[Scummvm-devel] DXA file format for videos

[Eugene Sandulenko]

On Sat, 29 Apr 2006 17:34:19 +0200
Gregory Montoir <cyx at users.sourceforge.net> wrote:

I tried PNG. It did not work well at all. Maybe because each frame
contains whole palette, maybe because additional format overhead, I
don't know. I didn't try advpng or whatever as that would slow down
compression insanely.

BS1: 100MB video (93MB zip archive)
BS2: 187MB video (182MB zip archive)

This is even worse that initial DXA results.

> > Since we don't really need to do seeking, another approach might
> > be interesting, too: For each frame, compute both the result of
> > encoding it as an inter AND as an intra frame. Then use whichever
> > is smaller.
> 
> And that's probably how the original encoder did it as well. If you
> look at some .dxa files, there's often a bunch of intra frames
> following each other in the stream.
Tried that. In short: DXA rocks.

Old results (first is intra frame other are inter):
> BS1: 94MB video
> BS2: 181MB video

New results:
BS1: 72MB video
BS2: 146MB video

for comparison. MNG results:
> advmng -S 64 -3
> BS1: 67MB video
> BS2: 136MB video
Taking in account insane complexity and nearly indefinite time to
encode MNG with above options makes DXA an absolute winner.

Ratios:
against Low Q MPEG2:
  ZMBV       MNG    DXA
BS1: 2.9x    2.1x   2.25x
BS2: 6x      5x     5.4x

against High Q MPEG2:
  ZMBV       MNG    DXA
BS1: 1.4x    1x     1x
BS2: 2.3x    1.9x   2.1x

Resulting archives with OGG audio:
BS1: 73MB
BS2: 147MB

So, may we switch to lossless DXA?


Eugene