dvd::rip's Zoom calculator let you control all parameters, which influence the aspect ratio and frame resizing calculation, if you want. For most uses the standard Clip & Zoom interface, particulary the presets, will fully suffice. But dvd::rip let you do the hard jobs, if you want them... ;)
Press on the corresponding button on the Clip & Zoom page to open it.
The window is divided into three parts: some parameters regarding
the resizing of the image, parameters for specifing the video bitrate
and a box, which lists the calculation results of all possible frame sizes.
This way you can understand how dvd::rip calculates frame sizes and you
can influence all corresponding parameters by hand.
You can adjust the fast resize alignment to use (8, 16 or 32),
or disable fast resizing by selecting the appropriate popup
Most video codecs expect a final frame size, which is divisible
by 16. You can modify this value, if you want - but first make
sure that your favorite codec supports it, otherwise you may
There are to ways to achieve the alignment of the result frame.
You can use the clip2 stage, but then you will loose some image
information, because you crop the borders of the image. Or you
get the final size in the zoom stage, but then you may get
bigger aspect ratio errors. It's up to
you to decide, which is more important for you: full image size
or exact aspect ratio. Just play around with the settings to see
how they affect the results.
You have three choices here: use auto clipping with clip1,
or with clip2, or use the manual clipping, you adjusted
already with the clip1 entries on the Clip & Zoom page.
The difference between clip1
and clip2 is as follows: if you use clip1, the image in the
zoom stage is smaller what's slightly faster. But you get
very unnatural resize values, which give less aspect ratio
accuracy if you use fast resizing. Using clip2 will produce
many result entries with 0% aspect ratio error, but the image
to scale is bigger, which is slightly slower.
You can specify the video bitrate, by selecting the target
size using the disc size presets, or by entering the target size
bitrate or BPP by hand. It's the same scheme, which is used for
Video bitrate calculation on the
Specifing the video bitrate
in this window makes sense, because a special
bits per pixel (BPP) value is calculated, which tells something
about the transcoding quality.
After changing a parameter press the "Refresh" button, and the list
of Zoom Calculations will be updated.
The lines are highligthed differently, depending on the aspect ratio error.
Red lines mean a perfect aspect ratio. Bold lines denote errors smaller than
0.3%, normal lines mean errors of 0.3% or above.
You can select an arbitrary entry and press "Apply" to copy the
corresponding values into the Clip & Zoom page entries. The preview images are
recalculated, so you can rate the result immediately. If you press "Ok",
the values are also copied, but the window is closed afterwards. "Cancel"
closes the window without copying any values.
The result list has the following columns:
width x height of the final frame.
This acronym stands for "bits per pixel". It sets the number
of frame pixels in relation to the video bitrate you specified.
The bigger the value, the more bits are available to encode a pixel,
which means good quality. So if you have small frames, the images
can be encoded with high quality. But a small frame means also
less image information, so one must find a good balance between
frame size and video bitrate. For MPEG4 like codecs, values around
0.25 are good VHS
quality, values around 0.4-0.5 result in DVD quality. Just play
around with this, to find out what's after your fancy.
This is the effective ratio of the
frame. It has to be 1.7777 for 16:9 and 1.3333 for 4:3 movies, but
it may differ, because resizing isn't always exact, particularly
with fast resizing enabled.
This is the aspect ratio error, in comparison
to the optimal aspect ratio.
These are the clip1 values, delimited
by slashes: top, bottom, left right.
This is the zoom size of the frame.
These are the clip2 values, delimited
by slashes: top, bottom, left right.