2 questions....

ushere wrote on 5/30/2008, 1:35 AM
end of a long editing day, so i'm going to unwind with a couple of badly thought out questions, to which the answers are probably under my nose, or buried it the senior plot...

a. i usually create a dvd with an extras folder, for my clients into which i dump the hd version m2t and an ipod / web version. (short format stuff - 5 > 10 minute promo's and the like). so far so good, but what happens now is if they play the dvd version on their pc they're going to get the washed out pal version (which of course plays colourfully on their tv / lcd). shoud / could / is it possible to put two dvd versions on it (selectable with menu), 1 for tv, the other for pc.

or am i expecting too much from my clients to understand the difference? (have never had a comment about this from them, other than, 'christ, the hd looks incredible!')

b. where does the loss occur in re-encoding mpeg / m2t's? i mean, it's all 0's and 1's isn't it? do some of them get lost? if i copy a jpeg endlessly, will it too suffer loss?

i know, but it is the end of a long day....

leslie

Comments

Chienworks wrote on 5/30/2008, 3:41 AM
A - Sure, you can put as many different copies on a DVD as you have room for. Drag them all to the main page and you'll get buttons for each one.

B - The loss occurs because the software expands the compressed format to uncompressed while processing it, then recompresses again to save the new file. Every compression loses data. Of course, smart rendering can render without recompressing, but in practical matters the requirements to allow smart rendering are often not met.

B(b) - Copy a jpeg endlessly? No loss whatsoever. Same if you copy an mpeg file, zero loss. Open a .jpeg file and save it again, the new saved version will suffer loss.
JohnnyRoy wrote on 5/30/2008, 6:21 AM
> Sure, you can put as many different copies on a DVD as you have room for. Drag them all to the main page and you'll get buttons for each one.

Yea but a DVD is not going to allow HD content on the main menu without re-encoding it to SD. So I don’t think you can do this in the context of the DVD menu structure.

I’m not sure if Leslie was asking about one menu with clips for both TV and PC or if the disc itself is to behave differently. If the latter, and I have not tried this, but the key is to have each platform (PC & TV) recognize the disc as something they can play. PC’s have a protocol whereby a CD/DVD can be auto-started by placing certain files in the root. I would imagine that you could have the HD content be auto-played on a PC while a DVD player will ignore this for TV viewing. In fact, I remember having some Hollywood movie DVD’s that actually install software on your PC when inserted so I know this sort of thing is possible.

> The loss occurs because the software expands the compressed format to uncompressed while processing it, then recompresses again to save the new file.

Just to expand a bit on what Kelly said: What happens is that compression tries to represent more with less. So, for example, you start out with 100 pixels and the encoder is trying to represent them with just 20 pixels so the encoder says, “these pixels look similar in color and luminance so I can represent them with just one pixel and copy it wherever I need it.” To you and me it looks pretty good. Then you encode it again and the encoder says, “hmmm… these other pixels look similar (now that I’ve altered them from their original color and luminance) and so I can represent those with just one pixel and copy it.” You see, each time the image gets further and further from the original because it starts with something that has been altered and alters it some more. This is because MPEG compression is "lossy". It looses data integrity each time is encodes. There are encoders that are "lossless" but those rarely get more than 50% compression. but the do guarantee that the image is the same each time it is encoded (sort of like ZIP and UNZIP)

~jr
ushere wrote on 5/30/2008, 7:09 AM
thank you gents, i can now sleep peacefully tonight ;-}

i hadn't actually thought through jr's suggestion - i was thinking two menu items for the same program - one encoded for tv, the other for pc.

i think tomorrow might be a quick play with seeing what prompts pc to play vs dvd (obvious structure).

if i'm exceptionally fortunate, someone might already know the answer to this and post it before i wake up.....

living in hope,

leslie
JohnnyRoy wrote on 5/30/2008, 7:34 AM
> if i'm exceptionally fortunate, someone might already know the answer to this and post it before i wake up.....

What you do is create a file called autorun.inf and place it in the root of the CD or DVD. The contents should look something like:

[autorun]
open=setup.exe
icon= icon.ico

As you can see, it wants to run a program. So you would have to either deliver a program on the DVD that could play the content, or point to the Windows Media Player that is already on everyones PC. If you go the Windows Media Player route it would look something like:

open="C:\Program Files\Windows Media Player\wmplayer.exe" MyMovie.m2t /play /fullscreen /close

where MyMovie.m2t is the movie name. It could be in a folder. If so add the folder name relative to the root (e.g., .\HD\MyMovie.m2t)

Like I said, I haven't tried this but google "autoplay cd" and you should get some worthwhile hits.

~jr
ushere wrote on 5/30/2008, 9:36 PM
jr, you're a wonder mate....

thanks. i've been using auto runs on cd's for years to open up web based projects. never thought to try it on dvd's.

many thanks.....

leslie
Laurence wrote on 5/30/2008, 9:53 PM
I usually stick to just the DVD material for a couple of reasons:

1/ DVD playback starts from the center out. As you write towards the outside edge of the disc, each spin of the disc becomes more spread out and prone to errors. Thus I find that the more space I have at the outside edges, the less likely I am to have playback glitches, especially if I encoded with a relatively high bitrate or VBR.

2/ Shorter DVDs duplicate faster.

3/ People naturally handle DVDs from the outside edges. Leaving a little unused space around the outside edge means it is less likely that smudges from dirty fingers are going to affect the already precarious playback of a DVD+-R.

4/ Most people never put their DVDs in a computer to look for extra data anyway.
ushere wrote on 5/30/2008, 11:44 PM
thanks laurence,

1. you're probably right, but with the length of these sort of programs i usually come in (with extras) at around 3gig - and i suspect their life is fairly short (that is, if they ever have one - love ceo's with money to spend).

2.thankfully not my problem - and from what i do, it's the mp4 element that's the most important for putting on the web. i give them the hd version for the 'wow' factor, and the dvd for the old farts among them.

3. as in one, i don't think my dvd's get too much handling...

4. see 3.

but i appreciate where you're coming from and agree wholeheartedly with you.

leslie
farss wrote on 5/31/2008, 4:50 PM
I think part of your problem is the StudioRGB Vs ComputerRGB problem. You could easily put two versions on the one DVD and the user select which one to play from the usual DVD menu.

Bob.
navydoc wrote on 5/31/2008, 5:03 PM
I use a program called Autorun Typhoon. With it, when you place the DVD in your computer drive, a menu autostarts so you can access files on the disk. In my case, pdf files of cruise books from the aircraft carrier I used to be stationed on. I also place a dvd movie on the disk. When the DVD is placed in a set top player, the dvd movie I have on the disk begins with it's menu. These movies are home movies taken aboard the ship too.

Although you don't need the autorun program, here's a link to the program...check it out...you can add lots of different types of files to a disk and have easy access:
http://www.autoruntyphoon.com/index.htm

Doc