15 Replies Latest reply on Dec 18, 2009 3:04 PM by robodog1

# Determining File Size

Is there a way to determine the file size of your video sequence BEFORE exporting/rendering?  It seems like there would or should be, but I've only been able to determine this once the video is exported, which means I have to wait for it to render, and then if it's over 2 GB (for YouTube), I have to import the video back in and edit/shorten it, even though it was already under 10 minutes to begin with!  Any help/advice is greatly appreciated!  Thanks!

• ###### 1. Re: Determining File Size

Bit rate is the single most important factor in determining file size. Bit rate is expressed in terms of amount ("bits") over time, for example 500kbps (500 kilobits per second) or 3Mbps (3 megabits per second). Since you're dealing with binary digits, the match gets a little funky, but here's how I generally roll:

bit rate (in kbps) / 8 X duration in seconds = filesize (in KB) / 1024 = filesize in MB

• ###### 2. Re: Determining File Size

Colin,

That's an 8 bit byte ?  Are all video formats 8 bit bytes when rendered - created ?

Rod

P.S.

I made this excel spreadsheet years ago for dead reckoning sailing... it's to calculate distance, time, speed..  and the "time" conversion gives you hours minutes seconds...any combination...  Put in 25 minutes and 50 seconds, and it will tell you how many seconds that is...

http://rodneybauer.com/whiteboard3.htm

• ###### 3. Re: Determining File Size

Yes, more or less. Bit rate is expressed as the amount of bits per unit of time--not bytes. So, 500kbps is 500 kilobits per second, not 500 kilobytes per second. To get to bytes (and so on), the first step is to divide by 8 (the number of bits in a byte). In our example above, 500kbps is actually 62.5Kbps. You'd do the same (divide by 8) to go from megabits to megabytes.

• ###### 4. Re: Determining File Size

The Media Encoder gives an approximation of file size for your export settings.

The preset I have for YouTube encodes is surprisingly accurate.

• ###### 5. Re: Determining File Size

If you use the Youtube preset in AME, it will size it correctly for you and be well under the 2G You tube limit for a 10 min clip.

fyi; Just exported a 10 min clip to the youtube SD widescreen preset.  It estimated a file size of 238M.  Actual file size was 244M.

• ###### 6. Re: Determining File Size

I'm thoroughly confused. Why 8 bits per byte and not 16 or 32, 64 ??  In which case " megabytes" would be very different (for the same bitstream amount) the more bits per byte.

I understand that the bit rate is important as it stands to reason the more bits going somewhere faster would mean more data faster...  but I honestly haven't got this figured out with video.

Does the 8 bits per byte have to do with how the transmission of video is handled with RGB channels ??

Rod

• ###### 7. Re: Determining File Size

Counting in binary is just like counting in decimal if you are all thumbs.

• ###### 8. Re: Determining File Size

There are 10 kinds of people in the world; those who understand binary and those who don't.

• ###### 9. Re: Determining File Size

No Jeff, there a only three kinds of people:

1. Those who make things happen,

2. Those who watch things happen, and

3. Those who wonder what happened.

• ###### 10. Re: Determining File Size

What just happened?

• ###### 12. Re: Determining File Size

ROFL....

Wow, all these years I thought bytes were becoming larger !   what a jerk !

When there was the 8 bit cpu and 8 bit memory, I thought there was like a silicon piece of material that could hold 8 'registers'....a physical thing that could hold an electric charge, or not....being "on" or "off"......and that way could be interpreted by programs as "yes or no" and so on.

Being binary I know the first register (usually depicted visually on the right side of 8 places) is 1, 2, 4, 8, 16 and so on....to eight places.

This I thought was a physical thing...like a transistor that is silicon based (maybe germanium doped) object....

So I figured, this physical thing as 8 bits ( per byte ) got BIGGER when it became 16 bits !!  hahaha, what an idiot I am...

I thought the physical object (the material in the cpu and the material in the memory chip) now could hold 16 registers and that it would now constitute a 16 bit byte !   Duh....

Instead, now that I've been reading up on this stuff, I find that there are "octets" with memory (same as 8 bit byte) that are addressed in order to use more registers than the original 8 that I was familiar with when I was younger.  So all these years, thinking about 8 bit, 16 bit, 32 bit graphics and the number of colors that can be represented, I thought was really the hardware (chips) being able to hold all those registers as a BYTE....  and not thinking it was in fact (for 32 bits) 4 bytes strung together sorta...(though I don't know how this happens exactly it apparently has to do with memory addresses or something)

Thanks a lot for explaining this simple thing to me because I really did think that the bits on the chip determined the size of the BYTE....

Like, a 32 bit cpu was now the "new" byte size ....

My total confusion about this is why I couldn't understand only 8 bits were being used to describe a byte. Thinking a new computer with a 64 bit cpu was still an 8 bit per byte machine...(in my warped way of thinking 64 bits was the new byte size) LOL....  All this would certainly have an effect on the math above, but luckily science can proceed without my having to understand it all.

That said, I have to admit I've learned even more than I expected...about 8 bits per RGB channel plus maybe one 8 bit alpha channel, and all kinds of other stuff which is still on my list of "things to figure out"

Thanks again

Rod

and talking about byte size....it's time to eat lunch !

Rod

• ###### 13. Re: Determining File Size

and talking about byte size....it's time to eat lunch !

and I always thought it was spelled BITE...

Experience is that marvelous thing that enables you to recognize a mistake when you make it again.

• ###### 14. Re: Determining File Size

Seen at a computer swap meet - t-shirt with "Byte Me" emblazoned on it.

Hunt

• ###### 15. Re: Determining File Size

haha...geez...I still can't believe I made that presumption... of different sized "bytes" depending on 8, 16, 32 bit systems...

And....talking about bytes .....(yes, that would be a great T-Shirt ! )....I just got my newsletter today...and guess what ??  More BITES...(written by yours truly I am proud to say....)