MPEG2 - Gaining maximum quality at the right file size?

organism_seven wrote on 9/18/2002, 2:21 PM
Hi,

Am I the only one to think that all the existing encoders (including MainConcepts) for converting DV to MPEG2 for transfer onto DVD, requires a degree in the black arts?

I am producing movies of varying lengths.
When I convert them to MPEG2, I want to know what file size is going to be produced at the end of this process to ensure that they will fit onto a DVD-R.
Surely this is an absolute requirement?

I don't want to have guess (and hope!) that it will fit.
And I don't want to have to use a calculator to try and work out the result.
Computers are made to do calculations for crying out loud.
Whats the point of a "high quality" option to convert your footage, if the end result won't fit onto a DVD-R?
Only TMPGEnc Plus provides you with the ability to modify the encoding settings and provides you with an estimated (pretty accurate) figure of the finished file before you press the start button.
Consequently, this is what I am now using, despite the slower conversion speeds.
I can now just keep tweaking the settings to maximise the quality and ensure the end result will fit on the disc.

Can anyone explain why commercial programs like Procoder, MainConcept and Cleaner don't provide this essential feature?
Does forcing the end user to estimate/guess/calculate the file size, mean it is only supposed to be of use to professional geeks?

Maybe I'm missing something obvious here?
If so, let me know.

Regards
Organism Seven



Comments

jetdv wrote on 9/18/2002, 2:41 PM
AC-3 PCM
Minutes Max Encode Rate Max Encode Rate
30 8.100 8.100
45 8.100 8.100
60 8.100 8.100
70 8.100 7.032
75 7.834 6.459
80 7.333 5.958
85 6.890 5.515
90 6.497 5.122
95 6.145 4.770
100 5.829 4.454
105 5.542 4.167
110 5.282 3.907
115 5.044 3.669
120 4.826 3.451
125 4.625 3.250
130 4.440 3.065
135 4.269 2.894
140 4.110 2.735
145 3.961 2.586
150 3.823 2.448


Here are the two basic formulas:

For AC-3 audio
(36096-((( TIME IN MINUTES *60)*192)/1024))/( TIME IN MINUTES *60)

For PCM (Wav) audio
(36096-((( TIME IN MINUTES *60)*1600)/1024))/( TIME IN MINUTES *60)
nolonemo wrote on 9/18/2002, 2:49 PM
I think the reason TMPGenc can do this for you is that you have loaded the AVI you intend to convert into it first (I'm assuming you're not frameserving since you have posted to the VV forum). Much more difficult for the program to do if you are using a plug-in encoder such as the MainConcept in VV3, where you will have mulitiple AVIs on the timeline, with different in and out points, not to mention overlap for transitions.

Having said that, I suppose it would be possible for VV to communicate to the ecoding module the length of the project (or the portion selected to encode) which would enable the encoder to calculate the final output size given the encoding parameters.

Good idea!
vonhosen wrote on 9/18/2002, 3:00 PM
Easy way to do it is

600/(number of minutes of video) = average combined bitrate for video/audio combined

example for 90 minute project

600/90 = 6.6Mbs

If you have to use PCM audio at 1600Kbs it means you could encode with MainConcept at 5.0mbs avg for video only stream.

If you can use compressed audio in authoring program (MPEG-1 layer II or AC-3) at say 192Kbs-224Kbs you could do 6.4Mbs avg with MainConcept video only stream.

This formula will allow for overhead & almost fill disc everytime but you can't go over 9.8Mbs combined bitrate just because you would say want to do 30mins project as 9.8Mbs is max permittable bitrate for DVD spec.
BillyBoy wrote on 9/18/2002, 5:14 PM
All the fomulas are at best a guess, if you use VBR, which you should use to have the best compromise between how large a video will fit on a disc compared to quality.

My experience is with average scene action, 10-40 thumbnails for chapters, minor loop of background music for the menu sytem I get about one hour and 45 minutes of video using the default settings for DVD NTSC. This ia literally burning the DVD to within a few hundreds of an inch of the disc end. I would suspect because of lower frame rates you would get more using PAL.

Using Ulead's DVD Movie factory it will give a accurate byte projection that allows me to get that close to maximum. This is useful if you have several seperate videos on one DVD, and not one monster video. The catch of course is the projection is based on files ALREADY rendered. It hasn't happened yet, but if needed one could always shave one of the videos down a tad, but that would require another render.

organism_seven wrote on 9/19/2002, 3:11 PM
Hi,

Thanks for the feedback.

snip>
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"Having said that, I suppose it would be possible for VV to communicate to the encoding module the length of the project (or the portion selected to encode) which would enable the encoder to calculate the final output size given the encoding parameters."
--------------------------
snip>



This would seem to be the best solution as far as I can see.
Just doesn't seem as if it will ever happen!

Hopefully, once DVD authoring gets over its "infancy" period, the whole process will be made more user friendly.

Regards
Organism Seven




nolonemo wrote on 9/19/2002, 4:46 PM
I remember when all PC's could do was beep. I remember paying $500 for my first CDR (2x) and sound card. I remember being blown away when you could edit CD quality stereo sound on your computer. Now I'm editing video and burning DVDs. I can hardly wait to see what amazing thing is next!
SonyEPM wrote on 9/19/2002, 8:55 PM
With CBR it is pretty easy to predict how big the file is going to be (system bitrate/sec x sec). With VBR, since the encoder has no foreknowledge of what is in the frames it will be encoding, there's not much we could do except make an educated guess. If the entire timeline got sniffed first, you could determine the size of the file prior to encoding...but that would take awhile, so you might as well render.