What Is 'Macro Blocking'

[KraGorn]

I've been frequenting here and AVS for well over 18 months but only in the last few weeks has the term 'macro blocking' registered with me, I don't recall hearing of it until recently.

Can someone point me at a description of it, which AIUI is something to do with MPEG decoding, and why I may be concerned about it?

Ta.

 

[Blue2]

Hi,
I believe Multiblocking is what happens when there is a delay/error in the display data being read (eg from a dvd player) or streamed (eg via satalite or web). The player still needs to output information to the display device even though it can't read it from the disk, to make up for this lack of data it uses the data normally used to describe a single pixel to describe a larger area. The result is a row of square blocks which momentarily apear on the screen/display. Same effect as when you get dodgy reception from cable or satalite, or some live streamed sports events -particularly where the cameras are mobile, helicopter, motorbike mounted etc.

Because the data shortfall occurs befor any conversion to analogue (ie s video, vga, component etc), it will effect both analouge and digital outputs.

Basically in a unit like a DVD player there is no excuse for it, it means that either some trade off has been made in the design (not large enough buffer, processor too slow, poor pickup etc) or there is an error with the disk or laser.

The new denons seem to be a little bit prone to it. When i contacted denon they recomended re-initialising the player. This was because vendors do often not re-initilise units after updating them to multi-region. I did and it eliminated the multiblocking i was getting on two new disks. So in this case it seems to have been aggravated by soft/firm ware.

I had a dig around but can't find a picture of it i'm afraid.

I'm not an expert, but that's what i think it is...

 

[Blue2]

http://www.avforums.com/forums/showthread.php?t=163084

Now i'm just confused...

 

[Wayde]

Hi

I hope you guys don't mind a link to another board. I frequent a similar board to this one out of Canada.

http://www.digitalhomecanada.com/forum/showthread.php?t=17715

To understand what macroblocking is it's probably worthwhile to know the difference between macroblocking and pixilation in digital video. Pixilation is any big blocks you see covering images. Sometimes this happens when you change channels on your digital source, or when the signal is weak.

Macroblocking are tiny pixels that occur when images are in motion. It's an upper limitation of the throughput of mpeg2 compression. You get this a lot on a High Def TV because it's capable of displaying more video information than the source can keep up with. You get macroblocking in the fine details of quickly moving images because all those extra positions being painted on your screen aren't being uncompressed fast enough. Usually only a problem on HDTVs and DVD players are better at hiding it than most HD sat receivers and Digital cable boxes.

We Canadian's are always glad to help out the old country when we can

 

[digisocialist]

I mentioned this to the Hi-Fi dealer I spoke to today..just in passing and his immediate response was that he would advise customers not to multi-region hack DVD players. The conversation moved on so we did not discuss this problem or it's causes in detail, but on reflection it appears that the experiences of his customers reporting this problem to him have done so in a fashion that infers mulit-region hacking is the culprit. Could this be so? If so,then the issue is not with the brand of DVD player, rather the means by which it's functionality is installed.....

 

[gandley]

2 types of macroblocking. 1 produced by the bandwidth problem of some faroudja DCDi chips(which Denon got alot of stick about) and the other is a basic encoding error from the mastering process. Thats why some get confused.(so all dvd players will exhibit a bit of macroblocking as its already on a badly encoded disc. so there is in truth no macroblock free dvd player)

The faroudja version isnt realy macroblocking, but as this was the nearest likeness to the issue its the name the artifact got dubbed with.
But what realy happens is the chip cant cope with all its processing due to a lack of bandwidth. So not macroblocking but a similar result

And MR`ing a dvd player has no effect on this. Thats just a cop out so if they(the manufactures) find out it is an MR machine they dont have to deal with the issue.
bastards!

 

[KraGorn]

Thanks chaps .. I searched on "macro blocking" not "macroblocking" :sigh: .. particularly for gandley's comments about the problem with Denons as, of course, there's where the problem is most talked about.

And thanks to Wayde from the old world to the new.