Can someone please tell me what Macroblocks look like?

[KeepItSimple]

I hear all this talk about Macroblock this and Macroblock that and how Panasonic has a bad Macroblock problem, but can someone please tell me what they look like? The Glossary for this website gives a technical explanation that's way over my head. What on-screen manifestation do I look for?
Thanks!

[trhouse]

Do you see the little rectangles in Morpheus's head and Neo's pant leg?

[redwudz]

Try encoding a very short clip with at a really low bitrate and you will see what they are. Generally green or black squares, usually small that tend to be in the dark areas of the video. Most prevalent in high motion scenes. Sorry, I don't have any samples as I avoid the problem by encoding at high enough bitrates to avoid them.

[Soopafresh]

Me no like Macro Blocks. There are a few filters in VirtualDub and AviSynth which will reduce the appearance of block noise. Trhouse posted a great example.

[jimmalenko]

Just to make it more clear, here's the original again:




and here's the highlighted section blown up 3x:

[KeepItSimple]

Oh ok I see it - wow those are ugly. Do they look like squares when the video is playing or just when freeze-framed? I recorded some video as recommended at 8 hr. speed on my Panasonic ES10 to see the critters. Things looked pretty fuzzy and squishy at that speed and completely unacceptable but I didn't see any macroblock squares. What's all the fuzzy and squishy stuff called?

[vhelp]

Just fwiw here..

Its more easy seen when you have an LCD monitor.
.
But, with TV (tube types) its a little harder to see.

To be honest with you, I would say that we are seeing
pixelation, but its mainly refered to as macroblocks.
And, we all hate them..(pixelation)

(Below), and without going too deep into the subject, is a..

Defination of Block and Macroblock ...

A Block is an 8x8 pixle area, and is most commonly
used (referenced) in DCT applications for JPEG compression scemes:

[ ][ ][ ][ ][ ][ ][ ][ ]
[ ][ ][ ][ ][ ][ ][ ][ ]
[ ][ ][ ][ ][ ][ ][ ][ ]
[ ][ ][ ][ ][ ][ ][ ][ ]
[ ][ ][ ][ ][ ][ ][ ][ ]
[ ][ ][ ][ ][ ][ ][ ][ ]
[ ][ ][ ][ ][ ][ ][ ][ ]
[ ][ ][ ][ ][ ][ ][ ][ ]

A Macroblock is an 16x16 pixle area, and is most commonly
used (referenced) in DCT applications, for MPEG compression scemes:

[ ][ ][ ][ ][ ][ ][ ][ ] : [ ][ ][ ][ ][ ][ ][ ][ ]
[ ][ ][ ][ ][ ][ ][ ][ ] : [ ][ ][ ][ ][ ][ ][ ][ ]
[ ][ ][ ][ ][ ][ ][ ][ ] : [ ][ ][ ][ ][ ][ ][ ][ ]
[ ][ ][ ][ ][ ][ ][ ][ ] : [ ][ ][ ][ ][ ][ ][ ][ ]
[ ][ ][ ][ ][ ][ ][ ][ ] : [ ][ ][ ][ ][ ][ ][ ][ ]
[ ][ ][ ][ ][ ][ ][ ][ ] : [ ][ ][ ][ ][ ][ ][ ][ ]
[ ][ ][ ][ ][ ][ ][ ][ ] : [ ][ ][ ][ ][ ][ ][ ][ ]
[ ][ ][ ][ ][ ][ ][ ][ ] : [ ][ ][ ][ ][ ][ ][ ][ ]
.
[ ][ ][ ][ ][ ][ ][ ][ ] : [ ][ ][ ][ ][ ][ ][ ][ ]
[ ][ ][ ][ ][ ][ ][ ][ ] : [ ][ ][ ][ ][ ][ ][ ][ ]
[ ][ ][ ][ ][ ][ ][ ][ ] : [ ][ ][ ][ ][ ][ ][ ][ ]
[ ][ ][ ][ ][ ][ ][ ][ ] : [ ][ ][ ][ ][ ][ ][ ][ ]
[ ][ ][ ][ ][ ][ ][ ][ ] : [ ][ ][ ][ ][ ][ ][ ][ ]
[ ][ ][ ][ ][ ][ ][ ][ ] : [ ][ ][ ][ ][ ][ ][ ][ ]
[ ][ ][ ][ ][ ][ ][ ][ ] : [ ][ ][ ][ ][ ][ ][ ][ ]
[ ][ ][ ][ ][ ][ ][ ][ ] : [ ][ ][ ][ ][ ][ ][ ][ ]

-vhelp 3407

[Marvingj]

Panasonic is not the only DVD recorder to have a macroblock problem. There are many others too.

[trhouse]

The image supplied above was recorded with a Panasonic ES-10 in LP mode from a fast action sequence in The Matrix. This was all part of tests done on the ES-10 at the link below,

https://www.videohelp.com/forum/viewtopic.php?t=263530

Yes, it is not always easy to spot macroblocks. The above thread shows the fives scenes around and including the above scene, but only that one scene has so many macroblocks. Watching the sequence above as video makes it hard to spot events in only one scene.

Some recorders handle the blocks better. Check out the still frames provided by gshelly61 at the end of the above thread taken from a JVC DR-M10 recorder.

I have the feeling reading these threads that sometimes macroblocks are thought of as an undesired by product of encoding to mpeg. This is not so. Macroblocks are a tool deliberately used by encoder designers to give the impression of greater data transfer when the bit rate is not really adequate to do so. Otherwise, these scenes might appear slideshow like.

Here is a thread to understanding how and why the are purposely created,

http://graphics.tomshardware.com/video/19990924/video-3-06.html

[edit]
No recorder can be truly block free. There are scientific reasons for this. From information theory, there are limits to the amount of data that can be transferred under given circumstances of noise and bandwidth. Here is a link to a key theorem, the Shannon-Hartley theorem.

http://www.answers.com/topic/shannon-hartley-theorem