An important note about GMC

the Black Monarch · Post by **the Black Monarch** » Tue May 04, 2004 4:48 pm

In some videos, GMC is a bad thing.

Scintilla · Post by **Scintilla** » Tue May 04, 2004 6:50 pm

... what the <i>hell?</i>

DemonSpawn · Post by **DemonSpawn** » Tue May 04, 2004 7:01 pm

I think that was exactly the point he was trying to make.

Scintilla · Post by **Scintilla** » Tue May 04, 2004 7:16 pm

No, I mean, what <i>is</i> GMC (besides a brand of General Motors), and why'd it make that scene look so horrible?

Zarxrax · Post by **Zarxrax** » Tue May 04, 2004 7:51 pm

GMC is global motion compensation. It basically looks for uniform change in the video and sets a single motion vector for the entire frame, or something like that. It requires a fair bit more horsepower to playback, and helps the compression very little, so it's generally considered to be a pretty worthless option.

Scintilla · Post by **Scintilla** » Tue May 04, 2004 8:04 pm

Ah, okay, thank you.

Will keep that in mind for future encodes.

sysKin · Post by **sysKin** » Wed May 05, 2004 1:12 am

Anyway, what encoder had been used, what decoder was used ??

DivX 5.00 's gmc was pretty b0rked, yet still, divx decodes it right. All good GMC videos are decoded by ffdshow or xvid, or at least they should. XviD's GMC cannot be decoded by divx.

In other words, give us some info ^^

Radek

the Black Monarch · Post by **the Black Monarch** » Mon May 10, 2004 11:23 pm

Encoding and decoding were both done with DivX Pro 5.11

That video was made in Constant Quantizer mode. A 2-pass encode with the same options produced a much better result.