AcidRip—a Gtk2 Front End to MEncoder
Some DVDs may give AcidRip trouble due to fuzzy borders, so if it returns with a “crop failed” message, you may have to set the crop manually. If this is the case, start with a width of 720, a height of 480 and go down from there. 720x480 is the size of a standard NTSC DVD frame. For PAL DVDs, the size is 720x568.
When cropping manually, the Horiz and Vert sections can be a little confusing. What they are is the offset from the top-left corner of the full frame of where the crop frame should be positioned. The crop frame itself is specified in the width and height boxes.
For example, take the image shown in Figure I from the film Charade, starring Audrey Hepburn and Cary Grant. This film is good to use as an example for two reasons. First, AcidRip could not detect the the proper crop settings. Second, due to a quirk in United States copyright law, when this film was released, Charade fell into the public domain, and it can be used by anyone for any purpose, including this one.
As you can see from Figure I, there is a black bar down the left side of the film, which exists throughout the film. There is also a small black border down the right side. Both borders are fuzzy, and therefore they are hard to detect accurately. The top and bottom borders of the film also exhibit some variation throughout. The manual crop settings that eventually worked for me were:
Width: 705 Height: 346 Horiz: 11 Vert: 71
This is simply another way of saying that my crop rectangle is 705 pixels wide and 346 pixels tall. The crop rectangle is offset from the left edge by 11 pixels and from the top edge by 71 pixels.
To get at these final dimensions, I first started with a width of 700, a height of 400, a horizontal offset of 10 and a vertical offset of 60, which were my best guesses of what the dimensions were. Then, by switching back and forth between the Video and Preview tabs, I was able to fine-tune the settings until I was happy with the result.
Now that I am familiar with encoding with AcidRip, my next project is to try to take it to the next level by using MEncoder directly. AcidRip's queue export feature really helps with this. You can export a small shell script of the exact commands that AcidRip passes to MEncoder. Using that as a starting point, I can tweak the settings even further.
The MEncoder documentation is also a great source for encoding instructions and ways to tweak the parameters to get the best image quality. Now if I could only find the time.
Resources for this article: /article/9389.
Daniel Bartholomew has been using computers since the early 1980s when his parents purchased an Apple IIe. After stints on Mac and Windows machines, he discovered Linux in 1996 and has been using various distributions ever since. He lives with his wife and children in North Carolina.
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