frame rate keeps dropping ???

[jovobas]

Hi everybody,
when I capture with VirtualDub at 25fps the initial average framerate is about 25.2500. When the capturing continues the average framerate begins to drop and goes below 25fps. Little time after that the first frames are starting to drop out. What is wrong ? I'm using the settings described here and I have an Athlon 1.4 GHz with 256MB RAM. Or is it the capturecard itself (Guillemot Maxi TV Video3) ? Just ran a test and it's the same scenario with 15fps...
tnx

[holistic]

CPU and Memory have little to do with capture.

The weak link in any frame droping capture problems is 'usually' your harddrive.

_What size are capturing ?
_Is it a huge frame drop? - small frame drops will occur in order to keep audio sync.
_Is the source material 'clean' - eg: an old video tape with 'noise' may cause the program to drop frames.

[jovobas]

I have a 60 GB harddirve 7200rpm with DMA enabled and I'm trying to capture about 90 minutes. as of the third minute, frames are being dropped. The framedrop is not huge (1 frame/3000), you might ask what I'm worrying about, but there's nothing like perfection...
Maybe I'm just overreacting and is this the best I can get.
tnx

[jovobas]

I just did a test
reading : 44 MB/s
writing : 34 MB/s
is that enough ? and if not, can I speed it up a little and how ?
jovobas

[holistic]

1 frame in 3000 - you are kidding me ! Unless it is the frame were 'Aerial' flashes in the lil mermaid i would say this is as close to perfection as it gets. Overreacting is putting it mildly .

NOTE 1: 640 * 480 * 24 bit color = 7.37 Mbits/frame * 30 frames/sec = 221.1 Mbits/sec = 27.6 Mbytes/sec
NTSC full screen format

Are those numbers BURST or SUSTAINED write speeds?

NOTE 2: drive write speed will slow down as it fills due to rotational speed differences and possible heat problems. Some drives perform recalibration tasks to realign themselves as they heat up.

It is very possible the frame drops you see is v-dub trying to sync the audio to the video.
Note the timeline when you see the frame drops. Play the AVI back when done . If you see no flaws - forget it. ENCODE away !

duh - just reread your post - for PAL sub in the full screen ## - transfer rates similar


<font size=-1>[ This Message was edited by: holistic on 2001-10-12 08:38:19 ]</font>

[neomaine]

great...now I have to watch little mermaid AGAIN.