One last time: MP4 bitrate calculator?

[Steven L. gotz]

A bit rate calculator is a bit rate calculator. The data rate time the number of seconds is your file size. The problem comes into play when the data rate is variable. How would it be possible to determine in advance how tightly the video can be compressed?

So they are inaccurate. A little practice out to get you the experience you need to avoid the need for a calculator, no?

Steven

https://www.stevengotz.com

[Mike Velte]

With a little use of Windows Calculator you can calculate any bitrate.
The basics are;
1. The size of video files sitting on your hard drive or this upload limit you have in question are measured in kilobytes, megabytes and gigabytes. Emphasizing BYTES.

2. The amount of data in one second of video or audio (or both) is measured in kilobits or megabits. Emphasize BITS.

3. 8 bits equals 1 byte.
4. Kilo=1,000 Mega=1,000,000

Note; bitrate is expressed as mbps megabits per second) or kbps (kilbits per second). Example; a good DVD bitrate might be 7 mbps or 7000 kbps (both are the same).

Ok, now for real life calculations. Your limit of 500 megabytes weekly involves plugging in one of 2 unknown values- the length of video in seconds OR the amount of data per second.

Lets begin with the unknown bitrate and plug it in as 500 kbps (which is ok for folks on a cable connection and half resolution-480×360). At some point in any of these calculation one must convert bits to bytes. 500 kilobits equals 62 kilobytes.

500 megabytes (500,000,000) (your limit) divided by 62 kilobytes (62,000) equals 8064 seconds OR/134 minutes.

So we can say if your total bitrate (video+audio) is 500 kbps, your 500 megabyte limit equals 134 minutes.

Now it does not make much sense to plug in duration as the unknown because the longer duration is, the lower the bitrate is and I guess you would like to have decent looking video.

In conclusion and in general, a good place to start is 500 kbps= 134 minutes. Twice that (1000 kbps) would be good for full resolution video and audio and half of 134 minutes.

[Tim Kolb]

While all the input you’re getting here is correct, keep in mind that in most MP4 applications of a non-realtime video encode, the bitrate is dependent on content as the bitrate is variable. More movement…more detail…higher bitrate, and that’s from instance to instance.

Using the max bitrate to control filesize works, but it can be tough to maximize quality. I personally find that CS3’s elaborate array of tweakable settings in the video encoder is a really good way to get yourself into trouble. I’ve experienced instances where I’ve raised the bitrate on H.264 encodes, and the results fell apart (?!?).

QT Pro ends up my H.264 encoding tool of choice many days when I tire of wallowing through the settings in CS3’s media encoder. It’s more of a pain as I need to export a timeline to a “master quality” (read:large) clip to then place in QT Pro, but the results are fairly dependable.

TimK,
Director, Consultant
Kolb Productions,

CPO, Digieffects

[Mike Velte]

While I agree that controlling quality with H264 and 2 pass VBR can be daunting, your “target bitrate” determines the resulting file size. The Target bitrate plus audio can be used to accurately predict the size of the resulting file.
Having too low of a Maximum Bitrate can result in pixelated high motion scenes and too high can result in poor low motion scenes.

[Dane Frederiksen]

I feel your pain! I’ve had poor results exporting 1280 x 720 29.97 MP4 H.264 with a bit rate under 5000kbps. Blocking, artifacts, etc…

I’m sure there is a way to optimize and get good results at lower bit rates and am looking into “episode” from Telestream. It looks like it may be a good solution if only I knew how to orchestrate all the variables. Does anyone know a good primer for optimizing H.264 low bit rate encoding?

[Tim Kolb]

Like I said, I’ve found the simplest is QT Pro…at 30 bucks, it’s the cheapest transcoding tool out there. The low bitrate default settings seem to work very well…

TimK,
Director, Consultant
Kolb Productions,

CPO, Digieffects

[Perry Cheng]

All,
Thanks for your input. I just wished someone out there made a table or calculator like that is more accurate. WEll, back to basic math then. Thanks again.

Sincerely,
Perry

[Paul Blonde]

Maybe for a Mac, but SUPER (Simplified Universal Player Encoder & Renderer) is free, and it does an awesome job. You have to decide your own bitrate, however, if you don’t like the default. Runs tolerably well in a Windows VM on RedHat Linux, so it should perform similarly on a Mac.