Bitrate for 720p video : Question

[jpsdr]

I'm wondering...
Is level 4.0 enough for real (and not upscaled) 720p video ?
(1920x1080)/(1280x720)=2.25...
Max bitrate of level 4.0 is 24000, but it's more than 2.25.
Advantage of 4.0 is to avoid slices, wich, from what i've read, reduce a very few little quality, but, if there is no necessery to have max bitrate at 40000, and 24000 is largely enough, and don't see the point to stay in level 4.1, and so finaly, avoiding slice will produce a little gain, even if max bitrate is lower. And, i'm talking here of encoding a 720p video at average bitrate around 8Mb-10Mb...
So, those who are specialists, what do you think ?

[nurbs]

I encode 720p at CRF 21 (--preset veryslow --tune film) and the average bitrates I get are mostly around 3 Mbps. The highest I got was around 6 Mbps. 8 to 10 Mbps should be plenty for just about every source and a waste of space for many. :)
I use level 3.1 and didn't notice any problems with the maximum bitrate.

[shon3i]

if you avg bitrate is ~10mbs you can set vbv-maxrate to 10000 and you will probably get same result as level 4.0 or 4.1 restricitions. Level 4.0 will not hurt quality if bitrate is under maximum restricition. It's always better to stick avg bitrate to max bitrate than leave room, and make possible room for muxing overflows.

I use level 3.1 and didn't notice any problems with the maximum bitrate.I suppouse his target is Blu-Ray, 3.1 is not allowed for 720p

[7ekno]

Same, I encode 720p at CRF 19 (--preset veryslow --tune film) and the average bitrates I get are ~ 2.5 to 5 Mbps (no limit on Level, they are flagged Level 5.0 solely due to 16 reference frames, but play fine in decent media players!) with typical bitrate graphs looking like this (peaks between 20 - 25 Mbps):

http://users.on.net/~tekno/screenies/bitrate0029.png

7

[sneaker_ger]

if you avg bitrate is ~10mbs you can set vbv-maxrate to 10000 and you will probably get same result as level 4.0 or 4.1 restricitions. [...] It's always better to stick avg bitrate to max bitrate than leave room, and make possible room for muxing overflows.

You're advertising CBR encoding? I cannot concur. I'd only agree if it was the other way round: you can set your average to the maxrate (that you get from spec limit and audio/subtitle tracks + overhead) if it will still fit on the medium you're going to use.