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| Introducing the variable bit-rate calculator for Mac OS X : Download
VBRcalc produces estimated file size and bit-rates for variable bit-rate encoded QuickTime movies. |
| Calculate, or frustrate Whilst constant bit-rate quicktime movies can have their total file size and bit rates calculated accurately, they do not produce the best quality results. Variable bit-rate encoding often produces much higher quality results. However, anyone who is experienced with this process knows the inherent problem with it: unpredictability. It is very difficult (almost impossible) to calculate the resultant file size. |
With some encoders (e.g. 3ivx MPEG4 constant quality setting), it can also be very difficult to establish the average bit-rate. The traditional solution is to complete the encoding (often taking many hours or days) only to find that the results are unusable. VBRcalc was designed to do one thing, estimate the results early on in the encoding process, so that you can terminate the encoding and adjust your settings. VBRcalc will save many wasted hours. |
| Quick Guide Whilst a Quicktime movie is being encoded, percentage complete and current file sizes should be noted from within encoding application and Mac OS X Finder. Enter the total movie length in minutes and the VBRcalc will give estimated results to allow you to stop the encoding process and re-adjust your encoding settings. |
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Instructions (VBR) 2, After starting the encoding process in the application of your choice (we recommend OpenShiiva). Open the Finder window that contains the output file so that the file can be clicked and a file size discovered. 3, Wait for the encoding process to complete some of the encoding, for example 10%. Click the file in the finder so that the file size is updated and make a note of the file size. Or use "Get Info" from the file menu if the finder window is not in list view, for example 130MB. 4, With the VBRcalc running, enter the current file size, percentage completed and total movie length in the appropriate fields. You can use the tab key to move to the next field, or just click in the appropriate field. 5, Press the return key or click the "Calculate" button. The bottom two fields in VBRcalc will then show the results. If the target file size is too high (e.g. 725MB) and thus would not fit onto a CD-ROM, you can immediately stop the encoding process and adjust your settings without waiting for the entire process to finish and wasting many hours of your time. Or, if the bit rate is too low for the quality you were trying to achieve, again, you can stop the process and re-adjust your encoder settings. Note: The higher the percentage entered, the more accurate VBRcalc's estimates are. |
Instructions (CBR) 1, Enter your desired file size 2, Enter 100% into the completed field 3, Enter your source movies length in minutes into the Length field 4, Click the Calculate button or press return. The Data-Rate (KB/s) field shows you the required data-rate. i.e. To fit an 83min movie into 700MB will require a target data-rate (audio and video) of 143.94 KB per second. You can now test your encoding to see if that data-rate will give you the required quality. Allowing you for example, to adjust your frame size to meet the desired quality etc. |
| Payment VBRcalc has no locks or time-outs so you can use it intensively, for as long as you like. We would appreciate a payment for VBRcalc if you use it productively. Please donate what you think the VBRcalc is worth, or $5 (£2.60) for domestic use and $20 (£10.40) for comercial use. ITY Software development is self funded and receives no external funding. Many thanks. |
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Copyright 2003-2005 Ian Thompson-Yates, All Rights Reserved
In the Future™ is a trademark of Ian Thompson-Yates
QuickTime™ is a trademark of Apple Computer, inc.
ITY™ is a trademark of Ian Thompson-Yates
Last modified 4 Jan 2005
