Re: whats important in a laptop to play dvds/divx

zwsdotcom@xxxxxxxxx wrote:

> Peter T. Breuer wrote:
>> zwsdotcom@xxxxxxxxx wrote:
>> > You can play back full-frame DVD on a 533MHz C3 with a reasonable
>> > graphics chipset with CPU cycles to spare. With a dumb framebuffer you
>> > won't get full framerate even on a 900MHz PIII.
>>
>> I guess my P300 is performing some kind of miracle, then!

> You've probably got a good graphics adapter. Note that a 533MHz C3 is
> slower than a 500MHz Pentium. It's probably in the ballpark of a 400MHz
> PII (but these things are hard to measure). PII (which I guess your
> P300 is) machines were in the vintage that might or might not have a
> special DVD accelerator card.

> PII-300 would require hardware motion compensation assist and
> colorspace conversion to get full frame rate.

I get about 22 fps, but the window is whatever size these windows are
naturally (which appears to me to vary at least in aspect, but possibly
be around the 640x320 range)). If I make it larger, frames will be
dropped, smaller and it's all no problem.

As far as I recall, I am using a direct imaging driver (this is X), but
it really doesn't bother me - for a whole long time I was doing all of
the graphics driving in software for a standard vesa card, since the
drivers for the laptop didn't appear till about six months after I got
the lappuppy, and I never noticed any sluggishness or cpu overuse (but
then, I'm not sensitive that way, although I AM sensitive to computer
and machine behaviours!).

I can certainly promise that decoding a real mpeg2 file off disk to
screen takes about 50% cpu on that P300.

It's a toshiba 7020 (if I recall the numbering correctly).

>> I really don't know the format of dvd output, but I alsways assumed it
>> was some real time bytestream of the mpeg, or whatever it is on the

> The DVD drive handles the CSS descrambling. What comes out of that is
> an MPEG-2 stream with at least one video stream (more for a multiangle
> DVD) and some number of audio substreams.

>> dvd. I guess you need some hardware to convert that into a picture, but
>> mpeg DEcoding is not hard - ENcoding is hard work, but decoding? No.

> It's a *lot* of work to do in a general-purpose microprocessor; read
> the MPEG-2 spec. Even a small amount of external hardware can make the
> task *much* lighter.

> Note also that you have to decode the full 720x480 video stream and

Ah .. 720x480 might well be "it". Thanks.

> then scale it to your output window, you can't just decode part of it
> to get a smaller picture size.

It's nowhere near a 1024x768 screen-full, though! It's about 40% of it,
so that's a fair amount of real estate that does not have to be
rastered.

Peter
.

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