DAT file shrink from MPEG file

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I have a .dat file about 340MB copied from a PAL VCD. First time, I use Nero drag to a new VCD layout and burn. It can play in standalone player, but the new .dat file size is ONLY 300MB, about 10% shrink.

Second time, I use VCDGear convert it to mpg. The mpg file size is 335MB, then burn it with Nero. The result .dat file size also shrink to less than 300MB.

Third time, I use VCDGear create a bin/cue, then burn it with CDRWIN. The result .dat file is just a few bytes than the original one. However, my player recognize it as CDDA, but hitting the play key, it still play video, just cannot random seek anymore.

I'm confused. Is there any quality loss due to size shrink? Which one actually stick to the *SPEC*?

-- snow flyer (snowflyer@usa.com), October 22, 2002


When you create an MPEG-1 file (encoding an AVI file to MPEG-1, for example) it will have a certain filesize that takes into account all the error-correction and checksumming that the OS (Windows?) will impose on it, such that transferring it in this form from one media to the next (from HDD to a CD-ROM, etc.) will guarantee either you have the original file intact down to the last bit, or transfer will not be allowed at all (if corrupt portions of the file cannot be recreated). Video CD however is hardly OS dependent and has a slightly different way of storing the same MPEG-1 file so that on inspection the same file earlier in windows as *.mpg is now smaller as *.dat. The data is identical; only the error-correction, header info, etc. have changed. One reason is that on viewing the video acceptable levels of performance do not require bit-perfect reproduction (as when it IS a file in a folder in Windows) with the VCD. Having said this it always best to store or backup important MPEG files as normal Windows (if that) files *.mpg on your CD-ROM or HDD, compared with storing the same as normal VCD. As a normal Windows file it will have a bigger filesize but it's better to re- author the VCD with it and create pristine copies all the time (even if taken from a slightly scratched CD-ROM) than copy an existing VCD, which, if scratched, will degrade the copy performance in varying degrees which WILL NOT be undone even with such programs like VCDGear (the stream can be re-timed and stabilized but the corrupt portions of video WILL BE permanent).

-- Mehmet Tekdemir (turk690@yahoo.com), October 23, 2002.

Just to add a few comments... I'm not sure if Nero truly sticks to VCD specs or not. It may. I know that VCDeasy does stick to the specs. I also know that Nero does not confirm totally to SVCD specs if you use it to make SVCDs at some point. It comes close, but it's not totally in line with the specs and this can cause some picky DVD players, like Philips' models, to have problems. I don't know if CDRWIN sticks to the specs or not. The only thing I know without a doubt that sticks to the specs is VCDeasy.

-- Root (root@yahoo.com), October 23, 2002.

Try U-lead, Y'll be surprised

-- rennie (rklafaille@home.nl), October 26, 2002.

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