Help In Creating 2.5 hour DVD!

beatnik wrote on 3/3/2004, 7:42 AM
Hi folks, I recently posted a message asking if anyone has burned more than
2 hours onto a DVD without any major quality loss. I have been trying to
render a video that is 2.5 hours long and it keeps rendering to around 5.1 gigs! I know I must get it down to around 4.5 or so to be able to create a DVD
using DVD-A. I am rendering to mpeg2, I have tried different bit rates to no
avail. I keep getting 5.1 to 5.2 gig files? What am I doing wrong and how can I fix this. It would be nice to have only 1 DVD and further editing is NOT an
option as this is a VHS to DVD conversion.

Thanks,

Alex

Comments

JohnnyRoy wrote on 3/3/2004, 7:58 AM
What bitrates did you try? I’ve gotten 2.5 hrs on a DVD using a max kbps of 5,000 and an average of 3,000 kbps. I think the average is the important one.

~jr
beatnik wrote on 3/3/2004, 8:12 AM
I have tried the constant bitrate of 4,000 kbs mpeg2 with
medium quality and still I get a file of 5.1 gig?
Chienworks wrote on 3/3/2004, 8:16 AM
Generally speaking, a VBR file at 3,000Kbps average will be about 3/4 the size or less of a CBR file at 4,000Kbps. For that matter, a CBR file at 3,000Kbps will be about 3/4 the size of 4,000Kbps too.
riredale wrote on 3/3/2004, 8:19 AM
I don't know the MainConcept MPEG2 encoder, so can't comment on how to set it. I do know, however, that you need a target bitrate of 600/150=4Mb/sec. Using .2Mb/sec for audio leaves you with 3.8Mb/sec as your average bitrate. With my encoder product I would set min=0, avg=3.8, max=8.

When you are this starved for bits, using CBR is the worst thing one could do. VBR allows the encoder to "look over" the whole project, and carefully allocate bitrate for those parts of the video that need it the most.
JohnnyRoy wrote on 3/3/2004, 8:24 AM
You want to use VBR to get better quality. Try the settings I suggested. This will allow the encoder to use 5000Kbps if it needs it for a scene with a lot of motion and steal from other scenes that don’t need it so the average is 3000Kbps. Chienworks calculations are correct. Your 5.1GB file at 4000Kbps x .75 (at 3000Kbps ave) will create a file around 3.8GB.

~jr
Zulqar-Cheema wrote on 3/3/2004, 8:32 AM
Just a thought, I know there is no editing but can you break the clips into smaller segments and code at different levels depending on the scene content.

for an example the speeches at a wedding can have a lower bit rate as the picture is fairly static, and the dancing a higher rate due to the extra movement.
JohnnyRoy wrote on 3/3/2004, 10:09 AM
> can you break the clips into smaller segments and code at different levels depending on the scene content.

Essentially, that’s what VBR already does. It determines which scenes need more bits to represent them and tries to meet your average objectives by giving more to some and taking away from others..

~jr
Jsnkc wrote on 3/3/2004, 10:34 AM
Go with a CBR of about 4Mbps, use AC3 audio and it should easily fit. You might even be able to get away with a 4.5Mbps rate. Don't even waste your time with VBR, it is basically useless unless your program offers 2-Pass VBR, even then it isn't the greatest unless you have a high end encoder card.
TheWoodsman wrote on 3/3/2004, 10:55 AM
Alex, are you bringing into DVDA a video which has already been rendered to mpeg format? If so, changing the bitrate within DVDA won't help. You need to go back to the captured or edited video and render to mpeg at a lower bitrate before importing to DVDA. Alternatively, you can render to AVI and then you can adjust the bitrate in DVDA to get an appropriate file size.
HarrieG wrote on 3/3/2004, 11:37 AM
If you need help in calculating the right bitrate for video and audio you might want to download the simple Excel calculator made by Fotis from www.sundancemediagroup.com
If you render a mpg movie of 2.5 hrs with video and audio in it, DVDA will rerender the audio and will amost certainly come up with much larger DVD-estimates than you would expect. If you render a movie of 2.5 hours best use AC3 audio. And render the video and audio in seperate files using the calculated bitrates. It should work out fine now.

Harrie
Rain Mooder wrote on 3/3/2004, 2:44 PM
I still recommend frame serving your video to TMPGenc and
doing a constant quality encode. If may take you three encodes
to find the right quality to get the right size but it will end up being
as good as a two pass VBR. I would start out with quality 80 and
some noise reduction, 9:1:6, and see how big the resulting file is.

There will be a massive difference between what the Mainconcept
will do on a 2.5 hour DVD and what TMPG on high quality will do.
Of course, it will take a lot longer to encode. Can't have everything.