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Old 02-11-11, 07:49 PM   #1
ktbos
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Default LG TV no video when no audio; when audio active, video works

I have an LG TV (37LD450) that I've just started using with MythTV as a secondary TV. The primary TV is a Panasonic that is working fine. The Myth PC has one HDMI output that I have split to the two TVs. I can see the Ubuntu desktop just fine with the Panasonic and can start MythTV and play a recording. But on the LG, there's no video display at all ("no signal") until the recording starts. And when the recording ends, the LG drops the connection again. I can show the same behavior in Firefox where I can pull up Hulu, hit play, the video shows on the LG, then I navigate to another page, and the LG drops the connection again. Even the simple speaker-test will turn on the LG until I end the test and the LG drops the connection.

(Before anyone asks, yes, I'm sure about it all. I've tested everything imaginable. The LG TV works fine with the Comcast cable box in the same setup - if I just pull the HDMI from the Myth box and plug it into the Comcast box, both TVs work fine. Also, if I plug my Win7 laptop into the chain, both TVs work fine. And there's no difference if I just run the cable directly from the Myth box to the LG TV. And yes, I've tried all sorts of different cables.)

The LG tech came today and confirmed the TV is working as LG says it should. And there is no service menu option for changing the behavior. Also, there is no firmware upgrade for my TV. I've found numerous other complaints on the net about LG TVs not working with MythTV and other linux installs.

In desperation today, I clicked on Ubuntu's System Additional Drivers and tried switching to the previous version (the one not recommended; "176", I think?). Surprisingly, the problem went away and the video immediately showed on the LG without needing any audio playing at all. Except then the video playback was broken - it went to black screen whenever I tried video in MythTV.

I then blew away all the drivers that come with Ubuntu and installed the latest released version from NVidia's site and returned to the working video only when audio was in use problem. In fact, all the 4 versions I tried from Nvidia's site all had the same result. Except when I dug too far back, then the driver didn't work at all and there was no display on any TV.

So I'm settling into the following conclusion: The NVidia driver needs to be fairly recent to get the video working. But the recent versions of the driver don't have the the audio active on the HDMI until an application needs it. That might be efficient somehow and it doesn't seem to matter for most displays. But for who knows what reason, it matters to the current crop of LG TVs.

I've considered trying to find away to get some sort of audio signal kicked off on startup and have it linger in a pause state or a silent active state for the duration of the ontime. But before I even figured out how I might do that, I realized that if one application has the audio in use, another application can't use it.

Therefore, the only way it seems I'll be able to use the TV with Ubuntu (and my MythTV install) is if I can somehow get the Nvidia driver to activate the audio connection on the HDMI port at all times. If anyone knows of a setting somewhere, I'd love to know about it! Or if anyone has other theories, I'd love to hear about that too. And if there's any chance to influence future driver implementations, that'd be great too. I'm up for testing anything!!

Thanks for any suggestions!
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Old 02-12-11, 08:17 AM   #2
freaksworth
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Default Re: LG TV no video when no audio; when audio active, video works

Hi,
I can second that problem on a LG32LD420.
I am using "speaker-test" to produce a 0Hz sine over hdmi, so the screen lights up, but there're still anyoing clicking sounds, because it loops over the channels.
(... and I can only do that, because I am using spdif)
Maybe it's even the same issue in this thread: http://www.nvnews.net/vbulletin/showthread.php?t=156785

regards
f
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Old 02-12-11, 09:06 AM   #3
ktbos
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Default Re: LG TV no video when no audio; when audio active, video works

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Originally Posted by freaksworth View Post
Hi,
I can second that problem on a LG32LD420.
I am using "speaker-test" to produce a 0Hz sine over hdmi, so the screen lights up, but there're still anyoing clicking sounds, because it loops over the channels.
(... and I can only do that, because I am using spdif)
Maybe it's even the same issue in this thread: http://www.nvnews.net/vbulletin/showthread.php?t=156785

regards
f
Right, good point, if I wasn't using the audio over the HDMI stream, I might be able to get away with something like that but I do need the HDMI audio. So even if there were no clicks, I'd still need something more than that.

It is interesting that the description in the other thread is similar, but that seems to be a no video at all issue. Still, since the problem seems to have started in about the same version, it may well be a related issue. And that may help if it results in some driver changes but the workarounds may be different so I think it is worth keeping this thread separate for now.

Also, I forgot to post my log. It's attached to this reply.
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Old 02-13-11, 01:24 PM   #4
kumy
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Default Re: LG TV no video when no audio; when audio active, video works

Hi,

I'm having the same issue !

"No image if there is no sound active"

I've lost 5 hours until I've mistakenly (blindly) launched an avi file from my desktop, and have my TV suddenly wake up !

It would be very cool if this "issue" could be corrected in the next driver !
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Old 02-13-11, 01:28 PM   #5
kumy
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Default Re: LG TV no video when no audio; when audio active, video works

Hum, sorry i forgot to link my nvidia-bug-report.log
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Old 02-14-11, 05:15 AM   #6
jaguza
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Default Re: LG TV no video when no audio; when audio active, video works

I have a 42LD420 and exactly the same problems, no audio=no video. I tried two older drivers, I think it was 173 and 185, both lit up the TV but I couldn't get vdpau to work on those so I'm stuck with this.

I have a ION LE chipset coupled with a atom which makes vdpau quite essential for a HTPC/media laptop and I have no other way to connect the TV if I don't use HDMI.
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Old 02-15-11, 11:18 AM   #7
Stephen Warren
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Default Re: LG TV no video when no audio; when audio active, video works

ktbos, you wrote:

> The Myth PC has one HDMI output that I have split to the two TVs.

What happens if you simply plug the one LG TV directly into the HDMI port of your GPU. Do you still see problems? A configuration where one HDMI signal is split between multiple TVs is not supported; the TVs are unlikely to have identical capabilities in the EDID.

Everyone,

You mentioned the same problem. Are you all driving a single display device from a single connector on the GPU?
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Old 02-15-11, 11:42 AM   #8
freaksworth
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Default Re: LG TV no video when no audio; when audio active, video works

... yes, "normal" setting here. just a single TV on a single HDMI output.
(LG 32LD420 & Asus at3iont-i deluxe)
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Old 02-15-11, 12:04 PM   #9
Stephen Warren
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Default Re: LG TV no video when no audio; when audio active, video works

I notice from the bug reports that very old drivers are being used; 190.53, and 260.19.06. Can you please try the latest (270.26) and see if there is any difference. Thanks.
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Old 02-15-11, 12:07 PM   #10
Stephen Warren
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Default Re: LG TV no video when no audio; when audio active, video works

FYI, I filed internal problem report #792613 to track this issue. We'll try to reproduce it.
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Old 02-15-11, 12:28 PM   #11
freaksworth
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Default Re: LG TV no video when no audio; when audio active, video works

Quote:
Originally Posted by Stephen Warren View Post
FYI, I filed internal problem report #792613 to track this issue. We'll try to reproduce it.
Thanks.

Quote:
Originally Posted by Stephen Warren View Post
I notice from the bug reports that very old drivers are being used; 190.53, and 260.19.06. Can you please try the latest (270.26) and see if there is any difference. Thanks.
Same problem with 270.18 and 270.26.

regads
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Old 02-15-11, 12:30 PM   #12
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Default Re: LG TV no video when no audio; when audio active, video works

freaksworth, thanks for checking. Can you please generate a bug report too. Thanks.
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