TechNote (Archived)

Why do my looping sounds pause between loops?

Issue
A sound loop that plays continuously in loop editing software such as SoundEdit 16 or CoolEdit may not loop seamlessly during playback in a Flash movie. A gap may be heard between the beginning and the end of the loop.

Solution
Import sounds in a WAV or AIFF format rather than MP3, which produces this problem more frequently. Also, use Event sounds rather than Stream sounds.

Import as raw sound instead of MP3
Importing raw sound files (WAV format on Windows, AIFF on Macintosh) works better for looping, and should help to avoid gaps between sound endpoints. This does mean that you'll be importing larger sound files into Flash, but this affects the FLA only. In the final SWF, you can still export the sound in MP3 format without any loop problems. If you do not have access to the raw sound from which the MP3 was produced, there are many sound editing programs that convert between formats, and allow you to adjust endpoints for smoother looping. Some are available as shareware; check your favorite shareware site or search engine for more information.

Set the sound's synch to Event
There are two synchronization options for playback of sound in Flash, Event and Stream. When a sound's Sync property is set to Stream, Flash breaks the sound into discrete "chunks" that are mapped to consecutive frames of the Timeline containing the sound. This kind of synchronization is not conducive to accurate sound loops, where a few milliseconds can make a tremendous difference. Streaming sounds contained in a looping Timeline cannot be guaranteed to match endpoints and loop seamlessly..

When a sound's Sync property is set to Event, it is decoded all at once and sent to the sound card. Seamless looping works much better when the sound's synch property is set to Event.