TBS 6981 audio and video not synchronised

[fobos8]

Hi all

Not sure if this is the correct place to post this.... but here we go..

I'm having some problems watching live TV. Audio and video are not synchronised. The video apears to lag behind the audio very slightly. Viewing is not a pleasant experience. I notice this when people are talking as the words seem to be spoken out of synch with their lips.

I have the ATI Saphire HD 6570 Graphics card. PC is connected to plasma with HDMI. When I watch TV with audio routed to the TV''s speakers via the HDMI everything is fine. But when I watch TV with the audio routed to my "proper" speakers via optical output it is out of synch.

Any ideas on what the problem could be would be very welcome.

Watching saved video films is fine - audio and video synched very well - its just live TV.

My tuner is the TBS 6981.

Best regards, Andrew

[CyberSimian]

I have the ATI Saphire HD 6570 Graphics card. PC is connected to plasma with HDMI. When I watch TV with audio routed to the TV''s speakers via the HDMI everything is fine. But when I watch TV with the audio routed to my "proper" speakers via optical output it is out of synch.

I am no expert in this area, but as no one else has replied I will offer the following explanation.

When a TV receives both HDMI video and HDMI audio, the TV has to do much more processing to the video signal than it has to do to the audio signal. The result is that the video lags behind the audio. At least, it would lag if the TV did not impose a delay to the audio, based on the knowledge of how long it takes the TV to process the video. Result: perfectly synchronised audio and video.

When you route the video and audio from the HTPC to separate output devices, no delay is applied to the audio (the HTPC does not know how long the TV will take to process the video). The result is that the video seems to lag behind the audio. The conventional answer is to use an AV (audiovisual) amplifier that allows you to adjust the audio delay to suit the video. If you have a simple hi-fi amplifier that does not offer this facility, you are out of luck. As far as I know, you cannot use the HTPC to impose a delay on the audio.

Watching saved video films is fine - audio and video synched very well - its just live TV.

I have no idea why saved video films might be different from live TV.

-- from CyberSimian in the UK

[fobos8]

thanks for kicking things of CyberSimian

I'm not 100% sure but I seem to have read something yesterday about using the AC3 filter and being able to adjust the level of delay between audio and video

It may be that there is a sync problem with downloaded films and I don't notice it. I notice it most on live TV when watching the news.

[barnabas1969]

Are your "proper" speakers being driven by an external AV Receiver? If so, then you need to adjust the "lip sync" delay in your AV Receiver.

If your "proper" speakers are being driven by the computer's audio adapter, then you need to adjust the delay in the computer's sound settings (probably by using the software that came from your audio adapter's manufacturer). Not all audio adapter software has a delay feature.

[fobos8]

My hi-fi speakers are connected directly via SPDIF/optical to a soundcard in my PC. There is no delay feature for the soundcard.

What options do I have?? any??

Is there anyway of introducing a delay to the video via a filter? There is no such feature on my video card

[barnabas1969]

It's not possible for the optical output from your PC to be connected directly to your speakers unless the speaker enclosure contains a digital-to-analog converter (DAC) and amplifier. If you are using a digital audio output from your computer, then there must be some kind of device that decodes the digital signal and then amplifies it before sending the (now analog) signal to the speakers. This device may or may not have a delay setting.

You should first check to see if your speakers (or whatever device is doing the decoding) have a delay setting.

The next step would be to look at the sound settings on the computer to see if you can find a delay setting.

I believe that AC3 Filter has some sort of delay setting, but I've never tried it.

[fobos8]

Hi Barnabas

The speakers have a DAC inside their case. There are no knobs or buttons I can adjust for the DAC.

I cannot find any delay settings for audio or video on my PC.

What to do??

Cheers, Andrew

[barnabas1969]

If you don't already have the software (this is more than just the drivers) installed for your audio adapter in the computer, you could try installing the software for your particular audio adapter. You can find the software on the audio adapter manufacturer's site. Sometimes this software gives you more options for adjusting the audio than what you can find in the Windows Control Panel "Sound" applet (and sometimes the software adds new tabs to the "Sound" applet).

Beyond that, I guess some kind of filter that has a delay setting is your only choice.

[fobos8]

The software for the sound card doesn't have any options for delaying sound.

I have played around with the AC3 filter and can get control over lip sync for video files but I cannot get any control of lip sync for live TV.

Lip sync for video file playback is absolutely fine - it is just live TV where there are problems.

Is there any filter or other way of sorting this out?? Please help??

[milli260876]

Can't u connect the tv to the amp/speakers by optical out instead of the pc...?

[fobos8]

Can't u connect the tv to the amp/speakers by optical out instead of the pc...?

I assuming you mean HDMI from HTPC to the TV for audio and video and then optical from the TV to my hifi speakers.

I could do that but then I wouldn't be able to use my soundcard which is terrific.

I mainly listen to music so I have a really good soundcard. When I do watch TV I don't really want the hassle of switching the audio to HDMI output within WMC setup.
One of the main reasons I went down the HTPC route is so I just have one control/setup to do everything.

The sync problem is just with live TV - is there not a filter I can use to sort this out?

[barnabas1969]

In order to get a filter to change the delay of live TV, you'll need to adjust some settings in the filter's settings program. I'm not sure how to help you with this because I've never tried it. But, basically, you want the filter to get involved when you play WTV files that contain whatever audio codec is being used for live TV.

[barnabas1969]

Can't u connect the tv to the amp/speakers by optical out instead of the pc...?

I assuming you mean HDMI from HTPC to the TV for audio and video and then optical from the TV to my hifi speakers.

I could do that but then I wouldn't be able to use my soundcard which is terrific.

I mainly listen to music so I have a really good soundcard. When I do watch TV I don't really want the hassle of switching the audio to HDMI output within WMC setup.
One of the main reasons I went down the HTPC route is so I just have one control/setup to do everything.

The sync problem is just with live TV - is there not a filter I can use to sort this out?

It doesn't matter which way you connect it, the sound card isn't really involved with the quality of the sound. It's just digital. However, if you connect it in the way that milli260876 suggests, you might only get 2.0 stereo sound and not 5.1. This is because most TV's won't pass 5.1 audio from the HDMI input to the optical output. You'll have to try it and see what happens.

[fobos8]

Looks like I've got this sorted.

As suggested by barnabas1969 I tried to find a way of adjusting the sound card's audio output. There is a setting called "latency" which adjusted the size of the buffer. The higher the latency or buffer the more of a delay there is on the audio. Delaying the audio brings it more in sync with the video. I have it set to the highest latency the card will allow and although the audio is not 100% perfectly in sync with the video it is good enough for me.

Many thanks to everyone for their input - I'm very grateful that you've helped me solve my problem.

Cheers, Andrew