3 Commando Brigade

Dxtory - Complete Guide to Basic Video Recording

Also remember to do this on your audio track. Some of your videos have really quiet sound. If you experience that after rendering do this.

This popcorn munching made me think...what are the numbers like for audio bit rates? Significant or not?
Don't know anything about this stuff, but here's some simple maths:

320kb/s - 128kb/s = 192kb/s

1 minute video = 60s
60s x 192kb/s = 11,520kb = 11.25Mb

So a 1 hour video could be 672Mb larger with 320kb/s audio rather than 128kb/s.
This ignores any compression that might be occurring?

I think he was actually referring to Megabits and not Megabytes.

Mb = Megabits
MB = Megabytes


So 672Mb / 8 = 84MB

Actually, I'm not sure about Apollo's maths (but I'm no Black Mesa scientist, so bear with me).



Shouldn't it be:
60 x 192kb/s = 11,520kb = 11.52Mb (not 11.25Mb)

So 1 hour would be:
60 x 11.52Mb = 691.2Mb (not 672Mb)

Into Megabytes
691.2Mb / 8 = 86.4MB

So a 1 hour video could be 691.2Mb (86.4MB) larger with 320kb/s audio rather than 128kb/s.


Someone correct me if I'm wrong.


Edit: My mistake: 11,520kb = 11.25Mb (as Apollo said)

I'm not too sure I understand why this is relevant. Maybe I'm just tired from studying all day

I think there may be confusion here between bits and bytes.

11,520 Kilobits = 11.25 Megabits (I was wrong earlier - it's 11.25 and not 11.52)

1 hour:
11.25 Megabits * 60 = 675 Megabits

Into Megabytes (8 bits per byte):
675 Megabits / 8 = 84.375 Megabytes

So the difference is still 84.375 Megabytes (MB).


Edit: In case you don't believe me:
https://www.google.co.uk/#q=11%2C520+Kilobits+to+Megabits
https://www.google.co.uk/#q=675+Megabits+into+Megabytes

Note that I wrote Mb rather than MB. But anyway, Jamie's right, it's kiloBITs not kiloBYTES, so to get megaBYTES we need to divide by 8.
Whether 84MB per hour is "significant" is open to debate.

Howl, I'm happy to admit that I know next to nothing about video codecs etc, so I'd like for you to explain why the simplistic maths which appears to show that changing audio bitrate has an effect on file size is wrong, as you seemed to indicate it shouldn't be relevant?
Please share your knowledge, inquiring minds wish to understand.

Lets not make this thread in to a 100 page argument over audio bitrate effecting file size.

Thanks Howl.
I see then that it's not an argument that audio bitrate doesn't affect file size as we agree that it does, but just over how "significant" it is (relative size on disk in comparison to the image part). I'm not sure I entirely agree with the logic to say that it's insignificant though - imagine you have space for 272GB, and not 273GB, then that 1GB of audio becomes more significant than it would seem. Anyway, that's just pedantic semantics.