View Full Version : Is VCD Burning Lossless (Nero / VCD-Gear)

25th February 2002, 19:21
I'll try to clarify that question a bit.

I am trying to figure out if the process burning a VCD (I'm using Nero) [from an appropriate .mpg source] and then re-aquiring the .mpg file from CD (I'm using VCD-Gear) is a lossless process.

I understand the burning process adds additional error correction, and the ripping process will likely remove this. I've only tried 1 sample so far and it looks very close.

- OrigMpg reffers to original mpg file
- VCD reffers to Nero .dat file
- DAT reffers to VCD Gear's .dat file
- Mpg reffers to VCD Gear's .mpg file

OrigMPG: 801,724,224 bytes
NeroVCD: 811,505,900 bytes

VCD->MPG: 801,721,900 bytes (Fix Errors) - lost 3,000 bytes
MPG->DAT: 811,381,244 bytes (FIX Errors)
DAT->MPG: 801,717,252 bytes (Fix Errors) - Lossy ?

VCD->MPG: 801,773,028 bytes (No Error Fix) - gained 5,000 bytes
MPG->DAT: 811,432,988 bytes (No Error Fix) - Lossy ?

OrigMPG->DAT: 811,383,596 bytes (No Error Fix)
AbovDAT->MPG: 801,724,224 bytes (No Error Fix) - Lossless?

OrigMPG->DAT: 811,381,244 bytes (Fix Errors)


Looking at the VCD gear VCD creation Nero seems to add more un-needed info. Perhaps it is the errors in the original MPEG file (definite changes on error fix), or just a few CD scratches.

I'm going to try a few more samples, and perhaps do a diff(*) if any files come out the same size.

(*) Linux/Unix command that checks files for differences.

Comments? Suggestions? Answers?

27th February 2002, 08:16
I don't think the burning process adds any error correction. It is for this exact reason why we are able to fit 740Mb on a 74-minute CD rather than the classic 650MB for data CDs.

28th February 2002, 15:48
Oops I've read the details backwards. The burning removes error correction and puts MPEG data in it's place. This increases the capacity.

VCD gear must pad the information back into place.

I've re-burnt the reaquired .mpg and the files are the same size.
There is a difference between the .dat files, but it seems minimal. I need to get a better file compare program though [keeps stoping after one difference].

Here is the VCD technical details from Nero if any one is interested

..... As this format [Mpeg-1] and video/audio data tolerate bit errors in general, the space usually spent on error correction codes can also be used for MPEG data. This increases the amount of user data in a block from 2048 to 2324 bytes per block thus raising the capacity of a VCD by 13% compared to storing MPEG files on a data disc.