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Converting video capture to VCD format
Question : My laptop has over 700 mega-bytes of random
access memory. I'm using a software to convert video camera capture to VCD
format. Which format do I need to choose before I start capturing the image?
Answer : Since you're going to be recording to video CD, we
will recommend MPEG-2. Actually, we recommend MPEG-2 as an all-purpose general
format. It's a fairly good compression protocol and should only need to be
converted if the video is going to be recorded on a "standard" VCD.
Question : During conversion from a 60-minute tape, it needed
almost a whole day to complete the job (from image capture to rendering to
copy to VCD). How can I cut down on the time taken?
Answer : It's not the capture that takes time (which takes
place almost instantaneously), but it's the conversion and burning. Video
conversion is very processor-intensive, so a faster processor will help in
this respect. If the video can be captured in MPEG-2 (for Super VCDs/DVDs) or
MPEG-1 (for VCDs), then the conversion process can be eliminated. This will
speed things up considerably.
Also, because different software use different ways to convert video, some
software will be faster than others.
The speed of the DVD-RAM/RW writer will also matter, of course. Some
DVD-RAM/RW writers have faster access times; some are capable of recording at
higher transfer "speeds" (SMILY_.png as opposed to 4X, for instance).
All these factors will have an impact on how fast the work gets done.
Question : Sometimes, after I finish the job and play the
VCD, I find that the quality is lacking - the picture breaks into little
squares. Did I choose the wrong format?
Answer : One problem with video is that if you pan (swing the
camera from one side to another) too fast, the video may break into little
squares. This happens because of the way the video is rendered.
To save on bandwidth, many codecs use what is called "delta compression". This
type of compression chops the image into small squares. The squares are
independent of each other and can be updated independently of each other. This
saves bandwidth because in any moving image, there are large parts of the
image that don't move, or don't move all the time.
For instance, if you take the standard "reporter at a crime scene" video, you
can see that most of the time, the only things that move are parts of the
reporter's face and maybe the cars on the road. A building behind the
reporter, for instance, usually never moves. So, by dividing the screen into
square sections and updating only the sections that change, a codec can save
bandwidth.
The main drawback with this approach is, if the whole screen suddenly moves
all at once, all the sections will need to be constantly rendered and updated.
If there isn't enough bandwidth to update the whole screen at once, the video
will break into squares as different sections of the screen update at
different times. To prevent this, avoid moving the camera too quickly.
Increasing the bandwidth (for instance, by recording to DVD video instead of
VCD) will also help.
Another possible reason for "squares" on a video is the capture bit rate is
set too low. The capture bit rate of a particular movie can usually be set on
the capture device or camera. |
