How does the Flash/AS3 player read the length of mp3 files? - actionscript-3

Question

I have an AS3 music player built into an app that I'm putting together. It works perfectly with almost every file I've used, but there is one file that it stops early on. The file is roughly 56 seconds long, the player stops at about 44 seconds. I'm using trace to show the length, and for every other song the length is correct. In this case, trace shows roughly 44 seconds instead of 56. Here's the code I use to load the file:
length = 0;
request = new URLRequest(fileAddress);
track = new Sound();
track.load(request);
track.addEventListener(Event.COMPLETE, TrackLoaded);
And here's the TrackLoaded function:
private function TrackLoaded(e:Event):void{
length = track.length;
if (playWhenLoaded == true){
trackChannel = track.play(0);
trackChannel.addEventListener(Event.SOUND_COMPLETE, TrackFinishedPlaying);
playWhenLoaded = false;
}
Works perfectly with every other file. What am I missing?

Answer 1

Are you willing to host this 56 sec MP3 somewhere for download & analysis? Or if you can yourself check the header info via a Hexeditor. I suspect either of two things:
1) Header has incorrect time length embedded and Flash takes that as final duration and stops there. After all why read anymore remaining bytes? they could be just metadata not audio samples Besides what encoder would lie about true duration? So its accepted as final duration even if your ears know that its incorrect.
2) MP3 samplerate /bitrate issue: Consider what sample rate is this one problem MP3? Check the sample rate against of a working MP3. Also are these various found sounds or you made each yourself? I ask to confirm you put the same settings for each file yet this one does not work?
In anycase I think you could solve this particular MP3 by re-encoding it. Maybe save as WAV or AIFF first then take that new uncompressed audio and convert back to a MP3 with samplerate of 44100 khz + Stereo sound + Constant Bitrate (avoid Variable B.Rate like hell if you dont want issues)
Checking and fixing either of the above should get you are correctly parsed MP3. Hope it helps