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Video formats

Posted on 2004-10-20
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Last Modified: 2007-12-19
I have a few (easy?) related questions.
I have a video (VHS, European PAL) camera and am interested in converting the films to digital format.  Some questions in general.

The video format VHS, what is the resolution (width x height) and frame rate?
mpg1 and mpg2 digital formats.  Are they lossy?  Would it be better to save the converted film (from VHS) as mpg2 or is that just a waste of time because the original analog format would be of low resolution so mpg1 suffices?
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Question by:AndyAinscow
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khyer123 earned 100 total points
ID: 12362358
VHS isn't measured in resolution the same as something in a digital form, so it does not have a lengthxheight measurement. It's measured in lines, VHS has about 200 lines. You would be better off saving it as an MPEG2 rather than MPEG1, to prevent distorting the already low-quality image. MPEG2 is DVD quality, and will be about the same as your VHS. If you have it more compressed, which would be your MPEG1, it will distort it further.
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by:weed
weed earned 100 total points
ID: 12362496
For info on PAL check out http://www.strata.com/support/3dmanual/ch13/ch13_7.html

Both MPEG-2 and 1 are lossy so you will lose quality. How much depends on the bitrate you encode at.
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by:daniel416
daniel416 earned 100 total points
ID: 12362893
to add to khyer and weed's info:

MPEG 2 352 X 576, 25 fps, progressive (non interlaced), 2520 kilobits (not Bytes!) VBR will be a good format to use for your vhs tapes.

i have to say that i'm not too clear on whether to use 720x576 or 352x576. maybe another expert can provide an opinion. from what i've read, using 352 x 576 will fit in a svcd.

http://www.digitalfaq.com/capture/software-resolution.htm

daniel.
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by:AndyAinscow
ID: 12373959
Thanks to all for the responses. One point to clarify


daniel416.
Interesting link, albeit I am no graphics expert it looks to be good.

Your recomendation.
352 X 576, 25 fps   2520 kilobits

How do you get the 2520 KB/s ?
352 * 576 * 25 / 1024 = 4950 which isn't even a multiple of 2520, but not far off.

as the link states: The ratio of bitrate per pixel dictates MPEG image quality.
also what is VBR?
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by:Jaime Olivares
Jaime Olivares earned 100 total points
ID: 12374209
I think you will have more quality with:
720 x 576 x 25 fps, it is the standard PAL resolution in 4:3 format for PAL DVD's, but that will be dependant on the quality of your digitizer device.
Read some theory at:
http://www.michaeldvd.com.au/Articles/PALvsNTSC/PALvsNTSC.asp
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by:Jaime Olivares
ID: 12374433
By example, Pinnacle Systems' Digital Video Creator 120 (DVC 120) has 720x576 capability with hardware encoding. It is a high quality home system.
Have a look to: http://www.pinnaclesys.com/
For reference pricing:
http://www.tigerdirect.com/applications/searchtools/item-Details.asp?EdpNo=931737&sku=P121-8056
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by:Jaime Olivares
ID: 12374644
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by:AndyAinscow
ID: 12374847
Hi Jaime
Thanks for the links (I have just purchased a pinnacle AV/DV system because I require input from an analog device).
Graphics isn't my strong point (to put it mildy) and I am trying to stay afloat in the flood of information.  Actually it is also to get information independant from the manufacturers of the hardware.

To recap, I am getting the picture form a VHS camera (200 lines - khyer123). Would 720x576 actually offer any advantage over 352x576 ?



It's late in the evening here, I'm off to get some sleep now (providing the kids allow - the eldest has a cold).  Hopefully my brain is functional tomorrow!
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Expert Comment

by:Jaime Olivares
ID: 12374927
Actually VHS has a low line scan resolution, as khyer123 mentioned, but some other sources like HI8 and DV cameras have 400 and more scan lines, so, it is a good idea to have a 720x576 device.
About horizontal resolution, it is virtually infinite in analog video sources, contersense vertical resolution which is limited to scan lines, so I think 720x576 could bring you a better quality, just try, but as I mentioned, it will depend in your specific hardware.
To have a hardware capable of 720x576 doesn't means that you will achive more quality necessarily, depending on internal filters and ADCs of the device.
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by:daniel416
ID: 12395232
hi andy,
hope your project is progressing :)
the settings i proposed are meant as a starting point. if you find that another setting gives you better results, please use it :)

what has worked for me is to capture the source material at full resolution (720x576 in your case), and compress further from there (using either 720x576 or 352x576)
it seems logical to me that the higher resolution will give you a better result.
it's easier to recompress if you're unhappy witht the result than to recapture the video again

the target bitrate is lower than what you calculated because the object is to compress the video to make it fit in an svcd. if you were saving to dvd you can allow yourself a much higher bitrate. i should have asked you if this was your goal before proposing these values.

also, i haven't calculated bitrates manually for a long time (i can't even find my old references!).  but here is a bitrate calculator to help you decide what bitrate to start at:
http://www.videohelp.com/calc.htm

vbr is variable bit rate. it distributes the available bitrate differently amongst the frames of your movie, giving more bitrate to the portions of the video that have lots of movement and changes (so higher quality) than the parts of the video that are more static (because they need less bitrate to look fine). the idea is to get a higher quality video without using more bitrate.

the oposite is cbr (constant bit rate). this allocates each frame exactly the same amout of bitrate. this is normally used for web video (in my experience anyhow)

hope i'm not being too confusing.
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by:daniel416
ID: 12395302
also,
when you say digital format: do you mean just a file saved in your computer? or is the final goal to save it to a  dvd, svcd? or a mini DV tape? the target media influences the type of compression you'll use.

best regards,
daniel.
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by:AndyAinscow
ID: 12464021
Sorry for the delay in responding.

Am I correct - the lower the bitrate for a given resolution, the higher the compression / the more lossy the compression?


The situation.
I have a video camera (VHS) and a number of tapes of my children.  Everytime a tape is played the quality will deteriorate.  I have relatives/godparents in another country who wish to see the kids growing up so it is nice to be able to send them a copy and not worry about an original being lost/damaged.
The idea.
Digitise the tapes and store on a hard disk(s) (keeping the original VHS tape just in case).  Then I can burn one or more copy to CD (no DVD burner) and send CD through post.  The digital copies will probably not be edited (else I would catch as AVI, edit then digitise to an mpg format).

I do appreciate that the higher the bitrate/resolution the less information is lost but also the more space on staorage medium is required.  Also at some point the law of diminishing returns comes in.  Ten times the size for 1% quality gain....

I guess the answer to a number of points is try it and see if it is OK.  


I am still puzzled by the 'width' of VHS.  Is the height (scan lines) set in a standard but the width variable - device dependant?
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Expert Comment

by:weed
ID: 12464480
Yes, that is correct.

VHS doesn't have a dimension. NTSC does, and that's what folks in the US are using. Your capture software should take care of it for you or at least give you some options to choose from.
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