Spectralcat's Blog

August 21, 2009

Turning DVDs into AVI Files the Easy Way: Acid Rip

Filed under: Uncategorized — Tags: , , , , , — spectralcat @ 6:28 am

One of the easiest way to create AVI files in GNU/Linux is to use Acid Rip.  Unfortunately, Acid Rip does not seem to scale .avi files properly.  Getting a quality .avi file at a low bitrate often requires one to scale the frame size of the movie down.  The resulting frame size should be multiples of 16.  Acid Rip does not keep the resulting frame size multiples of 16; therefore I would advise against using it if you’re concerned about creating the best quality AVI files.  If just want an easy way to create .avi files, may still be useful.    My previous post contains more detailed instructions for using mencoder to create avi files, but Acid Rip is easier to master than mencoder.

1) copy dvd to hard drive using vobcopy (Alternately, you can use Acid Rip to copy the DVD to the hard drive):

vobcopy -m

2) Open Acid Rip and specify Video Source in the upper-right hand corner; copy and past the full name of the folder vobcopy created and hit Load.

3) Select the Video Title you want to rip in the menu that Acid Rip just opened up.  (The length of the title should give you a clue.)

4) Enter the name of the .avi file you want to create in the “Track Title” box.

5) Make sure that .avi is selected in the list next to Filename

6) In the menu under Audio select the Appropriate Language Track

7) Make sure “mp3lame” is selected for the Audio Codec

8) If the video has subtitles, specify the Subtitle and check the box Sub File

9) Click on the tab Preview and click the Preview button.  Watch a little of the video and listen to the audio.  This should help you make sure that you selected the appropriate entries in steps 3) and 6) above.

10) Click the Video tab and under Codec select “xvid”

11) Set Passes to: 2

12) Make sure Crop is check and click “Detect”

13) Make sure Scale is checked and that the box “Lock aspect” is also checked.

14) Check the “Post filters” box and in the box next to it, type: yadif

15) Now for the hard part.  We need to figure out how small we can get away with making the video.  There are three inter-connected features that we’re interested in: 1. file size, 2. video bitrate, 3. frame size (the width and height values next to “Scale”).  We reduce the video size by reducing either the video bitrate or the frame size (or both of them together).  If we lower either the video bitrate or the frame size too much, however, the resulting .avi file will look awful. There is a value called bits-per-pixel (bpp) that is specified in the Bits/Px box next to Bitrate; this value measures the relationship between the video bitrate and the frame size.  Acid Rip will encourage you to aim for a bits-per-pixel value that is between .20 and .25; this will produce a relatively nice looking video (one that is somewhere between dvd and vhs quality).  Lowering the width size in the “Scale” section will raise the bits-per-pixel value.  Raising the file size on the General tab will also increase the bits-per-pixel.  If you scale the width down too much, the video will look terrible when you watch it at full screen.  If you raise the file size up too much, you’ll defeat the purpose of creating an .avi file.  If you need to, Acid Rip suggests that you can squeeze by with a bits-per-pixel value between .15 and .20. 

You’ll want to start by figuring out how big you want the file to be.  If you want to squeeze it onto a cd, you’re shooting for around 700 MB.  I generally assume that a nice looking .avi file will have around 10-15 MB for every minute of video, and I try to keep the screen resolution as close to the original as I can. 

15A) So first I click on the Video tab and make sure that Scale Width and Height are set to the same value as Crop Width and Height.

15B) Then I determine what I think is a reasonable file size (let’s say 1160 MB for a 116 minute movie) and after making sure that Lock Bits/Px is checked on the Video tab, I adjust the Bitrate on the Video tab. I then flip back and forth between the Video tab and the General tab and continue to adjust the bitrate value until the file size under the General tab matches my desired file size.

15C) By the time I get to my desired File Size, my Bits/Px value on the Video tab is probably too low (well below .20). Ideally, I would like to fix this by lowering my scale Width (making sure that “Lock aspect” is checked) until I get a Bits/Px value of .20.  (To get Bits/Px back up to .20, I have to lower my resolution to 550 x 375). Unfortunately, if you scale the video down, Acid Rip does not make sure that the resulting frame sizes are multiples of 16. (DVD:Rip, however, does.)  You may want to skip this step and just leave the .avi at its original screen resolution and reduce the file size by further lowering the bitrate (and thereby messing up your Bits/Px). Or you may want to settle for having a larger file size. Or you could try using DVD:Rip and mencoder to create the AVI file as I illustrated in my previous blog post.


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