Talk:Compression artifact

English dialects

For those searching using British spelling: Compression artefact. —Preceding unsigned comment added by 217.24.129.50 (talk • contribs)

Note that a redirect from the alternative spelling was added just minutes before the comment above was made. - dcljr (talk) 07:45, 17 February 2007 (UTC)

Audio section

Hi, the audio section looks a bit unprofessional; it seems to be a partial revert of a deletion I made a while back. I think it needs to be rewritten to become more precise and accurate. --Kjoonlee 03:37, 13 October 2006 (UTC)

Saying "aggressive" in the leading sentence sounds a bit NPOV, does it? - 88.73.236.209 00:50, 19 January 2007 (UTC)

Perhaps a mention should be made to the file size of audio files and the relation to kbs.--71.182.74.210 (talk) 23:51, 9 March 2009 (UTC)

Unclear

In its discussion of picture encoding, the article states:

Where predictive coding of motion pictures is used, as in MPEG-1, compression artifacts tend to remain on several generations of decompressed frames, leading to a "painting" effect being seen, as if the picture were being painted by an unseen artist's paint-brush.

Where motion prediction is used, as in MPEG-2 or MPEG-4, compression artifacts tend to move with the optic flow of the image, leading to a peculiar effect, part way between a painting effect and "grime" that moves with objects in the scene.

So, am I to understand that "predictive coding of motion pictures" and "motion prediction" are two different things? This should probably be explained a bit further. A quick glance through the linked articles didn't help. - dcljr (talk) 07:45, 17 February 2007 (UTC)

Yes, simple "predictive coding" of motion pictures and "motion prediction coding" of motion pictures are two slightly different things.

Simple "predictive coding" uses the last image to predict the next image, only painting the pixels that change, sending the new pixel colors. The "motion prediction coding" technique builds on top of it. It also paints only the pixels that change, but rather than sending the actual new pixel colors, it sends a message describing the "motion" of a block of pixels from the last image.

Say you have a movie that has scene with a white truck slowly moving left in front of a landscape.

If you transmit it using simple "predictive coding", and someone loses the signal in the middle of previous scene, then regains the signal in the middle of the picket fence scene, that person will see the white (at the leading edge of the truck) and the various landscape colors (at the trailing edge of the truck) slowly paint over the previous scene.

If you transmit it using "motion prediction", it will compress much smaller, but that person will see a truck-shaped cutout of the previous scene slowly moving left.

Please update the article to clarify the unclear parts. --76.209.28.72 21:02, 22 June 2007 (UTC)

Merge

I think JPEG artifacts should be merged into this article, as they are both practically the same thing, and this article is longer. --AAA! ^(AAAA) 07:45, 16 March 2007 (UTC)

A 42 kB thumbnail

The original image thumbnail is actually 7.95 kB now (I guess wikimedia's thumbnail generation has changed). That's smaller than the poor quality version below it, so can't really correct the size without making things confusing. —Preceding unsigned comment added by AbleRiver (talk • contribs) 16:11, 31 August 2007 (UTC)

Merger proposal (Datamoshing)

"Datamoshing" is a neologism (link to policy) for the purposeful manipulation of compression artifacts. The article is extremely short, and there are no real reliable sources that sup[port having a separate article. I suggest it be merged as a section here, until which time (if ever) it gains enough notability to be a stand alone article.--Cerejota (talk) 06:35, 2 March 2009 (UTC) (please use the appropriate section)

I support the merge proposal. I disagree with the characterization of the sources - the MTV link is detailed and from a respectable music journalism source. (I've removed the divisive merge-vote-heading-structure, as I don't anticipate this being a lengthy discussion/problem.) -- Quiddity (talk) 18:15, 2 March 2009 (UTC)

Support - Pointillist (talk) 15:13, 17 March 2009 (UTC)

'Support - I support this as well because it is only a fad and will not be remembered. —Preceding unsigned comment added by 166.77.6.4 (talk) 21:59, 21 April 2009 (UTC)

Missing audio example

The last paragraph of the "Compression artifacts in audio coding" section appears to be missing the example.

"This highly compressed track of applause will illustrate the "metallic ringing" and other compression artifacts very well." —Preceding unsigned comment added by 151.151.73.168 (talk) 12:21, 5 May 2009 (UTC)

This image shows...

This image shows the (accentuated) difference between a JPEG image and the original. Note especially the changes apparent on sharp edges.

Excuse me. What original? — Preceding unsigned comment added by 98.204.138.111 (talk • contribs) 19:28, 26 April 2010

Indeed, the image was deleted last year. But even more absurd is that "the original" is linked to a JPEG file, which cannot possibly be the original - unless it's either a Lossless JPEG (which would be foolish as not many browsers support this) or a PNG file that nonetheless has been given a .jpg extension.

I think we need a new example. But what would be a good image to use that we have in a lossless format in the first place? (OK, so scaling down a high-res JPEG to a size at which its artefacts become irrelevant and then saving that as a PNG would be another possibility.) FWIW I've just made some JPEG artefact images of File:Lenna.png but not uploaded them yet. I'm not sure what the right licensing label is for a derivative work of a fair use image. But one of us could still create an image to use for this, thereby avoiding this issue. — Smjg (talk) 16:21, 25 April 2011 (UTC)

Merge of content from Macroblock

The Macroblock article used to include a section on generic block-coding artifacts, probably because "Macroblocking" is commonly used to refer to any and all block-coding artifacts. I have now integrated the content into this article. See also the discussion on the corresponding talk page Talk:Macroblock#.22Macroblocking.22. Conquerist (talk) 20:36, 5 February 2014 (UTC)

Does color dithering count?

• Dither
  • Floyd–Steinberg dithering

Does a GIF (animated or not) with dithering have a type of compression artifact? NoToleranceForIntolerance (talk) 22:42, 7 July 2016 (UTC)

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