The accuracy of DVD+R DL scanning

[Womi]

I want to hear the opinion of other CDFreaks to a topic that bothered my quite long now.

I have burned and scanned many DVD+R DLs and I found the scanning results very irritating at times.
For SL media its easy. If theres a huge PIE/PIF block on the scan, its most likely unreadable.
But look at this DL example:

Judging by the scan, theres no way any drive could read this disc beyond the layer break. 969 PIE, 66 PIF peak.
Here's the TRT in my BenQ DW1650:

As you can see, no slowdown at all. Disc plays great in my Xbox 360 too.

Another example (fake media):

scan:

TRT (LiteOn):

I just dont get it how a disc can scan so extremely bad and is still perfectly readable.

[cd_pirate]

Scanning is not 100% accurate at all. The results can be exaggerated plenty.

Also, some drives have good error correction, that’s why they can read the disc without problems.

I’d say it’s a bit of a combination of both points I made.

[Womi]

Here’s another disc Ive just burned.
Cheap Hong Kong fake Media.

I think Ill give up on DL scanning, the results are just worthless.

Huge difference between LiteOn and BenQ.

[pepst]

[QUOTE=Womi;2012092]I just dont get it how a disc can scan so extremely bad and is still perfectly readable.[/QUOTE]

I have similar experiences. Most likely the most of DVD RW drives is not suitable for DL scanning. The only way to test them properly is to buy a professional testing equipment like DVD Cats, Prometeus, Datarius, etc.

[cd_pirate]

Hmmm if you want to compare TRT and scanning, I suggest scanning @ 12x on both drives. An 8x scan will not always correlate with a 12x TRT.

If there are even more errors in the scan than @ 8x, they simply just don’t correlate and your DL scanning is being ruined by some sort of other factor. Perhaps high jitter or low reflectivity or something strange.