Dave, thanks for the suggestion of a VST plugin. I added Voxengo's free Stereo Touch plug-in and it opened up the sound nicely, as if it were stereo.

Can you (or anyone else) comment on why the left channel audio would distort if the Vegas meters show the level gets no higher than -.1 dB? I thought anything below zero was safe and that there might even be a little headroom above that. (I wouldn't knowingly go that high though - sure wish my camcorder had audio meters).

I know that in the past I have had some audio in the "red" range, a little above zero in the Vegas meters, and there was no audible distortion.

Open a copy in Sound Forge, create a new L/R track from the good channel, and apply one of the stereo presets in the Echo/Delay effects.

Pretty simple, but it works.

Yes, Voxengo's 'Stereo Touch' works nice... though my usage of it has been limited to stereoizing S/FX and crunchy rhythm guitar tracks. Beware though, applying too much can be counter-productive.
'Stereo Touch' is an old concept though, us 'old school' engineers used tape machines, (tape or analogue echo machines and outboard DDLs.

"I was about 60 feet from the stage so I wouldn't think there would be much of a stereo effect in the original sound track anyway"

That is basically right. However the main effect of stereo in this situation is to give ambience to the sound. The auditorium reverberation appearing at the stereo microphones will be similar but have slightly different delays. That is what gives the feeling of spaciousness. You won't hear much spread in the placement of individual performers unless you recorded with little or no reverb, such as outdoors, and even then it would be minimal, depending on the width of the performers relative to 60 feet. So if you generate a reverberant version of your mono (good channel) and both add it to and subtract it from the mono to create two new pseudo stereo channels you might get something useful. De-reverberating first by suppressing frequencies that have low level would help control the overall reverb. All this is a pretty crude approximation of what happens in normal situations, so don't expect perfection. If you listen to mono with headphones it sounds as though the whole stage of performers is crowded inside your head, but if you reverse the phase to one ear then the effect sounds more spacious and more pleasant.

Since you've got Sonar, you may simply be able to edit out the distortion peaks, since you say they are very short in duration, and then simply use the existing stereo recording. Sometimes a good limiter plugin can fix these kinds of peaks also. I'd experiment with that approach if the time required isn't unreasonable.

Otherwise, google Haas Effect and play around with that...

For an el-cheapo solution to create stereo sim copy the track to another track and offest one of them just a hair.

"Can you (or anyone else) comment on why the left channel audio would distort if the Vegas meters show the level gets no higher than -.1 dB? I thought anything below zero was safe and that there might even be a little headroom above that"

If the true peak meters in Vegas are not hitting 0dBFS then that only indicates that digital clipping has not occured. Unfortunately that's not the only source of distortion in an audio recording system. Microphones and preamps can overload causing distortion plus the AGC and limiters employed in video cameras can introduce problems as well.
For any event where good audio is important I would recommend using a decent audio recorder. My tool of choice is the Edirol R-44 which has never let me down and having 4 discrete channels has been a considerable plus.

Bob.

The camcorder has no audio meters so I couldn't tell that the left channel was distorting until I loaded up the clips into Vegas. Vegas 10e, as well as Sonar, show the peaks get close to zero but never quite get there (like -.1 at times. I didn't think digital audio would distort as long as it was in the minus dB area (?). But

.... which sounds like a faulty camcorder to me ....

Maybe iZotope RX can repair those spikes?

Thanks everyone for the advice. At this point I am satisfied with the pseudo stereo from using the undistorted right channel with Voxengo's Stereo Touch plug-in. This wasn't a critical shoot - just something for personal use.

Andy L, I played around with a limiter in Sonar but couldn't eliminate the distortion. I am not all that good at using limiters etc. though. Wasn't sure where to set the various settings the limiter had.

ChristoC, I don't have Izotope RX. I checked out their website and it is more expensive than I want to spend. And the demo doesn't allow saving. Thanks for the suggestion though.

farss explained how distortion can come from more than just digital clipping from levels above zero. That helps me understand now how it could have happened. I suspect some circuitry in the camcorder overloaded because of the very loud music. I will plan to set the camcorder's mic level to "Low" the next time I record a loud concert and see if that helps.

I have a Zoom H1 recorder I have used for concerts - it allows setting levels and it has meters. But the logistics of this concert barely allowed enough room for my camcorder and me, so I didn't use the Zoom.

"Can you (or anyone else) comment on why the left channel audio would distort if the Vegas meters show the level gets no higher than -.1 dB? I thought anything below zero was safe and that there might even be a little headroom above that"
- I'm not exactly sure why it would only be on the left channel... but generally the microphone and/or the input stage (preamp) of your camera's audio could be overloaded. On many cameras, and portable DARs for that matter, the record volume control (or AGC) only affects the digital audio level. The audio input stage is at a fixed level, so your camera's record level could be set very low and it would still be the same distorted sound... just at a lower volume. An extreme example of this usually happens when someone plugs a feed from a mixing board directly into the camera, where as the mixer is putting out line-level (usually +4dB) and camera's audio input is set to mic level .. (-50dB) a huge difference! like trying to fill a shot glass with a fire hose.
In your case, a 10db pad between the mic and camera input will usually remedy this in situations with higher than normal SPLs.
PS- This should have been posted over on the Vegas Audio forum.

>>PS- This should have been posted over on the Vegas Audio forum.<,

rraud, thanks for the additional insight into possible causes of distortion. Given what you said, setting my camcorder's mic level to "Low" may not help. I'll try it next time and see what happens.

I didn't think about posting this in the Vegas audio forum (I've never visited there). Thanks for the tip - I will try to remember to post any future audio-related Vegas questions there.

Given what you said, setting my camcorder's mic level to "Low" may not help.
- Setting the camcorder's mic level to "Low" IS probably all you need to do. That usually changes the input stage gain setting. Decent mics can normally handle SPLs in excess of what would be actually painful to humans, so I would not suspect the mic unless it's real cheap.

dalemccl,

1) Glad you got a suitable workaround.
2) Although your description is quite good, rather than continue to entertain speculation, which could go on for a long time, why don't you upload a 30 sec. sample of the original audio somewhere that exhibits the distortion in one channel, along with posting all the physical and settings details used to record it.

There are people who have already responded to this thread who can probably pin down the cause in a heartbeat by listening to it and looking at the waveform. Whether caused by levels, a bad connection, or some other source of interference, knowing the cause will allow you to take the right steps to prevent a recurrence in some future situation that "might" just be mission-critical.

musicvid, thanks for the suggestion. A link to a .wav file is at the end of this message

The setup at the concert was: just me and my Sony HXR-500V camcorder, which is an AVCHD consumer-level unit. The audio was recorded by the camcorder's built-in mics with the audio set to "Stereo" (the other choice is "5.1"). There is a mic level setting, which was set to "Normal" (the other choice is "Low".) I was about 60 feet from the stage. The venue was a semi-outdoor theater with stadium seating of about 3,000 seats. It has a roof and side walls that come down to within 6 feet of the ground so it is as much indoor as it is outdoor. The band was very loud.

I placed the .mts file created by the camcorder into the Vegas Pro 10e timeline. Here are the properties of the event:

Streams
Video: 00:14:48.321, 29.970 fps interlaced, 1920x1080x12, AVC
Audio: 00:14:48.321, 48,000 Hz, Stereo, Dolby AC-3

I made a timeline selection and rendered it to a 16-bit 44K stereo .wav file. Here is a link to the .wav file. Sorry, I don't see a way to make a hyperlink in the forum.

http://www.mediafire.com/?d7ibv883utcqajl

My take is that it's either radio frequency interference or an internal connection issue in the mic element or camera. It does not show a pattern of audio program clipping. The program peak levels between L/R are nearly the same.

My take is this is good old fashioned analog distortion caused by too hot a signal to the mike. Why is one channel distorting and the other not? Guess number two is that your camera was aligned at a slight angle to the PA system such that the right mic was attenuated.

I assume if you record audio at normal levels with your camera, you get no distortion??

You might be able to identify the worst frequency offenders in the left channel and just eq the distortion down a bit.

Realistically, this isn't a great recording on either channel, so I don't think there's much incentive to spend a lot of time chasing CD quality here...

"My take is this is good old fashioned analog distortion caused by too hot a signal to the mike."

Really? That's certainly an odd conclusion . . .
No correlation of spikes to program peaks, randomized, no flat-topping, and channel levels are nearly equalized around -6dB.
Forty years in the trenches tell me this is something wrong in the mic capsule or splatter from nearby RF, even a cell phone or router.
Of course the OP should be using better mics ;?)

My comments/answers to Andy L's and musicvid's latest posts.

Andy L said:
>>My take is this is good old fashioned analog distortion caused by too hot a signal to the Why is one channel distorting and the other not? Guess number two is that your camera was aligned at a slight angle to the PA system such that the right mic was attenuated.<<

I was sitting to the left of the stage (from the audience's point of view) so the camera was angled a little toward the right for wide shots. And when I zoomed in and panned to the right side of the stage, the camera was at even more of an angle to the stage.

>>I assume if you record audio at normal levels with your camera, you get no distortion??<<

That's correct.

>>Realistically, this isn't a great recording on either channel, so I don't think there's much incentive to spend a lot of time chasing CD quality here...<<

I agree. I was disappointed in the recording. In addition, the sound in the room wasn't very good to begin with. Something wasn't right in the balance between the instruments and the vocals that resulted in the performance sounding "muddy".

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musicvid said:

>>Forty years in the trenches tell me this is something wrong in the mic capsule or splatter from nearby RF, even a cell phone or router.

The distortion is present throughout the concert (actually it is less distorted after the intermission - maybe the sound guy turned things down a notch at halftime.) If it was a cell phone within the theater generating RF, it would have been a long cell phone conversation and I don't know how the person could have heard anything over the loud music. Maybe it was a cell phone in a nearby home or passing cars. I don't know whether there was a router in the building, but.....here is a possibility:

Four of the band members used wireless mics for vocals, and the same four had wireless transmitters on their guitars/bass. Could those have been generating RF that would reach the camcorder?

>>Of course the OP should be using better mics ;?<

I agree. However, the logistics of the concert barely allowed enough room for my camcorder and me to squeeze in, so a rig with a separate mic and audio recorder wasn't realistically possible.
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Thanks for your insights and advice.

Cell phones and routers transmit a beacon signal whether they are in use or not.

Wireless mics usually don't generate that kind of RF interference, unless they are all-digital (most are FM UHF).

The OP probably cannot use better mics, there appears to be no external audio inputs on the camera. Better mics plugged into a standalone recorder is his only option and one that he couldn't use (??). In that regard a trip to the tapers forum might give him some clues on how to record reasonable sound in such venues. Mics can be mounted on glasses and the recorder is just a PDA that'll easily fit in a shirt pocket, most of the smart phones can be pressed into service these days in conjunction with an external preamp and A/D converter..

Not only does this camera not have external audio inputs it uses an array of microphones, it can record either stereo or 5.1. Quite likely the stereo signal is derived by some form of matrix from the surround array.

Looking at both channels and the difference (L-R) is interesting. I'm very much inclined to doubt it's an overloaded microphone, from my experience when a condenser mic bottoms out you get a much nastier outcome. Also as someone else pointed out the SPL required for that to happen is high enough to make your ears bleed and your kidneys rupture. RFI seems very unlikely as well, the errant "spikes" in the left channel seem well correlated to what the right channel contains.

What it seems more likely to be coming from is something in the camera's signal processing. I've seen this before, Megabit was the first to pickup a problem in the EX1's signal processing. Certain low frequencies would be distored even though their level was quite low. It's as though certain frequencies "sneek though" the digital AGC and then get hammered by something else.

Given what I've seen happen with the abominations that are being built into cameras and cheap audio recorders today I just ignore all prior knowlegde, these things do not obey the rules. That leaves me clueless as to exactly what has gone wrong with this recording. All I can suggest again is to never trust the camera, use a GOOD external recorder and mic. A good phased array stereo shotgun generally works pretty well in such venues. These can be very expensive but I have to say the relatively cheap Edirol unit that Megabit has been using does a pretty good job of cutting out the reflected sound.

Bob

musicvid said:
>>Cell phones and routers transmit a beacon signal whether they are in use or not.

Aah, I forgot about that. Thanks.


farss,

Thanks for the info. I'll do some more testing to see if I can reproduce the same problem. If there is a problem with the camcorder's audio circuitry, the left channel distortion may be a repeatable problem when sound levels are high.

Just to clarify, the camcorder does have an input for an external mic. Also, I have an inexpensive microphone and a hand-held recorder (Rode Video Mic Pro and Zoom H1). When possible/practical, I use those.