Just Curious About My DVD Player

[Dick Sutton]

As I was reading this newsgroup over the last few weeks, a question came to
mind.

This has to do with the Dolby Digital or DTS bit streams.

How many lasers does a typical DVD player have?

Does it have one for video and one for audio?

The reason I ask is that my manual says their machine looks for Dolby first,
but DTS can be selected. I just wondered how one laser could jump back and
forth between video & the selected audio.

Thanks in advance...

Dick

[Anon-E-Moose]

"Dick Sutton" <RichardMSutton@comcast.net> wrote in
news:ba6dnfaPablu0bvfRVn-gQ@comcast.com:

> The reason I ask is that my manual says their machine looks for Dolby
> first, but DTS can be selected. I just wondered how one laser could
> jump back and forth between video & the selected audio.

Most if not all DVD players have one laser.

DVD players can jump back and forth because the data can be read faster
than it can be played back.

[Dick Sutton]

Thanks for the reply, Anon-E-Moose. I guess that I'm still confused, if
there are audio tracks for analog, dolby digital, and DTS, they can't be in
the same data stream as the video, can they? I can't really see the laser
wiggling back and forth like a computer hard disk!

I guess that if they're all multiplexed into the same data stream the
onboard logic can discard what its not interested in. I'm just curious
about how all this 'magic' works.

Dick

"Anon-E-Moose" <anon-e-moose@yahoo.com> wrote in message
news:Xns960DEA1C43EFDanonemooseyahoocom@140.99.99. 130...
> "Dick Sutton" <RichardMSutton@comcast.net> wrote in
> news:ba6dnfaPablu0bvfRVn-gQ@comcast.com:
>
>> The reason I ask is that my manual says their machine looks for Dolby
>> first, but DTS can be selected. I just wondered how one laser could
>> jump back and forth between video & the selected audio.
>
> Most if not all DVD players have one laser.
>
> DVD players can jump back and forth because the data can be read faster
> than it can be played back.
>

[Anon-E-Moose]

"Dick Sutton" <RichardMSutton@comcast.net> wrote in
news:H6GdnZ6EM55p37rfRVn-sw@comcast.com:

> Thanks for the reply, Anon-E-Moose. I guess that I'm still confused,
> if there are audio tracks for analog, dolby digital, and DTS, they
> can't be in the same data stream as the video, can they? I can't
> really see the laser wiggling back and forth like a computer hard
> disk!

There is no analog track on DVDs : ) And yes, I believe the digital
audio is stored within the same file as the video. But regardless, a DVD
drive has random read ability - so even if the audio tracks weren't
within the same file as the video, a DVD drive can "move" back and forth
between different sections of the disc.

The laser doesn't wiggle back and forth, rather, the disc spins hundreds
of times a second, the laser selectively reads what information it
needs. The laser also moves inwards and outwards along the radius of the
disc and can focus between 2 translucent layers on a DVD disc.

A DVD player works the same way a computer DVD-ROM drive works. But also
look up how CD-ROMs work, DVD drives function basically the same a CD-
ROM drive but takes it one step further with multi-layers.


> I guess that if they're all multiplexed into the same data stream the
> onboard logic can discard what its not interested in. I'm just
> curious about how all this 'magic' works.

Here is a good illustration on how a DVD drive works:

http://electronics.howstuffworks.com/dvd12.htm

[Dick Sutton]

Great site! Thanks for the info...

Dick

"Anon-E-Moose" <anon-e-moose@yahoo.com> wrote in message
news:Xns960E98C1B4E3Fanonemooseyahoocom@140.99.99. 130...
> "Dick Sutton" <RichardMSutton@comcast.net> wrote in
> news:H6GdnZ6EM55p37rfRVn-sw@comcast.com:
>
>> Thanks for the reply, Anon-E-Moose. I guess that I'm still confused,
>> if there are audio tracks for analog, dolby digital, and DTS, they
>> can't be in the same data stream as the video, can they? I can't
>> really see the laser wiggling back and forth like a computer hard
>> disk!
>
> There is no analog track on DVDs : ) And yes, I believe the digital
> audio is stored within the same file as the video. But regardless, a DVD
> drive has random read ability - so even if the audio tracks weren't
> within the same file as the video, a DVD drive can "move" back and forth
> between different sections of the disc.
>
> The laser doesn't wiggle back and forth, rather, the disc spins hundreds
> of times a second, the laser selectively reads what information it
> needs. The laser also moves inwards and outwards along the radius of the
> disc and can focus between 2 translucent layers on a DVD disc.
>
> A DVD player works the same way a computer DVD-ROM drive works. But also
> look up how CD-ROMs work, DVD drives function basically the same a CD-
> ROM drive but takes it one step further with multi-layers.
>
>
>> I guess that if they're all multiplexed into the same data stream the
>> onboard logic can discard what its not interested in. I'm just
>> curious about how all this 'magic' works.
>
> Here is a good illustration on how a DVD drive works:
>
> http://electronics.howstuffworks.com/dvd12.htm
>
>
>
>

[jgmclean@my-dejanews.com]

Anon-E-Moose wrote:

> The laser doesn't wiggle back and forth, rather, the disc spins
hundreds
> of times a second,

Erm. Dozens, actually; a DVD player maxes out at about 1500RPM (24
RPS) near the center of the disc. Still pretty fast, and of course a
multi-speed computer DVD drive goes X times faster than that.

JGM

"Dick Sutton" <RichardMSutton@comcast.net> wrote in message
news:ba6dnfaPablu0bvfRVn-gQ@comcast.com...
> As I was reading this newsgroup over the last few weeks, a question came
to
> mind.
>
> This has to do with the Dolby Digital or DTS bit streams.
>
> How many lasers does a typical DVD player have?
>
> Does it have one for video and one for audio?
>
> The reason I ask is that my manual says their machine looks for Dolby
first,
> but DTS can be selected. I just wondered how one laser could jump back
and
> forth between video & the selected audio.
>
> Thanks in advance...
>
> Dick
> These things scan very fast, its really as simple as that.
If you have a DVD recorder you might have an onboard hard drive, and your
unit will sometimes read from the info it has stored on it.
Most optical disc players have one laser, I say most because there might be
one out there with more, but I haven heard of it
>