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Paul[_21_] Paul[_21_] is offline
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Default Typical first pass tutorial process on Windows 10 where NONEof the extent how to articles actually tell you what you really need to do!

Arlen Holder wrote:
On Thu, 05 Nov 2020 03:12:47 -0500, Paul wrote:

You need to select Stereo Mix as your sound source.

+-----+
Mic ------------| |
| | A D
LineIn ---------| Mux |---- ADC ----- to CPU
| |
Stereo_Mix +----| |
| +-----+
|
| From CPU -- DAC --+-- LineOut
} |
+-----------------------+


Hi Paul,
Thanks for that diagram, where just studying it is instructive.
a. Mic in goes to the analog side of the ADC to the CPU
b. Line in goes to the analog side of the ADC to the CPU
c. Where LineOut & StereoMix are, somehow, intertwined

Somehow, when I set Audacity to record from "Stereo Mix",
(and if I'm playing a twitter streaming feed in my browser),
but if I do NOT plug a "disconnected" cable into LineOut,
then Audacity gets no signal to record.

However, when I set Audacity to record from "Stereo Mix",
(and if I'm playing a twitter streaming feed in my browser),
and if I also plug a "disconnected" cable into LineOut,
then Audacity DOES get a signal to record.

I guess what your diagram is showing is that StereoMix is disconnected from
LineOut unless a 1/8th-inch plug is used to "connect" them?

Is that right?

If so, then by putting the 1/8th-inch plug into the "LineOut" jack,
that connects the twitter feed coming from the DAC to the
"StereoMix" feed which then goes to the ADC to the CPU (???)
and then from there, to Audacity as its digital input (???)

Stereo_Mix is a loopback signal. It takes a "copy"
of what is coming from LineOut and routes it back to the
input multiplexer. It's a feature in every HDAudio chip
(like the motherboard 48 pin square chip in the corner).


I looked on my motherboard but don't see a 48-pin square chip in any of the
corners, but I think I'm getting your point that the "StereoMix" is a
loopback of LineOut to the ADC (and then to Audacity).

Thus, to record streaming audio, that audio going out
the analog speaker connector, you need to select
Stereo_Mix as seen in Audacity.


I did select "Stereo Mix" since all the tutorials suggested that
o But I didn't know why

The choices I have in Audacity a
o For Host [MME] (Microsoft Multimedia Environment)
Recording choices are [Stereo Mix] or [Microsoft Sound Mapper]
o For Host [Windows DirectSound]
Recording choices are [Stereo Mix] or [Primary Sound Capture Driver]
o For Host [WASAPI] (Windows Audio Session API)
Recording choices are [Stereo Mix] or [Digital Output loopback] or [Speakers]

The good news is that they all have "Stereo Mix" as a choice.

Any mixer setting
on Record block (Record in Windows icon in corner),
the Stereo_Mix has to be turned up enough to hear it.


I don't understand that statement.

Remember that picture I made yesterday ? It had
a picture of Stereo_Mix in it for a reason. That
wasn't a lark on my part. The Stereo_Mix is part
of your request for recording audio from a Youtube
session, without using youtube-dl and "cheating"
to get it. We have to assume someday the RIAA will
cut off as much recording capability as possible,
and for a while at least, analog will work.


I think I get it that "stereo mix" is a loopback of the analog signal
_back_ into the ADC, is that what you're trying to teach me?

With the 1/8th-inch plug in place, is this sequence correct yet?
a. The digital stream comes in from the browser twitter feed
b. That digital stream goes to the DAC preamp output
c. That DAC preamp output goes to LineOut (to go to powered speakers)
d. If (and only if) a 1/8th plug is plugged into LineOut
e. Then that DAC preamp output also loops back to the ADC input
f. Where the ADC converts the analog lineout to a digital stream
g. Which is then fed to the "StereoMix" input of Audacity

I installed the RealTek driver over top of the
Microsoft driver, in order to bring back the
Stereo_Mix in my Win10 20H2 setup.


What does the "mix" mean in the term "Stereo Mix"?

I get what "stereo" means (i.e., 2 audio channels) but what's the "mix"?
a. Does the "mix" mean a mix of the two audio channels?
b. Or does the "mix" mean a mix of line out and line back in via loopback?

When we use that foot-long, 1/8" male to 1/8" male
cable for recording, it looks like this.

+-----+
Mic ------------| |
| | A D
LineIn +----| Mux |---- ADC ----- to CPU
| | |
| /-| |
| +-----+
|
| From CPU -- DAC --+-- LineOut
} |
+-----------------------+
1/8" male to 1/8" male cable

You can use a cable to take the place of Stereo_Mix,
and then you'd select LineIn as your recording
source in Audacity. This would be the case, if
for example, Windows 10 buggered your Stereo_Mix
capability with its clumsiness and stupidity.


Is that why they suggested that physical male-to-male loopback cable here?
https://davescomputertips.com/how-to-record-internet-audio-with-audacity/

Not everyone has one of those cables. They
might come with some TV tuner card perhaps.


I have an extensive cable box, like most people here.
o It even has RS232 cables in it, and SCSI cables too.

It had a 30-foot male-to-female 1/8th-inch cable & splitters
o In addition to a male-to-male 1/8th-inch cable

So I'm all set on cabling, if I need to use it
o But luckily, just plugging the plug alone into LineOut worked!


What's needed to record the output, is a path to get
back to the input side, and to the ADC.

The Stereo_Mix method, uses a wire which is inside
the HDAudio chip. Selecting that input, is a matter
of configuring software the right way, so it will work.

Every input has a level adjustment. You are adjusting
the level to avoid overloading while recording. You adjust
the gain, so the recording is loud enough.

Take for example, you play a DVD and get a LineOut output that way.
DVDs seem to be recorded really low, like -15dB or so.
There seems to be no way to drive a lot of signal that way.

When recording that DVD with Audacity, you need to adjust
the level, for a pleasant recording. Audacity has a VU meter,
so you can see the incoming voltage level. The VU Meter is
there, so you can judge whether you've still got headroom,
for a non-distorted recording.

Inputs have mutes. Or, a level slider can be set at zero.
The effect is zero volts on input and a very quiet recording,
if either of those happen.

*******

There is no particular reason for an interaction between
LineOut/LineIn and Stereo_Mix.

When you plug the 1/8" plug into a jack, the jack has a
side contact. The side contact closure is detected on the
HDAudio chip. It generates an event to the OS. The driver
presents a prompt "Did you plug something into LineIn?"
or similar.

One of the side effects of plugging in LineIn, is it can
be used to automatically switch the input mux in front
of the ADC, so that LineIn is used. And whatever your
previous choice was, is de-selected.

The loopback path only exists for one chip choice at a time.
To record through the RealTek Stereo_Mix, means the RealTek
LineOut has to be used and playing the content on the
analog computer speakers or similar. If the sound was
going to your TV set over HDMI for example, maybe the
NVidia video card HDAudio internal to the GPU is doing that.
And there would be no "virtual wire" to get to the
RealTek ADC/Mux.

As a consequence, you have to think carefully about where
that wire is.

There is at least one "virtual cable" driver, which is a
software technique for copying the Windows (output) mixer
stream and making a "pin" of it. Then, in Audacity, the "pin"
is offered as an "input choice". The virtual cable, in a
sense, bypasses DACs and ADCs and "just gets the job done".
This would be an alternative if someday soon, Microsoft
finds a way of permanently removing the driver ability
to get at the Stereo_Mix which is a hardware feature.
From a DMCA perspective, Microsoft could also choice to
block and prevent that "virtual cable" software from
running.

Summary: Plugging in 1/8" plugs to HDAudio jacks, has
as a side effect, the "side contact" signals to the
driver, that a change has occurred. And the driver
can use this as an excuse to switch input or output
settings, by signaling these facts to the OS handling
things. Without software to receive "plug events",
nothing would happen without software interference.

The Stereo_Mix doesn't need that. It needs selecting
Stereo_Mix in Audacity, to "wire up the input". But it
also needs a signal going through the output side
of that HDAudio chip, so that the signal can be copied.

Stereo_Mix and the black wire, are two of the same.
They're a path. The black wire also tickles the side
contact on two jacks. The Stereo_Mix does not, so to get
the Stereo_Mix to work requires two GUI actions
at a minimum. Something to set up the input side.
And some operation to get a signal onto the output,
so you can copy it with a feature put there in the
HDAudio chip for this.

Paul
 
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