Michael Shell wrote:
Unless these drives can see into the future, user data should not be corrupted. The last full sector should be written clean, and the partial (if any) sector should not be written at all. Other than some extra fill between sectors I don't see any obvious result when burnfree is on.Thanks for the tips Volker, Greg and Bill. ;)
Volker Kuhlmann wrote:
DVDs are much more precise in finding the spot again from which to
continue burning, especially DVD+ which I understand is similar to
DVD-RAM. DVD-RAM effectively goes on nothing but underruns. You
needn't be concerned about engaging underruns with DVDs.
You are right, but I just want to elaborate some more on this as I found some more sources of information on the subject.
My question directly plays out in the conversation here: http://club.cdfreaks.com/lite/t-91137.html
The point I want to emphasize is the second post which was by "Wesociety":
: AFAIK losslinking and buffer underrun protection are 2 separate : features and are both used when burning a DVD+RW.
To which "Henjie" replied:
:: I'm kinda under the impression that buffer underrun protection is :: an inherent part of the DVD+R/RW format though.
The key point is that the lossless linking feature of DVD+ allows data to be recorded at the packet level without having any data degradation as a result of buffer underruns. According to Andy's docs, the DVD+ "splice point" lies within sync patterns, not user data. In effect, from a practical standpoint, buffer underruns are of no consequence with DVD+ formats because the DVD+ system does not require the buffer to be continuously filled during the write process. This is why DVD+RW can be thought of, and used much like (with the few caveats Andy mentioned in his docs) a slow hard drive - no special writing software is even required. It is the same with DVD+R, except that each sector/packet can only be written once. IMHO, DVD+ is obviously superior to DVD- for this reason.
A good source for technical papers on the subject can be found here: http://www.dvdplusrw.org/Article.asp?mid=0&sid=4&aid=6
However, it is important to point out that this is NOT true
with DVD- formats. Interrupting the data stream during a write
will have consequences as it will result in several K bytes of linking
data added and that several bytes of user data will be corrupted
(and this will be true even on the best "burnfree" DVD- drives,
without burnfree this event = coaster). The ECC system is capable of
correcting these minor errors and so the data should appear error free
when read back. However, the errors do reduce what I call "ECC margin"
in that any existing (pre-corrected) errors on the media do reduce the
capacity of the ECC system to correct for *future* errors (due to dust,
scratches, etc.) Thus, a DVD- media that was subjected to underruns
will be less (how much so I don't know) reliable than if the buffer
had been kept full during the recording.
Feel free to to show why errors in user data would occur, other than bad firmware, of course.
-- bill davidsen <[EMAIL PROTECTED]> CTO TMR Associates, Inc Doing interesting things with small computers since 1979
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