What actually is HDMI Jitter and what causes it

[steevo]

I am bit confused about HDMI cable jitter.
If i have cable of a fixed length of say 10 meters and pass a perfect square wave of 50MZh (or ar nears as possible perfect) down the cable then if
the cables mechanical and electrical properties dont change then how can
the cable effectively change the frequency of the signal. Is there somekind of strange quantum uncertainaty about the cable.

Does anyone know.

 

[TLS Guy]

I am bit confused about HDMI cable jitter.
If i have cable of a fixed length of say 10 meters and pass a perfect square wave of 50MZh (or ar nears as possible perfect) down the cable then if
the cables mechanical and electrical properties dont change then how can
the cable effectively change the frequency of the signal. Is there somekind of strange quantum uncertainaty about the cable.

Does anyone know.

A digital signal is burst of binary data packages. I think the problem you are referring to is termination reflections. These can cause data loss. If error correction is exceeded there will be data loss. This is minimized by tightly controlling the termination impedance of the cable.

The best example is using an audio RCA cable which is 50 ohm for an RCA SPDIF digital connection which should use an RCA 75 ohm cable. Now you usually get away with it, (but not always) because the error correction can cope with the increased data loss.

 

[mtrycrafts]

I am bit confused about HDMI cable jitter.
If i have cable of a fixed length of say 10 meters and pass a perfect square wave of 50MZh (or ar nears as possible perfect) down the cable then if
the cables mechanical and electrical properties dont change then how can
the cable effectively change the frequency of the signal. Is there somekind of strange quantum uncertainaty about the cable.

Does anyone know.

There are a few interesting articles on line on this found through a Google search for HDMI cable jitter:
http://www.eetimes.com/design/audio-design/4013504/HDMI-DVI-and-DisplayPort-jitter-from-unbalanced-twisted-pair-and-differential-cables

http://www.national.com/news/item/0,1735,1241,00.html

Perhaps TLS can also comment on them?

 

[TLS Guy]

There are a few interesting articles on line on this found through a Google search for HDMI cable jitter:
http://www.eetimes.com/design/audio-design/4013504/HDMI-DVI-and-DisplayPort-jitter-from-unbalanced-twisted-pair-and-differential-cables

http://www.national.com/news/item/0,1735,1241,00.html

Perhaps TLS can also comment on them?

The real issue is people, and I include myself, tend to think with our old analog bandwidth brains. That is fatal.

I know from talking to my son, there are issues with digital signals traveling down copper you would never imagine. For instance as the article mentions tightly controlling cable length is crucial. Correct cable impedance termination is also crucial.

That is why I tell people on these forums to use RCA digital cables fro their SPDIF connections and not audio cables, But they just refuse to get it.

 

[6L6X4]

That is why I tell people on these forums to use RCA digital cables fro their SPDIF connections and not audio cables, But they just refuse to get it.

An RCA terminated video cable that was designed to transmit component video is suitable for use as a digital coax cable isn't it?

Thanks.

 

[Alex2507]

An RCA terminated video cable that was designed to transmit component video is suitable for use as a digital coax cable isn't it?

Thanks.

Yes YES YES !!!

I need a smoke.

 

[6L6X4]

Yes YES YES !!!

I need a smoke.

Ha! You nut!!!

Thanks for the confirmation about the cable.

 

[TLS Guy]

An RCA terminated video cable that was designed to transmit component video is suitable for use as a digital coax cable isn't it?

Thanks.

Yes, the termination impedance is 75 Ohms.

 

[steevo]

A digital signal is burst of binary data packages. I think the problem you are referring to is termination reflections. These can cause data loss. If error correction is exceeded there will be data loss. This is minimized by tightly controlling the termination impedance of the cable.

The best example is using an audio RCA cable which is 50 ohm for an RCA SPDIF digital connection which should use an RCA 75 ohm cable. Now you usually get away with it, (but not always) because the error correction can cope with the increased data loss.

So how does the HDMI eye pattern test work exactly what is acutally displayed on the osciliscope. what is the eye pattern test measuring with regard to the cable.