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Old 31 Jul 2003, 01:18 PM   #1
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Question Going from Video Capture, to Mpeg2, to VOB.

I've recently bought the Adaptec 'VideOh! DVD Media Center USB 2.0' Tv tuner/Video Capture device (very nice product - here's my review for anyone interested Review ). This unit only records in MPEG1/2, so I have a few questions. Is there any point recording a video capture at the highest bitrate (about 7.8Mb/sec), then compressing the file (using DVDShrink) so it will fit on a DVD, or would it be better to reduce the recorded bitrate so that the resulting file would be just under 4.3 GB, and therefore not need any compression? Obviously for the 2nd option I would have to do some testing to work out what bitrate is needed to record a given amount of time. I know this is subjective, but any thoughts would be appreciated.
Secondly, I am currently using Sonic's MyDVD which came with the device to convert the Mpeg2 file to DVD standard (VOB/IFO files). This is an amazingly slow process (about an hour), is there any other software that can do this quicker (shareware would be nice )? Also, I tried to compress the resulting VOB files using DVDShrink, but I kept getting a message that it couldn't find the file (even though the VOB files were in the same directory as the IFO files)... is this a problem with Mpeg converted files?
I've had no problem Shrinking files from DVD, or even files that I ripped from DVD to hard drive.

Anyone?

Last edited by starionx; 31 Jul 2003 at 11:22 PM
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Old 31 Jul 2003, 01:46 PM   #2
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"I am currently using Sonic's MyDVD which came with the device to convert the Mpeg2 file to DVD standard (VOB/IFO files). This is an amazingly slow process (about an hour)"

If you're convertin an hour or two hours video, that's actually quite acceptable.


"I tried to compress the resulting VOB files using DVDShrink, but I kept getting a message that it couldn't find the file (even though the VOB files were in the same directory as the IFO files)"

DVD Shrink requires a FULL complement of DVD files. It's undoubtedly unable to locate a "VIDEO_TS.IFO" file...
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Old 31 Jul 2003, 11:32 PM   #3
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Quote:
Originally posted by setarip
If you're convertin an hour or two hours video, that's actually quite acceptable.
It was a 2 hour video. I guess I will just have to invest in a good book or 50.

Quote:
Originally posted by setarip
DVD Shrink requires a FULL complement of DVD files. It's undoubtedly unable to locate a "VIDEO_TS.IFO" file...
I am actually getting all the files (including the 'VIDEO_TS.IFO'), but I found out what the problem was. MYDVD automatically creates a 'Title sequence', and assigns it to VTS_01_0.VOB. I was deleting this file because I didn't want it, which is why I was getting the 'Missing file' message from DVDShrink (I didn't know that it would cause a problem, but after thinking about it, I realised that there would be a file pointer in the IFO file ). I put the file back and DVDShrink worked just fine.
Thanks for your input Setarip, much appreciated.

Anyone have any input on my first question?

Last edited by starionx; 31 Jul 2003 at 11:37 PM
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Old 1 Aug 2003, 12:19 AM   #4
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since setarip answered the second part I will refer to the first
part of your question.

It depends on wether your mpeg2 encoder chip already uses a variable bitrate for encoding (I really have no idea of the
hardware specification though I know this card)
If it does , there is no point in capturing a big file first and then
recompressing it.( Now as I see what I wrote ,I wonder how this should be possible?... anyway)

If it does not , you could gain advantage of your plan "first big then recompress" since you can run several encoding passes on that big file with a variable bitrate.
This alone would reduce your filesize.

Do some test capturings and see if the picture still looks good enough for you with an appropriate bitrate that meets your
runningtime / filsize ratio.

There is also no need to do a lot of testcaptures to find good bitrate settings regarding the running time.

You can get good bitrate value approximations using a
BITRATE Calculator
(can be found in the software section of this site)

good luck!!!
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Old 1 Aug 2003, 05:26 AM   #5
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"Thanks for your input Setarip, much appreciated."

My pleasure ;>}
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Old 1 Aug 2003, 05:26 AM   #6
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Well, there is an option to change the 'Pack Length' from Fixed to Variable. I'm not exactly sure what 'Pack Length' is... but I changed it to variable anyways. I recorded 30 seconds of video at 7800 Kb/sec, the file size ended up at 36MB. I changed the 'Pack Length' back to fixed, recorded 30 secs at 7800 Kb/sec again, and the file length ended up being the same. I don't know if there was actually any difference.
I then did another test (leaving the 'Pack Length at fixed) . I recorded 30 secs of video at 7800 Kb/sec, then converted the Mpeg2 file to VOB. I then recorded 30 secs of video at 5450 Kb/sec, then converted that to VOB as well. I then used DVDShrink to compress the higher bit rate file to be the same size as the lower bit rate one.
I then watched both a number of times, and couldn't tell the difference.
I might just use a coin to decide.
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Old 7 Aug 2003, 02:08 AM   #7
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first of all I would capture at least 10 minutes to decide!!!!

then compare the two captures(higher and lower bitrate) regarding quality, without compessing them. just load them into powerdvd or windvd to examine what matches your expectations
on quality.

then decide!!
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