Sound Gaps

Lamar Lamb · June 9th, 2005, 06:13 PM

Take a look at the audio tracks from my PD170.
http://www.glassdolphinvideo.com/tem...soundprobs.gif
What went wrong here? I never heard anything wrong in the headphones at the shoot. This goes on for about 5 or 6 minutes then progressively improves with intermittent quick gaps for the next 15 to 20 minutes. Not problem at all with the video that I can see, just audio. No drop outs detected. It's wierd that it's just the audio. I was feeding from two independent mics straight into the camera. Switches were set Ch1, mic, 48v on, mic, 48v on respectivley. AGC was on. NR off. Wind Off. 48kHz. Brand new Sony Premium MiniDV tape. Ch1 was the factory Sony mic and Ch2 was an AT835B. I'm thinking a tape problem but why isn't something wrong with the video too?

Mike Rehmus · June 9th, 2005, 06:41 PM

Audio is mixed in with the video in DV. There are no audio tracks per se as there are in analog recording. Audio recording is mixed in with the video as tracks in amongst the video tracks recorded on the diagonal.

This may be something in the audio string that is causing the problem.

My immediate guess, since the sound disappears on both channels simultaneously, from two different microphones is either the Phantom power is cycling ( were you using phantom for the AT or battery?) or power to the audio chain inside the camera is going bad.

Microphones, cables, input connectors are all separate. The common bits are Phantom (perhaps) and the internal audio bits of the camcorder.

Now, having said that, I do believe I've read reports that recordings made with dirty or worn heads can exhibit that symptom. Since DV tape is is slightly abrasive, it may be that the tape itself cleaned contamination from the heads.

Have you run more tape through the camera and did it do the same thing or not?

Lamar Lamb · June 9th, 2005, 07:20 PM

I ran three tapes through that camera that night. The first had no problems at all. The second tape starts exhibiting problems at about 20 minutes and it is most severe at this point. This is the where the screen caps were taken. after five to six minutes the gaps are progressively of shorter duration and are farther apart. From 40 minutes on I don't see any problems. Tape three shows some intermittent problems at the beginning of the tape but they diminish after 15 to 20 minutes and for the last part of the tape I see no problems.

Lamar Lamb · June 9th, 2005, 07:32 PM

Well, the gaps occurred during the capture. I just recaptured and the audio problems are gone. I wonder if it was a head issue or software issue.

Mike Rehmus · June 9th, 2005, 08:48 PM

Ah. It is the tri-state logic empoyed in some computers no doubt. :-)

Jim Painter · June 11th, 2005, 05:33 PM

Lamar,

I've got 2 PD170's and am experiencing the identical problem with one of them. I've noticed however, many of the gaps go away when played back on the 2nd (good) PD170 - so most of it happens on playback.

You never know when this glitch is going to strike. I can run three tapes through in an evening and 2 will be good and one will have the gaps... go figure.

I spent quite a while with Sony Tech Support on the phone and found them very helpful. They seemed certain the problem was dirty heads as audio tends to mess up before video. They advised to first try head cleaner tape with a few 5 second passes. When that failed to clear up the problem they sent me documentation on how to disassemble the camera in order to do a manual head cleaning. Once I did that, it seemed to clear up - but not for long. Several weeks later I had another tape do the same thing mid way through a dance recital. I did a couple quick cleaning passes and subsequent tapes were ok.

I'm not convinced this is a head issue, although Sony would probably disagree. Both cameras get identical usage - one camera has NEVER had the heads cleaned and has NEVER had a problem. The other camera had numerous cleanings and still exhibits the audio drop outs - could something else be going on here?

Once dance recital season is over I'll send the camera back and hopefully Sony can figure it out. In the mean time I don't trust the camera for audio and won't use it without my second PD170 doing the primary audio capture.

If you ever get to the bottom of this problem please share it here on the board - I'll do the same....

Jim

June 9th, 2005, 06:13 PM	#1
Lamar Lamb Regular Crew Join Date: Jul 2004 Location: Baxley, Georgia Posts: 103	Sound Gaps - Tape or Camera? Take a look at the audio tracks from my PD170. http://www.glassdolphinvideo.com/tem...soundprobs.gif What went wrong here? I never heard anything wrong in the headphones at the shoot. This goes on for about 5 or 6 minutes then progressively improves with intermittent quick gaps for the next 15 to 20 minutes. Not problem at all with the video that I can see, just audio. No drop outs detected. It's wierd that it's just the audio. I was feeding from two independent mics straight into the camera. Switches were set Ch1, mic, 48v on, mic, 48v on respectivley. AGC was on. NR off. Wind Off. 48kHz. Brand new Sony Premium MiniDV tape. Ch1 was the factory Sony mic and Ch2 was an AT835B. I'm thinking a tape problem but why isn't something wrong with the video too? __________________ Lamar

June 9th, 2005, 06:41 PM	#2
Mike Rehmus Wrangler Join Date: May 2002 Location: Vallejo, California Posts: 4,049	Audio is mixed in with the video in DV. There are no audio tracks per se as there are in analog recording. Audio recording is mixed in with the video as tracks in amongst the video tracks recorded on the diagonal. This may be something in the audio string that is causing the problem. My immediate guess, since the sound disappears on both channels simultaneously, from two different microphones is either the Phantom power is cycling ( were you using phantom for the AT or battery?) or power to the audio chain inside the camera is going bad. Microphones, cables, input connectors are all separate. The common bits are Phantom (perhaps) and the internal audio bits of the camcorder. Now, having said that, I do believe I've read reports that recordings made with dirty or worn heads can exhibit that symptom. Since DV tape is is slightly abrasive, it may be that the tape itself cleaned contamination from the heads. Have you run more tape through the camera and did it do the same thing or not? __________________ Mike Rehmus Hey, I can see the carrot at the end of the tunnel!

June 9th, 2005, 07:20 PM	#3
Lamar Lamb Regular Crew Join Date: Jul 2004 Location: Baxley, Georgia Posts: 103	I ran three tapes through that camera that night. The first had no problems at all. The second tape starts exhibiting problems at about 20 minutes and it is most severe at this point. This is the where the screen caps were taken. after five to six minutes the gaps are progressively of shorter duration and are farther apart. From 40 minutes on I don't see any problems. Tape three shows some intermittent problems at the beginning of the tape but they diminish after 15 to 20 minutes and for the last part of the tape I see no problems. __________________ Lamar

June 9th, 2005, 07:32 PM	#4
Lamar Lamb Regular Crew Join Date: Jul 2004 Location: Baxley, Georgia Posts: 103	Well, the gaps occurred during the capture. I just recaptured and the audio problems are gone. I wonder if it was a head issue or software issue. __________________ Lamar

June 9th, 2005, 08:48 PM	#5
Mike Rehmus Wrangler Join Date: May 2002 Location: Vallejo, California Posts: 4,049	Ah. It is the tri-state logic empoyed in some computers no doubt. :-) __________________ Mike Rehmus Hey, I can see the carrot at the end of the tunnel!

June 11th, 2005, 05:33 PM	#6
Jim Painter New Boot Join Date: Apr 2004 Location: Metamora, MI Posts: 17	Lamar, I've got 2 PD170's and am experiencing the identical problem with one of them. I've noticed however, many of the gaps go away when played back on the 2nd (good) PD170 - so most of it happens on playback. You never know when this glitch is going to strike. I can run three tapes through in an evening and 2 will be good and one will have the gaps... go figure. I spent quite a while with Sony Tech Support on the phone and found them very helpful. They seemed certain the problem was dirty heads as audio tends to mess up before video. They advised to first try head cleaner tape with a few 5 second passes. When that failed to clear up the problem they sent me documentation on how to disassemble the camera in order to do a manual head cleaning. Once I did that, it seemed to clear up - but not for long. Several weeks later I had another tape do the same thing mid way through a dance recital. I did a couple quick cleaning passes and subsequent tapes were ok. I'm not convinced this is a head issue, although Sony would probably disagree. Both cameras get identical usage - one camera has NEVER had the heads cleaned and has NEVER had a problem. The other camera had numerous cleanings and still exhibits the audio drop outs - could something else be going on here? Once dance recital season is over I'll send the camera back and hopefully Sony can figure it out. In the mean time I don't trust the camera for audio and won't use it without my second PD170 doing the primary audio capture. If you ever get to the bottom of this problem please share it here on the board - I'll do the same.... Jim