>From: Andy Polyakov <[EMAIL PROTECTED]>
>> The write speed does not matter if you use BUrnProof or packet writing.
>> Of course DVD+RW _only_ supports packet writing...
>The page in question was updated with following two paragraphs:
>What does plus stand for in DVD+RW/+R? The key feature of DVD+RW/+R
>media is high [spatial] frequency wobbled [pre-]groove with addressing
>information modulated into it. This makes it possible to resume
>interrupted [or delibirately suspended] burning process with accuracy
>high enough for DVD[-ROM] player not to "notice" anything at playback
>time. Recovery from buffer underrun condition in DVD-RW/-R case in turn
>is way less accurate procedure, and the problem is that the provided
>accuracy is very much what average player can tolerate. Now given that
>both provided and tolerated inaccuracies are proportional to respectively
>writing and reading velocities there basically no guarantee that
>DVD-RW/-R recording that suffered from buffer underrun will be
>universally playable.
This is not correct.
High frequency wobbling does not help to make the DVD recording better
in case of buffer underruns. You always use the pre-groove only to find
the course place where to resume recording. The exact position is found
by reading the already recorded data and switching from read to write.
It is not possible to get the needed precision only from information in
the pree-goove. Fazit: a typical DVD+ marketing phrase :-(
>Sometimes DVD+RW/+R is erroneously compared with packet writing. Packet
>writing means that every chunk of actual user data gets surrounded by so
>called link, run-in and run-out sectors, which wastes some capacity, not
>to mention that it requires explicit support by player's DSP [Digital
>Signal Processor] performing the actual decoding of user data. Again
>thanks to high frequency wobble, no such things are needed for DVD+RW/+R.
>This is exactly why it's commonly referred to as "designed from scratch
>for maximum compatibility with DVD-ROM specification."
Call it ho you like, it _is_ some kind of packet writing.
Of course, there is no run-in/run-out blocks as the DVD uses a different
scheme for cross interleaved error correction.
A real DVD "sector" is 32k. If you call this a packet, then you are excatly
were we are with CD packet writing (except for the run-in/run-out blocks gaps).
On A CD, there are two different types of packet writing:
- write packets to a blank disk (no overwrite possible)
- write random addressed packets to a pre-formatted disk (overwrite works).
DVD- supports both modes, DVD+ only supports the second mode.
In addition, DVD- supports a streamed de-facto uninterrupted write called
SAO (Session At Once).
Jörg
EMail:[EMAIL PROTECTED] (home) Jörg Schilling D-13353 Berlin
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URL: http://www.fokus.gmd.de/usr/schilling ftp://ftp.fokus.gmd.de/pub/unix
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