I have some files which after adding up Mpg2 + AC3 ends up with about 6GB in VOB files. I think it would be a waste to split that in two DVD discs, so I tried compressing them with DVDShrink, as I have done many other times. The problem is that on my first test (learnt the hard way to do DVD-RW when in doubt), there are some "blocky" and "choppy" sequences. This is after setting my compression at about 87% on DVDShrink. What do you people do so as not to waste unnecessary space on a disc? I am not a newcomer to authoring DVDs, but I never wanted to get too much into finer setup except when absolutely necessary. E.g.: on 23.976 to NTSC conversions or on anamorphic films.
Bitrate is the determining factor for how much you can fit on a disc. If the video is 5 hours your bitrate will have to be much much lower than if it was 1 hour. Try using a bitrate calculator to help you figure out exactly how big your video will be before you even encode.
We got into this bitrate topic some time ago, but it's not quite clear to me yet. Apparently the higher the bitrate the better the quality, that being resolution, lack of artifacts and so on. But I still wonder how bitrate may not be wasted on converting originals that are Divx compressed, even if coming from DVD-rips. Perhaps it's a question of trial and error to see where the right combination is, though there might be an already tried way that I don't know yet. Apparently the lower the bitrate the smaller the size file, but how does that compromise image quality? And how much of that quality is already compromised by the Divx compression? What I am talking about is how will that show on a 32" screen or larger. From what I have seen on the many files I have been converting, all coming from similar sources (probably VCD originals), there is a limit to the image quality you can get. As this is the only option for me, because I can't get them anywhere else, I have to live with that limited quality. But that may make unnecessary using multiple discs wasting bitrate in an image quality that I will never get. Let's hope I am making this reasoning clear to get.
There are tools to tell you what the bitrate of your files are. Since it's Divx it's probably under 1000kbit/s. That being the case, re-encoding them to a bitrate of 6000kbit/s would be wasteful. You're dumping in decent bitrate but you'll never achieve the picture quality you would if you had converted a pristine source with lots of bitrate. As I mentioned, use a bitrate calc to see how big your disc will end up before you convert. If you have 5 hours of Divx to fit on one disc then your converted bitrate will HAVE TO BE no greater than 1803kbit/s (depending on the bitrate of the sound it may have to be less). If you make it more than that you'll end up not being able to fit it. Since you are working with Divx, that low bitrate (1803) may be ok. Divx is already compressed, and the bitrate dramatically reduced when it was converted to Divx, so 1803bit/s may be enough for them to look ok on a DVD, but you may have to fiddle around to get it to look the way you want.
OK. Now we are getting somewhere. My video is 2h 13min 38sec, which on the bitrate calc is 4335 Kbits. Would I have anything to gain by going up to 4500 or 5000?
That's the point of that calculator, to tell you the maximum bitrate that you can use. Put that number into TMPGEnc for either constant or variable bitrate encoding and your show will exactly fit on a DVD. If that's all you want to put on that disc, then use the maximum you can, and don't worry that it's too much. As long as the source is decent, and you encode it right, it should look great.
Ok. Let me tell you the end of the story. After exhaustive (for my patience) tests to correct image artifacts I was having, I could arrive to several concepts: 1) The bitrate calculator really works well. I could fit the whole film on one disc with no apparent sacrifice in quality. That will be a variable I will use well from now on. 2) My "stretching routine" of going up to 5.1GB, with image and sound, is perfect and allows using less compression. 3) The artifacts problems I was having was due to some DVD-RWs I was using. Apparently they degrade with time or the air, and some develop some hard to see darker spots in the inner surface, which seem to causemisreadings and subsequent artifacts. As all it's well when it ends well, thanks for the help, and hopefully my experience will serve others.
