File size issue - from mpg to DVD

[s.burnley]

Is there a consistent and/or reliable way to predict what size the final DVD will be from the size (or sizes) of constituent AVI or mpg files.

My problem is that I am trying to create a DVD from two clips each of about 45 minutes duration. My old rule of thumb says that you get 1 hour at 8000 kbps, 90 minutes at 6000 kbps, and 120 minutes at 4000 kbps. So if I sample them at around 6000 I should be OK - but not so!

Even after I have created the two mpg files from the clips at 4500 kbps, they are each about 1.5 Gb in size. So it would appear that I have just over 3 Gb to get onto a 4.4 Gb DVD and it should be OK. But when I go to "Create Disk" (in UVS8 by the way) the computed DVD size is nearly 4.8Gb.

Is this uplift normal - it is nearly a further 1.5GB - a 33% increase over the mpg files?

Stuart

[Trevor Andrew]

Hi Stuart

Your thinking I correct. I would expect that at 4500 you would be able to fit the two onto a disc.

33% seems as though you are trying to fit three video’s to the disc.

Are you sure the timeline is empty when you Share create Video File???????

Trevor

[s.burnley]

Are you sure the timeline is empty when you Share create Video File???????

Hi Trevor,

Yes - I close UVS before doing the DVD creation and go straight to Create Disk after restart. No project open, nothing on timelines at all. I click "add video" and open each mpg file in turn.

Other posts in the forum still suggest that both files should easily fit on the DVD - so I wonder if my UVS has developed a wierd glitch!

[s.burnley]

The first mpg file is 1,534,963 and when it is added to the DVD size "progress bar" it becomes 2.52 (2.35) GB.

The second file is 1,673,877 and when it is added to the DVD size "progress bar" it becomes 2.75 (2.56) GB.

So the total to be written to the DVD is 4.91 GB from 3,208,840 kB!

[Trevor Andrew]

sorry but you've got to laugh, Ha Ha Ha

I know its not funny from your end.

'Output disc format' top left does it indicate DVD

Press F6---disc type 4.7Gb

Oh i do wish i had VS 8 installed!!!!!!!!!!

Trevor

[s.burnley]

Hi again,

'Output disc format' top left does it indicate DVD

Yes it indicates DVD.

I have done something that appears to sort it all out but I'm not exactly sure what the effect will be ...

In the intervening few minutes I decided to do further checks on the properties - after re-reading part of your Guide to UVS.

The clip properties (right click on the thumbnail) showed VBR at 4500 max which is correct. The project properties showed VBR 6000. So I set the project properties via the custom option to 100% quality and a lower bit rate (sorry forgot exactly what setting I used). This brought down the DVD size to within DVD capacity. I left the box ticked to 'not render compliant MPEG files'.

All appeared to work fine and I have created my DVD ISO file which I'll check shortly.

It leaves me with a question or two:

If an mpg file has been created with a certain bit rate, does the create disk option in UVS 8 allow you to change that on the fly as it were?

What exactly was UVS going to write to DVD at the 4.8 Gb amount if it did not re-render the mpg files totalling 3.2 GB - blank space?

Stuart

[jchunter]

If an mpg file has been created with a certain bit rate, does the create disk option in UVS 8 allow you to change that on the fly as it were?

What exactly was UVS going to write to DVD at the 4.8 Gb amount if it did not re-render the mpg files totalling 3.2 GB - blank space?Stuart

Yes you can change the bit rate by re-rendering, when you create a video file.

It seems that you did this when you created your video file, lowering the bit rate from 6000 to 4500. However, when you burned, I think you forgot to set the BURN properties to match your video file properties. I think the Burn properties had the bit rate set to 6000, so the Burn module cheerfully rerendered (or planned to) the video files back up to 6000, which would just bloat them a larger size that no longer fit in the DVD.

BTW, version 8 had chronic Audio/Video synch problems that, AFAIK, were never fixed. Upgrade to 10+ ASAP.

[s.burnley]

I think the Burn properties had the bit rate set to 6000, so the Burn module cheerfully rerendered (or planned to) the video files back up to 6000, which would just bloat them a larger size that no longer fit in the DVD.

Hi John,

Does that mean that anyone can actually create the mpg file risking what might be too high a sample rate and then cut it down to fit the DVD at burn time - if so that's great! I presume that doing it the other way - originally rendering at 4500 and the burning at 6000, would mean that quality had already been sacrificed.

Stuart

[jchunter]

It is much better workflow to edit at full resolution and then do the bitrate adjustment when you create the video file. If you let the burn module rerender it will take just as long as if you created the video file yourself and you will NOT have the advantage of being able to preview the results prior to burning.

Yes, rendering to a higher bitrate than the source material does not improve quality at all.

[Trevor Andrew]

Hi Stuart

I think John is correct.

When you burn a dvd you have to change the project properties to match the video file used.

You can do this in the burner window by selecting the cogwheel and change mpeg settings.

I prefer to change the project settings prior to going Share Create Disc.

Do this:-

1/ File – preferences- Show messages when inserting first video file.
2/ Start a new project
3/ Insert your video file to the timeline
4/ select ‘yes’ to the info window
5/ Delete/remove the video file—you have an empty project using the correct settings.
6/ Share Create Disc—Add video

Having said that I still do not understand why the Gb indicated 2.5 as this is the file size not the project.

You Said:-

Does that mean that anyone can actually create the mpg file risking what might be too high a sample rate and then cut it down to fit the DVD at burn time - if so that's great

Not Great

This would involve rendering the whole video again in the burner stage, not what you want to do.
The purpose of Share Create Video File is to produce a file that will fit to disc, Which
Is why you chose 4500.

Trevor

[s.burnley]

This would involve rendering the whole video again in the burner stage, not what you want to do.
The purpose of Share Create Video File is to produce a file that will fit to disc, Which
Is why you chose 4500.

Thanks for your replies - it all makes sense and I certainly shan't try the trick of rendering at a potentially too high bit rate. The reason I chose 4500 was because when I tried 6000 the files were too big for the DVD. It's obvious now that whatever bit rate I had chosen for these files, if I had not changed the "burn" settings it would still have given me too much for one DVD. The apparent 33% increase in my first post is spot on for an uplift from 4500 - my sample rate - and 6000 - the UVS burn rate. I never tried to do the burn so I never discovered that it would have taken a long time.

I shall use the technique of loading the mpg file to set the burn rate and then delete the file from the timeline.

Regarding V10+, I am intending to purchase it in due course.

Stuart

[sjj1805]

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