Crackling Noise Overdubs; Realtek/Windows Twilight Zone

[default device]

Windows 7
AMD Athlon II 620 Quad Core
Realtek Super Duper POS integrated sound ha ha
6 GB RAM

Although I can make clean initial recordings all day long, stereo or mono, with microphones and guitars (plugged into a stereo amp that has tape in/outs and microphone inputs), and capture the output from the computer's synthesizer as played by Tux Guitar, I cannot make an overdub of anything over anything without a clicking, scratching sound. The sound is not constant, but varies with the volume level of the overdubbed track. To me this would indicate some kind of clipping but it doesn't matter where you set the levels of anything, either recording the first track, playing it back while overdubbing, or the recording level of the overdub track.

As least so far as I can tell because the Realtek/Windows level-setting regime is an utter bafflement to me. The confusion starts when you have to accept that the computer's line ouput to the amp is described by the software as "default device speakers." I don't know what default device means, though I take it to be something like on/off.

What does "stereo mix" refer to? Does it mix the line in with something? or vice versa? Which comes first in the signal path? What is being output to what and where and how is it controlled?

I've tried doing the initial recording through "stereo mix" as well as "line in". Each time with the matching setting in Audacity Edit > preferences > devices. The method that came closest to eliminating the clicks was to record the initial track on "stereo mix" and the overdub on "line in" although that's a rather tedious way to work. In any case, am I supposed to set, simultaneously, the level of the "playback device" and the recording level of the "recording device", because the aggregate is the recording level? I noticed that in the menu of Windows playback devices (set to "speakers") > properties > levels there are sliders not only for "speakers" but line input and everything else including "Realtek HD AUdio Output" and microphone. Why are there microphone and a line-in controls in the menu for "Playback device"?

The real surprise is that the "front speaker" slider controls the recording volume. What else does?

[whomper]

Windows 7
AMD Athlon II 620 Quad Core
Realtek Super Duper POS integrated sound ha ha
6 GB RAM

Although I can make clean initial recordings all day long, stereo or mono, with microphones and guitars (plugged into a stereo amp that has tape in/outs and microphone inputs), and capture the output from the computer's synthesizer as played by Tux Guitar, I cannot make an overdub of anything over anything without a clicking, scratching sound. The sound is not constant, but varies with the volume level of the overdubbed track. To me this would indicate some kind of clipping but it doesn't matter where you set the levels of anything, either recording the first track, playing it back while overdubbing, or the recording level of the overdub track.

As least so far as I can tell because the Realtek/Windows level-setting regime is an utter bafflement to me. The confusion starts when you have to accept that the computer's line ouput to the amp is described by the software as "default device speakers." I don't know what default device means, though I take it to be something like on/off.

What does "stereo mix" refer to? Does it mix the line in with something? or vice versa? Which comes first in the signal path? What is being output to what and where and how is it controlled?

I've tried doing the initial recording through "stereo mix" as well as "line in". Each time with the matching setting in Audacity Edit > preferences > devices. The method that came closest to eliminating the clicks was to record the initial track on "stereo mix" and the overdub on "line in" although that's a rather tedious way to work. In any case, am I supposed to set, simultaneously, the level of the "playback device" and the recording level of the "recording device", because the aggregate is the recording level? I noticed that in the menu of Windows playback devices (set to "speakers") > properties > levels there are sliders not only for "speakers" but line input and everything else including "Realtek HD AUdio Output" and microphone. Why are there microphone and a line-in controls in the menu for "Playback device"?

The real surprise is that the "front speaker" slider controls the recording volume. What else does?

two issues
look at realtek mixer for changes
note you have to mute input to kill it
as the mixer mixes all of the unmuted
then set the volume on the wheel at the left
there are no sliders

stereo mix is a mystery term that i cant find info on anywhere
i just try using it and muting it to see if i get what i want with one or the other

http://forum.audacityteam.org/viewtopic ... 20&t=26522
notes some places that audio gets diddled
i just set them all because i have no clue yet as to how they play together , interact, or what priority there is to them.

[steve]

"Stereo Mix" (called "What U Hear" on SoundBlaster cards) enables you to record whatever is being played out of the sound card. It enables you to record sounds that are playing on the computer without needing to use a microphone or any other external routing. For example, if you are playing a CD on your computer, and playing a MIDI file at the same time, and both of these are playing through your sound card, then if you were to record from "Stereo Mix" you would get a recording that was a mix of the CD and the MIDI file. People mostly use this option for recording things from the internet that are playing through their web browser.

The important thing with stereo mix is that it records everything that is coming from your sound card, so if you have a microphone plugged in and enabled while you are recording from YouTube, then the recording will sound bad because it is not only being recorded from the web browser, but anything picked up by the microphone will be recorded as well. When recording from Stereo Mix you should always ensure that any sound card inputs that are not being used are muted.

When recording from a microphone, or a "Line in" (for example, connecting a keyboard to the Line In socket on the computer), it is better to select the actual input that you are using (for example "Mic" or "Line") rather than "Stereo Mix". This way, the sound signal is taking a much more direct route through to Audacity and the sound quality is likely to be better.

RealTek sound cards can be a bit of a nightmare, not just because the sound quality is usually not very good (and the microphone input is usually really bad), but because they have so many hidden settings (Environmental effect, Noise Reduction, Equalizer, Echo Cancellation .....) For recording purposes ALL of these effects must be hunted down and switched off. Unfortunately there are hundreds of variations to RealTek sound cards making it difficult to offer more than very general advice about them.

If you're half serious about recording, you will want to upgrade your sound card. If you are going to stick with the RealTek (for now), spend some time getting to know where all the settings are hiding.

[kozikowski]

If you have a surround sound card (front-left, rear-left....), and you want to overdub musical performances, it's possible you have a terminally complicated system.

Each new edition of Windows tries to simplify things by leaving out bits of the system -- in effect making the system appear relatively simple when it's profoundly not.

Your particular problem may involve Mix-Out. Mix-Out (or Stereo Mix) must be selected when you want to record music or anything else from the internet. It should not be selected when you want to perform music to yourself (overdubbing) or any other live performances.

One of the bad things that happens if it's running at the wrong time is the volume of the performance inexplicably doubles causing high volume distortion and overload. This is not a good thing.

There are writings on the Windows Control Panel that can help.

Windows Control Panel
http://audacityteam.org/wiki/index.php? ... trol_Panel

You understand you made this much worse by wanting to overdub. That involves unnatural crosses between the Windows sound systems. If all you wanted to do was straight recording, it would only be difficult.

And you're doing this on Win7 where the hardware vendors are just catching up with the software.

Oh yes. The surround card. I had a surround card in one PC and I got it to work right once, (1) times. Do you have a surround sound system to plug in?

Koz

[whomper]

"Stereo Mix" (called "What U Hear" on SoundBlaster cards) enables you to record whatever is being played out of the sound card. It enables you to record sounds that are playing on the computer without needing to use a microphone or any other external routing. For example, if you are playing a CD on your computer, and playing a MIDI file at the same time, and both of these are playing through your sound card, then if you were to record from "Stereo Mix" you would get a recording that was a mix of the CD and the MIDI file. People mostly use this option for recording things from the internet that are playing through their web browser.

The important thing with stereo mix is that it records everything that is coming from your sound card, so if you have a microphone plugged in and enabled while you are recording from YouTube, then the recording will sound bad because it is not only being recorded from the web browser, but anything picked up by the microphone will be recorded as well. When recording from Stereo Mix you should always ensure that any sound card inputs that are not being used are muted.

When recording from a microphone, or a "Line in" (for example, connecting a keyboard to the Line In socket on the computer), it is better to select the actual input that you are using (for example "Mic" or "Line") rather than "Stereo Mix". This way, the sound signal is taking a much more direct route through to Audacity and the sound quality is likely to be better.

RealTek sound cards can be a bit of a nightmare, not just because the sound quality is usually not very good (and the microphone input is usually really bad), but because they have so many hidden settings (Environmental effect, Noise Reduction, Equalizer, Echo Cancellation .....) For recording purposes ALL of these effects must be hunted down and switched off. Unfortunately there are hundreds of variations to RealTek sound cards making it difficult to offer more than very general advice about them.

If you're half serious about recording, you will want to upgrade your sound card. If you are going to stick with the RealTek (for now), spend some time getting to know where all the settings are hiding.

thanks
that helps a lot
is that info in the docs ?

is the entire signal flow path documented anwhere??


realtek puts all their settings in one place
click on the orange speaker in the bottom right
the realtek panel comes up with all options available
but some windows panels may still diddle the data
although realtek claims they control them all
my experience says you need to find all the windows places
and unmute them all and max the volume to make realtek work right

go to sound effects tab
flatten the eq sliders
save the settings
and it will load correctly next time

mixer tab controls record and playback
mute all record channels not in use
set the volume on the wheel on the left
note on playback you can scroll right/left to see more devices

the other three panels can be ignored after you
check them to make sure nothing is turned on

right click on it to get direct access to more control panels
start settings control_panel and then
sound etc
system
maybe others
also provide access to more settings
many are the same you can find by going down other rabbit trails
but some of them do have additional options you do not get by the other paths

[steve]

is that info in the docs ?

I don't think that it is covered in as much detail, though there is some information here: http://wiki.audacityteam.org/wiki/Mixer ... trol_Panel
and I think there's a bit more somewhere else though I don't remember exactly where.

[default device]

I've found at least a partial solution. You have to push the Audacity recording input slider all the way to

max, then go into Windows recording devices and set that recording input slider to about 75%, then return to

Audacity and set the recording input slider way down low. IOW to set the recording level you have to set two

sliders, in three stages. Kind of like stopping your car to get in the back seat to drive with the other

steering wheel.

Also, and this is mystifying, I have to turn down the playback level of the recorded track while recording the

overdub track. This indicates that they are being added some how, some way, although the tracks are not mixed.

In any case I've been able to make three overdubs over an original track withou crackling.

My mode of procedure:


1. Using Tux Guitar I write (as music) a drum part and a bass part. When I hit play, Tux Guitar "plays" the

windows MIDI synthesizer. This creates what I call the "metronome track".

2. Which is recorded by Audacity, through "stereo mix".

3. Plug the microphone into my 1974 Sansui Stereo Amplifier, which has ins from and outs to the computer. It

will mike my electric guitar amp. Stereo speakers are off, I'm monitoring in headphones.

4. Back at the computer, switch Audacity and Windows Recording Devices both to line in. Yes, I know this

shouldn't be necessary. But it is. On my system Audacity won't record the Windows synthesizer on anything but

"stereo mix".

5. Anyway, having switched toi Line In, on the far left hand side of the window of the recorded MIDI track in

Audacity, I reduce the gain by 3-4 decibels.

6. Make level test recordings, starting with the Audacity record level slider at .1 Sometimes crackling begins

at.3, but I've been as far as 1.0 without crackling.

7. Overdub a track.

8. Repeat as desired, but seems to work best the fewer tracks you monitor, i.e. lay down each successive track

monitoring only the "metronome track", the MIDI-generated track.

Of course this won't work for you because Realtek changes their stuff every day or so no one can ever find

specific enough information to pinpoint their stupid driver interface as the problem. Between them and Windows

it's a real Twilight Zone.

[default device]

You understand you made this much worse by wanting to overdub. That involves unnatural crosses between the Windows sound systems. If all you wanted to do was straight recording, it would only be difficult.

Ha! It's simple. You have to synch, two ways to do it: read and write simultaneously in real time, or at different times, but synchronized afterwards.

In the old days to record audio that was synchronized to film, they used to tune the respective motors of the camera and the tape recorder and run them on special power supplies to get them to run at the same speed, governed by some kind of pulse generator, for both recording and playback. That's complicated.

For a time playback and recording synchronized in real time was done by combination play/record heads on tape recorders. Dependent on very high quality mechanics and electronics. But at least the overdub track went down physically adjacent to pre-recorded track.

I suppose there could be a "two head" hard drive that reads and writes at the same time. Failing that the only remaining way, to my knowledge, is the synchronize-later-by-offset way. The original track is played, serving as a metronome for the overdub. Rather than try to play and record at the same time, the overdub is offset by software in such a way that *when played* it begins playing by Time X ahead of the original track. If Time X = system latency the synchronization is perfect. It could have been written to disk an hour after the performance, having been held in a buffer in the meantime.

The two tracks already have the same "tempo" before synchronization because they are two performances, the second done in time to the first. Now all you need is a way to START the performances both at the same time, which is done by offsetting *the recordings* of the performances. I take that this is why in Audacity you work on "projects" not "files".

Anyway it's not difficult. You already have a computer with a clock controller and a recorder. All you need is a proper interface, ha ha.

[steve]

That method looks about right.

A few comments:

In step (3) you don't say exactly what output you are using on the amplifier to plug into the computer "Line In" socket. Is it marked "Line Out", "AUX", "Headphone", "Speakers", or what?

1. Using Tux Guitar I write (as music) a drum part and a bass part. When I hit play, Tux Guitar "plays" the windows MIDI synthesizer. This creates what I call the "metronome track".

If you are recording a mixture of live and sequenced MIDI, that is a very good way to do it - get the sequenced stuff recorded first.

Which is recorded by Audacity, through "stereo mix". ... On my system Audacity won't record the Windows synthesizer on anything but "stereo mix".

Here we have some sound card variations. On some sound cards there is an option to set the recording source to "MIDI" (or "MID") and it will record only midi sounds. These types are sound card are becoming less common. On other sound cards there is no option to record MIDI directly and then you have to use "Stereo Mix" to record the MIDI sounds. On sound cards that do support recoding from "MID", the MIDI player must be configured to play through the correct MIDI Device (the hardware midi module on the sound card) otherwise there will be no sound recorded.

4. Back at the computer, switch Audacity and Windows Recording Devices both to line in. Yes, I know this shouldn't be necessary. But it is.

That's normal. You were recording sounds playing on the computer - that is using the "Stereo Mix" input from the sound card. The "Stereo Mix" input is for recording sounds that are playing on your computer. Then you were recording from "Line In" - so you are doing the correct thing in switching to "Line In". Ideally you would only need to change this on Audacity and the sound card would follow suite, but some sound cards do not support this and you have to do it manually. - There is a short-cut round this, which if I have time I'll come to later.

5. Anyway, having switched toi Line In, on the far left hand side of the window of the recorded MIDI track in Audacity, I reduce the gain by 3-4 decibels.

That's also quite normal, and the more tracks that you record the more you will need to turn the other tracks down. When you listen to multiple tracks simultaneously, the sounds from all the tracks are "added" together, so the sum of the tracks is greater than each individual track on its own. If you don't turn the volume of the tracks down, they will add together until the "mix" goes over 0dB and distorts.

6. Make level test recordings, starting with the Audacity record level slider at .1 Sometimes crackling begins at.3, but I've been as far as 1.0 without crackling.

That depends how "hot" your signal is. The bigger (hotter) the signal from your amp is, the lower the recording volume is. The important thing is as you point out, to keep the level below "crackling". That "crackling" we call "distortion" or "clipping" and is caused when either the input or the output go too high (normally around 0dB). If you have to turn the recording level down as low as 0.1, then you have a mismatch between the output level of the amplifier and the "sensitivity" of the computer input and you should try and find a way to either reduce the signal level (from the amp), or use a less sensitive input. (Some sound cards have combined "Line" and "Mic" sockets, which, even when set to "Line" are not able to handle a real "Line Level" signal without distorting).

Overdub a track. ... Repeat as desired, but seems to work best the fewer tracks you monitor, i.e. lay down each successive track monitoring only the "metronome track", the MIDI-generated track.

Using the MIDI-generated track as the dominant sound that you are monitoring can help a lot with getting the timing accurate in the whole recording. If each overdub track is in sync with the metronome track then they should also be in sync with each other. Personally, for this type of recording I like to keep the MIDI track as the main sound in the headphones, but mix in just a little of the other tracks.

Of course this won't work for you because Realtek changes their stuff every day or so no one can ever find specific enough information to pinpoint their stupid driver interface as the problem. Between them and Windows it's a real Twilight Zone.

So true, but we have our own Twilight Zone over here on Linux also.

[steve]

My mode of procedure:
....

I think that's the first full write-up of how to do multi-tracking that we've seen on the forum. Have you ever used a "wiki"? I think a write up of this on the Audacity wiki could be really useful. (possibly as a Tutorial? http://wiki.audacityteam.org/index.php?title=Tutorials )