Audio problem > scratchy noise when capturing

[brodwidr]

Hi -

I just ran into a problem I haven't had before, when doing a capture from video that was recorded using a wireless mic plugged into the camcorder.

Even though the audio sounds great when played back on the camcorder, and sounds fine when I monitor the audio while capturing over the PC speakers, it sounds bad when I play the clip back while in edit mode, and the same problem is heard when I render the clip out to an MPEG file.

Specifically, on loud portions I hear a scratchy sound, my guess is that it's some sort of clipping. But, I reiterate that it sounds fine on the camera and sounds fine while monitoring the capture. So it wasn't clipped during the recording process.

The audio properties on the original captured clip show up as "DV Audio -- NTSC" 32 kHz 16 bit stero.

A couple of other strange things I noticed with this capture: (1) there is only sound on the left channel when I play it back, even though sound is on both channels when I am listening to the audio while capturing (2) when I click on the *clip* alone and hit play I hear no sound at all; but when I click on the *project* containing the clip and hit play, I *do* hear sound. I shut down and restarted the computer and the problem recurred in exactly the same way as before.

What might be causing this? Is there any change in audio codec settings that might resolve it? Or any filter that can clean it up?

Here's a clip on youtube - you can listen to the problem.
http://youtube.com/watch?v=e64yUIxFFDg

Thanks in advance for any suggestions.

[Ron P.]

My only guess would be your integrated sound. It probably is using Realteck AC-93, which has been noted to cause clicking, pops and scratchiness. I think it is Heinz-oz that replaced his with a PC soundcard and the problem went away.

[etech6355]

The audio properties on the original captured clip show up as "DV Audio -- NTSC" 32 kHz 16 bit stero.

You may want to perform a fast test.
Record a new DV Clip into the computer from the same source tape video.
This time though start the tape somewhere's in from the beginning of the tape so it's clean dv data.
Hit play on the cam and after VS shows the preview playing smoothly then hit the record icon. Record about a minute or so.
Then exit the capture screen and on the timeline right_click on the captured video, select media properties or properties and in the pop-up display of the videos captured attributes check the audio and see if it differs from the original recording.
It's possible the original videos audio track is either 12bit 32khz or 16bit 48khz and the header information in the original recording is incorrect.

I would double check the true audio settings that the cam recorded to tape before trying to troubleshoot to much further. Usual settings on cams is 12bit 32khz or 16bit 48khz. I have experienced these incorrect settings in the file when starting a recording session from the absolute beginning of the tape. Now I pre-roll the tape a few seconds and then hit the record button. Just thought I'd mention this as was my experience with one cam I have. Converting the audio never worked correctly because of the incorrect header information in the dv file. I had to record the tape again and use the pre-roll method described above.

[brodwidr]

Following etech's suggestion (thanks, Etech), I checked the audio settings, and sure enough the other files from this same cam are 48khz/16 bit while this one is coming up as 32kHz, 16 bit. Good call! And it did this regardless of where I was in the video, in other words, pre-rolling did not make the difference.

I also checked the sound card (thanks, Vidoman) by recording the sound out through the cam's headphone jack, in through the sound card's line in, and it recorded fine, no distortion or clipping.

I did a quick test on some other tapes I have, and it captured without a problem in the audio track. But, the one difference on this particular recording session is that I had a mono wireless mic going into the stereo channel on the camcorder, and perhaps being recorded on one channel only. I think perhaps the camera recognized it was only getting one signal and incorrectly reported it as 32kHz 16bit stereo instead of recognizing it as normal 44 kHz stereo. Maybe the software in VS10+ was trying to reconcile silence on channel and high volume on the other channel, and misallocating the bits causing the clipping. Has any one else had strange results trying to do a capture on a source that was only feeding one audio channel?

In any case, it's clear now that all the hardware is working and that the audio can make it into the computer without a problem. It just can't make it into a VS capture without this clipping noise.

Any thoughts?

[bop]

Just a thought, maybe you could try capturing with "windows movie maker"? i had a similar problem to yours that wasn't there with movie maker.

Brian

[brodwidr]

Terrific suggestion!!

It encoded perfectly under WMM.

Thank you so much.

- David

[bop]

Great to here that it worked, to fix my problem i had to disable the "1394 NET adapter" (control panel/network connections/1394 net adapter) not to be confused with the 1394 card in the device manager

After disabling the NET adapter MY capture problem went away. I'm don't know why my problem started or why the NET adapter affected my captures but the same as you WMM worked properly but VS wouldn't

BOL Brian,

[etech6355]

I also disable the 1394 net adapter. Also know of many that have it enabled with no problems.

I am curious though, In the actual session on the tape that's given this problem. Is the audio 16bit 48khz or not. In other words if you use another program to capture the video what are the audio properties versus VideoStudio recording the file? Pretty sure VS10 has a setting to quickly make a mono track (left channel) to stereo. If not you can always set your project to mono. Other methods to do this also.

I would look in your cams manual & in the setup menu to see if your cam can even record in a 32khz 16bit mode, usually it's 32khz-12bit or 16bit-48khz.

Audio on dv tape is set to a certain area of the tape. You can only fit so much information in this area.
Full Audiio Bandwidth of the tape area is 1536kbs
(16bit x 48khz) * 2tracks = 1536kbs (each channel being 768kbs)
(12bit x 32khz) * 4tracks = 1536kbs (each channel being 384kbs)
LP Mode? Ever use it?

[brodwidr]

Hi, etech -

In the clip that was successfully encoded by Windows Movie Maker, when I open that within VS10+, it is recognized by VS as 48 kHz 16 bit mono, which is absolutely what it should be, given that I had the camera set to 16 bit at the time I shot it, and I recorded on one channel only.

When VS plays back the clip that was captured by WMM, it plays back fine; the audio sounds much better than when the same clip was captured by VS. Not only is the clipping gone, but the high end is crisp and clear compared to the version captured by VS, where the high end is slightly rolled off. All this points to a potential bug or limitation in VS capture code, at least when confronted by a "difficult" piece of miniDV recorded footage. I would be happy to ship the tape to Ulead programmers if they wish to investigate further.

per your suggestion I checked the manual for my camcorder, a sony dcr-pc9. It's as follows:
Audio recording system
Rotary heads, PCM system
Quantization: 12 bits (Fs 32 kHz,
stereo 1, stereo 2), 16 bits
(Fs 48 kHz, stereo)

Apparently, when the clip was seen as 32 kHz 16 bit, VS was seeing it in a mode that is impossible given the camera's specifications. What do you make of all this?

[etech6355]

Apparently, when the clip was seen as 32 kHz 16 bit, VS was seeing it in a mode that is impossible given the camera's specifications. What do you make of all this?

I wouldn't call it a bug. Using VS it happens sometimes with my JVC cam, never using the Canon Optura 60 DV camcorder so I suspect something in the 1394 cam's chipsets is causing this until the cam see the true dv data stream. Like I said though only when starting from the absolute beginning of the tape which has a small amount of blank area before the recording actually started. So I pre-roll into the video a few seconds, let the preview windows sync and then hit the record button. Also it doesn't always happen all the time.

I'm confused how the DV file recorded in Win_Mov_Maker can be mono. Should still be stereo but maybe this is a feature in your cam when using the external mic inputs, maybe a smart cam... or a smart *** cam.

I'd do some more experimenting with the external mic & see what works best. If it's a continuous problem probably the techs would like to test the tape. Also curious if you used a different dv cam to playback the tape how that records.

[brodwidr]

I need to do some more experimenting, but let me respond to some of your questions/comments

1.) this problem does not occur whenever I use an external mic; I've done other recording with different external mics and it has been fine.
2.) I think it may have something do with having the level set a bit too high, and that confusing the VS+ software. or the combination of high audio levels with only recording one channel, and/or not pre-rolling the tape.
3.) I played back the tape on the same camera I recorded it on, so we know that's not an issue.

There is definitely something a bit strange about how VS interprets the levels of incoming audio. The audio on the tape was loud but not distorted when listening to it played back. When I recorded the audio directly via analog output to MP3 and then imported that as an mp3 file into VS, it was showing at normal levels. When I captured the clip using windows movie maker and imported the clip into VS, it was showing at normal levels and sounded fine.

One possibility is that the camcorder was outputting 16 bit audio, but it was taken in by VS as 12 bit audio, throwing out the 4 high order bits instead of the 4 low order bits. That result in taking what was a reasonably well recorded signal and making it clip all the time, as all the headroom was lost in the capture process. This is just speculation, but it's the best possibility I can think of at the time.