Webcast A/V Sync

Conversations around originating a webcast for conference, including cameras and mixers.
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Webcast A/V Sync

Postby edwhicker » Sat Mar 03, 2012 6:24 am

With a standard, Optiplex 740 (4 MB Ram), Win XP, Roxio I/O, Webcast 3.0, I am unable to maintain AV sync. After one hour, the audio lags the video by about 4 seconds. It gets worse with time.

Webcast 2 ran perfectly through several Stake Conferences.

Any suggestions would be appreciated.

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Location: Provo, Utah, USA

Postby rpyne » Sat Mar 03, 2012 8:40 am

Sync problems are usually on the receiving end as a result of an underpowered playback computer, though there is almost always a small sync error. You don't say what your stream bit rate settings were, but running a higher bandwidth (bit rate) stream will aggravate the problem.

If you use VLC Media Player (videolan.org) it will give you extremely good options to control the sync as well as other video parameters. I like to put the playback laptop in dual screen mode so I can put the video on the second display output connected to the projector and the tools dialog on the laptop screen. From the tools dialog you can adjust the A/V sync as well as almost total control of the audio and video parameters.

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Postby edwhicker » Sun Mar 04, 2012 6:36 pm

I have tested this system in the low and medium resolution settings. Our ISP is DSL, which always tests on the high side of 0.5 MBits upload and 3.0 MB down.

A Church Internet/Webcast fireside indicated that 75% of unit broadband is DSL. The same fireside also indicated that the number one issue with webcast is AV sync (the presenter called it lip sync).

When testing, I have logged onto the download site 2-3 hours after starting the test broadcast, in different locations. The poor sync is evident when first logging on and amounts to audio lagging behind video by about 4 secs for each hour of broadcasting.

I have tried using the actual building audio and Sony D70 camera as well as audio and video from the satellite receiver.

I have tried three different capture devices. The Roxio is the first to actually achieve audio and video input through the same device.

I have unloaded and reloaded all of the device drivers and software with no change.

All windows updates are installed.

I have balked at paying $475 to try the Osprey 230e, but one of the devices tried is the Osprey 100 taken from our Webcaster box.

Is anyone successfully using an MLS issued 740 computer with Win XP and Webcast 3.0?

Please reply with your equipment list/procedures.

Thanks for your input.

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Location: Texas, United States

Postby sammythesm » Mon Mar 05, 2012 1:54 pm

Other threads in the forum suggest that audio synch issues can be caused by the capture device more often than the software. It's been indicated that USB capture devices or video-only capture devices (where you capture the audio through a separate sound card) are the real culprits here.

I'd recommend the Blackmagic Design Intensity Pro card. I've had great luck with it - it is HD compatible (if we ever get there) and have run it for hours and hours (on a Dell 740) with no audio synch issues. You have to get a PCI riser card for the Dell 740 (because it is a full-height PCI card), but that's only about $40 extra from Dell. Much less expensive than the Ospreys, more capabilities, and just as rock solid.

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