lost synchronisation with mp3 and LD showtime

A

Alwin

Member
Hi fellow LD users,

Currently I'm working on a lasershow with Pangolin LD2000 version 3.50

The show has a duration of about 6 minutes (!) of length and the music is played with the internal multi media player of LD2000.
The soundfile is one with mp3 format., (system is a Pentium 733Mhz running win2000.) Also: the entire show consist only of a single scene.

However, the problem i've encountered is that when I enable the audioscrolling feature and I place frames on the timelime according to
the music I hear, the result is that the frames are not in sync when the entire show is played. It becomes worse and worse when approaching the end of the show.

An other symptom occurs when I've placed the beatmarks through the entire song, and then placed the frames properly aligned with the beatmarks.
When I now play only the last part of the show (play user time) the frames have lost completely sync with the music. This loss of syncromisation becomes worse the further my ctrl-B (user time staring point) is approaches the end of the song. When I play the entire song (play ALL), the beatmarks and frames are perfect in sync again.

I haven't had such an experience when I''d used a .wav file as autio yet.

The conclusion I've drawn is that the multimedia player calulates wrong time offset when the file is an mp3 and when playing not the entire show from start, but somewhere in the middle of the song.

Maybe the problem is whithin the mp3 codec or something else. I don't know that, but I hope somebody can help me in trying to tackle this problem..

Did someone experienced the same thing??


regards
Alwin
 
Alwin,

Yes MP3s have slightly variable playback speed, so they can drift up to 1/4 second per minute that you're playing. Therefore, if you play an entire song, you might easily be off by a second or two by the time you get to the end. The easiest solution to this is to convert the MP3 to a Wav file, which will remain perfectly synced. This has the added advantage that LD will display the waveform for the song above the tracks, making it easier to choreograph.

Best of luck,

David
 
Hi,

Thanks for the response.

I've converted the music into wav and indeed it solved the problem.

I've posted this topic to inform all you other users about the problem,
Maybe William and his team can give any comments just to be sure it's not LD2000 bug within the media player.

regards,
Alwin
 
Actually, I recently found a bug which may be causing this problem. The solution is includes as part of the 4.0 BETA which is now in testing. Send me an email to request this BETA and I would be interested in hearing if this solves your problem.

Bill
 
Hello Bill,

i have a show which has the same problems with mp3-playback. Playing with .wav works fine.
The problem still exists with the 4.0 beta-release.

Greetings,

Winfried
 
Hi again,

I guess there no solution for the problem yet, since I've seen no postings about it on this forum.
Bill, are you still working on it?

regards,
Alwin
Alwin
 
I believe that the latest version of LD2000 is much better with respect to synchronization. A few people have sent me MP3 files and shows, but due to being out of the office exhibiting at trade shows, I have not yet had a chance to review them and compare them.

I have heard, and it seems plausible that, the timing of MP3 files is not precise. It could be that this is the case and if so, then the solution would be to always use the original music in CD or WAV format, or to re-time the show as needed for MP3 playback.

More later...

Bill
 
Just as a follow-up, I tested the latest version of LD2000 (version 3.59) with several shows that were sent to me by users who were complaining about loss of synchronization. The average time tracking error between Showtime and the music never got above 12 milliseconds when not using the Preview Window, and never got above 18 milliseconds when using the Preview Window. Our earlier studies have shown that the time tracking error would have to be on the order of 125 milliseconds before it became perceptible, so clearly our system is tracking the music very closely.

While looking into a problem with our CD2000, we did find a problem with this tracking in August 2005, and this problem would likely affect all versions of software from 3.58 and earlier. The latest version (currently 3.59) is certainly the best we have ever created in terms of time tracking.

Also while looking into this, we found a problem with "drop outs" when using our TC2000 timecode device. In the past, a few customers had reported "drop outs" when using the TC2000, but the problem had always been blamed on incorrect audio level feeding the TC2000. During the investigation into this, we found the cause of this problem and the solution.

Bottom line, although the problems were obscure and rarely seen, LD2000 version 3.59 and later will solve any timing related problems that have ever been seen.

Best regards,

William Benner
 
We also noticed a problem with this but it was not such a big problem as just a minor anoyance. Sometimes when designing shows my chief designer shows me a demo of a clients show, I say hey the show is not syncronised. Actually it is but windows adds some problems. We find that when only previewing a show without a laser present we have some delays which change according to the audio source even WAV, when the laser is present the delays arnt there. Not sure if this helps but thought to say. We find designing a show with a laser prsent is very accurate and the pangolin system is excellent.
 
Hi All,

You should try Showtime version 4.10. I did some more testing regarding synchronization recently for an unrelated reason. Tracking was quite good. I even injected errors just to see how the system would react. It reacted correctly...

So if there really are problems, unfortunately we can't see them in our testing at Pangolin. If someone has something that is absolutely reproducible, please send us the frame file, show file, and music file along with full instructions of what we must do to see the problems for ourselves. If we see the problem, we can fix it!!

Bill
 
The problem with sync lost is not very noticable with standard .mp3 files (CBR - constant bit rate).
But when using VBR - variable bit rate songs, showtime just can't sync with them. There could be up to one minute delay between them.

So, my recomendation to all users is, to use .WAV files.. :N

Aljaz.
 
Hi Aly,

I am not sure that this is the case... I mean, right now sitting here, I just don't believe it. Please send me a variable bit rate file that you are having trouble with and we will check it out. The problem could actually be something specific to your computer.

Best regards,

William Benner
 
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