4-Output Video Interface for MBP?



  • I am putting together an art project where I will have four different videos playing on four different vintage televisions from at the same time. The TV's are all black and white and from the 60s/70s/80s, so they have the old fashioned UHF/VHF inputs. I don’t need audio to output from the TVs; the TVs will be synced to an audio track. Thus, an interface with low latency is very important.

    My computer is a Macbook Pro (Retina, 15-inch, Early 2013) with USB 3.0, Thunderbolt, and HDMI ports.
    Does anyone know of a video interface that can handle 4 outputs? 4 is the bare minimum, ideally I'd like 5.
    Thanks in advance!


  • You will need a lot of conversion to get your outputs going, if you tell us a bit more information there may be better options. First you need analogue outputs, you can use 2 triple head to go DP editions and then 6 DP to VGA converters and from there 6 scan converters to get you to composite video and from there 6 RF converters to get to the TVs. This is a pretty expensive undertaking.

    You could also look for an old video wall controller or a cheap HD one like this (http://www.ebay.com/itm/GEFEN-EXT-HD-VWC-144-2X2-VIDEO-WALL-CONTROLLER-/251762824452?pt=LH_DefaultDomain_0&hash=item3a9e3bd504) and convert to analogue from here. This will give you 4 outputs but HDMI.
    Depending on what you need to do you can very cheaply use a raspberry pi for each TV (they cost about €40 each and have a composite out- easily converted to RF), it is pretty easy to make an OSC controlled video player or even slightly more complicated GFX display using openframeworks) this will be much cheaper and take a huge load off your computer.
    Alternately again, if it is just video, you can also look for something like this http://www.ebay.com/itm/BrightSign-HD962-Electronic-Digital-Sign-Controller-Module-with-AC-Adapter-/380916473501?pt=LH_DefaultDomain_0&hash=item58b0641e9d
    You need one for each TV but they can be programmed to play in sync and receive external triggers to play different videos.
    Fred


  • Thanks for the info Fred.

    Basically four different videos will play on each TV and must be synced to a music track. Each video will be the same length, say 4 minutes. The reason I was leaning towards using my computer is because I'd imagine with external standalone devices, it would be hard to trigger four videos plus one audio track all at the same exact second...right? I have no experience with Isadora (yet) but I know with Max/MSP this can be set up fairly easily. You see this type of thing at big music concerts all the time (though maybe they have really expensive standalone equipment syncing the video/audio).
    I don't think I can use 2 TripleHead2Go DP Edition units. According to the Matrox website, "Multiple GXMs are supported under Windows only."
    Which device do you think would be ideal for my purpose?


  • With a single triple head to go you could have 5 outputs (your retina has 2 thunderbolt outputs and 1 hdmi) you could get to 6 with one of these (but it is expensive)

    http://www.datapath.co.uk/products/multi-display-products/datapath-x4.

    Triggering videos all from Isadora is not really a problem and there are ways to get sync (Izzy uses a similar system to max anyway).
    If it is just videos then I would go for bright sign or if you are feeling up to it raspberry pi. Bright sign is a no brainer commercial solution that is used at a lot and can do what you want. It is just a matter of choosing one that is good for your needs, ie a newer ones with HDMI are more useful but need a few additional boxes per unit to get to RF video. Older SD models will also need conversion but maybe cheaper, but less useful in the future. They are designed to do sync playback exactly for this. You will need to specially format a message to trigger them (some have IO pins for this so you can use hardware). You can also leave the sound attached to a video as they have audio out and keep themselves in sync quite well - they are designed for video walls so you get framesync.
    I would go for the raspberry pi personally, it is cheap but will require some work- essentially you will have to write a very simple piece of OSC triggered video playback software with a simple sync check- not much work, in fact if you go with OF for raspberry pi you will just need to modify an existing example to get it going.
    Yes, big concerts have stand alone video wall and LED wall processors and pro equipment that can chase timecode, locking connectors everywhere, and redundant everything. Dedicated hardware is pretty much always the go if you can afford it.

  • Tech Staff

    Fred is the man!

    I us brightsign units at my work in the museum. I like them but they cost £200+VAT per unit for a standard HD model. 


  • I need to get one BrightSign unit per TV, right? Then how would my laptop feed one video to each BrightSign unit?

    I think a Raspberry Pi is too adventurous for me at the moment.
    Could you explain why I couldn't buy a USB hub and then simply buy RF to USB adapters, plugging each TV into a USB port? Or, replace the word "USB" in the previous sentence with "DisplayPort"? Wouldn't using a USB or DisplayPort be the simplest and cheapest route?


  • Brightsign run the videos from an SD card in the unit.

    Can you actually find a display port to RF adaptor- pretty sure they dont exist, same with USB to RF. At any rate, you have 2 mini displayport/thunderbolt connectors on your laptop which would get you 2 RF outputs if such a thing exists.


  • Sorry, what I meant is something like this.

    1\. Buy a USB hub like this:
    http://www.amazon.com/AmazonBasics-Port-USB-power-adapter/dp/B00DQFGJR4
    2\. USB 2.0 to HDMI converter:
    http://www.amazon.com/Sabrent-2048x1152-1920x1200-DisplayLink-USB-HRHD/dp/B008S08ADI
    3\. HDMI to RCA cable:
    http://www.amazon.com/MOTONG-Extension-Cable-Converter-Adapter/dp/B00NOARBL4
    4\. RF Modulator:
    http://www.amazon.com/Modulator-Switch-Audio-Output-Converter/dp/B00J41Y4YY
    5\. Coaxial to UHF converter:
    http://www.amazon.com/RCA-VH54R-Matching-Transformer-VH54R/dp/B00005T3EY
    Repeat steps 2-5 for the other 3 televisions.
    Alternatively I could purchase a MiniDisplayPort hub instead of a USB hub, not sure what the functional difference would be however.
    What's wrong with the above?


  • The cable hdmi to RCA is not a converter, it is for a specific system that has the converter already and is just a breakout it says-
    • Please Note:This cable functions as a signal transmitter, so you should have a signal converter box to use this cable

    , you will need a box like this to do it.

    http://www.ebay.co.uk/itm/HDMI-to-Analog-AV-Converter-Composite-S-video-Scaler-converter-1080P-Fast-UKSHIP-/291338962223
    Also the USB to HDMI dongles are pretty dodgy, I highly doubt you will either get 6 of them to run, nor will you get Isadora to see them, they have no open GL and will use a lot of CPU to run, on top of that the bandwidth needed to generate 6 PAL signals will overload your USB bus, so if these could work (and then not drive you crazy re addressing the output channels), you would need at least 2 USB busses, but likely 3, which means getting a thunderbolt . Also it says "Mac beta-quality drivers available but with important limitations" however the limitations are not listed. The data rate of PAL is 160 megabits/sec and a USB bus is 480, the hub you picked says up to 480, not all hubs are equal and low speed controller chips are the first thing they save money on. Most cheap USB hubs such as this can not sustain full bandwidth of full voltage for all ports, even with a transformer plugged in.
    The RF modulator does not give details of the frequency- it could be UHF or VHF
    The Coaxial to UHF converter just converts cable impedance not signal.
    There is no such thing as a mini display port hub, essentially that is what a matrox triple head is, or the datapath box is above. Mini display port and display port and not made to be chained or used for hubs in the same way as USB.
    All in all you could buy all of this stuff and try it, it is highly likely it will not work, but you would be doing us all a favour by trying it out. 
    For the price once you get everything delivered you will be coming close to the cost of brightsign boxes from ebay, and with a pretty slim chance of it all working and maybe getting a decent picture.
    Personally I would go for the brightsigns and they are easy to sell once the show is done, plus they are designed exactly for this job so they will work.
    Otherwise, I would look at the datapath box with 4 outputs, plus the HDMI and the second thunderbolt output of your retina- there is your six, then the HDMI to analogue boxes, and then the RF converters. Even then you are asking a lot of the computer.
    Fred


  • Thanks for weighing in Fred. This is clearly more complex than it seems.

    You think 6 USB to HDMI dongles would be too much for my computer, even if the videos are Standard Definition? My computer has a 2.4 GHz Intel Core i7 processor and 16GB of RAM by the way.
    What if instead of the USB 2.0 to HDMI adapters, I used [USB 2.0 to VGA adapters?](http://www.amazon.com/Sabrent-USB-DH88-2048x1152-1920x1080-DisplayLink/dp/B001B7H39W/) Could my MBP then handle 6 outputs more easily?
    You are right; the Mac drivers for Sabrent adapters have unspecified "limitations", but many reviews say it works on their Mac.
    This USB hub:
    http://www.amazon.com/AmazonBasics-Port-USB-power-adapter/dp/B00DQFGJR4
    supports 5 Gbps. What's wrong with this?
    Wouldn't the RF modulator support both UHF and VHF?
    Aren't these DisplayPort hubs:
    http://www.amazon.com/EVGA-Compliant-Multi-Stream-Displayport-200-DP-1301-L1/dp/B00HK8V5KE/
    http://www.amazon.com/StarTech-com-MSTMDP123DP-DisplayPort-Triple-Monitor/dp/B00JLRBC7S
    http://www.amazon.com/Accell-K088B-003B-Mini-DisplayPort-Multi-Display/dp/B00F90H98M/
    I tried reading a BrightSign manual but it didn't have a lot of information. If you could link me to an in-depth manual that would be great. My main question is what is the mechanism that syncs the units together? And how hard is it to program? Also, could I do this for 10 different 4-minute videos for a show?
    The Datapath X4 looks awesome but at $1400 for only 4 outputs, it's out of my budget.
    I really view external standalone hardware as a last resort. I know they're more reliable but ideally I would like to run everything from my MBP because this gives me the most control. Increasingly it looks like my only option then is the TripleHead2Go. Do you know the difference between the TripleHead2Go DP vs Digital SE?


  • Yes running 6 Sd displays is a lot of work for a CPU that is not design for such work, but it might be ok, you would be testing. As for whether 6 would be recognised by the driver is another thing.

    USB to HDMI or to VGA will make no difference, it is the same number of pixels.
    The USB hub says up to 480 mbps, sustained throughput is something you will have to test. I was using a system for a few years that required full bandwidth from USB hubs and very few made the grade.
    The things you found as display port hubs are essentially just like the dat path and the triplehead, but different brands, not hubs. One of them specifies mac compatibility, no idea what resolutions any of them will give you, probably 1024x768 will be the smallest, then you need to use scan converters to get to SD composite.
    Brightsign systems can be directly controlled from your computer, in different ways depending on the model. Check the forums for more info
    http://support.brightsign.biz/categories/20036772-Forums
    Yes, what you want to do will cost money, as I said above display walls are expensive, you could get the 6 going for 1500, this is very cheap.
    Matrox website has a good compatibility table of the different units, there are a few discussions on this forum as well.


  • Hi Fred. I've decided to give this route a try: 4 USB to VGA adapters + 2 Mini DisplayPort to RCA adapters. If this ends up not working well, I will have to try a more expensive set-up.

    Do you know if there is there a brand of USB adapters that are particularly fast on Macs? And do you think using USB 3.0 adapters instead of USB 2.0 adapters will result in a significantly better playback response? I ask because the USB 2.0 adapters can be found used for cheaper, while the USB 3.0 adapters I would have to buy new.


  • Re: TH2Go DP vs Digital SE

    _Basically..._
    TH2Go DP is 1x DP in, 3x DP out.
    TH2Go Digital SE is 1x DP in, 3x DVI out.
    _Delving deeper into it for getting 6 outputs (running two matching units on same firmware)..._
    TH2Go DP can be doubled up, one on each Thunderbolt port, to give 2x triple output groups via mGXM.
    Digital SE can't. See output table yonder (bottom of page): http://www.matrox.com/graphics/en/products/gxm/connect_multiple_gxms/


  • PS: Long term, you may be better off purchasing a ViDock (http://www.villagetronic.com/g4/expansion/shop) and suitable graphics card (which doesn't need to be anything massively meaty, just summat with enough outputs for you). I'd consider this the midway option between USB adapters and adding dedicated players to each screen. Probably doable for the cost of a pair of TH2Go or less.



  • Hi Marci. On the Matrox webpage you linked to, it says, "Multiple GXMs are supported under Windows only." So whether I use a DP or Digital SE, I can only use one TH2Go with my MBP at a time.

    Also, the ViDock looks like a great solution. However, it looks like each ViDock can support 2 graphics cards per Thunderbolt output, so I could get 4 outputs from my MBP at the maximum? I would be paying several hundreds of dollars for only 2 extra outputs then.


  • @Marci do these work with gfx cards on OSX? As far as I have heard there are no solutions for this on a rmbp (external video card) they work fine for other peripheral cards, but maybe things have changed since I last checked.

    @[ovrarrest](http://troikatronix.com/troikatronixforum/profile/6179/ovrarrest) where did you find mini display port to composite video? As far as I knew the displayport standard (mini display port is the same thing with a smaller plug) does not support this. 
    As for the better performance in USB2 vs 3 it does not really work like that. When you plug in USB devices they use a subset of the controller which is limited to USB 2, when you use USB 3 devices it uses the USB 3 controller. The speed issue I mentioned was for hubs not controllers. You are still in unchartered territory trying to use 4 of these. If I am correct about the mini display port not having composite you still need to convert from VGA or HDMI to composite (also dont forget your macbook retina also has a dedicated HDMI). On the plus side, many of these USB adaptors do support multiple monitors on windows - you could run your patch on windows installed on your mbp. Here is a working setup that would be close to what you want https://www.youtube.com/watch?v=pYUdAWOGJ_Y


  • @Fred Here are some Mini DisplayPort to RCA (composite) converters I referenced earlier:

    http://www.amazon.com/DisplayPort-Composite-Video-S-Video-Converter/dp/B004VV8R86
    http://www.amazon.com/J-Tech-Digital-Mini-DisplayPort-Converter/dp/B008CS0J9O
    http://www.amazon.com/ViewHD-DisplayPort-Thunderbolt-Universal-Converter/dp/B00713AA5E/
    Isn't USB 3.0 faster than USB 2.0 though? That's why I might have thought USB 3.0 could handle 4 adapters better than USB 2.0 could?
    Yeah I've thought about running Windows on my Mac as there are many videos online with people using their Windows computers with multiple displays. I view this as a last resort since I'm not really comfortable in Windows.
    My rMBP has 2 Thunderbolt outs and 1 HDMI out, but keep in mind the computer only allows me to use a total of 2 of these outputs simultaneously.
    I do think the ViDock would work on Max OSX. From their [FAQ page](http://www.villagetronic.com/g4/expansion/products/nano/faq):
    _"Compatibility of ViDock to Mac OS_
    _Apple and Intel officially do not support external GPU. This is why getting external GPU to work on Mac OS can be rough. Once it works, it works great. Instead Windows 7 / 8 support external GPU and the experience is great right from the start. This holds still true when running Windows OS on Mac hardware._
    _Back to ViDock on Mac OS:_
    _- You need to use a GPU that has drivers built-into MacOS_
    _- Better to choose a Mac that has no discrete graphics"_
    So it seems it is possible to use ViDock on Macs.

  • Tech Staff

    @ovrarrest

    _My rMBP has 2 Thunderbolt outs and 1 HDMI out, but keep in mind the computer only allows me to use a total of 2 of these outputs simultaneously._
    I can use all three outputs simultaneously.

    Best
    Michel



  • Yes, you can use all three at the same time on the rMBP.

    for vidock
    _- Better to choose a Mac that has no discrete graphics"_
    _And your retina has discrete graphics so it is outside of the advice._
    As for the display port stuff, looks like these will be display port to VGA with a cheap scan convertor built in- that is what the USB is for- to power the scan convertor, otherwise composite, and the need for USB power are outside of the display port spec. As you are using old TVs you might not notice the image quality, but generally cheap scan converters don't look so good.
    I guess I have a different opinion on setups, for me possible to work is never good enough. My reputation is the reliability of my systems, I need them not to fail and not to be a pain to setup if I am not there. In this way I try to always use tested, supported and professional solutions. In the end if you are comfortable with un tested/unreliable/unsupported systems and can handle the risks then there are a lot more options to work with.


  • @Michel and @Fred Oh, wow, I didn't realize that the rMBP could output to three external displays simultaneously! Which means I only need 3 USB adapters to get 6 outputs going.

    @Fred I understand where you're coming from. What scan converter would you recommend to connect an old TV to a Mini DisplayPort? And do you recommend a specific RF modulator?

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