Odd behaviours on joining and splitting stereo tracks

[Gale Andrews]

A possible solution would be for the envelope of the upper track to be applied to both channels (both visually and in effect) when making a stereo track?

Kind of goes against "no problem so far" above?

Agreed, but it would be much better than the current behaviour in that the behaviour could be concisely and accurately documented and would be predictable.

Martyn felt a few years ago on -devel that "the current behaviour isn't unreasonable. It would be impossible to decide which of the stereo pair was correct... This is useful for some stereo effects."

Isn't clicking in the stereo pair having the effect that it would have on the other channel if you clicked at that point in that other channel when split? If that is happening, it seems predictable to me? If not wanted, split the tracks?

The better solution would be for full support for per-channel envelopes but I don't see that happening until track overlays are implemented and that puts it well after 2.0 release.

Does this mean that when we make stereo track and the envelopes are different, you can't apply the same point to both channels in one move? Or you can't do that in any circumstance? And putting a point in one channel has no effect on the other channel, or something else?


Gale

[steve]

Martyn felt a few years ago on -devel that "the current behaviour isn't unreasonable.

I agree that the behaviour is logical, but I still think that it can create some weird results that look wrong.
For example:

http://youtu.be/F3WaXDC4E8w

[billw58]

Part of the confusion could be because Audacity IS doing something more complex than just sticking the two pieces together and that is with the (mis)handling of the track sliders and envelopes. As I hinted at before I don't think that there is a sensible way for "Make Stereo Track" to take account of track pan and gain sliders without rendering the tracks, but that would just be duplicating the function of "Tracks > Mix and Render" at the loss of simply sticking them together. The only solution that I can see to this issue is for "Make Stereo Track" to ignore the pan and gain sliders and only deal with the audio content of the tracks. Can anyone think of a better solution?

Oh dear. I just did some mucking about with splitting and joining stereo tracks. Try this:

• Import a stereo track
  Split stereo track (to stereo)
  Reduce the gain on the right channel to -20
  Make stereo track

Now play it back. The right channel of the stereo track plays back with the -20 dB gain applied, but there is no indication why.

Stop and do Split Stereo Track - the -20 gain setting on the right channel is still there.

Do Make Stereo Track and play it back, then touch the Gain slider - the -20 dB gain setting on the right channel goes away permanently.

There are other "gotchas" involving pan and gain settings before doing Make Stereo Track, which I won't detail now.

-- Bill

[Gale Andrews]

I just did some mucking about with splitting and joining stereo tracks. Try this:

• Import a stereo track
  Split stereo track (to stereo)
  Reduce the gain on the right channel to -20
  Make stereo track

Now play it back. The right channel of the stereo track plays back with the -20 dB gain applied, but there is no indication why.

Yes I already mentioned when giving an example of make stereo with right above left.

Stop and do Split Stereo Track - the -20 gain setting on the right channel is still there.

Do Make Stereo Track and play it back, then touch the Gain slider - the -20 dB gain setting on the right channel goes away permanently.

I think those two are probably "expected" when you think about it. I can't see ignoring the gain/pan when making stereo is a solution. I would say when Bill touches the Gain slider as above, Audacity should render then apply whatever gain change was made to both channels.

What are the other gotchas?


Gale

[steve]

I would say when Bill touches the Gain slider as above, Audacity should render then apply whatever gain change was made to both channels.

So if some one is in the middle of editing a really long recording and they accidentally nudge the Gain slider, they then have to wait for however long while Audacity renders? Perhaps Audacity could pop up a message asking if the user wants to render?

[billw58]

Stop and do Split Stereo Track - the -20 gain setting on the right channel is still there.

Do Make Stereo Track and play it back, then touch the Gain slider - the -20 dB gain setting on the right channel goes away permanently.

I think those two are probably "expected" when you think about it. I can't see ignoring the gain/pan when making stereo is a solution. I would say when Bill touches the Gain slider as above, Audacity should render then apply whatever gain change was made to both channels.

I didn't "change" the gain - I just touched the gain slider. It did kind of what you suggest - it applied the gain - 0 dB - to both channels.

I don't think Audacity should render the change when the gain slider is touched - that defeats the (time-saving?) purpose of these functions. Can you imagine a user doing this to a 30=minute track, touching the gain slider then waiting for Audacity to render the gain change?

What are the other gotchas?

• Split stereo to mono
  Pan the top channel 100% right
  Pan the bottom channel 100% left
  Make Stereo Track
  Play

You get silence. Huh?

Now "touch" the Pan slider. You get the expected playback from the right channel only. Drag the pan control to 0 - you get the expected stereo playback.

In both cases, "touching" the relevant slider undoes the pan and/or gain settings that were applied to the lower track before combining the two tracks. If this is the case, why is it bad to ignore those gain and pan settings before making the stereo track?

That's probably it. Everything else is a variation of these. My point is that, after Make Stereo Track, playback does not correspond to the visible settings on the gain and pan controls, which can't be good. The visible settings come from the top track.

Now, I would never use these functions in this way. But that is because I understand the difference between these functions and "Mix and Render". Given the discussions in this thread I was wondering how they would behave when "mis-used". The result would be user confusion.

It would be much clearer that these functions are for "gluing together" two tracks to make one stereo track if they ignored the gain and pan settings and we could tell users that. Also given Steve's examples of envelope behaviour, I think "Make Stereo Track" should ignore envelopes as well. I'd say they are "specialist" functions for performing a small sub-set of tasks, and are not meant to be a "quick mix and render".

-- Bill

[Gale Andrews]

I didn't "change" the gain - I just touched the gain slider. It did kind of what you suggest - it applied the gain - 0 dB - to both channels. I don't think Audacity should render the change when the gain slider is touched - that defeats the (time-saving?) purpose of these functions. Can you imagine a user doing this to a 30=minute track, touching the gain slider then waiting for Audacity to render the gain change?

I can well imagine... But Audacity can't know if user meant to brush the gain slider or not. If user wants their -20 dB on the right retained, and then +2 dB on both channels (assuming they did mean it), don't we need to render? Or can a future Audacity store the separate right channel "request" and so produce +2 on left + -18 on right until user really wants to render that?

It would be much clearer that these functions are for "gluing together" two tracks to make one stereo track if they ignored the gain and pan settings and we could tell users that. Also given Steve's examples of envelope behaviour, I think "Make Stereo Track" should ignore envelopes as well.

I still don't think that's any solution. It would be weird for gain/pan to audibly work until you made stereo. Predictable maybe, but very limiting. You have a stereo track, you want to adjust the gain or even the envelope on one channel so you split, then you're told you can't keep the changes and make stereo unless you render?


Gale

[billw58]

You have a stereo track, you want to adjust the gain or even the envelope on one channel so you split, then you're told you can't keep the changes and make stereo unless you render?

Yes. Better than now with the gain and pan sliders not representing what you hear, then erasing your changes to gain and pan to the bottom channel when you adjust the gain or pan on the resulting stereo track.

What happens now is, as you say, predictable when you think about it [and if you look at the AUP after the various steps you can see it happening]. As soon as you touch the gain or pan control on the stereo track that gain or pan setting is applied to both channels of the stereo track (as they should), potentially changing the gain and pan settings of the right channel.

I think we may be expecting Make Stereo Track to do more than it was intended to do.

In terms of documenting what it currently does, I would warn users that having non-zero gain and pan settings on the pair of tracks acted upon may give unexpected results and the safest course of action is to leave them at zero.

In terms of changing and/or improving the behaviour of these commands, I'd reckon that's post-2.0, if at all.

-- Bill

[steve]

With regard to Pan and Gain:
One way that Audacity could "do the right thing" and make transparent what it is doing would be to replace the pan slider on stereo tracks with a second gain slider so that there is one gain slider per channel. Assuming that the sliders were labelled in some way, this would also address the op's original question.

With regard to Envelopes:
This would not be a problem if there was an option to adjust only one channel. Say, click and drag with the Envelope tool to adjust both channels, or shift+drag to adjust only one channel. This would have benefits beyond the specific problems being discussed here.

[billw58]

With regard to Pan and Gain:
One way that Audacity could "do the right thing" and make transparent what it is doing would be to replace the pan slider on stereo tracks with a second gain slider so that there is one gain slider per channel. Assuming that the sliders were labelled in some way, this would also address the op's original question.

I like the way Pro Tools handles stereo channels. Two pan controls, as well as the gain control (fader). This gives total flexibility. You can mix the stereo channel to mono by putting both pan controls in the middle. You can reduce the stereo spread by panning each control a bit off maximum. You can flip the channels in the mix by reversing the pan controls. You can't do any of those things with two gain controls.

I don't think we should design stereo channels according to what "Make Stereo Track" does when it glues two tracks together.

-- Bill