Step 1. From DV camcorder
to capture board. DV is decompressed in the camcorder.
Recompression to MJPEG on the capture card results in quality loss.
Step 2. Editing: Clips
which have transitions or effects are being decompressed, merged or edited
and subsequently recompressed to MJPEG. This results in quality loss.
Usually not noticeable, because the effect (fade, wipe etc.) usually hides
Step 3. From capture board
to DV: MJPEG is decompressed
on the capture board, converted into analog video and the compressed to
DV in the DVCR. Results in quality loss.
Editing DV the old & tired way.
Most DV camcorders, such as the ubiquitous Sony VX-1000,
have analog (and/or S-video) outputs. You can use them for editing just
like a regular camcorder. Since the Sony
VX-1000 does not have analog inputs, you will need a DVCR such
as the DHR-1000
for your final edits. You can also record to any VCR (SVHS, Hi-8 etc.)
that accepts analog input. Kiss your quality good-bye when you do that.
Many DV camcorders and DVCRs accept LANC
(CTL-L) device control. You can connect with it to standalone device control
equipment, or to device control equipment which interfaces with linear
editing applications, like Video
Director, now owned by Pinnacle Systems.
The analog I/O of DV equipment can also
be used to connect with standard video capture boards which usually
employ the MJPEG compression standard. Results usually are quite good.
One area of concern is that the DV format employs a "lossy" compression
scheme which trades supposedly redundant information for higher
compression ratios. MJPEG also employs a lossy scheme. The combination
of two lossy codecs can result in a loss of quality due to repeated transcoding.
Two lossy codecs combined often equal one lousy codec.
In real life, the loss involved in these steps
is less severe than it sounds. One of the reasons is that the DV signal
usually is very clean and free of noise. A clean signal lends itself better
to compression than a noisy signal. Recommended: Analog capture boards
which employ high quality analog-to-digital (A/D) stages, such as the Plum
from Interactive Images. It processes analog in an external, shielded
Editing DV the old & tired way works while there are no other alternatives,
but eventually, you want to edit DV the firewired