Better buffering and playback

[rylleman]

It should include audio if you have a soundtrack attached, and MP3 shouldn't be a problem.

I just did some tests (both with mp3 and wav) and it turns out that the audio only gets rendered if you start with the first frame of audio (which always is frame 1, right?), so with an audiotrack spannig 25 frames you can render frames 1-25, 1-10 or any other range starting with #1 but not frames 2-25, 10-20 or anything else you chose not starting with #1.

[Lost Marble]

Hmm, that could very well be true. I'll have to look into it...