POV-Ray : Newsgroups : povray.off-topic : DVD (-ROM) image access speed question : Re: DVD (-ROM) image access speed question Server Time
5 Sep 2024 13:13:17 EDT (-0400)
  Re: DVD (-ROM) image access speed question  
From: Invisible
Date: 8 Jul 2009 08:19:36
Message: <4a548ed8$1@news.povray.org>
gregjohn wrote:
> I'm presuming they'd have every processor
> speed and OS under the sun.  I have a cover page on which I display thumbnails
> of twenty different images from various directories across the DVD.
> Understandably, it loads a little slowly.

All optical disk formats that I'm aware of have very long seek times. 
Reading lots of small files is very slow with such disks.

I'm no expert in this field, but I don't think any of them have a very 
high maximum transfer rate either. For example, a 1x CD-ROM drive 
transfers 10MB of data *per minute*. That's 1MB every 6 seconds. Of 
course, newer CD-ROM drives are usually 48x or something, which takes 
you closer to 10MB per second. And DVD is faster still. (But I don't 
know exactly how fast off-hand.)

[Wolfram Alpha claims a DVD transfers 5 megabits per second, which would 
be about 0.6 MB/second.]

> Q: How can I speed this up?  What's the best approach:
> i) put all of the images into one directory to reduce DVD access time (tried,
> didn't help much)

This is unlikely to help at all. It might minutely reduce the amount of 
seeking required to read the directory tree, but it won't help read the 
files any faster or seek to them any quicker.

> ii) If I'm going to do < i m g s r c ""  h e i g h t = X,  then I should just
> save a new, resized copy of the image with  that height instead of asking HTML
> to resize images which are 5X that size.

This may well help, since you have less data to transfer. (You still 
have the seek times, however.)

> iii) Make one composite image and then use that click-on-a-bitmap- thing in
> HTML.

This should also help, by putting all the image data into a single 
contiguous block, thus eliminating seek time penalties.

> Q: Can anyone point me to an online tutorial, or better yet, to the exhaustively
> correct terminology so that I may google it, of how to create autorun files?

http://en.wikipedia.org/wiki/AutoRun

You need to add a file named Autorun.inf to the root directory on the 
DVD, containing something like

   [autorun]
   open=root.html
   icon=icon.ico

This works ONLY for Microsoft Windows; I'm not sure if any similar 
functionality exists for other operating systems...


Post a reply to this message

Copyright 2003-2023 Persistence of Vision Raytracer Pty. Ltd.