File Size ?????

[Leepz]

I did some searching, but don't see anything specific for this issue.

DVDMF6 - I load a compliant DVD MPG file (1HR 45MIN) and click that I want the project settings to match. Immediately my 4.14GB file is reported as being 7.43 (7.98) GB. If I change my project settings to not convert compliant MPG files the reported file size drops down to 4.27(4.58)GB.

On this file I wanted Dolby Digital 3/2 so changed the file settings ( I discovered you need to uncheck to not convert compliant MPG files to get Dolby). As expected the file jumps up - 7.92(8.50)GB. Ater adding menus the final file size reported is 8.10(8.70)GB. Too big to even burn to DVD 8.5GB.

I go through the process of creating files on the hard drive specifying DVD 8.5GB settings. The total of all files created on the hard drive in the VIDEO_TS is a whopping 4.45GB, way under what MF reported it was going to be.

What's going on here? Is MF shrinking the file that much ("Trying to make it fit"), or is it just over reporting the final file size?

I've been creating files on the hard drive because I don't trust the reported file size, then using a shrink program if needed to burn the DVD. In many cases this appears to be an unwarranted step because MF could burn the DVD.

Last question, when MF decides to try and make the file fit, is it attempting to shrink the file size like other third party programs, and if so how good is it compared to these programs.

Thanks,

[Ron P.]

Welcome to the forums,

This "over-size" reporting generally will occur if DMF thinks that your video file(s) do not meet DVD specs. You stated that you used DVD compliant MPEG-2 files, what were the properties of those video clips? There are differences between MPEG-2 and MPEG-2 that do meet DVD specs. The audio has to be considered, along with bitrates, and frame sizes.

Basically what DMF does when it shrinks the file to fit, is adjusting the bitrate. Lower bitrates = smaller file sizes and lesser quality, while the higher bitrates = larger file sizes, better qualtiy and less video to fit on a disc. Any other program that shrinks video for burning to disc does the same thing.

There is a two-pass encoding feature. This is used when variable bitrates are used. This scans and analyzes the video for fast and slow motions, on the first pass. It then adjusts the bitrates to the lowest for no motion or the slower, and uses a higher bitrate where there are fast motions. Doing this is suppose to allow for better quality video, and smaller file sizes. The files are then created/burned on the second pass.

[Leepz]

Thanks Vidoman,

Here are the specs on the source file:

MPEG files
24 bits, 720 x 480, 29.97 fps
MPEG-2 Video Upper Field First
(DVD-NTSC), 4:3
Video data rate: Variable (Max. 9800 kbps)
Audio data rate: 192 kbps
MPEG audio layer 2, 48 KHz, Stereo

So if I'm reading you correctly, MF probably just "thought" the file size needed to be larger, but actually created a smaller file when it got into producing the file? Is it the Variable bit rate you pointed to that is causing the file size being over stated? It does it's calc using the highest bit rate possible, rather than some sort of averaging algorythm?

[heinz-oz]

There are two things at play here.

MF reports the file size for a bitrate as set in your project settings. It can only estimate the file size since it hasn't had a chance to analyze the file yet.

Since it will not be doing any re-encoding, the original file size will not change. If you were to let MF re-encode the source file, it would do so at the settings for this project. The file size could work out bigger or smaller but you would take a quality loss due to the re-encoding.

[DVDDoug]

You are not the first person to report problems with Movie Factory's file-size calculation.

I usually use this handy online Bitrate Calculator.

I don't know why Movie Factory can't figure it out. (It's not that hard to convert kilobits-per-second into megabytes-per-hour.) You can estimate file size with the following formula:
File Size in MB = (Bitrate in kbps x Playing Time in minutes) / 140
The bitrate in the formula is the combined audio & video bitrate, and it's not an exact calculation because there is some space required for "overhead". And if variable bitrate is used, you need to know the average bitrate, of course... It doesn't really help to know the maximum, except that would give you an upper limit estimate.

When you un-check Do Not Convert... it will re-code the file per your project settings. (DVD Workshop has separate audio & checkboxes, but Workshop is old and it's being phased-out, so I can't recommend it.)

FYI - MPEG-2 audio is not DVD-compliant for NTSC, so it is a good idea to change it to AC3.

On this file I wanted Dolby Digital 3/2 so changed the file settings

How is that working for you? In general, you are better-off leaving it as 2.0 stereo and using your Dolby Pro Logic receiver to decode/generate the surround-sound at playback-time.

[Leepz]

Thanks all. I think I get it.

The Dolby 3/2 actually is working out quite well. For example, voice seems directed at the center channel while I can hear foot steps walking down a hallway coming from the rears. Have not tried doing a side by side with the same file with 3/2 and 2.0 stereo, however.

Thanks again.