Bitrate v1
Calculator
What & Why
Bitrate is just that, a bit rate calculator.
Initially this was created because I often use an MP3 player, and often want to get as much music on it as possible. This means that I have to do one of two things, encode and hope all the tracks fit, or actually work out how many minutes of music my MP3 player can fit at a given bit rate.
Now, doing the calculations manually is not that difficult, but having something automate the process is much better, since it just saves me time which I can then use to actually encode the tracks.
How
How you use this calculator is very simple. All you need to do is input the bit rate that your encoding to, and then input the capacity of your media player in Mebibytes/Megabytes.
Caveat
Of course, given that this is the first version, there are a few notes that have to be attached to make sure that you know why something is wrong, and how to fix it and so on.
So, here's a list of some of the limitations so far
- The results assume a constant bit rate, this calculator will become very inaccurate with variable bit rate encoding, especially if the range between the selected lowest and highest bit rates is very large.
- The flash player check box is to make the calculation more accurate for high capacity (typically hard drive) media players. If the box is not ticked, then the number in the capacity box will be assumed to be a decimal number, in other words, 1000 bytes per kilobyte, 1000 kilobytes per megabyte, 1000 megabytes per gigabyte and so on.
If it is ticked, then the capacity will be assumed to be a binary number (or 1024 bytes per kibibyte, 1024 kibibytes per mebibyte and so on). - As such if entering hard drive media player capacities, make sure the flash player check box isn't checked, and, when entering the capacity of the player, multiply the number of Gb by 1000 (not 1024).
Notes
You'll notice that I have attempted to avoid saying things like 'MP3 player', or naming specific audio and video codecs on any part of this page, barring the 'What & Why' section.
That's because, regardless of the codec you're using, if you're encoding any audio or video at a constant bit rate, the file sizes will always be the same.
This means, if you encode a file at 128k in MP3 and AAC, you'll end up with the same file sizes (give or take a few kilobytes).
The myth is that, if you encode with AAC (or WMA, or OGG or whatever else you choose to encode at), you'll end up with smaller files when compared to MP3. This isn't true. What is true, however, is that AAC is a more efficient format. Which means that you can encode at a lower bit rate while having equivelent sound quality. In other words, a 96k AAC file probably sounds the same as a 128k MP3 file (of course your mileage may vary).
The same is true, of course, for video codecs. MPEG 4, for example is more efficient than MPEG 2 (as far as I am aware), however, if you encode a video file with the same settings, you'll end up with two files that have nearly indentical sizes. The whole point of the newer codecs is to be more efficient than the older ones, thus, allowing you to encode a video at a lower bit rate, while still having the same (or better) image quality.
And, of course, finally, if you encode a video file and an audio file, of equal length, at the same bit rates, you should, once again, end up with near indentical file sizes.
Download
Download source code. No documentation (save for what you see on this page).
Requirements - PHP 4, some knowledge of PHP capable web server software (for example, Apache) and some knowledge of PHP