🚀 go-pugleaf

In article <1993Nov1.152825.21529@waikato.ac.nz> Lawrence
D'Oliveiro, ldo@waikato.ac.nz writes:

>Were these the actual capture resolutions? (i e not 384*288 or 
>192*144,which would be more typical for PAL). 

No they were the standard 160 x 120 and 320 x 240.  I was using
Adobe Premiere 2.0 which defaults to those resolutions.  I didn't
use it in those tests, but the bundled FusionRecorder does in fact
default to 188 x 144, 282 x 216, 376 x 288 and 752 x 576, ie. it
takes PAL resolution into account.

>I ask because the 
>difference in speed can be quite dramatic for a VideoSpigot. 
>Perhaps this doesn't apply so much to the AV Macs, because of the 
>built-in hardware for scaling and so on.

Well, I just tried FusionRecorder at 188 x 144 and recording to RAM
with no compression only achieved 14.34 fps!?? Hmm.  Anyone care to
comment?

>For comparison with the above, I can get about 24 fps direct to 
>disk with the VideoSpigot in my Centris 650 at 192*144 
>resolution. At 384*288 resolution, I can get about 12.5 fps. I 
>did these tests back when I had only 8MB of RAM; at that time, I 
>found very little difference in performance between captures
>to RAM and captures to disk.

Thanks for the comparative Spigot figures Lawrence.  With our
MoviePak and 24stv's I hardly ever use any of our Spigots.  It
certainly shows up the performance differences, though it's very
interesting that you say recording to RAM differed little than
direct to disk?

>Of course, I should point out that the AV hardware is capable of 
>rather better video quality than the Spigot. The Spigot seems 
>best suited to resolutions around 160*120 or 192*144; at anything 
>much larger, you notice a certain amount of jagginess.

Mmm, yes I have been very impressed with AV's video quality. 
Anything up to half size (376 x 288 in the case of PAL) is
gloriously sharp and vibrant.  However, as soon as you go larger up
to full screen, some annoying line pixelation becomes evident when
viewed at moderately close quarters.  I wondered whether it was due
to digitization of a single field of the interlaced input or
something.  However, I guess it's just typical interlaced video
comparing very poorly with high quality non-interlaced display. 
(The sample video images were from a PAL videodisc, so it wasn't
just a poor quality VHS tape I was viewing!)

>Do you recall in the options 
>for capture on the AV whether there was a choice of YUV versus 
>RGB format as well? I was reading the developer notes for the AV 
>machines over the weekend, and I recall some mention of support 
>for YUV, which might be faster than RGB capture.

Yes, one of the compressor choices is "Component video -YUV".  On
trying that I achieved only 5 fps at 188 x 144.  Not what I would
term much of an improvement!

>As far as I'm concerned, the AV machines are definitely the 
>sexiest bits of hardware Apple has come up with to date. No 
>question, this is the architecture to support today! And 
>hopefully there'll be a generation of "PowerAV" machines, which 
>combine the AV architecture with a PowerPC CPU--now _that_ would 
>be something...

Well, I guess the PowerPC upgrades of the current AVs will give
something along the lines of a PowerAV.  I guess we'll just have to
wait and see.

-Mart

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