ThomJ Posted October 7, 2014 Share Posted October 7, 2014 I know this is probably a 'physics' thing but, Are there any ways of eliminating or at least reducing video lag in a live situation. The sound source is coming from various stage mics and the camera is going through a media server from about 50m away from the stage (co-ax cable or cat5 depending on the situation). Any advice would be welcome. Thom Link to comment Share on other sites More sharing options...
Brian Posted October 7, 2014 Share Posted October 7, 2014 ... Are there any ways of eliminating or at least reducing video lag in a live situation. Yes, either... a) switch to using analogue video orb) switch to kit with less compression going on. Link to comment Share on other sites More sharing options...
paulears Posted October 7, 2014 Share Posted October 7, 2014 The delay is just one of the problems with analogue to digital conversion. If you can set up your system so that the conversions back and forth are minimal, it may help - but we've had it for probably 15-20 years now since they started putting frame stores in video switchers to remove genlock complications. If your cameras are HDMI, or output SDI, you have the first delay in the camera, the device you connect to then adds more to align them, and then some projectors ad yet another delay - so you can easily end up with maybe 5 or 6 frames delay, which is pretty obvious. You see it all the time at big events when they use screens for IMAG, and even the best planned system has visible delay. For post production, it's simple to just delay the audio - but that doesn't help when playing live where that can't be done - however, with digital mixers, there is a small delay in the chain from them, so you end up with sound and video at least a little closer. If it's really annoying you or the audience, you could try delaying the audio to front of house, until the stage sound and the audience sound breaks apart - in some venues that are cavernous, the performers are not really aware of it too much, if their monitors are nice and tight - so it might work - but in smaller venues, the drums start to break away quickly. If it's lip sync that causes the annoyance, how about shifting just that a little bit so it's more closer to the screens - and not shift the obvious sources. I've not tried that, but it might work? Link to comment Share on other sites More sharing options...
patrick_keys Posted October 7, 2014 Share Posted October 7, 2014 It sounds like it's processing delay on the part of the media server, rather than cable delay. If you need to run through the media server, the best approach is to delay the audio to match. Link to comment Share on other sites More sharing options...
Brian Posted October 7, 2014 Share Posted October 7, 2014 ...rather than cable delay... The delay of any electrical signal, either analogue or digital, down a length of cable is of the order of 1us per 200m. It is never noticeable as a delay. Link to comment Share on other sites More sharing options...
mac.calder Posted October 7, 2014 Share Posted October 7, 2014 If possible move away from the media server for processing imag. Run it through a hardware vision switch. PC's (when properly configured) can get down to about 3-4 frames delay. A good hardware vision mixer is around 1.5 frames. Use the keying functions to fit the imag where required and away you go. Link to comment Share on other sites More sharing options...
MarkPAman Posted October 7, 2014 Share Posted October 7, 2014 of any electrical signal, either analogue or digital, down a length of cable is of the order of 1us per 200m. It is never noticeable as a delay. The owner of a club I did an install in suggested I could save money on a processor for the delayed speakers by using longer cables. When my back of fag pack calculation came to over 3000 km he changed his mind! Link to comment Share on other sites More sharing options...
Dave m Posted October 7, 2014 Share Posted October 7, 2014 what camera and what for? Link to comment Share on other sites More sharing options...
ThomJ Posted October 8, 2014 Author Share Posted October 8, 2014 It's a Cannon XL2 (we plan to upgrade soon but if it's not broken etc.) It's used quite a lot for rock n roll (Queen Tribute) Video on to LED screens so the Media Server is a must for that. This weekend gone though, I was sending it to 2 x NEC Projector and 4 Plasmas. I didn't see the Plasmas but the delay was quite obvious on the Projectors. I had thought about the audio delay but that would only work in some situations (not many though). I send out an analogue signal via cat5 with video balens, would BNC to BNC co-ax help? Link to comment Share on other sites More sharing options...
Brian Posted October 8, 2014 Share Posted October 8, 2014 I send out an analogue signal via cat5 with video balens, would BNC to BNC co-ax help? No. Link to comment Share on other sites More sharing options...
Joe Fernand Posted October 8, 2014 Share Posted October 8, 2014 Have you tried the camera direct to the Projectors? Have you disabled all unnecessary image processing on the Projector? Joe Link to comment Share on other sites More sharing options...
Dave m Posted October 8, 2014 Share Posted October 8, 2014 what are the connections? what does the server actually do? Link to comment Share on other sites More sharing options...
Tim gregory Posted October 8, 2014 Share Posted October 8, 2014 On our setup Camera > Video Mixer > Projector, I have found that the projector adds the most latency by far. On our projectors you can change the delay which makes a huge difference!This is at the expense of loosing the ability to keystone. As others have said though you are probably getting a lot of latency from the media server. Tim Link to comment Share on other sites More sharing options...
mac.calder Posted October 8, 2014 Share Posted October 8, 2014 Video on to LED screens so the Media Server is a must for that. The problem is your media server is using a capture card - so your camera signal is getting processed by the pc. A hardware vision mixer generally does it more efficiently. You still have your visuals from the media server, you just mix your camera in after it. So instead of Camera->Media Server->Projo, both camera and media server go into a switcher then into the projectors. Also, if you run everything at the same resolution you may save some time in the scaling - but primarily make sure that the native resolution of your projector and the output you are providing it are the same, eliminate key-stoning and any digital zoom. All that combined gives you the best chance. Link to comment Share on other sites More sharing options...
AHYoung Posted October 8, 2014 Share Posted October 8, 2014 latency is cumulative, everything adds it. by far the biggest culprit is probably your capture into the server. Most capture devices are optimised for editing when its important that you dont drop any frames irrespective of how long this takes, In events its the other way round where dropped frames arnt the much of an issue as long as the proccessing is fast. That said when we do events when we capture cameras into a server, its a struggle to minimise the latency and you have to be carefully to minimise it elsewhere in the chain if you can save a frae here or there it makes a difference. . Link to comment Share on other sites More sharing options...
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