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Posted by Bill's News on 01/03/07 05:57
AndrewD wrote:
> Can someone explain to me why I can only record around one
> hours worth
> of TV on my Sony DVD recorder on the highest quality setting?
> I can
> buy a DVD box set of a TV series (24 for example) on which
> they manage
> to fit 4 episodes in high quality dolby 5.1 surround sound.
>
> Why can I not fit the same amount of data onto a normal
> recordable
> DVD?
>
> Thanks
What a fascinating thread. I trust you took nothing from it;-0)
1X, as far as CD and DVD goes, is one hour of playtime. If the
recording is at the MAX specified bit rate, on a specified disc,
the complete disc will contain one hour of audio or video.
That translates to a SPECIFIC transfer rate when PLAYED. The
specified transfer rate is 1X.
If a CD or DVD reader can read the data faster, then its
transfer rate is often quoted as NX, or some number greater than
1X - but it is better cited as bytes per second to avoid
confusion. The recording itself is still 1X, or whatever bit
rate was used by the author. Thus, I might read or write a 1X
recording at 16X, or one hour's worth of data will be
transferred in 3 and 3/4 minutes.
For a disc of either type to contain MORE than one hour of audio
or video its bit rate must be LESS than 1X or the disc's
capacity must be greater than 1X. Thus, typically, 2X play time
is half the specified bit rate, 4X is one forth the specified
bit rate; dual layered discs contain nearly twice the capacity
of "specified" discs and may play 2X the time at 1X the
specified rate.
N.B. Reduction of bit rate, while permissible, implies reduction
in playback quality.
While discs may contain a HIGHER than specified bit rate,
playing these back reliably depends upon the hardware involved
surpassing the SPECIFIATION. Contemporary devices often do,
their forbears often do not.
Confused? Try asking a plumber for a washer;-0)
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