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best hardware for low video latency
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Joined: 2/13/2014(UTC) Posts: 33 Location: France
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Hi,
I often use vmix in live event, and the video latency is a major issue in that kind of use. Of course, you can put a audio delay but it is unpleasant for the speaker. The video delay is caused by all the video component of the chain : hdsdi output from the camera, hdsdi input from the video ingest card, processor, and output. The price of the config is not the most important factor.
The use of one of the the BMD quadlink for having real hdsdi output for vmix put a big video latency, and in my experience, the lowest latency is to use the monitor output directly from the graphic card. BUT, it is not a real video output, so i have to convert it with a highend scaler like the VP790 from Kramer. (convert 1080p60 RVB --> 1080i50 YUV). This scaler also have a latency.
I would like to be under 200 msec to avoid to use the audio delay that people on stage doesn't like at all. So, i need to build a new PC with that goal and to choose every component with the lowest latency. For the scaler at the end of the chain, i will buy the latest kramer 4p794 wich have a very low latency.
What would you recommend for the HDSDI 4 input PCI card ? Matrox ? Magewell ? Blackmagic ? Osprey ?
And for the graphic card, i think i will go with the Titan 6G. Any idea of wich component to optimize inside the PC to have the latency at the lowest ?
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Joined: 2/13/2014(UTC) Posts: 33 Location: France
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Today, i made a small test with my PC and BM quadlink. I used a hdsdi video from interview (to see the sync lips) and made a x4 output connected to the BM. Here are the results : - with one decklinck only, CPU is 3% and the sync is nearly non visible - With 2x decklink, CPU is 11% and the lip sync is sensible - With 3x decklink, CPU is about 21% and the lipsync is about 1/2 sec - With 4x decklink, CPU is about 35% and the lipsync is about 1 sec
The good news is that the lipsync is the same on all the decklink at the same time (lipsync could have move). The question is with a different input card, shall i get the same ?
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Joined: 4/30/2014(UTC) Posts: 2 Location: Caribbean
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Are you saying that increasing the number of outputs is what is increasing the latency.
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Joined: 3/7/2012(UTC) Posts: 503 Location: The Netherlands Thanks: 9 times Was thanked: 45 time(s) in 39 post(s)
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in my experience it is almost impossible to avoid latency on a vmix output. with mixing and recording a latency to the actual event can be observed. in the recording it is no problem but for mixing and projecting on a screen, latency will be a problem.
what could be done, and i sometimes do, is feed the video to the screen direcltly from the main camera to the screen and use a seperate feed for mixing and recording.
greetings stefan
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Stefan - in your experience is it totally impossible to use the Vmix switched output for Imag
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Joined: 2/27/2013(UTC) Posts: 312 Thanks: 8 times Was thanked: 78 time(s) in 43 post(s)
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Our church is currently using vMix for our IMAG system for our whole service.
Depending on what is "acceptable" latency means to an individual, I believe that vMix is definitely usable for an IMAG situation. We have been running multiple cameras through vMix for IMAG for a few months now and It has been working quite well. We are not even using the low latency capture option either. Our render time is between 8-15ms.
How much latency are you experiencing now?
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thecloudmediagroup wrote:Our church is currently using vMix for our IMAG system for our whole service.
Depending on what is "acceptable" latency means to an individual, I believe that vMix is definitely usable for an IMAG situation. We have been running multiple cameras through vMix for IMAG for a few months now and It has been working quite well. We are not even using the low latency capture option either. Our render time is between 8-15ms.
How much latency are you experiencing now? That sounds great - well done. But it begs a question or 12 :-) How many cameras, what model and how are they connected to what capture card? What resolution and data rate are you using for capture? What is your IMAG display and how is it connected? Are you recording and/or streaming as well as mixing? Do you use any other inputs? What is your PC system spec?
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Brian Hazelden wrote:thecloudmediagroup wrote:Our church is currently using vMix for our IMAG system for our whole service.
Depending on what is "acceptable" latency means to an individual, I believe that vMix is definitely usable for an IMAG situation. We have been running multiple cameras through vMix for IMAG for a few months now and It has been working quite well. We are not even using the low latency capture option either. Our render time is between 8-15ms.
How much latency are you experiencing now? That sounds great - well done. But it begs a question or 12 :-) How many cameras, what model and how are they connected to what capture card? What resolution and data rate are you using for capture? What is your IMAG display and how is it connected? Are you recording and/or streaming as well as mixing? Do you use any other inputs? What is your PC system spec? Here is a link to a video of our church this morning. You can see our screens as well as our vMix window. How much latency are you experiencing now?Take a look at the video above. I would have to guess between 100-200ms. Ill have to measure it. How many cameras, what model and how are they connected to what capture card?Camera 1 - Canon HF R20 at 1080i60 into a Intensity Pro HDMI Camera 2 - GoPro Hero 3+ Black Edition at 1080i60 DeckLink Recorder HDMI Desktop Capture - 1600x900 30FPS Medium JPEG What resolution and data rate are you using for capture?Not sure of the data rate. What is your IMAG display and how is it connected?We have 2 different feeds in the sanctuary. One center screen that is used only for lyrics and movie displays. Its a Christie LX500 Side screens are the vMix feed and they are 60" LG TV's. They are currently hooked up over VGA but will switch to HDMI next week. Are you recording and/or streaming as well as mixing?We are recording at 1080p30 We are streaming at 864x486 at about 950kb We are outputting 2 outputs feeds from our videocard. -(Mon 1)DVI vMix Screen 1080 60Hz -(Mon 2 Duplicated)VGA External Output 1080 59Hz -(Mon 3 Duplicated)HDMI External Output 1080 59 HZ Do you use any other inputs?About 8 overlays for lower thirds What is your PC system spec?i7-4770 12gb ram Sapphire Radeon 6950 2GB video card Decklink Recorder Intensity Pro X-Fi Soundblaster (Optical Toslink input from AES/EBU audio feed) Hope that helps someone! Let me know what you think :)
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Thank you for your very detailed reply and the video link, great stuff indeed. The delay looks better than I'm getting feeding 6 cameras into a lower spec PC, but I'm only recording - no desktop capture, no streaming, no external outputs or overlays. Did you have to adjust many settings etc. to get the low latency or did it more or less work straight out of the box? Do you have a link to the video you streamed or recorded, I guess the link you gave was recorded with a camera? Thank you once again.
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Brian Hazelden wrote:Thank you for your very detailed reply and the video link, great stuff indeed. The delay looks better than I'm getting feeding 6 cameras into a lower spec PC, but I'm only recording - no desktop capture, no streaming, no external outputs or overlays. Did you have to adjust many settings etc. to get the low latency or did it more or less work straight out of the box? Do you have a link to the video you streamed or recorded, I guess the link you gave was recorded with a camera? Thank you once again. You bet! We really didn't adjust too much. Pretty much started out great. Below is a link to a podcast of one of our services. The only thing that is added is an intro video. Everything else is basically how it is recorded through vMix We did notice a decent improvement switching from a first gen i7 to a i7-4770. How much latency do you think that you are getting? What motherboard do you have? In my experience, the processor and video card have had the biggest difference in performance with streaming and external output. I could be wrong but that has been my history. What are the specs of your computer?
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That's good quality video, well done. I have no idea how much latency I'm getting, except that it appears to be slightly more than yours. Up to now it has been of no concern because I was simply recording live music events. I've now been asked by a potential client if I can add a video projector, hence my interest. My feeling, as a musician, is to say no on the grounds that I can't sync perfectly, but perhaps audiences are not so picky. I had considered using an analog YUV switcher to split the cameras, but that might get a tad confusing. My PC is over 4 years old now , although I upgraded the GPU :- Gigabyte AM3 mobo, AMD Phenom II quad core cpu 3.4GHz, 16 GB RAM, NVidia GeForce GTX 460 GPU Capture cards - 5 BM Intensity Pro PCIe cards + 1 BM Intensity Shuttle USB3 I generally capture 1920x1080 50i PAL MPEG2 video at 50mbps but that seems to be overkill as most of my stuff ends up on DVD. I'm not even sure how I would measure latency other than to point a camera at timecoded video being displayed on a local monitor as well as the projector. Ultimately it will come down to what the client sees as ok, and that will mean a demo I suspect. But if I can show him the delay on a split screen it might save me abortive hire fees. Here's a link to a video mixed live with vMix and just 4 cameras http://vimeo.com/54679923and some more recent stuff that was edited in post with Edius 6, but only because I didn't have time to plug the cameras in http://vimeo.com/89168783Both are just 1280x720 25 fps.
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pceg wrote:Stefan - in your experience is it totally impossible to use the Vmix switched output for Imag I did tests today to see how to improve latency. inputlag is a great clock tool, thank you to Rehan. But I had to do about 5 or 6 pictures at each time to be sure to a good result. My test is : Film the first PC screen with te clock (inputlag) with a JVC HM600 camera (HDSDI output),then a HDSDI multiplier, then scaler (to convert 1080p60 in 1080i/50 wich is my standard for recording, live events, etc.) The camera has about 40 msec delay, and the scaler has also 31 msec delay. I had a very very big delay on my PC shuttle i7 with zotac GT610 (nvidia) GPU and 4X HDSDI input black magic : 1,4 sec !!!! with 4x HDSDI connected to it and about 250 msec with only one. The CPU charge on vmix says 35% with 4x HDSDI !! The GPU is the weakest element in my chain but i wanted to be sure. So, I changed first the BM card for a magewell 4 HDSDI input card. The CPU charge was the same but the delay decreases to 700 msec with 4 HDSDI connected. Conclusions : - 4 HDSDI simuultaneously connected drain more delay than one. - when your GPU is "out", the magewell drains lower power and has less delay than the black magic. Then, I changed the computer for an old i7 x980 3,33 GHz 32 G RAM (3 years old config) and a GTX 480 GPU The delay is between 220 and 250 msec. To have one or four HDSDI input simultaneously does not change much about the delay. Then I changed for a 680 GTX wich is much more powerfull than the 480, and the delay is around 200 msec. Don't forget that you have 40 msec for the camera and 30 msec for the scaler included. So, the vmix delay in this config is actually 130 msec. You have to delay the sound if you want the lips to stay in sync in live event. I will do some test with titan GPU and bigger i7 processor in a few days. Olivier
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Joined: 1/14/2014(UTC) Posts: 25 Location: Ireland Thanks: 3 times
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Here's something we use to check latency/audio sync. Whilst it doesn't give you a msec reading - it's quite good. Interested in difference between Decklink Quad and Magewell card. Looking forward to seeing your next results. Pete
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Joined: 5/13/2014(UTC) Posts: 518 Location: Manchester, UK Thanks: 2 times Was thanked: 183 time(s) in 130 post(s)
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I started doing some tests on latency recently, as it's something I get asked about quite often. My tests involved both Blackmagic and Magewell capture devices, and I tested using both vMix & VidBlaster. The result was typically about 4 frames (at 25fps), plus or minus a frame. Here's a shot of the setup using VMix with a total of six HD inputs (a mix of 720p50 and 1080i50) in which the latency through the PC is ~4 frames. In a nutshell, timecode A (far right) is the source reference being fed into a capture device on the PC on the left (i7-930+GTX660), and timecode B is the result after the round trip back out of an HDMI o/p from the graphics card. The setup is more fully explained in a video clip that featured on That VidBlaster Guy - Latency Tests video excerpt. The full version (in which the audio sync is perfect, BTW), includes both vMix & VidBlaster tests using PCIe and USB3 devices, and will be on YouTube when I get round to finishing the edit.
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Joined: 2/18/2014(UTC) Posts: 1,838 Location: Stockholm
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whow Martin! super pedagocical - and what a cliffhanger in the ThatVidBlaster guy's youtube version ;) thanks for sharing. It would be interesting to know when testing with 1080, and at different frame rates as well as progressive vs interlaced.
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Joined: 1/14/2014(UTC) Posts: 25 Location: Ireland Thanks: 3 times
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Hi Martin,
Think you may have done some research for us already. Which, have to say, was unexpected and extremely appreciated.
Curious to see your findings for Decklink Quad (Single input and fully loaded) vs The Magewell XI400DE-SDI (single input and fully loaded).
Thanks again,
Pete
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Joined: 5/19/2014(UTC) Posts: 2 Location: Halifax
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Perfect thread for me as I am looking to outfit a new system with a 4 input capture card.
---> Was looking at the Matrox offering VS4, anyone using this card and can tell me about it's latency / stress using all inputs.
Also the big thing for me is to iso record and edit after in Premiere CS6(maybe CC) -
Are there any comparisons with Magwell/matrox/black magic on quality of ISO record
I heard (in one of the threads here) that you can't capture 4 inputs and still use vmix with the Matrox card???
Thanks for the info.
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Joined: 8/15/2013(UTC) Posts: 97 Location: Could be Australia could be Europe/UK! Thanks: 1 times Was thanked: 7 time(s) in 7 post(s)
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Hi Guys, I am fighting the latency beast too :) I tested two of my systems, an 1155 socket i7 49xx 3gb Nvidia GTX 960 and a new i7 6700 w 2gb Nvidia GTX 670. Both of the systems set to low latency capture... the best I can get is about 4-5 frames latency @ 59.97i. I calculate that to be 67 - 83 milliseconds (I tested counting back fields on a video delay, with deinterlace blending turned off.) My question is, is this the best I can get? Is it GPU or CPU that I need to upgrade to make it more snappy? Also... vMix site says that latency can be as low as 2-3 frames... ( Latency) What frame rate is that measured at... Also what is a good standard to stay under for latency... I find that this is not that noticeable on its own, but when you have to run it through another scaler/ mixer / system a frame or two more starts to look bad. Thanks Mike
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aircooled76@gmail.com wrote:the best I can get is about 4-5 frames latency @ 59.97i50. Just to clarify. How did you measure the latency? Is it measured between: - vMix program image and external screen from vMix PC or - camera LCD image and external screen from vMix PC I'm asking, because I noticed, that cameras add some latency too. If you connect the camera to normal monitor there may be a latency between image shown on camera LCD and the screen.
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I connected my camera as an input to vMix and recorded it as a video delay... then I pointed my camera at the output screen of vMix... I did a "clap" where I can see my clap and the clap in the vMix output on the screen. Save the video delay. You can ether watch the video delay at 4% or open the clip in an editor and count the frames between your initial clap and the clap and the clap in the monitor.
This measures the full round trip delay including camera and everything.
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