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mark089
24th February 2002, 13:39
Hello, I have some questions concerning vertiacl reduction.

First of all how does it work at all? Does quality get lost when I reduce from 384*576 to 384*288? What quality do I get compared to VHS/SVHS? How is the quality compared to capturing in 576*432?

Second: How many kbsp are best applied for 384*576 with intention to reduce to 384*288? How many kbps are best for 576*432, 640*480, 768*576?

Third: When I capture from VHS, does it matter to capture in a higher resolution then 384*576 reduced to 384*288 or 576*432?

Thanks a lot!

anarco
27th February 2002, 17:41
Regular VHS resolution is about
320x240 resolution so you donīt have any
loss when capturing in 352x288
the resolution for sVHS is about 640x480


if you like some confusion with horizontal and vertical lines stuff ;-)

check:

http://www.hometheaterhifi.com/volume_1_1/v1n1vcrs.html


however if you capture with a lossy codec it is always better to capture in higher resolution scaling down afterwards

mark089
27th February 2002, 18:43
Thanks a lot for the info!

mark089
27th February 2002, 18:48
I tried capturing in 384*288 before without compression and the picture didn't have much sharpness. You have an idea why?

anarco
27th February 2002, 19:35
did you use to capture ?

of course a vhs is not as sharp as a dvd is
if lot of sharpness-loss appears you probably use a bad codec
or the vcr is not the best at playback ?

----


oh didnīt notice you captured raw... hmm
how is the picture quality when just doing playback ?

what program ?

mark089
28th February 2002, 19:16
I used DivX 3.11 to capture and compared the pictuer to the one directly form the VCR. You think it might be possible, that the capturing chip doesn't catch the pixels exactly the way they come from the VCR as these signals are analog?

mark089
28th February 2002, 19:17
Yes, raw I captured too. I capture with my Hauppauge application, but mainly with VirtualDub (for me it works better then AVI_IO).

anarco
28th February 2002, 19:53
I wasnīt too amazed by the results with divX

iīd have to see the capture quality to get a closer idea what could be the point though

I just can say for sure that freeVCR and picvideo mjpeg works fine for me and raw somehow seems to produce files with too high
throughput... the results look jerky here, like the card couldnīt handle the datarate...

mark089
1st March 2002, 08:28
Hello Anarco, some people comfirmed to me that for them it works better when capturing from VCR with a higher resolution. Lover resolution or resizing to a smaller format always reduces quality. However video noise is reduced when downsizing. My impression of what I've heared and read is that when capturing from an analog source you can maybe well capture the vertical resolution, but the horizontal you don't capture one to one. This confirms my experience.

anarco
1st March 2002, 09:31
capturing in high resolution and scaling afterwards is of course better... not that capturing in 352x288 wouldnīt work but since most tapes nowadays are sVHS you do a downscale while capturing and if you use a lossy compression you even add noise

so it is always better to capture in higher resolution, because
the downscaling afterwards smoothes the picture

on the other hand if you have slow hardware and not much diskspace a capture in 352x288 shouldnīt make a lot of difference to a regular VHS tape though... since when you convert such a capture to VCD you end up with a bitrate that is anyway going to be worse than your capture quality...

lets say a capture in that size of 45 minutes ends up in 3-4 GB filesize mjpeg and then you squeeze it down to a 70 min CDR size
MPEG for VCD

ok, we shouldnīt forget the fact that if the source is better the target will be better but sometimes (i.e. VCD) it really doesnīt matter much

at the end it is important what you want to do with the capture at the end, for example it is wise to have a better capture quality for sVCD than for VCD simply because you donīt have the chance to smooth the picture as you have for VCD because of two reasons:

- mpeg1 does more smoothing itself than mpeg2
- downscaling 704x576 to 352x288 is exactly divided by 2
which turns out smoother results than downscaling from 704x576
to 480x576

okay, you may use a blur filter at sVCD for smoothing
but thats kinda stupid ;)