) are you using?

Nearly all modern (or newest versions of legacy) DAW programs can read
the number of samples that a particular plug-in delays from the driver
and automatically compensates for this.

Most modern DAW programs can also do that automatically when going out
to an analog processor and back in to a track or as an effect return,
but you may need to measure and manually enter the round trip delay.
Your software probably offers instructions for doing that.

But automatic delay compensation isn't always accurate, so you may have
to do a little trimming. Your ears will tell you whether or not it's
correct.




--

For a good time, call http://mikeriversaudio.wordpress.com

[James Price[_5_]]

On Saturday, September 2, 2017 at 12:09:31 PM UTC-5, Mike Rivers wrote:
On 9/2/2017 12:32 PM, James Price wrote:
What's the best way to compensate for phase shift (due to latency) when bussing things out in digital?

What program (or programs) are you using?

Nearly all modern (or newest versions of legacy) DAW programs can read
the number of samples that a particular plug-in delays from the driver
and automatically compensates for this.

Most modern DAW programs can also do that automatically when going out
to an analog processor and back in to a track or as an effect return,
but you may need to measure and manually enter the round trip delay.
Your software probably offers instructions for doing that.

But automatic delay compensation isn't always accurate, so you may have
to do a little trimming. Your ears will tell you whether or not it's
correct.

I'm specifically referring to sending / returning from outboard gear. Do most DAW's handle latency, when sending to and returning from external hardware, automatically or is it generally a case of having to measure and manually enter the round trip delay?

[Mike Rivers[_2_]]

On 9/2/2017 1:56 PM, James Price wrote:
I'm specifically referring to sending / returning from outboard gear. Do most DAW's handle latency, when sending to and returning from external hardware, automatically or is it generally a case of having to measure and manually enter the round trip delay?

It depends on the program. That's why I asked what you were using. But
the simple answer is: "RTFM"

--

For a good time, call http://mikeriversaudio.wordpress.com

[Scott Dorsey]

James Price wrote:

I'm specifically referring to sending / returning from outboard gear. Do most DAW's handle latency, when sending to and returning from external hardware, automatically or is it generally a case of having to measure and manually enter the round trip delay?

Okay, that's a different matter altogether. Some systems have an automatic
function where it will measure the latency in an effects loop. Some do not,
and you just have to measure it yourself and line the pips up on the screen.

The good news is that for most analogue processing, the latency is close
enough to zero that you don't have to worry about it. You only have to
worry about the latency of the A/D and D/A converters.

Now, a lot of systems which have integrated software and hardware, like the
higher levels of ProTools, and the Merging Technology systems and RADAR,
all will compensate for this automatically because the software is designed
to work with those converters, and the people who designed the software knew
precisely what the converter latency was. But for systems that are not
so carefully integrated, you're on your own.

Personally, I just use the DAW as a big tape machine, I run the outputs of
the DAW into a console and I mix on the console. If I want analogue processing
I put it into the console insert. If I want digital processing, I do it on
the DAW. Doing this eliminates all of your latency issues since all of the
channels are going through the same converters and so all have the same
latency. I understand this technique is not for everyone, however.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[James Price[_5_]]

On Saturday, September 2, 2017 at 2:26:17 PM UTC-5, Scott Dorsey wrote:
James Price wrote:

I'm specifically referring to sending / returning from outboard gear. Do most DAW's handle latency, when sending to and returning from external hardware, automatically or is it generally a case of having to measure and manually enter the round trip delay?

Okay, that's a different matter altogether. Some systems have an automatic
function where it will measure the latency in an effects loop. Some do not,
and you just have to measure it yourself and line the pips up on the screen.

The good news is that for most analogue processing, the latency is close
enough to zero that you don't have to worry about it. You only have to
worry about the latency of the A/D and D/A converters.

Now, a lot of systems which have integrated software and hardware, like the
higher levels of ProTools, and the Merging Technology systems and RADAR,
all will compensate for this automatically because the software is designed
to work with those converters, and the people who designed the software knew
precisely what the converter latency was. But for systems that are not
so carefully integrated, you're on your own.

Personally, I just use the DAW as a big tape machine, I run the outputs of
the DAW into a console and I mix on the console. If I want analogue processing
I put it into the console insert. If I want digital processing, I do it on
the DAW. Doing this eliminates all of your latency issues since all of the
channels are going through the same converters and so all have the same
latency. I understand this technique is not for everyone, however.

Correct me if I'm wrong but, isn't phase frequency dependent and not necessarily a one dimensional constant that can be fixed by delaying a signal? Thus, is it possible to have phase issues when running multiple tracks to multiple compressors within a DAW and/or externally (to outboard gear) despite delay compensation?

[Mike Rivers[_2_]]

On 9/3/2017 11:50 AM, James Price wrote:
Correct me if I'm wrong but, isn't phase frequency dependent and not necessarily a one dimensional constant that can be fixed by delaying a signal?

You're correct here


Thus, is it possible to have phase issues when running multiple tracks to multiple compressors within a DAW and/or externally (to outboard gear) despite delay compensation?

Yes. Any time you have a time difference between two waveforms of the
same frequency and amplitude _that are summed together_ the sum will be
affected by the time difference. At the proper time difference for a
given frequency, it the two waveforms will be 180 degrees out of phase,
and the sum will cancel to zero. At another time difference, the two
waveforms will sum to double amplitude. At other time delays, there will
various degrees of boost or cut.

The trick is that the original waveform and its processed version need
to be summed. If you send a track out to a hardware compressor and then
bring the compressor back into the mix _and only use the processed
track_, then there will be no phase issues, only a time delay which,
chances are, will be negligible, but which can be completely corrected
if you know the delay time through the D/A and D/A converters (plus
associated computer time necessary to talk to them) and, if any, the
delay through the processor.

If you're mixing the outboard-processed and original signals, however,
such as with "parallel compression," then, unless you compensate for the
time difference between them, the sum will contain frequencies that will
be cancelled and other frequencies that will be emphasized. This is what
the jargon has corrupted the original meaning of phase shift and what we
speak of, more correctly, as "phase problems."

What you need to be aware of is "unplanned summing" of the original and
processed tracks. For example, if you run a snare drum through a
compressor, the processed snare track will be mixed with the leakage of
the snare in other drum tracks (they're everywhere) and there, you have
a potential "phase problem" that you didn't expect. But this is often
small enough to be ignored unless the amplitude of the snare in some
other track is pretty close to that of the real snare track.




--

For a good time, call http://mikeriversaudio.wordpress.com

[Scott Dorsey]

James Price wrote:

Correct me if I'm wrong but, isn't phase frequency dependent and not necess=
arily a one dimensional constant that can be fixed by delaying a signal?

In this case we are speaking specifically of time delay which is constant
and independent of frequency.

There are plenty of other sorts of phase shift, but most of them you will
not encounter as problems in the digital world.

Th=
us, is it possible to have phase issues when running multiple tracks to mul=
tiple compressors within a DAW and/or externally (to outboard gear) despite=
delay compensation?

What is an "issue?" If you put signal through an analogue equalizer, it will
change the phase in a specific way that isn't constant with frequency. That's
not an issue, it's just part of what a minimum phase equalizer does, and it's
part of why we use equalizers. There's no need to compensate for it, it's
just there.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Mike Rivers[_2_]]

On 9/3/2017 9:55 PM, James Price wrote:
As soon as you sum two signals where one was processed with EQ, the
phase relationship changes, doesn't it? I'm not talking about a pure sine
wave but rather a complex signal.


That depends on the signals and the type of equalization.

For instance, if you add a .5ms delay
to a sound, won't 1k, 3k, 5k, and 7k be 180 degrees out of phase whereas
2k, 4k, 6k and 8k will still be in phase?


If you finish the sentence. Those frequencies in the delayed version of
the signal will be 180 degrees out of phase with those frequencies in
the unprocessed signal. A single signal isn't "out of phase" unless you
state what it's out of phase with. Oh, and any other frequency will be
some amount of out of phase with its undelayed counterpart.

How you use those two versions of a signal determines whether or not you
have an audio problem - or fix a problem - or create a desirable effect.


Doesn't using a compressor for
color add overtones?


Yes. That's what "color" is. But a compressor adds harmonic distortion,
introducing overtones that weren't in the original signal.


What happens to the phase between the altered and
unaltered material?


It depends on how long it takes for the signal to pass from the input to
the output of the compressor. With an analog compressor, which has
essentially no throughput delay, there will be no cancellation when the
compressed and uncompressed signals are mixed. This is why "parallel
compression" became a popular technique before we had DAWs and plug-ins.

On the other hand, if the compressor introduces a delay, then, when you
sum its output with the uncompressed signal, either you'll get some
phase cancellation (typically called "comb filtering").

From what I understand linear phase EQ's do keep phase in check, but
have other undesirable issues.


A linear phase filter doesn't really exist in the analog world (there
are some squirrelly exceptions so don't get all "what about..." with
me). It's a product of digital filtering, which is based on delays.
Linear phase equalizers can introduce several hundred samples of delay.

As for latency, I've heard that a lot of plugins report none, but
there's still a change. Ever checked it with a test tone?

All plug-ins that affect the signal cause some delay. Some introduce a
negligible amount of delay and don't affect musical timing, or, when
combined with an unprocessed version of the same signal, only introduce
significant comb filtering at high frequencies, or, for a small enough
delay, outside of the audio range.

Some plug-ins report a theoretical amount of latency, through the audio
driver, based on the number of calculations that it's doing. It's up to
the DAW program to interpret that information and do something with it.
Some do a better job than others. And of course if there's no latency
reported, there's no compensation.

Nothing in digital audio "just works" all the time, on all systems.
Whenever you introduce some processing in the signal path, you need to
listen and decide if you've made the sound better or worse.


--

For a good time, call http://mikeriversaudio.wordpress.com

[James Price[_5_]]

On Saturday, September 2, 2017 at 2:26:17 PM UTC-5, Scott Dorsey wrote:
James Price wrote:

I'm specifically referring to sending / returning from outboard gear. Do most DAW's handle latency, when sending to and returning from external hardware, automatically or is it generally a case of having to measure and manually enter the round trip delay?

Okay, that's a different matter altogether. Some systems have an automatic
function where it will measure the latency in an effects loop. Some do not,
and you just have to measure it yourself and line the pips up on the screen.

The good news is that for most analogue processing, the latency is close
enough to zero that you don't have to worry about it. You only have to
worry about the latency of the A/D and D/A converters.

Now, a lot of systems which have integrated software and hardware, like the
higher levels of ProTools, and the Merging Technology systems and RADAR,
all will compensate for this automatically because the software is designed
to work with those converters, and the people who designed the software knew
precisely what the converter latency was. But for systems that are not
so carefully integrated, you're on your own.

Personally, I just use the DAW as a big tape machine, I run the outputs of
the DAW into a console and I mix on the console. If I want analogue processing
I put it into the console insert. If I want digital processing, I do it on
the DAW. Doing this eliminates all of your latency issues since all of the
channels are going through the same converters and so all have the same
latency. I understand this technique is not for everyone, however.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Correct me if I'm wrong but, isn't phase frequency dependent and not
necessarily a one dimensional constant that can be fixed by delaying a
signal? Thus, is it possible to have phase issues when running multiple
tracks to multiple compressors within a DAW and/or externally (to
outboard gear) despite delay compensation?