ErMaC's Guide to All Things Video - Part 5

DVDs: What They Are and How To Use Them

It's no secret that DVDs are the latest craze in Home Theater. Of course, DVD has been a very long time coming. Now the DVD standard is over 3 years old, and DVD sales have soared while market penetration of players is through the roof. DVD has done ten times better than Laserdisc did (even though some would argue that LD is a better standard in terms of video quality), but the average consumer has no idea what DVD is - it's just some magical disc they stick in their player and great-looking video comes out.

In this article I'm going to focus on what DVD is as it concerns AMV creators, and how (when used correctly) they are the highest quality source footage available for digital AMV creation.

I. What is a DVD?

DVD stands for Digital Versatile Disc - not Digital Video Disc as many people think. It was supposed to be that, but due to the many other uses of the actual optical data format, they changed it so as not to pigeon-hole the possible uses of the format. It would've been like calling CDs Compact Music Discs, when in fact they can be used to store a lot more than just music. DVD-Video is the standard which defines what most people think DVD is - a specific format for distributing MPEG2 video paired with digital audio and even menus.

Since we're really only interested in the video part of DVD (we're probably not going to be using the menus in our videos, and the various ways of storing audio on DVD are so numerous that I don't want to cover them all in this article) we'll focus on how the video itself is stored.

In the file structure of a DVD you have Video OBject files, or VOB files. These files are multiplexed MPEG2 streams that contain Video, Audio, and Subpicture tracks. The actual video is encoded in MPEG2 at a resolution of either 720x480 for NTSC discs or 720x576 for PAL. In 95% of DVDs, they are also encoded at 29.97 FPS or 25 FPS for NTSC and PAL, respectively. Some discs that are in 23.976 FPS do exist, and more are coming, but I'm not going to talk about them because they're so few.

II. How do I convert a DVD?

So how do we get this video off of our DVDs and into our computer so that we can use it to edit with? There are 2 different ways to get it onto a PC, both of which have their advantages and disadvantages.

Digital -> Analog -> Digital

This method basically involves taking a DVD player and outputting the video through an S-Video or Composite cable and hooking it up to your video capture card.

This way provides not as good video quality since you are basically converting the digital data to an analog format and then back again, but it does provide real-time conversion to a format you can use (if your capture card goes straight to MJPEG, it means you get real-time MPEG2 to MJPEG transcoding). It's also a lot easier because you can just watch the DVD, then capture the exact scenes you want, which is easier to do with this method than the next one - even though the next one provides higher video quality.

Digital -> Digital

This method means sticking the DVD in a DVD-ROM drive, decrypting it, then either editing the VOBs directly or converting them to a format which you can edit with more easily.

This provides the highest video quality as you're doing a perfect digital transcode of the MPEG2 data on the DVD, without any analog conversion. However, this process can significantly increase editing time. If you're converting the MPEG2 to a format you can edit with easily on your specific hardware (like converting to MJPEG or DV) then you have to spend a significant amount of time on the actual transcoding process, as you have to decompress every MPEG2 frame and recompress it as your own format. This can take a LONG TIME. On my own Dual 933MHz Pentium III machine, I can transcode MPEG2 to my DV500's DV AVI format at about 2.5x realtime (so for 50 minutes, it takes around 2 hours).

Also doing it this way can mean a lot of work trying to find the footage you want. If you're working with a long series as your footage, and you want to make all of it available, instead of simply going through and capturing the clips you want, you'd wind up having the whole series on your harddrive, and you'd have to scrub through everything to find the right scenes to either 1) convert to your own format or 2) place on the timeline in Premiere or whatever video-editing program you're using.

Both of these methods have a place. For instance, in my latest round of Evangelion videos, I used the first method to capture footage from my Evangelion TV DVDs, watching the whole series through and capturing the scenes I wanted using the S-Video capture on my DV500, but I used a direct digital conversion on the Region 2 Evangelion Movie DVDs, since I wanted all the footage of the movies available to edit with. So I basically have 3 enormous files: Death DV.avi, Air DV.avi, and Magokoro Kimi Ni DV.avi which contain a pure digital conversion of the movies on the DVDs (I didn't bother converting Rebirth since 99% of the footage in it is also contained in Air), while the rest of the files are all short captured clips from the rest of the TV series.

Now I do it this way because I have a DV500 which means I can edit DV files in Real-Time. If you don't have such hardware there's a much better way to edit DVDs in their digital form right on the Premiere Timeline! That means no recompression at all until you either render a preview on the timeline or export your final video. This provides the best possible video quality, but it can be very slow. However, it's worth it for the increase in video quality and the disk space you save only storing the VOB files (which at most are 9MBit/sec) instead of storing whatever editing format you have (which can be as large as 25 Megabits/sec with DV, 13 Megabytes/sec with MJPEG, or even more with Huffyuv!).

Page 2 - Editing/Converting VOB Files Directly in Adobe Premiere