I posted this in the Media Composer PC forum about a month or so ago but this section is probably more appropriate for the topic... so here goes.

Is there any way we could get a solution within the Avid interface to compensate for the latency inherent in lcd/plasma monitors and video projectors so that the timeline window, client monitor and audio can all be in sync at the same time?  Yes, there are many ways to delay the audio in the monitor path so that it is in sync with your client lcd/plasma...but, then the timeline and monitor windows will be out of sync with the client monitor.  I don't know about anyone else, but I find it very distracting when monitor playback is out of sync even by a couple of frames.

Now add to that the possiblity (or probability) of a flat panel broadcast monitor with a different latency than either the Avid monitor or the client monitor and this problem becomes even more dicey.  Here are the possible solutions as I see it.

1)  Add a video delay to the audio delay so that the broadcast monitor, client monitor, and audio monitor pathways are in sync.  Signal to decks would not pass throught the delays so no problems with sync on video masters would occur.  Avid timeline/monitor window would still be out of sync so this solution is not ideal.

2) Add a monitor delay compensation setting in milliseconds or 1/4 frames which would delay playback in the timeline/monitor window on the Avid monitor.  Keep the delay in the signal path to whichever external monitor is fastest and now all video and audio is in sync.  Only issue here would be in trimming on the fly, where keystrokes would potentially be off by the value of the delay compensation (assuming ones keypunches are normally frame accurate ).  So this solution is better than option 1 but still not quite ideal.

3) Switch the delay compensation setting to effect the signal coming out of the Avid.  Have the setting be defeatable during a digital cut or possibly only apply to one of the video outputs (I kind of prefer the ability to defeat the setting but there could certainly be reasons for the alternative).  Now the video signal would leave the Avid ahead of the audio signal and the monitor/timeline window but the latency of the client monitor would bring everything back in sync. You'd still need a hardware delay in the signal to the broadcast monitor (assuming that it is the faster of the two external monitors) but now everything is back in sync. Of course, this assumes that the latency is always the same for all framerates, datarates, and definitions - it surely must be...right...

Well, probably not, so you would potentially have to change the monitor delay when you change project settings (ie. from hd to sd) or change projects.  However, it is very possible to measure the delay and the correction to make sure sync is maintained.

This option is the most ideal as all monitor paths are in sync and trimming on the fly by "feel" is still possible.  Also, the issues with variable latency exist with all the options so they're really not specific to this solution.

4) Forget the flatpanel monitor - stay all crt.  Anyone think we're going to be able to do this.

5) Use a lcd/plasma/projector that has less than a full frame of latency.  Does one exist?

6) Don't have a consumer (high end) monitor in the suite - Fine, but just like having multiple monitors in the audio path, it's nice to have a well calibrated consumer monitor as a option in the suite.  Not in exception to a true broadcast monitor, in addition to one. 

I'm not a software engineer so I don't know what the challenges are in doing this but we all know that flat panel monitors are here to stay with their inherent latencies.  We really need a way to compensate for them and eliminate the distraction of having one monitor out of sync with others.

Thanks for reading, any thoughts?

Taylor Warren

Sunrise Pictures, LLC

This issue has been raised before. For now, the easiest way to handle it is to insert an audio delay box to your audio monitoring path. A solution like the Behringer Sharl DP110 is pretty cheap and straight forward. I have a pre-amp between my mixer and my speakers, and this preamp has a delay setting. My Panasonic TH-50PF11 with HDSDI-board has about 30ms delay, and I've easily compensated for that.

Hi Job-

Yes, I know that this issue has been discussed before but, due to the increasing presence of flat panel displays (and their inherent delays) in the edit suite, I thought that the issue bared rehashing.

Thanks for the heads up on the Beheringer Shark - I wasn't aware of that one but I am familiar with other methods of delaying the audio path.  Two hardware options that come to mind are the Rane AD series of AV sync delays http://www.rane.com/ad22s.html and this one too http://www.felston.com/ (which I belive you posted about a while back).  Also, many digital consoles can insert a delay on the main bus, but this doesn't get around the central issues that having a video delay within in the system would solve.  Delaying the audio monitor path means that you have to pick which video monitor will be in audio sync.  The client monitor will still be out of sync with the Avid timeline. 

In my situation, the 42 inch flat panel client monitor is just above my head.  When a cut occurs on the timeline, and on the crt broadcast monitor to my right, there is a noticable lag (to me) before the cut occurs on the client monitor.  It's the lack of sync between the Avid Composer window/Crt broadcast monitor and the flat panel client monitor which I don't like.  Fixing the audio sync in the monitor chain is easy, if you only want one monitor to be in sync at a time.  I would like all video monitors and the audio to be in sync (including the Avid composer window) like we all got used to back in crt - land. That would require a means of delaying the Composer window to match the  latency of the client monitor, inserting a second video delay to the broadcast monitor, and delaying the audio monitor path. 

Better yet  - as I mentioned in my other post - let me have a means of offsetting the output of one of the sdi outs of the system so the signal for the client monitor leaves the system ahead of the Composer window (to compensate for the client monitor's latency).  In a multiple monitor environtment you'd still need to add a video delay in the sdi "monitor line" after the slowest monitor so that the client/broadcast monitors would be in sync, but you wouldn't have to delay the audio so the edit interface would still be instantaneous with the Composer window.

If that's confusing, let me paint a hopefully clearer picture - assuming a flat panel client monitor, a professional lcd broadcast monitor, and the Avid composer window.  Also, we assume the Composer window and the audio are in sync and the latencies of the two external monitors are different.

Step 1 - measure the sync delay of the two external monitors using a tool like Pharoah Editorial's Syncheck II.

Step 2 - Use the mythical "In - Avid" video offset to back time the outgoing sdi video signal to match the llatency of the slowest monitor. 

Step 3- split the sdi "monitor" signal to second video delay to adjust the video sync of the faster external monitor and bring everything in sync.

Step 4 - Repeat Step 1 to make sure you got it right.

Job - thanks for the reply, I've gotten a lot of great info from your posts over time and appreciate how active you are as an educator/advocate within the online editing community.  You are a tremendous asset to us all.

Taylor