You know this is a common problem with certain brands of media...... Can anyone (techy) actually explain why this occurs, or is it just something we all take for granted that it just happens.... Post your theories here...... My theory..... Cut out a circle (disc) in some paper and stick on top of a pin.....what happens....it droops... Now rotate the pin......slowly then increase speed.....what happens now.....it starts to raise up around the outer circumference, bringing it level with the centre....... Now if you place a little weight (small piece of card) on the one of the edges and rotate....what happens......it now throws the disc out of balance which is only visibly noticeable around the outer circumference...... Now discs are quite sturdy, but this same thing can be happening along the outer circumference....except it is not 'visible' however it is just enough to alter the distance between the optic pickup - and therefore invokes data transfer problems.....and this would be more evident on older players which have been hammered..... This could be basically down to the print side of the disc........ Any other theories......out there.....
The discs are spinning fairly rapidly i would imagine (at least several hundred RPM i would imagine, a thousand or two doesnt seem unreasonable).... i dont think droop we be a factor.
No there would be no droop exactly the opposite actually......the outer circumference would be rising up due to the centrifugal force acting on the disc.....think about helicopter blades....... The spindle covering is over the center and not the complete disc so therefore there could be vertical movement upwards on the outer edges....don't forget we are taliking about microns.......and at higher speeds this effect would be amplified towards the outer circumference...... If you removed the spindle cover at top speed, the disc would rise and spin out..... A little off topic....just had a news flash......looks like they have caught that S.O.B Saddam Hussein....hope so.....
Actually, it is more to do with the quality of the dye on the outer edge of the disc. The technique and quality control used by some manufacturers is poor to see the least. The most difficult area of a disc to apply a coating of dye to is the inner and the outer areas. The reason we dont tend to notice problems with the inner layers is mainly due to the size. 1 line or even two lines of pits on the inner part of the disc is merely seconds at the start of a DVD. However, at the end of a disc, a few lines of pits can be minutes. Look closely at cheap media and notice the outer edges are shabby looking. Compare it to a Ritek disc and you will see a difference. By the BaaBaa, the url you were trying to use for the sheep skipping was wrong, that was the only problem. Here is the correct url. Apply it the same way using the [ img ] [ /img ] without the spaces. http://www.click-smilies.de/sammlung0903/tiere/animal-smiley-085.gif
I love luring...these techies out..... Good comment and a good theory...I also think what you are saying is spot on...... Back to sales and marketing again......they omit the bad things......purposely..... However the substrates are mass produced so what is the process which causes the difference between the inner and outer being so 'different' in terms of quality, after all this is what they do.....why can they not produce a uniform disc..... How do they produce the 'pits' are these basically burned/stamped into the layer...... Did you like the original theory though...I thought it was believable....... It was the way I put the url in and not the url itself......but thanks for the tip....nothing escapes the wise one...... Have you looked at that site, some real cool ones......and have you seen the rude smily's....LMFAO...... However bet you can't guess what I did last night (bet you can't - oh Great Oriphus).....LOL BTW: C'mon Man Utd, Thankyou Bolton, you superstars........._X_X_X_X_X_[small]Beware of the Pixies - they move in over night and turn your life upside down [/small]
lol - Im not sure i want to guess what you did last night ;-) ON your theory about the outer edges, it sounds plauseable, but im not expert. Pits are formed by moulding, using a stamper, which is created by the glass mastering process. Bonding is also required for DVD discs. Both CD and DVD glass mastering require a laser beam recorder whereby a laser is used to expose minute areas of a photo-resist layer on top of a rotating glass master disc. The lengths and spacing of these areas is defined by the data to be stored on the disc. These areas are then developed to form pits and coated in a thin layer of nickel, on which a nickel Father is grown using an electroforming process. A Mother is then grown from the Father and the stampers grown from the Mother. Development times for DVD are critical and most systems use automatic endpoint detection for consistent results. Silver has been used for CD metallisation, but to maintain good pit geometry Nickel must be used for DVD (like Ritek G04's). The Nickel is deposited by sputtering and becomes part of the Father. The sputtering process can create problems and special techniques are often required to ensure that the photoresist is removed from the Father. Hence, the technique being the main area to look at when determining why the outer layers of a disc can have problems. Now, on your theory of the disc being at a slight bend, you may be on to something. Stamper finishing requires more care than for CDs, since tilt (variations in flatness of the final disc) is critical for DVD. Maybe it is at this time that the poorer quality manufacturers f*ck up their discs? If you want more information on this, and possibly and answer that isnt based on opinion but fact, why not email these people: DVD@disctronics.co.uk They manufacture around 300,000 discs an hour. Im sure they know....;-)
Now thats what I call an answer......cheers, beeen looking for something like that across the net.......nice to see you spend time locating good information..... I think I shall drop them a line......cos it really intrigues me. BTW, that email......there gonna get penis enhancement ideas now......LOL
lol - very true on the email, but im sure they have a spam blocker It didnt take to long to find it. You may have be searching for creating DVD discs or something. Manufacture was the key word
Interesting answer from Oriphus, and correct as far as it goes. the manufacturing process for DVD's (and cd's) have always encountered issues with the OD of the disk and the creation of the OD track Geometry, this issue historically originated from the mastering process. The pits on a DVD are formed in the photosensitive layer on the glass master by exposure to Laser light and developing, exposed material washes away to form the track/pit. The track formed is a spiral, any errors however tiny would be magnified at the OD of the DVD. When the actual stamper is made after going through the nickel electroforming process it's placed in the moulding machine, here again the process has dificulties with the OD, due to, injection speed, mould temperature, pressure and then the release of the bare substrate from the mould and handling. Then dyecoating (your blue or green dye) again difficulties spinning the dye to the OD of the disk, spin speeds, times, temperatures, tank pressures, cure times and more handling. then metalization.... As can be seen any part of the process can affect the final product. not to mention clean room environments, contamination, material impurities. and don't forget packaging. IMO: the disks giving the problems have not been given the care and attention from day 1 and if so many places are churning out the DVD+/- to fullfil customer requirements something is going to suffer
to add IMO (in my opinion): the constantly good quality DVD+/- we see and use are a result of care and attention at the manufacturer. All the questionable dvd+/- giving the problems and low yields are not being processed to quality, but quantity. But don't forget the DVD +/- Drives we use will also differ by manufacturer and type and since no standard has been finalised some of yet So we can't blame the blanks disks for this...
This is more like it....... Although I was led to believe there is a standard for +/- r discs, however there are variations within the software for which it is written and the 'better' one is that which is contained within standalone recorders and not pc based ones........but I am a gullable sod.....anyway
I believe the actually burning process of red laser to disc is a standardised series across all manufacturers. The methology stays constant. Where you notice the difference in quality between the various producers of the DVD Recorders/writers tends to be in components used, not in software, IMO.
