I am a big fan of DIVX , in fact I paid for the full DIVX encoder. About a year ago, I acquired some
Hard Disk Media Players that I just love. They play back DIVX files, and XVID as it is a clone of DIVX. These devices have allowed me to keep my original DVDs stored away, where they do not get touched. With DIVX, I can compress the videos down to a reasonable size and maintain video quality. My dabbling with this and other devices has led me to this Post.
Lately I have downloaded some TV series and movies and I see the same issues arise. (See my feelings on legality below).
Frame Rates and Program Length
Consistently, I see that programs that should be about 44 minutes in length with commercials cut out, often play back at 40 minutes in length. I pondered this problem a lot, and as a former television technician, I reasonably sure that 44 minutes or so constitutes 1 hour with commercial breaks.
Here is what I finally concluded.... There is a process called 3/2 pull down, where a 24 FPS film is converted to roughly 30 FPS (by inserting an occasional "extra" frame) when transferred to video in North America (NTSC). There is a similar process used in PAL however I have not done all the math exactly, but I did do enough math to identify the problem. Some software, or the users of software, are removing these extra frames. This is not unusual and is a good idea to reduce file size. The problem lies in that the file still is playing back at 25 FPS, not the 24 that it should play back at. Most of these files originated from PAL systems I can tell due to the PAL video sizes. The most annoying part of this problem is that sometimes it is noticeable that the dialog, and motion, on such ripped programs seems hurried. I remember the advent and discussions of a device called the Lexicon in the 80s which performed a similar function for broadcasters and allowed them to pack more commercials in a 1 hour program. I can not emphasize to all of you DVD rippers enough that you need to keep the proper frame rate, which should reflect whether the pulldown was removed or not. If so, the resulting video is 24 FPS , not 25 FPS, and definitely not 30 FPS, as this affects the playback duration and presents the content in a hurried format.
Aspect Ratio and Cropping
I know there are given aspect ratio "standards" but I have seen some home rippers making some serious mistakes. I do not worry about "proper" resolutions so much, as long as the aspect is correct. I recently downloaded some files for testing via torrents. Now in the case of one film in particular , every copy I found had the same butchering to it when it came to aspect ratio. That file which you can find easily is the 1994 film "The Little Rascals" . It was butchered because when downloaded from a torrent, it is in a 16x9 aspect ratio. Hhowever, the DVD that it was ripped from apparently was 4x3, so it was cropped when ripped. The bad part about that is that it was already cropped when presented in 4x3 and cropping it again yields only a fraction of the original frame. When I downloaded and viewed this file it looked very odd to me, although the quality was good tops of heads were frequently cut off, so I connected the old VHS and started comparing my old 4x3 aspect VHS tape of this movie with the downloaded 16x9 version. I should see more on the sides of the 16x9 from , however in this case I see less of the top and bottom. Clearly that file on the torrents (700.18 Meg) was from a 4x3 aspect DVD then cropped to 16x9. This is a horrible mistake for anyone ripping DVDs!
Comments about my downloads
I want to clarify that my downloads were for testing purposes, and all downloads were of movies that I already own original media. Since I do own original media, I do not feel that I am infringing on copyrights by downloading a back - up copy.
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