16 bit to 12 bit with Canon XL1s
 

recently I was videotaping using the Canon XL1s, I monitored the audio with earphones and watched the viewscreen; there was no indication that anything was wrong until I downloaded the tape; 18 minutes into the tape the audio disappeared and the image went black, when I played the tape back in the camera I noticed that it changed from 16 bit to 12 bit at the 18 minute mark, my question is what caused this to happen?

Hi Ann,

What happened after the glitch at 18 minutes? Did the tape stay in 12 bit or go back to 16 bit after the glitch? If it switched back, the momentary switch to 12 bit was just the camera trying to figure out how to play back the glitch. It may switch SP to LP at the glitch also.

If it switched to 12 bit and didn't switch back it sounds like a camera problem.

Jeff, the camera stayed in 12 bit, interestingly, the video download was not one continuous stream, i.e. it was split at the 18 minute mark,
we did a test using another tape and it seemed to work fine but I am really hesitant to use it again for fear of losing footage
many thanks for your reply, pepps

Was it a new or used tape?

Jeff, it was a brand new tape, phyllis

18 minutes sounds suspiciously like a 4GB limit......

<<<-- Originally posted by Edward Troxel : 18 minutes sounds suspiciously like a 4GB limit...... -->>>

That's what I'm thinking.

You say it's fine on the actual tape, but when you captured it...after 18 minutes of capture it goes bad? Were you capturing it all at once? 18 minutes is around the limit on windows machines if I'm not mistaken.

I'm not following you, Ann. Are you saying that your tape has a glitch or you have a problem capturing your tape to your computer? There is no 4gig limit on a tape, but your OS could impose a capture limit. The download process would not change the audio bit rate. Either the operator accidentally changed the rate or the camera glitched in the record process.

Was the change in mode at the a break between scenes? Did some time elapse between the scenes whre the audio mode changed? As far as I know, you have to be in the menu to make the change in audio mode, but that can be done with the wireless remote control.

Can you share any additional information about the shoot and other circumstances surrounding this happening.

I detected the problem when I downloaded the DV to an editing program; however, I believe that the actual conversion from 16 bit to 12 bit took place in the camera during the taping and I don't know why this happened; I discovered that this conversion took place by placing the tape in the camera and watching it in the viewfinder, I noticed the conversion there, any clues?

Don, this was a continuous taping, i.e. no breaks in the scenes and I was not using a remote;

Also, there was no problem downloading the DV to the editing program, it just came in black with no audio after 18 miniute; I know it's not a problem with the editing program or my system cause the tape plays this way in the camera using the VCR.
thanks for your continued help.......

Hmmm. Really unusual. BTW. what is type of PC, NLE program, and operating system that are you using?

As I understand the posts:
1. When playing and watching the camcorder analog output on a monitor (or in the viewfinder) it continues to play OK thorugh the 18-minute point with normal sounding audio, and the audio mode changes to 12-bit without missing a beat or droping a frame.
2. If you try to capture using your NLE, it burps at the 18-minute point.
3. If you start the capture just past the 18-minute point, capture is normal, but from 12-bit audio.

Would be interesting to see the tape on which this happens.

Don, yes your observations are correct, except for #3, capturing past the 18 minute mark is not normal, there is a break in the capture, i.e. it splits and the image goes black with no audio.
in answer to your questions;
NLE is Vegas 4, operating system is Wind XP pro ver 2002, computer Pent 4 CPU 2.40 GHz, 1.00 GB RAM, (I have pretty much ruled out the computer and operating system since I tried it on a Mac station and got the same 18 minutes of good video and then black with no audio) rather I am thinking that it has something to do with the cam but am at a loss as to what,
many thanks for your reply, pepps

What happens if you start the capture just after the 18-minute point, so the NLE does nto se the earlier segment with different audio parameter? Can you capture OK then? What is the sound then?

Don, I tried this but there just doesn't seem to be any digital information there either audio or video, pepps