[Scummvm-devel] DXA file format for videos
sev at scummvm.org
Fri Apr 28 15:27:14 CEST 2006
On Fri, 28 Apr 2006 15:24:24 +0200
Torbjörn Andersson <eriktorbjorn at telia.com> wrote:
> Here is my comparision between the size of the (low-quality) MPEG
> cutscenes and the DXA cutscenes for Broken Sword:
> BS1: 35M (32M video + 3.3M sound)
> BS2: 30M (27M video + 3.2M sound)
Adequate quality mpeg2 videos take somewhat more:
BS1: 68MB video
BS2: 70MB video
Someone played with mencoder setting and provided cutscenes from German
version of the game. Above figures were based on that. Still it adds
some visible artifacts.
> BS1: 117M (96M video + 21M sound)
> BS2: 211M (186M video + 24M sound)
BS2 compresses badly because (a) it has compression artifacts which add
up to frame difference (b) it has moving background.
> The reason the DXA sound is so much larger is, of course, that it's
> uncompressed WAV. (From what I understand, compressed WAV isn't
> working as it should yet.)
As we discussed briefly, it would be natural to use sound-less DXAs and
reuse existing OGG files.
Mention of motion compensation on ZMBV (Zip Motion Blocks Video) used
by DosBox motivated me to give it a try. Adding it to existing DXA
encoder was matter of 15 lines of code.
Results weren't that impressive:
BS1: 100M video
BS2: 180M video
It seems that its move compensation scheme doesn't work that well.
Also I tried MNG, however this is a big beast, and I think it's even
bigger than libmpeg2. Results on it are much better, though it takes
enormous time for these settings:
advmng -S 64 -3
BS1: results are incomplete, but it gives 31MB where DXA gave 45MB
so approximately I expect 75MB which is comparable with better
BS2: 136MB video
However I don't really think adding libmng dependency is a good idea.
Another things I plan to try are:
- zlib compression quality settings
- png compression of frames
I'll report on these later, when they're done.
So current DXA results against adequate quality MPEG2 videos are:
BS1: 2x bigger
BS2: 3x bigger
Not that good as it appeared in the first place.
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