When using a the [flv] shortcode to embed an MP3 file, I noticed progressive download was not working properly. Rather than starting playback after buffering a few seconds, playback wouldn't start until after the entire MP3 had been downloaded.
I did some troubleshooting with the JW Player's Setup Wizard and have isolated it to the use of the "image" flashvar. By default VVQ uses the URL of the MP3 as both the "file" and "image" flashvar.
If you remove the image flashvar, progressive download works as expected.
So I'm wondering if the next update could include a fix for this? Potentially checking the file extension and not including the image flashvar if it detects an MP3.