shinywhitebox docs

• Contents

Registration Issues

Troubleshooting Audio

What's Soundflower?

iShowU & Logic

Audio solutions for ProTools

Reinstalling Soundflower

Application Audio Levels

Shortcuts not working

Undesired Capture Results

My capture looks jerky

Capture is fuzzy

Watermark still showing

I see a thin black rectangle. What is it?

3vix Trial Still Showing

Removing the mouse

Checkerboard Pattern with Lion

Variable Frame Durations

Tips & Tricks

Why is port 8000 in use?

The Issue

Variable frame durations occur as a result of realtime capture on preemptive multitasking computers, such as your Mac.

In essence, it isn't possible to guarantee an exact timing between frames. This happens for all kinds of technical reasons that we won't go into in this document.  

The result is better shown visually.  The first (topmost) image shows frames landing perfectly on frame boundaries. The lower image shows what happens in realtime capture, where you have frames occuring close to, but not exactly on, frame boundaries. It also shows that it is possible to skip entire frames.

Most of the time, if the frame durations are "close enough" then visually we don't see this occuring. There is however one application that "throws a wobbly" when encountering variable frames. Enter: Final Cut Pro (not FCPX.  FCPX is quite happy to take in most any digital footage).

Final Cut - Solutions

1. Disable "Variable Frame Durations" and then reduce the load on the machine such that you get a reasonable real-time recording rate with iShowU HD Pro.  Reduction of load takes many forms: Switching codecs to Apple Intermedia or JPEG (10.6/10.7 respectively), lowering the capture resolution, or using a faster machine.
2. Record using your codec of choice, but re-encode the footage later (which can be done in iShowU HD Pro by right clicking the movie and choosing "Fix Frame Durations").

Note that on Lion - number (2) occurs automatically if you disable variable frame durations. That is to say that when you record using Lion you are always recording using variable frame durations.  After recording is complete, iShowU HD Pro will automatically run the "fix frames" process on the video.

Which solution you take is dependent upon your situation. If you have sufficient CPU resources you may be able to achieve reasonable rates using Option 1. In most cases however; you're better to choose Option 2 and re-encode later. In general Option 2, while it introduces another step in the workflow produces smoother captures.

In cases where you are using a slower machine (Core2Duo) or are recording CPU, Disk or OpenGL intensive applications, you will almost certainly have to choose Option 2.