Playback speed wrong, but pitch correct!

[orubin]

I will start with the usual apologies if this has been posted before, as I cannot find any reference to this exact problem by searching...

With both releases 1.3.11 and 1.3.12, while I can record and get sound into the program from my audio card, when I play back (in the program) the recorded audio, it seems to be playing back at about 1.5 to 2.0 the normal speed, but at the correct pitch This is not the same as a chipmunk issue as the pitch is correct, the speed is just much faster as if the sound is being sampled a faster rate.
I have tried all sample rates with no difference in play back effect.
I have tried changing the rate of my card, no difference.
I tried playing back on the internal sound card, and it sounds the same.
I suspect the problem is in the recording, as exporting it to an MP-3 plays the at same accelerated speed.
The variable speed playback slider cannot be used to fix this. if I slow it down to about the right speed, the pitch drops very low.

I am on Windows 7 Ultimate N 64-bit
This is an AcerPC with Intel Core Quad Q9400 @ 2.66 Ghz, 8 GB Memory
I am NOT using the internal sound card as I was unable to get that to work at all. Instead, I installed a PCI C-media card (exact card unknown).
The drivers installed are the same ones that were working on earlier versions of Audacity, and claim to be "up to date" in a driver update check. (C-Media 7.12.8.1740 dated 12/1/2009)

Any ideas? Bug, bad setting, problem with sound card all of a sudden? By the way, the sound card plays back older recordings just fine. Just anything recorded now is recording too fast.

[orubin]

Update: This seems to not be an Audacity problem after all. I downloaded "Free Hi-Q Recorder" and recoded a stream, and it is showing the exact same problem, audio recorded is played back at a much faster speed, although the pitch stays correct.

Sound recorded via a USB mic is recorded and played back correctly FYI

Still curious, anyone have any ideas why this might happen?

Cheers

[steve]

I have an idea of what may be causing the problem if the playback speed is exactly 2 times the correct speed.
I suspect it is a driver/Windows configuration problem and it could take some digging to fix it.

Before we delve too deep, could you run a test to check that I'm not heading in the wrong direction with this:

Try recording something of known length, then check to see how long the recording is.
Is it exactly double speed?

[orubin]

I did a few tests, and yes, it appears to be exactly 2x the speed. I tried recording 10 seconds, and playback was 5 seconds, and I opened the playback file with VLC, and set it to 0.5x playback, and it sounded correct (except for the choppiness of the recording and playback alteration taking place.)

I tried updating the driver, no change. Interested in your ideas. This is an odd one.

Thanks

[kozikowski]

<<<Sound recorded via a USB mic is recorded and played back correctly FYI>>>

That's a significant clue. The analog sound to digital bit converter is in the "sound card" in your computer. Every conventional microphone or analog sound signal has to go through that to get to Audacity or anything else.

Not so with a USB microphone. In those, the conversion from analog to digital happens inside the microphone completely divorced from the computer.

<<<I am NOT using the internal sound card as I was unable to get that to work at all. Instead, I installed a PCI C-media card (exact card unknown). >>>

That's pretty much entirely bad news. You never figured out why your internal sound failed and it's possible whatever is causing that is killing off your other sound services as well.

Koz

[steve]

I think what is happening is that you are trying to record in stereo, but Windows 7 is trying to record in mono, so a "mono" data buffer is sending data alternately to one channel then the other resulting in each channel only having half the amount of data that it should have. This will explain why the microphone works OK, because it is mono but your sound card is stereo.

What we need to do is check that everything is set to stereo from start to finish.

I think this is the most likely place that it is wrong:

Click Start > Control Panel > Hardware and Sound > Sound (if you're using "Classic View" there's a direct link to "Sound" in the Control Panel), then click on the "Recording" tab.

Right click on the device input that you are using (for example "Line In: PCI C-media") and select "Properties" - somewhere in there you should be able to set the recording format to something like "44100Hz (CD Quality) Stereo".
(sorry I can't be more exact, I don't use Windows 7)

Click OK on everything and restart Audacity.

[orubin]

Thanks KOZ. I was told that Acer disabled the loopback ability of their card to "reduce copying of copyrighted material." When i list recording devices, the internal card does not show up at all (there was no "stereo mix" shown.) I have no idea who's hardware the mother board card is, and it is driven by a Microsoft driver, and I am told that it may be Microsoft's driver that limits the loopback as well.

That is why I added the C-media PCI card. As soon as I did that, Stereo Mix appeared and I could now record streams.

It worked fine for a long time, and then just stopped working.OK, it actually would often record in Audacity with distortion, but stopping and restarting the recoding seemed to fix that. Playback of MP-3, movies, Pandora, etc all play correctly. I believe the problem is in the recording actually, as other recording software is having the same problem.

Steve:
That is a VERY interesting idea, and would explain the pitch being correct as well. It also sounds "choppy", which sounds even more like what you are describing.(by the way, for future reference on W7: Control Panels -> Sound. Click "Recording" tab, right click device and select Properties, Click "Advanced" tab. Setting is there. OR, if volume control is showing on task bar, right click, select Recording Devices".)

Sadly, everything checks out.. For the Stereo Mix input, the only choices are "2 channel, 16 bit, 48000 Hz (DVD Quality)" and "2 channel, 16-bit, 44100 Hz (CD Quality)" settings, and I have tried them both. No difference. but this is a great clue. back to more experiments.... thanks

FYI: As a test, I set Audacity to Mono, 1 channel, and it did the same thing, although it ran at 4x!

[orubin]

One more update:
if I change the input device from "Stereo Mix" on the C-Media card to "Wave" from the same card, the audio is recorded correctly.

Might have to be a work around for me.

Odd!

[steve]

(by the way, for future reference on W7: Control Panels -> Sound. Click "Recording" tab, right click device and select Properties, Click "Advanced" tab. Setting is there.)

Thanks - useful feedback.

FYI: As a test, I set Audacity to Mono, 1 channel, and it did the same thing, although it ran at 4x!

Ah - so it looks like it's something along these lines.

if I change the input device from "Stereo Mix" on the C-Media card to "Wave" from the same card, the audio is recorded correctly.

That is strange, but it's also good. Changing from Stereo Mix to Wave should not cause a change in speed, so my guess is that there's a sound card driver bug involved.
As long as this is working for you this is a good workaround and in some ways preferable to using Stereo Mix as it cuts out some audio pathways that could potentially (and in this case does) cause problems.

So you are back in business now?

[orubin]

Thanks Steve, this will work for now. Odd that it just stopped working, and given some time, I will track it down. But yes, this works for now, and glad to see it was not an Audacity problem.

Now, if I could just figure out how to identify the on-board audio chip to remove the Microsoft driver, I could get rid of this sound card all together.

Thanks for the help.