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Audio sync problem, but only when streaming!

G

GanChan

macrumors 6502a
Original poster
I made some long (over 90-minute) Final cut programs into Quicktime movies. The .mov files play perfectly in sync throughout when I play them directly off a computer's hard drive. But when our web guru tried to stream them from our server, he found that the audio drifts out of sync.

Just to recap:

Final cut Pro - program stays in sync.
Quicktime file playing on hard drive: - program stays in sync
Streamed from server - begins in sync, then drifts out of sync!

What kind of troubleshooting should we do to isolate the problem? If the trouble only occurs when streaming, then is the server to blame?

the QT movies are Sorensen 3, keyframe every 300 frames, 15 frames per second, with audio RMA 4:1, 32 kHz 16-bit mono. Any advice appreciated.
 
Sorry, can't help, but I can sympathize. We have been trying (on and off) to troubleshoot the same problem for a few years. Have a Helix streaming server, should handle QT but our sync drifts as well. Not so bad after even 20-30 minutes, but very noticeable around 50-60 mins (at 320 x 240).

Of course, no such problems with streaming RealMedia files.

FWIW, I watched an archive of a professionally-produced webcast recently using Flash player on the Mac, and it had a similar problem.

Good luck, and I'll be watching this thread.
 
2jaded2care said:
Sorry, can't help, but I can sympathize. We have been trying (on and off) to troubleshoot the same problem for a few years. Have a Helix streaming server, should handle QT but our sync drifts as well. Not so bad after even 20-30 minutes, but very noticeable around 50-60 mins (at 320 x 240).

Of course, no such problems with streaming RealMedia files.

FWIW, I watched an archive of a professionally-produced webcast recently using Flash player on the Mac, and it had a similar problem.

Good luck, and I'll be watching this thread.
Click to expand...

Thanks. So, do your QT files stay in sync during non-streaming playback, like ours?...I wonder if I can convert these videos to RealMedia....I may have to.
 
In my experience (mainly with Flash), there are often sync problems because of the NTSC frame rate of 29.97 being encoded into 30fps or frame rate divisible of 30, like yours of 15fps. When that happens, you can see a drifting out of sync in longer pieces.

Don't know if this would be applicable in your case (especially because the local file runs fine), but you might want to try to encode at a different frame rate to see what happens.
 
Yes, the QTs stay in sync when played from the hard drive.

We used MPEG4 video and audio (AAC) codecs, so I don't think your codecs are related to the problem.

I seem to recall some problem exporting RealMedia files from iMovie, was very slow and I think there were sync problems right off the bat. Hopefully you don't have any problems. I've had to use cleaner.

I think we are going to try *gasp* Windows Media next. RealPlayer on the Mac is OK, but seems to be problematic on PCs -- keeps trying to take over as the default player, etc. Plus, hate to say it but Windows Media looks really good, and there is a player for OS X...
 
Has this issue been resolved?

I’m running into a similar situation. My 90-minute presentation is fine if run locally, but if I stream it with QTSS (Tiger) the audio drifts out-of-sync with the video.

I exported out of iMovieHD 6.0.1 using the following:

File Format: MP4

Video Format: H.264
Data Rate: 1024 kbits/sec
Optimized for: Download
Image Size: Custom 640 x 360
Frame Rate: 30
Key Frame: Every 24 frames
Options: Restrict Profiles to: Main
Encoding Mode: Best Quality (Multi-pass)

Audio Format: AAC-LC (Music)
Data Rate: 128 kbps
Channels: Stereo
Output Sample Rate: 48.000 kHz
Encoding Quality: Better

Enable Streaming
Max Packet Size: 1450 bytes
Max Packet Duration: 100 ms
Optimize for Server


I’m exporting out of iMovie and then using QTSS Publisher to upload the 1.3GB file to the Tiger server. I have it create a webpage for me. On the client end, I click on the image on the webpage to make it play in Quicktime Player. The audio starts out fine, but gradually drifts out-of-sync.

Any thoughts you might have would really be appreciate. I’ve spent numerous hours trying to get this working.
 
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