[MacDV] erasing miniDV tapes

[Rauno Teravainen]

My take on it has always been that the erase head just cannot get the 
old pattern completely of the tape, you can hear that also on analog 
audio cassettes, when the music is very low or a complete silence, there 
is a faint "left-over" from the previous recording, until the higher 
volume of the new recording "kills" it.  The "left-over" could also be 
detected as bits on the DV, I assume, until the dynamic range of the 
"active" signal suppresses it.  I have never researched this, just an 
old belief coming from the analog audio era.  Don't shoot me for this, 
just rambling.

Rauno.


Brett Conlon wrote:

>Hi Rich,
>
>If you're talking about the very beginning of recording over old footage 
>and the end where it changes back over to the old footage... I've seen 
>this on most of the VHS players I've ever had. Where the old picture 
>flickers and statics (new word?) away until the new picture has completely 
>taken over. Sometimes the new picture kicks in but the sound is still the 
>old footage for a few seconds, can make for amusing viewing sometimes. But 
>once the recording has fully kicked in, the new footage completely erases 
>the old footage.
>
>I can't answer exactly why this happens (perhaps as the rolling tape moves 
>towards and away from recording heads) but I'd like to suggest that you 
>try recording over an old tape with the lens cap on from beginning to end 
>- recording just black. Then when you shoot with this tape give yourself a 
>few seconds lead in.
>
>Coj
>