What is your frame rate?
If you select the layer your sound is in and check the properties panel is Sync set to Event or Stream?
If you remove the audio from the timeline does it play better? Does the audio itself studder or artifact while playing? Do you have other audio files you can import and try to see if you get the same results?
I've never had audio slow down an animation. The opposite is usually the case. The animation is extremely complex and the computer cannot keep up so the animation can skip and bog trying to keep frame rate.
frame rate: 24 fps
sound is set to stream, but I have tried it as Event with same results
If I remove the audio from the timeline it plays perfectly
I have not noticed any studder on the audio itself.
Right now I have only one mp3 in there to test ( 44 khz 16 bit 1.5 s 23.4 kb.) I would like to put a lot more in. I have tried a few different audio files, but they were all exported the same way through soundbooth.
I have tried using a .mov audio file with the same results
The animation doesn't slow down, it seems to speed up or skip frames, like you say. It doesn't do this consistently. I have seven movie clips, each on a frame in the timeline, set with actionscript 3 to play on random. Sometimes the movie clip plays perfectly, sometimes, it plays way too fast.
Thanks for your help!
Any chance this error might have anything to do with it?
Perhaps if you use any TLF text. What that dialog is telling you is that your SWF does not merge full TLF functionality into itself. It places a file, as it shows, textLayout_220.127.116.115.swz in the same path as where you publish and you'd need to upload that to your web server. It will be loaded by your SWF when it needs it.
To get rid of the dialog but slightly increase the file size of your SWF you can do this:
File->Publish Settings->Flash (.swf)
Inside here there are 2 drop-downs at the top. Next to the Script: ActionScript 3.0 dialog there is a wrench icon. Click that.
Now you want to select textLayout.swc in the Library path tab. Click the button above it. Uncheck to use the default shared library linkage. Change the Link Type drop-down to "Merged into code".
Now you won't see the error any longer but your SWF will get slightly larger (22kb?).
Do you have any example SWFs I can test to verify it speeds up or slows down? You can private message me if you don't want to link them here. I see no reason why a mp3 would slow down your animation but I don't know the animations complexity.
I'm on a dual quad xeon machine with 32gb ram. If you're on a laptop with built in (intel HD2-4 series, etc) graphics then it requires system resources to accelerate. Also what hardware acceleration setting are you using? Are you selecting None, Direct or GPU?
Like Sinious mentioned earlier, Frame Rates affect performance of your animation. When setting Frame Rates, its best to start from values equal to that of the number of frames you have created. And increase the value in steps based on the performance of your animation, repeatedly. See this article for more information: http://www.adobe.com/devnet/flash/learning_guide/animation/part02.html
Please let us know if you have further questions.
I have figured out a workaround, but I'm not sure why it works. For some reason, when I put my audio on the timeline, I get inconsistent (never slow, always too fast) playback. However, when I use actionscript to play my audio, everything works perfects. I have added the following code onto the frame where I want my sounds to play:
var audio:Sound = new Sound();
Timeline playback takes on the heavy burdeon of essentially wrapping the audio in a MovieClip (very heavy object) before it plays. ActionScript is almost always faster. However I can definitely tell you I've used audio in layers tens of thousands of times over the last decade and I never had this issue.
Either way, glad you found something that worked for you!