See what's coming out of the HDMI through VNC?

[MrOaiki]

I managed to setup my Raspberry without a USB keyboard not a monitor. It took some time to figure out it's IP address, but after that everything went like a charm.

Now, as an almost beginner when it comes to programming, I'm trying to see what the little device is capable of when it comes to video playback. Using omxplayer, I'm getting sound and - it says - I'm getting video. I do however not know if that's the case, because I don't have any monitor to plug into the HDMI output.

Question:

1. I have tightvncserver installed, and it works well. I can see the Raspberry desktop. Is this the same view as what's being streamed out from the HDMI port when omxplayer is running? In that case, something is wrong because I don't see any video on my desktop.

2. If omxplayer is sending out hardware accelerated video in full screen through the HDMI output only, then is there any way for me to set up the VNC server to display what's coming out through HDMI? It won't be smooth, it won't be watchable, I just want it to see if there's a video stream coming out from there or just a mirrored image of the desktop.

[topguy]

omxplayer uses hw-acceleration to create a video overlay on the HDMI. There is no way VNC can pick this up.

So if you want to see video you have to use a non-accelerated videoplayer like mplayer or vlc.

But then you will not see what the Pi is capable off, but that is only possible on one of the physical video outputs anyway.

[MrOaiki]

I understand. But all I want to see is if there's something coming out of the HDMI port when I use omxplayer. So, from your answer, I understand that this is only possible if I plut it into a HDMI port? I can't see any information from the Pi what is actually being shown through the HDMI?

[PiGraham]

I understand. But all I want to see is if there's something coming out of the HDMI port when I use omxplayer. So, from your answer, I understand that this is only possible if I plut it into a HDMI port? I can't see any information from the Pi what is actually being shown through the HDMI?

The Pi will output to the composite RCA connector if no HDMI is connected.
You can force HDMI in the config file if you need to.

[ghans]

No variant of VNC can currently pick up
what the Pi GPU draws.

xvncserver does work though - what ever a "normal" Linux app
does on my DVI monitor i can watch on my remote Windows
laptop.

ghans

[MrOaiki]

No variant of VNC can currently pick up
what the Pi GPU draws.

xvncserver does work though - what ever a "normal" Linux app
does on my DVI monitor i can watch on my remote Windows
laptop.

ghans

Hmmm… So, if I launch a video in omxplayer while watching the desktop on my VNC client, and I get sound from the sound jack, and it says it's playing but I see no video, that means the video isn't working? Or does it simply mean that no HDMI screen is attached and therefor I can't see the video stream?

[dom]

Hmmm… So, if I launch a video in omxplayer while watching the desktop on my VNC client, and I get sound from the sound jack, and it says it's playing but I see no video, that means the video isn't working? Or does it simply mean that no HDMI screen is attached and therefor I can't see the video stream?

VNC only knows about the X framebuffer. omxplayer (and GPU accelerated apps) doesn't use the X framebuffer (it's very slow). So not seeing the video through VNC is expected behaviour.

Check here:
www.raspberrypi.org/phpBB3/viewtopic.php?f=29&t=48369
www.raspberrypi.org/phpBB3/viewtopic.php?p=376546

for a way of grabbing what the GPU is displaying.

[PiGraham]

What are you trying to test?
If you want to know if the video is on the HDMI output plug a screen into the HDMI. (or to DVI or VGA via an adaptor)
If you have no screen why does it matter?
Can't you borrow someone's HDMI TV or monitor for 10 minutes to test it?
Most TVs will work with composite, either direct to an AV input or via a SCART adaptor. That will tell you if the video is being rendered correctly.
You may be able to force your player to use a software renderer for display. It will be slow, especially if you then stream it via VNC, but it should show up.

[MrOaiki]

What are you trying to test?
If you want to know if the video is on the HDMI output plug a screen into the HDMI. (or to DVI or VGA via an adaptor)
If you have no screen why does it matter?
Can't you borrow someone's HDMI TV or monitor for 10 minutes to test it?
Most TVs will work with composite, either direct to an AV input or via a SCART adaptor. That will tell you if the video is being rendered correctly.
You may be able to force your player to use a software renderer for display. It will be slow, especially if you then stream it via VNC, but it should show up.

I'm trying to test the HDMI output without having a HDMI screen. And yes, the solution is to borrow one from anyone but I was hoping I wouldn't have to. Having the HDMI work matters because I will eventually plug it in. My questions is about being able to test the output without having a screen to test it on.

When I run a software renderer for display (with mplayer i.e) I do get a picture to show up on my desktop over VNC.

[topguy]

A: My questions is about being able to test the output without having a screen to test it on.

B: When I run a software renderer for display (with mplayer i.e) I do get a picture to show up on my desktop over VNC.

A: This is basically impossible. The connector can be broken, the cable can be cut in two, still the picture would show great over VNC.

B: What you see is the result of transferring data from the Pi memory to another computer. It has still no direct connection to the hardware output from the Composite or HDMI connector. Its possible to create many desktops in memory that isn't visible at all from either Composite or HDMI.

You just have to belive us (until you get a screen) when we say, that if you play a video with omxplayer, you will get the picture (and sound) on the HDMI.

[jamesh]

TopGuy is right - the only surefire way to know if something is being output over HDMI is to plug it in. You can find out what the HDMI expects to be displaying, but you cannot determine if it is actually coming out of the HDMI (it may not if there is a HW fault)