Question for WHF team

[Ragworm]

I was reading the supertest of Blu-ray players in this month's WHF and a question occured to me. As well as picture quality, you make quite a lot of mention of the relative sound quality of each player. I'm curious to know how they are connected to the amp.

If connected via analogue then I can see why the players sound different but if connected by digital, with the decoding being performed in the amp, then, without significant processing going on in the player, I can't see why there should be any noticable difference between then. Enlighten me.

 

[Andrew Everard]

Well, it's the weekend, and I've just got off the plane from the Munich High End show – bloggage to follow once I've gone through about a thousand pictures and a sheaf of notes – but I'll ask the test-team to respond on Monday.

 

[strapped for cash]

I'm not WHF staff, of course, but your question (or statement?) is a common topic of dispute on this forum.

Many are of the opinion that, with digital information sent as bitstream over HDMI, there can be no difference between players in terms of Blu-ray performance.

This assumes no processing is occuring within the player before digital information is sent; and of course purists argue that the ideal scenario is for no processing to occur, thus preserving the integrity of source material.

As you state, in principal, the only way there can be differences in performance is if processing is occuring within players before data is output. How this can be determined without extensive dismatling of a wide array of kit by somebody who really knows their tech, I don't know.

I only know that I can notice differences between the performance of Blu-ray players when it comes to picture, but not with audio on the various kit I've owned, unless the data output is LPCM (which really can make quite a difference). I can only conclude that internal processing prior to digital output is taking place in at least all but one of the players I've owned.

I can't imagine the debate will be resolved on this thread, but welcome to the forum, nevertheless...

 

[Andrew Everard]

but welcome to the forum, nevertheless...

Ragworm's been here for several years!

 

[strapped for cash]

And precisely 65 posts. I can't imagine where I got that idea from!

 

[Ragworm]

But hardly ever contribute to the home cinema forum!

 

[Anonymous]

I'm not WHF staff, of course, but your question (or statement?) is a common topic of dispute on this forum.

Many are of the opinion that, with digital information sent as bitstream over HDMI, there can be no difference between players in terms of Blu-ray performance.

This assumes no processing is occuring within the player before digital information is sent; and of course purists argue that the ideal scenario is for no processing to occur, thus preserving the integrity of source material.

As you state, in principal, the only way there can be differences in performance is if processing is occuring within players before data is output. How this can be determined without extensive dismatling of a wide array of kit by somebody who really knows their tech, I don't know.

I only know that I can notice differences between the performance of Blu-ray players when it comes to picture, but not with audio on the various kit I've owned, unless the data output is LPCM (which really can make quite a difference). I can only conclude that internal processing prior to digital output is taking place in at least all but one of the players I've owned.

I can't imagine the debate will be resolved on this thread, but welcome to the forum, nevertheless...

hi strapped, i can't see how processing can be performed before data is output, we're talking about digital data that needs to run through various codecs, 1s and 0s, i am of the opinion that such data remains uncorrupted by the player.

i also can't see how a given blu-ray player can enhance a picture (talking 1080p material here) or sound without some form of corruption of said data, in fact i can't see how a player could know what to add, or how it would be capable of adding, anything to the original data on the disc.

all of which ties in with the fact that many people and tech sites cannot find differences between blu-ray players in terms of 1080p playback.

 

[Anonymous]

Max, I try not to get drawn into these type of conversations, and I am only asking the question, but is it not more about the player being built to protect the signal from the point of reading it from the media, by ensuring no interference from power supplies etc? So it outputs the purest signal possible at the output.

 

[Anonymous]

Max, I try not to get drawn into these type of conversations, and I am only asking the question, but is it not more about the player being built to protect the signal from the point of reading it from the media, by ensuring no interference from power supplies etc? So it outputs the purest signal possible at the output.

hi mark, yes that's how i understand it, that there is nothing added but i guess the potential for data loss/interferance is there, but a digital signal is either 100% or it doesn't work, so imo players don't dffer.

 

[strapped for cash]

I try not to get drawn into these type of conversations

That sounds a sensible policy. I think I'll abstain hereafter as well.

 

[Anonymous]

It's a strange point really, but I have a very expensive HDMI cable that I assume is faulty, as when I plug it into my BR player (fullHD with HD audio) it's snowy, but when plugged into my sky HD box (just 1080i and 2.0 sound) it has a perfect picture - go figure.

Also on BR players why would someone like panasonic make such a big deal of of it's ( I think it's called) P4HD chip which is used for processing and authoring both at studios and with it's players, if no processing is done.

I think what I'm saying is I don't know definitively, but it would be nice to know.

 

[strapped for cash]

Hi Max,

The thing is, we go round in circles with this debate. I can't prove, scientifically, that there are differences because I don't have detailed knowledge of how every single component in assorted Blu-ray players work. In fact, I can't offer a detailed technical account of the how the individual components of any single player function and interact (and with respect, neither can you).

It comes down to a simple question: is there any alteration (or corruption, as you put it) of data at any stage of the chain between source and reproduction? This same question applies to digital cables, since they're also part of the same chain.

My broader point was that we don't gain anything by arguing this point on forums. As a non engineer, I don't know how any degree of alteration to data could be measured, but I'd like to see the results of thorough and objective testing in this respect.

In the meantime, I've been reluctant to spend a lot of money on a Blu-ray player or cables, but I was prepared to take a punt on an older (second hand) high-end player as an experiment.

If I state that the image and sound produced by the 2500BT is better than the S-370, I'm only inviting responses to the contrary (and then we go round in circles again).

 

[The_Lhc]

a digital signal is either 100% or it doesn't work

That simply isn't true Max, have you never seen a Freeview broadcast breaking up just before it fails completely? Most digital systems can deal with a certain amount of data loss before complete failure occurs.

 

[strapped for cash]

Thanks for being so generous, Ragworm, but that doesn't let me off the hook!

On a broader point, it's frustrating not being able to edit posts once they've been replied to. There's a schoolboy error in my post above. It seems I need to be more attentive in every regard...

 

[The_Lhc]

It's a strange point really, but I have a very expensive HDMI cable that I assume is faulty, as when I plug it into my BR player (fullHD with HD audio) it's snowy, but when plugged into my sky HD box (just 1080i and 2.0 sound) it has a perfect picture - go figure.

What HDMI version does the cable conform to (how old is it?), SkyHD boxes are only HDMI 1.1 compliant, so a cable that conforms to that spec will work fine with SkyHD but may not have the bandwidth to handle full blu-ray, which would require a 1.3 spec cable.

 

[Anonymous]

Hi Max,

The thing is, we go round in circles with this debate. I can't prove, scientifically, that there are differences because I don't have detailed knowledge of how every single component in assorted Blu-ray players work. In fact, I can't offer a detailed technical account of the how the individual components of any single player function and interact (and with respect, neither can you).

It comes down to a simple question: is there any alteration (or corruption, as you put it) of data at any stage of the chain between source and reproduction? This same question applies to digital cables, since they're also part of the same chain.

My broader point was that we don't gain anything by arguing this point on forums. As a non engineer, I don't know how any degree of alteration to data could be measured, but I'd like to see the results of objective testing in this respect.

In the meantime, I've been reluctant to spend a lot of money on a Blu-ray player or cables, but I was prepared to take a punt on an older (second hand) high-end player as an experiment.

If I state that the image and sound produced by the 2500BT is better than the S-370, I'm only inviting responses to the contrary (and then we go round in circles again).

hi strapped, i know these debates go round in circles sometimes, so i'll try and put a different slant on things..

i have a satelite dish, it picks up the various airbourne digital signal transmissions, this digital data is then fed into my humax, it then sends it via hdmi to my tv which shows a picture and sound, i'm not sure if there is a codec in the humax, probably, either way a codec be it in the humax or the tv decodes the data.

so you have source, in this case the transmission data, codec, and pic on digital tv.

in the case of hd material every pixel of the tv's screen is given instructions, ie what colour, brightness etc it should be at any one time.

the instructions are given by the codec/s, which decodes the 1s and 0's, now i'm not sure if this is done by the humax and then reconverted to digital before being sent to the tv then re-decoded by the tv's codec.

but either way i cannot see how anything can be added, i haven't heard anyone saying that one tv receiver is better than another with 1080i content, and if nothing is added then the only thing that can happen is data is loss, why would blu-ray players be any different?

but digital data transfer is flawless, there is no data loss, so imo anything that is decoded from a digital source, blu-rays, digital tv, cd's, music files etc, will be reproduced flawlessly, whether the chain includes hdmi cables, the airwaves or whatever, least that's how i see it.

 

[Anonymous]

a digital signal is either 100% or it doesn't work

That simply isn't true Max, have you never seen a Freeview broadcast breaking up just before it fails completely? Most digital systems can deal with a certain amount of data loss before complete failure occurs.

yes if there is not a strong enough signal then failure due to data loss can happen, but if there is a strong enough signal, as there is where i live, then there is no problem, digital data from space arrives, all of it intact, at my house, yet people are convinced said digital data is lost all the time in their living rooms :~

 

[The_Lhc]

a digital signal is either 100% or it doesn't work

That simply isn't true Max, have you never seen a Freeview broadcast breaking up just before it fails completely? Most digital systems can deal with a certain amount of data loss before complete failure occurs.

yes if there is not a strong enough signal then failure due to data loss can happen

Exactly, so it's entirely possible for a digital signal to lose data.

 

[Anonymous]

it's possible if their isn't a strong enough reception in a given area, i've temporarily lost mine when there has been extremely heavy rain, but i seen no break-up first, the screen sometimes freezes but then returns to normal.

there's no heavy rain, lighning or hurricane force gales etc in peoples living rooms, and in the case of digital data transfer there's no data loss either.

 

[John Duncan]

it's possible if their isn't a strong enough reception in a given area, i've temporarily lost mine when there has been extremely heavy rain, but i seen no break-up first, the screen sometimes freezes but then returns to normal.

there's no heavy rain, lighning or hurricane force gales etc in peoples living rooms, and in the case of digital data transfer there's no data loss either.

Google "packet loss"...

 

[Anonymous]

It's a strange point really, but I have a very expensive HDMI cable that I assume is faulty, as when I plug it into my BR player (fullHD with HD audio) it's snowy, but when plugged into my sky HD box (just 1080i and 2.0 sound) it has a perfect picture - go figure.

What HDMI version does the cable conform to (how old is it?), SkyHD boxes are only HDMI 1.1 compliant, so a cable that conforms to that spec will work fine with SkyHD but may not have the bandwidth to handle full blu-ray, which would require a 1.3 spec cable.

It is a back rhodium, 1.3b, I bought 2 and the other handles full HD 3D video and HD audio simultaneously with no problems.

 

[daveh75]

it's possible if their isn't a strong enough reception in a given area, i've temporarily lost mine when there has been extremely heavy rain, but i seen no break-up first, the screen sometimes freezes but then returns to normal.

there's no heavy rain, lighning or hurricane force gales etc in peoples living rooms, and in the case of digital data transfer there's no data loss either.

No, but peoples homes are full of b/band routers, wirless devices, DECT phones, microwaves, fridges, freezers and c/h thermostats TVs etc, etc and unless you live in the middle of nowhere, you're surrounded by other homes full of these devices, which can/do cause RF interference, which can/does cause reception issues (or data loss if you prefer)

FWIW the DVB standard includes Forward Error Correction to help deal with data loss caused by the above, but it can only do so much, and when you get picture break up/sound distortion thats because the Error Correction is starting to fail, because it can no longer correct the amount of errors (data loss) being intoduced...

 

[Andrew Everard]

it's possible if their isn't a strong enough reception in a given area, i've temporarily lost mine when there has been extremely heavy rain, but i seen no break-up first, the screen sometimes freezes but then returns to normal.

there's no heavy rain, lighning or hurricane force gales etc in peoples living rooms, and in the case of digital data transfer there's no data loss either.

...And then there's the effect of global warming...

 

[John Duncan]

FWIW the DVB standard includes Forward Error Correction to help deal with data loss

Which proves that data loss exists. Next!

 

[Anonymous]

FWIW the DVB standard includes Forward Error Correction to help deal with data loss

Which proves that data loss exists. Next!

The whole point of error correction is that transmissions errors are recoverable, i.e. minor errors do not lead to data loss. And when they do lead to data loss, like in max' examples, the consequences are usually catastrophic rather than subtle, like audible bleeps or green/purple squares.

The HDMI case is even more interesting, because of HDCP. With hdcp, the data stream is encrypted to prevent the data from ending up on torrent sites et al. The whole point of encryption is that it prevents tampering, in other words, change one bit and the entire stream fails to decode. Or to put it succinctly: with hdcp, every single data loss, no matter how minor, results in a black screen. That said, I don't know how widely-used hdcp is.

edit: in case I may sound too presumptuous: the above thoughts are my own, and are not based on any scientific research