As above.

-- (jayc_nz@yahoo.com), October 30, 1999

Answers

Let's first be clear what .dat file we're talking about here: it is a White Book compliant mpeg-1 file that originally had an .mpg extension and mow has been processed and readied by the recording s/w to be included in the MPEGAV folder of a VCD and now has a .dat extension. If it's a .dat file like this on a typical VCD, then there should be no problems transferring (copying) it to the HDD; there is no copy protection. This distinction is important because there are other files, within and without a VCD, that also have a .dat extension and it's certainly possible that they will not be copied onto HDD.

-- EMartinez (epmartinez@hotmail.com), November 01, 1999.

I don't know but I suspect so.

I own about 300 VideoCDs and always used to copy the \MPEGAV\AVSEQ01.DAT onto the hard disk to play with Xing.

None of new ones work. Copy always fails with Physical Media errors on the VCD. I just thought I was having a really bad run until I read your question. I can't make disk images anymore to bit-copy the CD for friends (same problem) My Pioneer DVD player has NO problem at all with them.

If you find out anything can you e-mail me at m815261@hotmail.com ?

-- Brian Crosse (m815261@hotmail.com), November 03, 1999.

Have you tried extracting the .dat file in question to .mpg and if successful playing the .mpg file then? There is a command-line utility called VCDGear to do this floating on some websites, like everyone's fave http://come.to/powerkiller/ Maybe there's a pattern here. Aside from your new VCDs do all your other CD-ROMs and audio CDs behave properly on that particular CD-ROM drive? I've come across once a CD-ROM drive that had dirt on the slider bar the optical assembly runs on and couldn't read the extremes of the CD. If the TOC can't be reliably read then maybe that's why the type of data on the rest of the disc can't be identified.

-- EMartinez (epmartinez@hotmail.com), November 03, 1999.

One thing to consider (here comes the techie answer :) is that those DAT files, when stored on a real VideoCD, are formatted differently than normal CD's to get more space available. Why does a CD hold 74 minutes of audio, but only 650 data? 74 minutes of .wav's is more than 650 MB, right? It's because a CD-ROM DATA formatted sector holds (I'm going to get these numbers wrong) 2048 bytes of data with 256(?) bytes of ECC, an Error Correction Code, stuck on the end. This means for every chunk of data, you 'waste' a bit of space to make sure that data doesn't get corrupted. The drive reads the data, calculates a new ECC, reads the ECC on disc, and if they don't match, it knows either the data or the ecc is corrupt (ie the disc is damaged).

Audio is stored differently... Since a minor corruption of data will basically destroy a program, it really does need the ecc mentioned above. But damaged audio is barely noticeable (unless there's ALOT of damage). So by using that ECC space to hold more audio data, you effectively increase your storage capacity.

VideoCD data is stored in what's called Mode 2. It's not exactly the same as audio, but pretty close - it gets rid of the ECC to be able to store more data. This is normally acceptable because mpeg files are pretty resistant to lost or damaged data in the bitstream -- even though the drive may be reading data imperfectly, it won't totally destroy the picture. These errors most commonly show up as black or green (or sometimes multicolor) blocks on the screen.

SO why can't you read the files, especially if you once could? Well, some VCD out there aren't really videoCD's, they're just regular CD- ROMS with the appropriate files in the appropriate places. True VCD's are in that special format, and each (with some exceptions) video clip is stored in its own track. You should be able to read the .dat's fine from "fake" videocd's. BUT in some cases, you WILL GET THOSE READ ERRORS from a true VideoCD, either because the disc is damaged or dirty and the drive insists it can't read it, or because it's being stupid and thinking it's NOT mode 2, and trying to verify the data with the ECC (but since there's no ECC but other data there.... get it?) Some drives also don't support the read long command that is needed to get the mode 2 data to the software (or the OS) so Windows may be trying to read mode 2 data with a read instead of read long. This could happen with particular drives, software, and/or other hardware (like IDE & SCSI interfaces).

So you may be stuck, but try a few things... Examine the disc VERY carefully for dirt, smudges, or scratches. If you play the VCD and notive blocky corruption, that's a good indication the disc is dirty or damaged. So clean/polish/whatever. If that still doesn't work, it may just be windows or the drive. Get a program that can extract the data from the CD, like WinOnCD or FireBurner. Most CD-R software will be able to extract the image, but those two can create CUE/BIN files, which VCDGear can then convert into .mpg's for you. I know, it's the long, annoying way to do it, but at the very least, it should work.....

If you have any questions feel free to mail me! -d

-- David Karl (dkarl@ameritech.net), November 05, 1999.

David, I take out my hat before the clearness of your answer.

Matias.

-- Matias (petrellm@telefonica.com.ar), November 05, 1999.