What is the average bitrate (9200 MAX)

[jyeh74]

I am trying to convert mpg to a dvd compliant video.

What is the image resolution for TMPGEnc Xpress? When I try to burn a mpg file of 55 mb at 720 X 480 (highest resolution) it becomes an output 377 mb. That is 6.8 times the original. I remember when I used DivxtoDVD it was 120 mb (about twice the size) Here are the other options"

704 X 480
352 X 480
352 X 240

Even if I change the resolution to 352 X 240, it still stay the same at 377 mb output.

I then noticed that the "average bit rate" is at max of 9200 - "used at 7.52% of capacity" If I lower the average bitrate, the the output of 377 mb DECREASES. As I decrease the average bit rate, the % capacity also decreases. Can you educate me on this? What is average?? I think it its says about 25-29 frames per sceond for this mpg, but not sure of average bit rate.

Also, the aspect ratio was set at Pixel 12:11 (PAL 4:3) Will it not run on my USA dvd player since I think it should be Pixel 10:11 (NTSC 4:3)? What happens if I leave it on PAL??? wil it not play?

[daamon]

When I try to burn a mpg file of 55 mb at 720 X 480 (highest resolution) it becomes an output 377 mb. That is 6.8 times the original. I remember when I used DivxtoDVD it was 120 mb (about twice the size) Here are the other options"

704 X 480
352 X 480
352 X 240

Even if I change the resolution to 352 X 240, it still stay the same at 377 mb output.

The output file size from any type of (re)encoding is only dependent on two things: the bitrate and the running time of the footage. Put simply, bitrate x running time = filesize

So it doesn't matter what resolution you choose, if the running time is the same (which it will be for the same clip) and the bitrate is the same (which it sounds like it was) you'll always get the same filesize (or there abouts).

I then noticed that the "average bit rate" is at max of 9200 - "used at 7.52% of capacity" If I lower the average bitrate, the the output of 377 mb DECREASES.

Based on what I've put above, this is explained.

As I decrease the average bit rate, the % capacity also decreases. Can you educate me on this? What is average??

I'm not familiar with TMPGEnc Express, I use the slightly older TMPGEnc Plus v2.5, so I can't comment on the "% capacity" you're referring to. As for "what is average", well it's easier for you to read up on "VBR encoding" (look up Rate Control Mode 2-Pass VBR, and do a search of the forums) and see what the average bitrate is used in that.

Also, the aspect ratio was set at Pixel 12:11 (PAL 4:3) Will it not run on my USA dvd player since I think it should be Pixel 10:11 (NTSC 4:3)? What happens if I leave it on PAL??? wil it not play?

The general consensus is that PAL encoded footage is unlikely to play on NTSC machines.

Hope that helps...

[jimmalenko]

http://members.dodo.net.au/~jimmalenko/AVI2DVD.htm

Read it.

Do only what it tells you to do - nothing more, nothing less.

Do everything it tells you to do.

[jyeh74]

jimmalenko,

There is no autodetect on average bitrate? The lower the bitrate (thus the longer the clips) does that necessarily mean the lower the quality? How do I know at what point do I reach a bare minimum where I am reducing quality. In other words, how do I know if I should encode and burn 100 mpgs on one dvd-r at say 2000 average bitrate or split it into two dvd-r at 4000 average bitrate EACH?

[drjtech]

All else being equal lowering the bitrate does reduce quality.

To determine at what point your particular video crosses the threshold of unacceptable quality loss the best instrument is your own eyes.

-drj

[jyeh74]

drjtech,

Well, I would hope that before I spend hours encoding and then burning, I would be able to know what my output is. Plus I am limited on time so I dont have the flexiblity to play around. Any other suggestions?

[jman98]

I suggest rather than using TMPGenc Xpress, which I assume is making everything so easy for you that you don't really understand what it is doing, that you use plain old TMPGenc and do this manually. Try setting an average bit rate of 6500, a low of about 4000 and a high of 9000, 3 passes, and hopefully you will end up with a nice looking final product. Please note that everything you encode will end up larger than the source unless you use a really low bit rate and don't care about the quality.

PAL may or may not play on any given NTSC DVD player. Many players can convert PAL to NTSC on the fly, but not all. I would not recommend converting the video from PAL to NTSC in TMPGenc. Usually the final results are not good.

[junkmalle]

Don't worry about bitrates. Use TMPGENC is single pass Constant Quality mode. Select the quality you like and encode. It's faster (single pass vs 2 passess) and every frame of every video will use only the bitrate necessary to get the quality you specify.

Try quality settings in the 70 to 90 range to see what you like. You only need to encode short segments for testing.

The drawback of course is that you don't know how big the file will turn out.

[daamon]

In a PM to me, posted here so that all can see the question(s) and answer(s):

What I am trying to do is encode and burn my mpg music videos onto a dvd-r. My problem is that I used DivxtoDVD, very easy, but it doesnt tell you about the quality. It kinda just encodes nad burns it for you. So using this freeware, how do I know if the resulting output is gonna be 3 gigs or over my 4.7 gig (dvd-r) capacity? I dont know until the end.

So I downloaded TMPGEnc but was confused on the average bitrate. Now I dont know when I should split up my files and burn them onto two separate dvd-r or do them all on one. Will I be sacrificing quality? I mean, they arent that great to begin with. how can I tell if I should encode and burn (for example) 100 mpg @ 2000 average bit rate or do 50 mpgs @ 4000 average bit rate on TWO separate dvd-rs?? Assuming the total time is cut in exactly half on each dvd-r? How do I know at what point will I be sacrificing quality? DivxtoDVD doesnt tell me that...does it?

Use GSpot (the beta v2.52) to get details of your MPEG files and post a screen shot here of a representative file. It's hard to advise on bitrates and resolutions when we don't know the probable quality of the source.

The MPEG files may already be DVD compliant. You might be lucky...

As a rough guide, good quality sources can be encoded to MPEG2 at full D1 resolution (720 x 480 / 576 for NTSC / PAL) at a bitrate of, typically, not less than 5,000kbps. The bitrate is either for CBR, or the average for VBR.

Whereas poorer quality sources can be encoded at half-D1 resolution (352 x 480 / 576) at a bitrate of around 3,000 - 4,000kbps.

You can even encode to a resolution of 352 x 240 / 288 (same as VCDs) - but I've never done this so can't comment on suitable bitrates.

The idea of going to lower resolutions is twofold:

1) A lower resolution softens the image, and so masks (to a degree) the lower quality of the source.

2) You don't need as high a bitrate for lower resolutions, meaning that you can use relatively high bitrates (for that resolution) and so hope to address quality issues, without exceeding the max limit for DVDs.

Why have I told you this? Well, when you get the info on your source files, you can judge how close they are to one of the above and encode accordingly. Unfortunately, the ultimate decision on bitrate and resolution is with you as you are the only one who can see the outcome and judge how acceptable it is. This, by default, requires you to experiment a little...

The thing to remember is GIGO: Garbage In, Garbage Out. You will never make anything better than it's source - you can only hope, at best, to make it appear to look as good.

Try setting an average bit rate of 6500, a low of about 4000 and a high of 9000, 3 passes

Where did you get those figures from? The settings are dependent on the quality of the source - you need to know the source details before you can recommend settings.

Also, a min of 4,000 is way too high - a min of 1,000 is much more like it. Why? Because VBR works by allocating bitrate according to what's needed whilst maintaining an overall average (that's why a Max, Min and Average are set).

If a scene doesn't need much, it will go down towards, and as low as, the Min value. Likewise, if a scene needs a lot of bitrate, it will go up towards, and as high as, the maximum.

Now, if it is trying to maintain an average (as it is), having too big a figure for the Min means the encoder can't go as low as what it might get away with, meaning that more bitrate is used than necessary and therefore, because it's aiming for an average, less bitrate is available for scenes that require higher bitrates.

In essence, setting the Min too high is overkill for low bitrate scenes and throttling the encoder on high bitrate scenes.

On top of this, 3-pass VBR could well be unnecessary - not to mention time consuming. Most often, 2-pass VBR is sufficient.

@ jyeh74: I agree with junkmalle's suggestion - try CQ mode. Follow his recommendations on settings, as I', not that familiar with it. However, here are the benefits:

1) Gives a constan quality output.
2) One pass, so isn't time consuming.

The downside is that, as mentioned, you won't know the file size. But I'd say to encode using CQ and fit as many as you can on a DVD, and use as many DVDs as needed.

Phew! There - done. I hope that helps...