continuing video fail.

A few hundred dollars later, my ongoing attempt to have my second monitor cloned onto my video projector is still made of fail. What am I doing wrong here?

My plan was this:

My plan fails in two ways:

  1. If I just do this:

    then the monitor just sits there and flickers, trying to display a message about input being out of range. So clearly that splitter confuses the hell out of either the Mac or the monitor. I don't know which.

  2. And if I just do the second part:

    I again get no signal on the projector. Sometimes I saw the projector displaying snow-crash; sometimes it appeared to be trying to lock on to various resolutions that were changing every 5 seconds; briefly, I saw something that appeared to contain the right colors in the static; and now it's decided to just always be black. Anyway, no worky. I tried all permutations of the various switches on the device, and all permutations of the 3 RCA cables.


Update, 2011:

Here's what I'm using now, and it works:

Previously I had been using an "Audio Authority 1366 HD Scaler" instead of the Atlona AT-VGA300CV, and that worked fine for three years, but then it unceremoniously croaked. All evidence suggests that the Atlona has exactly the same hardware inside, but is $30 cheaper.

A full scaler is necessary because my projector will not accept a 1600×1200 signal encoded as component video. It has a small set of standard video resolutions that it can cope with on component (e.g., 480i, 720p, 1080p).

I haven't found a solution that gives me a digital (DVI) pass-through from the Mac to the monitor, but with a good, short VGA cable, it looks fine anyway.

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19 Responses:

  1. raindrift says:

    It's possible you're having a problem with automatic detection of the display capabilities. There's a piece of software called SwitchResX. It will allow you to force a display resolution instead of having the mac choose it.

  2. a_0001 says:

    First, I'm skeptical of your DVI-splitting cable. It might work in some applications, but good practice would provide an active device to regenerate the signal. You may need a DVI distribution amplifier if you want to drive both an LCD panel and (a box that converts the signal for use with) a projector from the same source.

    If the computer is producing a 1600x1200 signal to drive the LCD panel at its native resolution and this is beyond your projector's capability, you'll either need to accept a lower resolution on the LCD panel or install a scan converter, not just an HDMI to RGB converter. I hope this isn't true, because DVI-D scan converters aren't cheap -- I'd suggest, but can't vouch for, something like the Analog Way SSV1600 ($1500).

  3. scullin says:

    Regarding the second part, have you done the "Gather Windows" trick with the Displays system preference to bring both display windows onto the main monitor to see what's being sent to the second monitor?

  4. I think it may be a combination of the splitter freaking out the mac's display auto-detect and the cable being too long to use without amplification.
    You may want to drop the resolution to something like 800x600 and try the projector again.
    Keep in mind, I'm no expert.

  5. ultranurd says:

    I've got a 50' DVI-D to HDMI cable run (no repeaters or anything) in my setup, and it has no problems, so I don't think the distance is the issue.

    Do you know someone with a newer flatpanel TV with HDMI in, so you can make sure the problem isn't the component converter?

  6. fnivramd says:

    Just checking, did you try both possible connections for part 1? If I were crazy enough to sell a DVI-D splitter I guess I would wire the back channel directly across to one of the two "output" connectors and either let the other side float in the breeze or tie it to earth or something. Assuming that the people who did build it felt the same way only one of the two "outputs" will work on its own.

    In both cases it would be good to know what the Mac thinks is connected to its ridiculous Apple-proprietary DVI-D out. If anything. And for comparison try just connecting the DVI monitor and see what it detects then. In a perfect world you could trivially find this from a remote SSH session even with all the displays haywire, but in our less than perfect world I'm sure you'll find a way.

    I continue to be amazed at how few of the problems available to be solved were actually addressed in a meaningful way by DVI.

    • pmb7777 says:

      Another vote for trying both halves of the splitter with a real display first. There's nothing "Apple-proprietary' about the DVI-D out on the iMac. It just wants to see a display that talks back to it with its EDID capabilities. This happens on the DDC pins, and it wouldn't make sense to split them; they probably only go to one side of the split cable.

    • jwz says:

      Yes, I tried both sides.

      Yes, the monitor works when plugged in without the splitter.

      • pmb7777 says:

        Suck. Maybe the split cable doesn't pass the DCC pins to either side. If the split cable fails as a simple pass through cable with one output dangling, it seems to be the cause of the problem.

    • badc0ffee says:

      The proprietary connector is more like DVI-I, i.e. you can output to analog VGA or DVI-D.

      I would only use those inexpensive DVI splitter cables on a real DVI out, with a video card that supported multiple monitors.

      If you want to stay with your DVI splitting plan, you should follow a_0001's advice and get a powered splitter:

  7. laptop006 says:

    You have checked that the HDMI-to-component works at all (on a 3' cable)? And at the resolution you hope to use?

    And a straight DVI monitor on the 30' cable? (again at full res)

    As other people have mentioned I'd be tempted to swap the splitter cable for something like this Monoprice active splitter.

  8. Someone one shared with me their theory that you just may have a technology-fuckery field about you. I am starting to see the truth in this.

    • wikkit42 says:

      It doesn't seem like technology-fuckery, really. It's that he actually expects technology to work in a reasonably friendly manner, whereas my last expectation after plugging in all those cables would be for anything to work at all.

  9. badc0ffee says:

    If you don't mind connecting your LCD monitor with VGA instead of DVI, this will work:
    On Amazon:

    It supports iMAC DV and VGA in, and VGA, Component, S-Video, Composite out. It's powered over USB.

    • jwz says:

      I can't tell what that thing actually does. It looks like it has four USB cables coming out of it?

      • legolas says:

        I see a component video (3 colors), a vga (or 2?) an usb (can't see what that is for, control/setting perhaps?) and the last one must be to connect to the iMac.

        Avery site seems to confirm:
        * Input Signal: VGA or iMAC DV
        * Output Signal: Composite, S-Video, YPbPr, VGA Pass Through Output

        But also has this:
        3 Levels Flicker-free Control
        which would make me slightly suspicious.

        • badc0ffee says:

          The 3 levels of flicker control are to control sharpness and interlacing on the composite and s-video out, so you can strike a balance between readable text and flicker.

          It's there because NTSC sucks. A video driver on Windows for a card that outputs to TV will have these options too.

      • badc0ffee says:

        Like all the AVerKey products, it converts VGA to various TV video standards, but it also has a pass-through so you can still use a monitor. Usually these things are powered with a wall wart, but this one gets power from USB.

  10. megabytemike says:

    Sounds like the DVI splitter is not passing through a proper sync signal. While pricey, something like this: ( Will most likely get you by.

    As for the DVI to eventual component conversion, I'm not sure how hell bent you are on using HDMI, but you could make the switch from DVI-D to analog VGA with this: ( Again a bit pricier.

    The problem seems to be with the passing of the EDID resolution. The splitter seems to make no reference on how it determines which EDID to send to both outputs. The same issue seems to be going on with the HDMI->component conversion. Since it's converting the digital DVI signal into an analog signal, the box needs to know what resolution to output the analog signal. It mentions EDID "learning" ability, but nothing too specific involving that. I'd suspect whatever learning ability it has, it's not working since you are then converting to the three RGB outputs for the projector without a sync signal for the converter to learn from.

    What you might try testing is to see if the converter will work with a normal VGA connected monitor. If it does, then it might be the lack of a sync signal when connecting to the projector to learn the EDID to send.