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  1. First, this is truely an amazing forum. Even better than usenet groups. Real lot of very knowledgeable people. Thanks for everybody who responded to my earlier question on PAL/NTSC compatibility confusion.

    Now the current problem and its background:
    A Google Groups link (edited by vitualis -- consider using the URL bbCode in the future. )
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    Basically since I didn t know VCD disc doesn t merely contain a iso 9660 file system, I mounted a VCD in linux and archived ( tar -cvf ) the contents.
    Now of course when I unarchive and try to play the video stream, I can hardly see any picture at all.

    I understand that VCD is basically recorded as form 2 format and that its video stream has lesser error correction, but more thickly packed data. And such a recording cannot be read in the usual way.

    1. Is there any way at all to recover anything from my archives


    2. I read somewhere that microsoft platforms, know the form 2 type recordings and will copy such files using a different mechanism than that used for ordinary files. This is why the video file can be copied to the hard disk and played using the media player just like any other files.
    Is this true. If yes, when such a copy is done to the hard disk, does the resulting file become a pure MPEG file.

    3. If I copy a file to teh hard disk in windows platform will the resulting file size be bigger than the size shown in linux ( which doesn t know anything about the special form 2 recording ) ( I dont have an original VCD with me anymore to try this out )

    4. If I copy all files from a VCD to teh hard disk and then burn a CD-R ( assuming that the bigger sized files can still be contained in a CD-R ), will the resulting CD-R be playable in a VCD player.
    5. In 4 above will the resulting CD-R be playable in a computer.

    Thanks for reading
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  2. Let me begin by saying that I am only a casual user of Linux, but I will try to answer the best I can...

    I just tried copying and reading one of the "DAT" files off a VCD with Mandrake 9. I was not able to do it (I got an I/O error). Other files in the ISO filesystem (e.g., a text file) could be read and copied with no issue.

    I am certain, however, that you can extract the media files off a VCD from the disc to standard MPEG with the linux build of VCDXRIP. VCDXRIP is one of the tools in the VCDImager suite of programs ( http://www.vcdimager.org ).

    Originally Posted by francise
    1. Is there any way at all to recover anything from my archives
    If the data is screwed up, then there is probably no way you can recover it (at least, no way I know how).

    2. I read somewhere that microsoft platforms, know the form 2 type recordings and will copy such files using a different mechanism than that used for ordinary files. This is why the video file can be copied to the hard disk and played using the media player just like any other files.
    Is this true. If yes, when such a copy is done to the hard disk, does the resulting file become a pure MPEG file.
    That's right. Windows can read Form2 sectors just fine. However, it does append a RIFF header to all the files. So, just copying it over to the HDD does not give you the vanilla MPEG. Under Windows, you can use one of two tools (VCDGear or CDXA2MPEG -- again part of VCDImager -- can use GNU VCDImager Tools GUI as a GUI) to convert the "DAT" files back to standard MPEG (essentially, they just remove the RIFF header).

    3. If I copy a file to teh hard disk in windows platform will the resulting file size be bigger than the size shown in linux ( which doesn t know anything about the special form 2 recording ) ( I dont have an original VCD with me anymore to try this out )
    I can't say. As I stated, I wasn't even able to copy the file over on Mandrake 9.

    4. If I copy all files from a VCD to teh hard disk and then burn a CD-R ( assuming that the bigger sized files can still be contained in a CD-R ), will the resulting CD-R be playable in a VCD player.
    It most certainly will not. A VCD is not simply an ISO filesystem. In fact, the ISO filesystem exists mainly for the benefit of PCs and stand-alone VCD players don't read the filesystem at all. Rather, there is some pertinent PBC information that is ALWAYS located at specific sectors on the disc. Then, from track 2 onwards, MPEG tracks are written in MODE2 Form2 sectors. The ISO filesystem them maps "files" so that you can access this data (both PBC data and media data) on the PC.

    If you simply copy over the "files" onto the HDD and reburn it as a CD-ROM, you will have destroyed the physical layout of the VCD and it will not work.

    For more info on this, I suggest you read the VCDImager manual. It talks about the actual structure of the VCD in more detail: http://www.vcdimager.org

    This is why you must use a VCD authoring program to make VCDs. Furthermore, if you make a copy of an exisiting VCD, the best way is to do a DAO copy.

    5. In 4 above will the resulting CD-R be playable in a computer.
    If you actually did do it that way, it will be readable on a PC. It may or may not work on a software DVD/VCD program depending on how it was written (probably will). Most software players just read the info off the logical filesystem rather than looking at the underlying physical sectors.

    Best of luck.

    Regards.
    Michael Tam
    w: Morsels of Evidence
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