Which HDMI lead?

MagicBoy said:
If it turns out like 011101 then it'll trip the error correction and reconstructed back into 010101 using CRC.

Digital signals are transmitted as on/off therefore there's no nuances like with analogue. There's sufficient flexibility built in to the spec that even a coathanger would make a decent coaxial digital cable.
Click to expand...

As far as i'm aware (and feel free to correct me) there is no form of error correction in hi-fi (even in HDMI)
 
oli collett said:
As far as i'm aware (and feel free to correct me) there is no form of error correction in hi-fi (even in HDMI)
Click to expand...

True for S/PDIF. HDMI is designed to be very resilient to errors with various things going to to pre-empt them and does actually have ECC for part of the signal (not the main audio/video streams themselves). But it's still one-way so a loss is a loss.

Not that any of this matters!
 
There is error correction.

Shamelessly stolen from the spec document : http://www.hdmi.org/download/HDMI_Spec_1.3_GM1.pdf

Audio, video and auxiliary data is transmitted across the three TMDS data channels. A TMDS clock, typically running at the video pixel rate, is transmitted on the TMDS clock channel and is used by the receiver as a frequency reference for data recovery on the three TMDS data channels. At the source, TMDS encoding converts the 8 bits per TMDS data channel into the 10 bit DC-balanced, transition minimized sequence which is then transmitted serially across the pair at a rate of 10 bits per TMDS clock period.

Video data can have a pixel size of 24, 30, 36 or 48 bits. Video at the default 24-bit color depth is carried at a TMDS clock rate equal to the pixel clock rate. Higher color depths are carried using a correspondingly higher TMDS clock rate. Video formats with TMDS rates below 25MHz (e.g. 13.5MHz for 480i/NTSC) can be transmitted using a pixel-repetition scheme. The video pixels can be encoded in either RGB, YCBCR 4:4:4 or YCBCR 4:2:2 formats.

In order to transmit audio and auxiliary data across the TMDS channels, HDMI uses a packet structure. In order to attain the higher reliability required of audio and control data, this data is High-Definition Multimedia Interface Specification Version 1.3 protected with a BCH error correction code and is encoded using a special error reduction coding to produce the 10-bit word that is transmitted.
Click to expand...
 
Talking about digital audio over coaxial or optical, usually what's used for CD's. It still looks like HDMI doesn't have error correction how can it, unless it then gets timing errors?
 
I was under the impression that the "signal" remained in digital form untill its decoded by the TV, which takes the cable out of the equation?

So there we have it, what is sent (via HDMI) is exactly what is recived and decoded at the other end by the TV's decoder/DAC (or what ever its called), so how the 'ell can one cable possibly be any different from another, unless its broken and dosent work?:confused:
 
My point being, a "1" is a "1".

There is no partial "1" or poor quality "1" or indeed a "1" thats a deeper shade of black, its either a "1" or its not.
 
Ok you have to look at this technical graph by russ andrews, it has labelled axes and lines of best fit. Almost looks like a materials stress vs strain graph from my degree.

o wait, read the bottom bit that is cut off from the pic but in small print on his website :D:D:D:D

interconlhu6.jpg


Please note this is not a technically measured graph
Click to expand...
 
AbsenceJam said:
I'm guessing you just quoted that without reading or understanding it, yes?
There's no real error correction really.

CRC by the way is just a means of checking consistency, it's not error correction.
Click to expand...

I'm not going to claim I'm an expert, but check section 5.2.

I realise what CRC is, I was just try to use a more easily recognised term than BCH ECC parity bits!
 
Personally i believe that a heap hdmi cable is as good as any other. However my friends who work in the audio and video business tell me that cheap cables don't have a high enough bandwidth to carry very high bitrate 1080p video and high definition audio and this can cause problems, how true this is i don't know and for the time being ill stick with my £5 cable.
 
hyper_piper45 said:
Personally i believe that a heap hdmi cable is as good as any other. However my friends who work in the audio and video business tell me that cheap cables don't have a high enough bandwidth to carry very high bitrate 1080p video and high definition audio and this can cause problems, how true this is i don't know and for the time being ill stick with my £5 cable.
Click to expand...

Over long distances yes, but company’s selling a 1M HDMI cable as I linked to above for £300 no two ways about its daylight robbery, I wonder what type of people buy products like these?
 
You must log in or register to reply here.
Back
Top Bottom