IS bitrate calculator off?

[jyeh74]

Everytime I put in my time(6 hrs 48 mins) in the bitrate at 192 kbit for sound, it gives me a bit rate (around 1300) to use in TMPGEnc. But when I use Nero to load that vob files (after conversion), it always goes over. I must then use DVD Shrink to shrink it and burn. Is bitrate calc a little off?

Should I just use a little less than what it suggests everytime?

Or maybe when in output setting in TMPGEnc, I should make output capacity 100%. Because when I use what bitrate tells me, it usually goes over 100%, like 105 or 108%. Then why would anyone use the bitrate calculator when you can just set capacity to 100% and not have to worry about bitrate since it adjust automatically????? thanks guys

[jman98]

You have to take bitrate calculations iwth a grain of salt. How big a grain of salt depends on several factors.
1) Are you encoding variable bit rate video or constant bit rate video? CBR encodes should come pretty close to the predicted output size. VBR is, by name, variable and a multitude of unpredictable factors can cause your video to come out larger or smaller than you intend. You can try narrowing the range between your maximum and minimum bit rates to keep VBR output close to the expected size. For example, for an average bit rate of 3000, I might set the minimum to 2000 and the maximum to 4000.
2) It also depends on what you encode with. Please note that TMPGenc (which is a good encoder) routinely laughs at your suggestions for bit rate and it will go higher than you want it to. These spikes that sometimes go higer than your expected maximum bit rate increase the size of your video because the bit rate is higher. This happens on both CBR and VBR encodes. CCE is a well behaved encoder and I have never had it spike above the maximum bit rate.

I always use a lower bit rate than predicted just in case. In your case, you have a lot of video to encode and it doesn't take much to go wrong for you to have too much. I'd try a bit rate of 1250 or 1260. You might even get away with 1270 or 1280, but you'll be pushing it at those rates and have a good chance of going over your target.

[jyeh74]

jman98,

I am encoding at CBR cause its faster. My question is why would I even use the bitrate calculator when I can just set the output capacity in TMPGEnc Xpress 3.0 to 100%
It automatically sets the bitrate for me.

Thanks!

[TBoneit]

Setting to 100% actually gives a safety margin on the encodes. I usually set it to 102% to 103% and they always fit for me. Caveat: I don't usually put more than 2 hours of video either. Maybe if I was adding as much as you then it would be different.

[jyeh74]

whats the bitrate calc do then if tmpgenc does it for u?

[manono]

I don't know what bitrate calculator you're using, but there's more involved than just figuring the audio and video bitrates. There's also muxing overhead involved, and there's a significant amount of space it requires. So, if you're not taking that into account, and if you're trying to fill the DVDR completely, then you're just about guaranteed to go over.

[lumis]

I always take 75-100 off the video bitrate, it will usually get me in the 4.2-4.3GB area.

[jyeh74]

This is the one I am using

https://www.videohelp.com/calc.htm

With audio bitrate of 192 kbit/s

[manono]

OK, that's a good calculator. The amount of overhead needed (I think) increases with the length of the video. If I were you, if you're going over by pretty much the same amount every time you do such long videos, I'd suggest going into Advanced Mode and changing that 25 MB to 100 MB or whatever it takes, and then refiguring the video bitrate. That 25 MB is meant for extra files, but can be used for overhead. You can see in the Advanced section that it's allowing a certain amount for the overhead, but evidently not near enough for your super-long videos, as the overhead amount doesn't change with the length of the video.

TBoneit's and lumis's suggestions are also good. I think it's better to be a bit undersized than have to go back and run an oversized video through Shrink afterwards.

[jyeh74]

can i just disregard using the calculator altogether and just set output capacity to like 95-100% in TMPGEnc? then i dont have to worry about bitrate cuz it will audjust according to the % i set.

[manono]

TBoneit gave his answer, but qualified it for the 2 hour videos he usually does. I don't use TMPGEnc, so I have nothing intelligent to say on the matter, except to agree with you to start at maybe 95% and then work your way up a little bit until you come up just short of filling up the DVDR.

[FulciLives]

When I use the VIDEOHELP.COM bitrate calculator I always change the default ISO size from 25MB to 200MB

That usually makes the final size come up "short" but "close enough"

Also I usually do the bitrate in 50 increments and round down.

For instance if it says 1340kbps I use 1300kbps

If it says 1380kbps I use 1350kbps

etc.

It's a good bitrate calculator you just can't try to cut things "too close" or you end up going over more often than not.

- John "FulciLives" Coleman

[TBoneit]

true I only do one movie per disc, they're cheap. But I can use the 100% setting TMPGEnc Xpress and still have room to add the TDA file saved when I save the project + Case art and descriptive text such as video description, stars etc. found via a Google search.

I should say that for movies I do one per disc, could be 80 minutes ro 2hour 30 minute long. For episodic discs I add until around the two hour running time, IOW five 23 Minute long after trimming 1/2 hour episodes. Then I put them into cases. I use cases that hold 1, 2, 3, 4, or 5 discs in standard width case. For longer I uses other cases that hold 6, 8, or 10 discs.

Never had the output files not fit on one DVD after creating with TDA and a 100% setting. I only go larger if I know I won't be adding to the authored disc. I go less than 100% if I plan on using a motion menu.