Changing resolution to equal smaller file size

[MeekloBraca]

What im looking at doing is this.

Recording say 2.5 hours of DVD. Recording it onto 2 discs using a bit rate that would make the total file size about 5.5-6 million megs. I dont really want to shrink the file size because it keeps the original resolution. But id like to make it fit onto 1 disc with the best possible quality given these options. Can this be done by changing the resolution of the output file or is that something thst is completly unreasonable?

[guns1inger]

It can, however resolution does not govern file size, bitrate does. You could cut the resolution in half, but if you keep the same bitrate, you will get the same file size. What reducing the resolution does do is allow you to use a lower bitrate with less detrimental effect from compression. That doesn't mean you get away scott free. Have a look at What is DVD (top left corner) to see the allowable resolutions for your format. Half-D1 is a real possibility. It effectively reduces the horizontal resolution by 50%, which is restored by stretching during playback. The downside is that it can result in a softer image.

I suggest you take a 5 minute sample and expeirment. Encode one version at half-D1, encode another at a lower bitrate. See what works for you.

[kush]

Softer image, but assuming you're starting with a quality source, you probably won't notice it. I took the liberty of using a tool from the calculators section to input your 2.5 hours parameters (screenshot below)...ps disregard the * Divx choice, I forgot to switch it to DVD when taking the shot..Makes no difference in the resulting info for DVD/MPEG2 encoding and authoring.



..given your 2.5 hour length, assuming a single 192k audio stream, and leaving ~50 megs for menus/nav information, you end up with the above average bitrate for a full DVD.. 3840kbit (average) is certainly enough for 1/2 D1 res (subjective opinion)..Like previous reply said, try doing a small section of video and play with encoding settings, see what is acceptable to you.. Who knows, maybe you'll be satisfied w/ the above bitrate, even while keeping full D1 (720) res...

Also, another option (or 2) in the size quest, if you have 2 already authored DVDs, you could combine them via DVD Remake Pro (or similar) and burn to a dual layer disc...Or take the combined video (in which Remake creates an entry menu where you select either video to view) and re-encode *that* -- with whatever you decide to do regarding the resolution issue.

[edit] One more thing, you didn't say anything about your audio info that you used in your calculations..If your #s are assuming WAV/PCM audio, you could make the audio AC3 or MP2 (although NTSC requires AC3 for primary track IIRC alot of DVD players will play NTSC/MP2 anyway). It would allow you the bitrate given in the shot above -- assuming same video length, but with WAV audio, you bitrate would be just south of 2500kbit..Too low, even for 1/2 D1 (and 1/4 D1 [352x240] IMO isn't an option since you do care about the quality here).