DivX vs. DVD: What's the real difference?

James Roberts87 said:The image isn't identical for one simple reason.
I watch movies on a TV, not a computer monitor.
On my bedroom set, I don't even notice a difference.
But when I switch to the living room, where there's a Samsung 35 inch 100Hz flat screen,
the difference becomes obvious.
Same thing happens with an LCD.

I am talking about TECHNOLOGY—MPEG-4 is objectively superior to MPEG-2. You're arguing against things hundreds of experts at organizations like the MPEG group already know for a fact.

Debating a single specific movie is pointless. If you insist, you’d need data on who encoded both versions and how. Your DVD came straight from a Hollywood studio, whereas the DivX version was likely compressed by some kid who doesn't know what he's doing. There's a whole mountain of technicalities to explain, like what dustycanyon6 mentioned: DivX encodes an already degraded file, while the DVD encoder works from the master.

I fail to see the connection between the encoder, the TV, and the room layout.

Carl Brown4 said:I don't really follow how the coder, the TV, and the room are all connected.

If you're using a cheap TV, you won't notice much—but on a high-end set? You definitely WILL!

Carl Brown4 said:I'm talking about actual TECHNOLOGY here—mpeg4 is objectively superior to mpeg2. You’re arguing against stuff that hundreds of experts (like the MPEG association) already know is true.

Debating a single specific movie is pointless. If you really want to go down that road, you'd need data on who encoded both files and how they did it. Your DVD came straight from a Hollywood studio, whereas that DivX file was probably made by some kid who doesn't know what he's doing... I shouldn't even have to explain things like what dustycanyon6 mentioned above—how DivX encodes an already "damaged" file while the DVD encoder works from the original source, and so on.

I don't see the connection between the encoders, the TV, and the room setup.

The DVD came out of Hollywood.
The DivX was my own handiwork; I spent 9 hours on it, and it's the best I could do.
I explained the comparison above.

James Roberts87 said:It’s actually pretty simple why the picture looks different.
I watch movies on a TV, not some tiny computer monitor.
Honestly, even on my bedroom TV, I don't really notice much of a difference...
But when I switch over to the TV in the next room—it's a Samsung 35 inch flat screen with a 100Hz refresh rate.
And man, then the difference is HUGE.
Same thing happens when you're looking at an LCD.

James Roberts87 said:The DVD came straight out of a Hollywood studio.
That DivX file was my own handiwork... took me about 9 hours to finish, and I think it turned out as good as I could make it.
I laid out the comparison above.

Encoding time really just comes down to your settings and how fast your PC is. Plus, were you using two-pass (or multi-pass) encoding for that DivX file? Were those settings cranked up to the slowest, highest quality level? Did you go with a high bitrate, say maybe 3000-4000 kbps? When you're watching stuff on that Samsung, is the source the same for both the DivX and the DVD (like, are they both coming from a PC, or both from a dedicated player)? And did you resize the DivX file at all? What kind of deinterlacing did you run through? Etc., etc., etc...

By the way, there are a few big things to keep in mind when playing back DivX or XviD files on a computer. You have to be careful with your post-processing settings. For instance, the XviD decoder can sometimes overdo the deblocking, which makes everything look blurry and kills the fine detail. Sometimes adding a little bit of grain helps, because most DVDs have a bit of noise anyway... it can actually make the image look sharper and more dynamic. And if you're dealing with a low-end TV that tends to blur everything, a sharpening filter can be a lifesaver. You can actually overdo it, though... making it look terrible on a monitor, even if it looks great on the TV. There's a lot to it...

MaxB said:Encoding time really comes down to your specific settings and how fast your PC is. Also, were you using two-pass (or multi-pass) encoding for those DivX files? Were the settings dialed in for maximum quality at the slowest speeds? Did you push a high bitrate, say 3-4000 kbit/s? When watching movies on that Apple device, is the source material the same for both DivX and DVD (meaning, are you using a computer for both, or a DVD/DivX player for both)? Did you resize the DivX files at all? What kind of deinterlacing did you run? And so on...

By the way, there are a few key things to consider when playing DivX/XviD video on a computer. You have to be careful with post-processing settings—for instance, the XviD decoder can sometimes overdo the deblocking, which makes the image look blurry and kills the fine tonal transitions. Often, adding a little bit of noise helps because that grain is usually visible on DVDs anyway; it actually adds sharpness and makes the image feel more dynamic. If you're dealing with a low-end TV that tends to blur everything, a sharpening filter can work wonders. Just don't overdo it—you can easily over-sharpen an image until it becomes unwatchable on a monitor, even if it looks great on the TV. There's a lot more to it...

The DivX was set to the highest possible quality for viewing on the TV.
I don't do single-pass encoding; everything I do is two-pass.