copying vcd's

[minne1969]

Hello to everyone, once again thanks for helping this "newbie" get started. I made my first vcd yesterday and it played fine in my dvd player.I don't have that much disk space to hold alot of movies, so since i have the movie on vcd i'd like to delete it from my harddrive. In the future if i want to make a copy of the vcd, i don't think my cd writer can do it. My question is do i need a dvd/vcd writer in order to do this?is there a program available? I've tried searching but so far i've come up with nothing.

[dunamis]

Interestingly I had this same question yesterday. I burned a VCD using NERO and it worked perfectly on my DVD player. I then made a copy of it using Nero Express and the copy worked perfectly. You should be able to do this quite easily. I hope this helps.

[KingJohn]

You should be able to do a simple "Disk To Disk" copy, even if you only have one drive, the source and destination can be set to the same.

However, if you wanted to re-make the VCD like you did before, you can copy back the .dat file from the VCD to your hard drive and use it in the same way you used the .mpg (No conversion necessary)

The only downside is, if you scratch the disk at any point, you wont be able to make another copy

[davemcg37]

i agree with king john if you copy the original back to your hard drive then you're guaranteed to get a new copy as good as the original

[dunamis]

Hi minne1969:
Have you had time to try making a copy yet? I'm interested to knowif you were able to do this O.K.

[Saito]

You can copy a VCD with any cd-copy option/program. Anyway you should always backup the video source(just in case).

[tendtend]

Do not fool others if you do not really know the VCD copy issue.

A copied VCD can not be 100% (sometime may be only if you are lucky) identical to its original. The reason is simple: not all the data in VCD can be read correctly with 100%. I am not kidding. A VCD is similar to a Audio CD, which is without any data correction.

The best way to backup a VCD is: write the VCD image file that is crated on the hard drive into the data CD. A data CD has data correction so when you read the data from it, the data is near 100% correct.

[KingJohn]

Do not fool others if you do not really know the VCD copy issue.
A copied VCD can not be 100% (sometime may be only if you are lucky) identical to its original. The reason is simple: not all the data in VCD can be read correctly with 100%. I am not kidding. A VCD is similar to a Audio CD, which is without any data correction.
The best way to backup a VCD is: write the VCD image file that is crated on the hard drive into the data CD. A data CD has data correction so when you read the data from it, the data is near 100% correct.

It sounds like you are having problems then, because any VCD/MUSIC disk I copy is exactly the same as the original. But there again, I use a plextor drive, maybe it has something yours don't

[Saito]

hey King, what speed do you use to burn/copy VCDs/SVCDs?
[/quote]

[rsuave5]

ive used nero to copy my vcds at 8 x and ive done 50 or so flawlessly!

[ya_jai]

I used to use NERO to copy audioCD but it kind of strange 2-3 cd out of 10 I hear a beep sound before the first song begin. It might be becuz I don't have PLEXTER. Anyway now I use CloneCD which does a very good job for 1:1 copy. BTW I use lite-on which can copy safedisc2 perfectly but PLEXTER can't

[Hong Kong Phooey]

You should be able to do a simple "Disk To Disk" copy, even if you only have one drive, the source and destination can be set to the same.

However, if you wanted to re-make the VCD like you did before, you can copy back the .dat file from the VCD to your hard drive and use it in the same way you used the .mpg (No conversion necessary)

The only downside is, if you scratch the disk at any point, you wont be able to make another copy

@KingJohn. Would it only just be an issue of scratches though. I've been archiving a set of homemade VHS to VCD's, (one set for playing, the other intended for storage so I can delete the mpegs off my harddisk).

Although Nero's CDSpeed File checker has reported no file errors, the Scan disk & CD quality check's occasinally reveal a small percentage say between 0.12-1.5% yellow sectors on the burnt CD's. It doesn't always happen,( I know it's related to the quality of the CDR Media you use), but wouldn't the possiblity of ANY yellow sectors mean the risk of an error in the DAT file when you converted back to an mpeg file? (In thereoy)??

The VCD's all play fine on both PC & my DVD player , (no glitches),it wasn't until I ran the Nero utils I even noticed that certain CD-R's had yellow sectors on them.

[xed]

Both TendTend and KingJohna re correct, in their own way.
Here's the deal with copying VCD's digitally:
VCD's store data in a different way than CDA (audio CDs) and also in a different way from data CD-ROM. The difference boils down to crappier data error correction.
Data CD format has extremely robust data error correction - the CRC's are very sophisticated and insure that you get zero bits changed. The way the spec does this is to read after write, check the CRC to see if the checksum is correct, then if not, burn a marker indicating the previous written block is invalid and write the same block again, then repeat. Data CDs as a result of this massive error correction can hold somewhat less data than audio CDs.
For example, the .WAV files on a 74-minute audio CD, when stored as a data CD, tyipcally require 2 data CD-Rs to store, but only one audio format CD-R to store as an audio CD.
Audio CDs have Reed-Solomonon CRC error correction which is pretty good, but not perfect. The Reed-Solomon does not use a read-after-write then mark as bad method, but instead a CRC check with interleaved error correction. This depends on the low-pass output filters of your CD player to work -- if you get a string of corrupted data or a block fo zeroes, the CD player fetches the previous block from memory and intervles it withthe corrupted or zeroed data. The low pass output filter drasticallly smoothes this out, creating an appporximation of the musical waveform plus harmonic distortion instead of a click.
Of course, if the bad blocks go on for too long, you will get a click. But Reed-Somon's pretty robust.
The VCD data correction is the least robust and simply gives us and gives you macroblocks if you get corrupted data. Fortuantely the human eye is much less senitive to video noise than the humane ar is to audio noise, so most of the time we don't notice bad blocks on VCDs.
Because of the low quality of the VCD error correction, you can get enough bad blocks to produce visible macroblocking on playback. This can be due to a CD-R defect or a computer glitch during writing.
---
Consequently it is typically impossible to get a 100% bit-for-bit copy of a VCD. TendTend is therefore technically correct on that point.
However, KingJohn is also correct that most of time the erro rate is so low you don't even notice it.
TendTend is correct in pointing out, however, that if you want to be absolutely positively certain of getting the best possible quality of VCD reproduction, save the disk image as data, or save the component MPEG-1 or MPEG-2 files as data. That way you will get only the tiny percentage of inevtiable errors when writing your VCD toa CD-R.
The _worst_ thing you can possibly do is to copy a VCD to another CD-R, then copy that, then copy that. The errors will rapidly accumulate. You want to either start with a VCD and copy that one, or preferably start with the disk image or comopnent MPEG files on a data CD-R and use that to regenerate the VCD.

[vitualis]

Data CD format has extremely robust data error correction - the CRC's are very sophisticated and insure that you get zero bits changed. The way the spec does this is to read after write, check the CRC to see if the checksum is correct, then if not, burn a marker indicating the previous written block is invalid and write the same block again, then repeat.

I'm not entirely sure if it actually does the read after write thing... If it does, can you provide a link?

CD-ROMs on top of the actual user data you are burning also commits a portion of each sector to ECC and EDC codes. These can correct otherwise unreadable block of data (i.e., uncorrectable by C1 and C2).

Data CDs as a result of this massive error correction can hold somewhat less data than audio CDs.
For example, the .WAV files on a 74-minute audio CD, when stored as a data CD, tyipcally require 2 data CD-Rs to store, but only one audio format CD-R to store as an audio CD.

For numbers: there is about 747 MB of "WAV data" on a 74min audio CD. The same disc used to make a CD-ROM will only hold 650 MB of user data.

Audio CDs have Reed-Solomonon CRC error correction which is pretty good, but not perfect. The Reed-Solomon does not use a read-after-write then mark as bad method, but instead a CRC check with interleaved error correction. This depends on the low-pass output filters of your CD player to work -- if you get a string of corrupted data or a block fo zeroes, the CD player fetches the previous block from memory and intervles it withthe corrupted or zeroed data. The low pass output filter drasticallly smoothes this out, creating an appporximation of the musical waveform plus harmonic distortion instead of a click.

Um, these are separate things. Cross-Interleaved Reed-Solomon code can correct the data to a limit (i.e., C1 and C2). For audio CDs, when C1 and C2 fail, THEN it will interpolate the audio samples. C1 and C2 exist for ALL CDs. When C1 and C2 fail for a CD-ROM, it can then further use ECC to help maintain data integrity.

Quotation from CD-R FAQ: "...All of the data written to a CD uses CIRC (Cross-Interleaved Reed-Solomon Code) encoding. Every CD has two layers of error correction, called C1 and C2. C1 corrects bit errors at the lowest level, C2 applies to bytes in a frame (24 bytes per frame, 98 frames per block). In addition, the data is interleaved and spread over a large arc. (This is why you should always clean CDs from the center out, not in a circular motion. A circular scratch causes multiple errors within a frame, while a radial scratch distributes the errors across multiple frames.)

If there are too many errors, the CD player will interpolate samples to get a reasonable value. This way you don't get nasty clicks and pops in your music, even if the CD is dirty and the errors are uncorrectable. Interpolating adjacent data bytes on a CD-ROM wouldn't work very well, so the data is returned without the interpolation. The second level of ECC and EDC (Error Detection Codes) works to make sure your CD-ROM stays readable with even more errors. .."

The VCD data correction is the least robust and simply gives us and gives you macroblocks if you get corrupted data. Fortuantely the human eye is much less senitive to video noise than the humane ar is to audio noise, so most of the time we don't notice bad blocks on VCDs. Because of the low quality of the VCD error correction, you can get enough bad blocks to produce visible macroblocking on playback. This can be due to a CD-R defect or a computer glitch during writing.

VCD data correction is more robust than audio CD. It too uses C1 and C2 (like all other CDs) but also at least contains EDC (though not ECC). However, unlike audio CD, interpolating bits wouldn't work very well (well it doesn't so bits don't get intepolated... ) so any glitches can't be simply hidden away.

It depends on your perspective I suppose but "audio interpolation" isn't so much a form of data correction as it can't give you back the original data. However, it is a good way of HIDING the loss of data integrity.

BTW, depending on the quality of your VCD/DVD player, many can "error correct" or "hide" errors in the mpeg video stream as well.

Consequently it is typically impossible to get a 100% bit-for-bit copy of a VCD. TendTend is therefore technically correct on that point.

Um, no it isn't. If your CD doesn't have any errors uncorrectable by C1 and C2 (treat your discs well, use good media and a good burner) you can definitely make a bit for bit copy. And by bit-for-bit, I mean bit-for-bit of user data. You should not have errors uncorrectable by C1 and C2 immediately after you burn a disc -- if you do, there is a problem with your burner +/- media.

Regards.

[vitualis]

Although Nero's CDSpeed File checker has reported no file errors, the Scan disk & CD quality check's occasinally reveal a small percentage say between 0.12-1.5% yellow sectors on the burnt CD's. It doesn't always happen,( I know it's related to the quality of the CDR Media you use), but wouldn't the possiblity of ANY yellow sectors mean the risk of an error in the DAT file when you converted back to an mpeg file? (In thereoy)??

The VCD's all play fine on both PC & my DVD player , (no glitches),it wasn't until I ran the Nero utils I even noticed that certain CD-R's had yellow sectors on them.

That just means some C1/C2 errors (jitter), but they were correctable. As long as they remain correctable, there is NO data loss.

If you converted this DAT back to MPEG, it will be identical to the original (in terms of the data anyway -- muxing + headers may have rearranged things a bit).

Regards.