Author Topic: Reference guide for spotting encoding problems  (Read 34205 times)

Offline der richter

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Reference guide for spotting encoding problems
« on: October 02, 2011, 01:23:48 am »
We present you our new project a "Guide for spotting encoding problems". The goal of this project is to serve as a knowledgebase and reference for spotting various problems, helping evaluate the best releases. The guide is only limited to encoding problems for now, but it's open to expansion. If we get some good suggestions for other areas to include, then we'll add those as well. This is only the foundation for what we plan to be an ever-growing source of information which we hope to steadily improve upon.

For now it's rather blank and only "Banding" is added as an example. That's where you come into play. We want your help to gather the examples and information for the various problems, which are listed on the project site. We'll take more than one example per problem. If there are too many for one problem we will take the best examples.

What you can contribute:
    ● Comparison screens and videos for the various problems
    ● Information about the problems (see site for examples)
    ● Additions to current information
    ● General additions to the site and improvement suggestions
    ● Report of site errors

List of Problems:
Sorry but you are not allowed to view spoiler contents.
Requirement:
    ● Resolution of images (PNG) and videos not bigger than 1280x720
    ● Only up to 10 seconds of video samples
    ● We want a correct and incorrect example of the same frame/scene for every problem (e.g. one image from the same frame with and without banding)
    ● Please highlight and/or format your contribution for easy perception
    ● We don't want only extreme examples, we want moderate and harder to spot examples too

Every contribution will be reviewed and if sufficient formatted and added as soon as possible.
Please refrain from group bashing or spamming. If you would like to contribute, do so in a constructive and respectful manner.

We are looking forward to a successful collaboration. ^^
« Last Edit: October 02, 2011, 09:36:25 pm by Duki3003 »

Offline morset

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Re: Reference guide for spotting encoding problems
« Reply #1 on: October 02, 2011, 01:28:12 am »
Nice idea.
I think banding in many cases not encode problem, if it's in the source you can't blame the encode for it and fixing it might take other details.

Offline Desbreko

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Re: Reference guide for spotting encoding problems
« Reply #2 on: October 02, 2011, 02:19:55 am »
Banding is common in TV and DVD sources, yeah, but I'd consider leaving it in to be poor encoding since the gains from removing it far outweigh the tiny bit of detail that might be lost.

I take it H.264 in MKV is fine for example videos? I think I have a DVD sitting around that can provide a good example of dot crawl.

Offline der richter

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Re: Reference guide for spotting encoding problems
« Reply #3 on: October 02, 2011, 02:41:49 am »
h264 in MKV is just fine. i didn't specify the format and container because you may find some problems on AVI files with XviD/DivX rather than h264. also keep in mind we want an example with the error and one without for comparison.

this is a guide containing various problems which can occur in video releases. banding is one of those problems, which is rather common. the name of the guide may be a bit misleading for now but it is debatable and we will change it when a better name arise. any idea is appreciated. something more general.

Offline Southrop

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Re: Reference guide for spotting encoding problems
« Reply #4 on: October 02, 2011, 02:44:12 am »
I take it H.264 in MKV is fine for example videos? I think I have a DVD sitting around that can provide a good example of dot crawl.
That should be fine. Just remember to provide both a correct and incorrect version.

Offline Desbreko

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Re: Reference guide for spotting encoding problems
« Reply #5 on: October 02, 2011, 07:17:42 am »
k, here's some clips for dot crawl. Bad is unfiltered, good has had it filtered out.

dotcrawl1_bad.mkv, dotcrawl1_good.mkv
This example shows dot crawl on graphical overlays while the rest of the video is clean.

dotcrawl2_bad.mkv, dotcrawl2_good.mkv
And this one shows dot crawl on the entire frame. Notice in the good clip that the right edge would need to be cropped beyond the black border since the dot crawl can't be completely removed there. Edge noise is another problem to watch out for in videos that have dot crawl.
« Last Edit: October 03, 2011, 05:04:57 am by der richter »

Offline jackoneill

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« Last Edit: October 02, 2011, 09:44:13 pm by der richter »

Offline DeamonEyes

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Re: Reference guide for spotting encoding problems
« Reply #7 on: October 02, 2011, 09:11:05 am »
This is perfect for people like me who have no idea about encoding and what mistakes can be made, knowing them and what they look like. Very much appreciated. Great idea. thx
fly fishing, fly tying, fly only! Oh, and I forgot anime

Offline Desbreko

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Re: Reference guide for spotting encoding problems
« Reply #8 on: October 02, 2011, 09:38:01 am »
Minor aliasing, bad and good

Extreme aliasing, bad and good


Edit: Oh, and I'd suggest adding  "double-hard telecine," "undecimated 29.97 fps," and "field blending" to the list of video examples as those are somewhat common errors made by people who haven't learned to do good IVTC. Though you might want to call that second one something else as I'm not sure how best to describe in only a few words the error of field matching but not decimating a telecined source.
« Last Edit: October 02, 2011, 09:44:41 pm by der richter »

Offline kureshii

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Re: Reference guide for spotting encoding problems
« Reply #9 on: October 02, 2011, 10:05:07 am »
I'm all for self-explaining phrases like "telecined source, field-matched but undecimated".

Now I need a term to describe that temporal macroblock crawl which happens with some scenes (namely fades, and sometimes scenes with changing brightness), when they're not given enough bitrate. Don't have any samples atm but I'll post if I find them.

Offline Mirek

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Re: Reference guide for spotting encoding problems
« Reply #10 on: October 02, 2011, 11:49:37 am »
I suggest adding wrong scenechange decimation to video problems.
« Last Edit: October 02, 2011, 09:45:04 pm by der richter »

Offline Desbreko

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Re: Reference guide for spotting encoding problems
« Reply #11 on: October 02, 2011, 06:07:39 pm »
Now I need a term to describe that temporal macroblock crawl which happens with some scenes (namely fades, and sometimes scenes with changing brightness), when they're not given enough bitrate. Don't have any samples atm but I'll post if I find them.

Wouldn't that fall under banding crawl? About the only time you find banding moving and shimmering is during fades or other changing lighting. I have a couple sources that I could make examples of that from.

Speaking of fades, interlaced fades would be another good video example. You get that all the time on hard-telecined DVDs.

Offline doll_licca

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Re: Reference guide for spotting encoding problems
« Reply #12 on: October 02, 2011, 07:13:38 pm »
Do you guys need examples from really old series?  Most of the material I work with have a lot of problems, most of which cannot be removed without extreme measures and/or a lot of time which most folks don't have.

Offline Lillymon

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Re: Reference guide for spotting encoding problems
« Reply #13 on: October 02, 2011, 08:10:01 pm »
Edit: Oh, and I'd suggest adding  "double-hard telecine,"
Double-hard telecine, bad and good.

Wedding Peach DX. The bad is my first, ham-fisted attempt at encoding. The good is what's currently on BakaBT.
« Last Edit: October 03, 2011, 03:40:34 am by der richter »

Offline kureshii

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Re: Reference guide for spotting encoding problems
« Reply #14 on: October 02, 2011, 09:11:10 pm »
Wouldn't that fall under banding crawl? About the only time you find banding moving and shimmering is during fades or other changing lighting. I have a couple sources that I could make examples of that from.
Ah, is that the common term for it? I suggested that as a name when helping with the list, but idk if that’s what it’s called in encoding circles.

Offline der richter

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Re: Reference guide for spotting encoding problems
« Reply #15 on: October 02, 2011, 09:50:06 pm »
Do you guys need examples from really old series?  Most of the material I work with have a lot of problems, most of which cannot be removed without extreme measures and/or a lot of time which most folks don't have.
it doesn't matter how old it is, but a good mix of old and newer series would be nice.

Edit: Oh, and I'd suggest adding  "double-hard telecine,"
Double-hard telecine, bad and good.

Wedding Peach DX. The bad is my first, ham-fisted attempt at encoding. The good is what's currently on BakaBT.
he suggested "double-hard telecine" for the video section. so i would rather add your images to "poor deinterlacing" in the static problems section. that is how it looks to me.

i hope you all don't mind, i will cross out everything i added to the guide. i don't want to lose the overview. also as feedback for you. if i missed something don't hesitate to inform me.

i may need some help to describe some of the problems especially the one in the video section. i would appreciate some help. ^^
« Last Edit: October 02, 2011, 09:54:23 pm by der richter »

Offline tormaid

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Re: Reference guide for spotting encoding problems
« Reply #16 on: October 02, 2011, 09:58:42 pm »
I think 1080p screens should be allowed. Often the drop to 720p eliminates or marginalizes problems like aliasing, haloing, etc. that would otherwise be very noticeable at full resolution.

Speaking of Haloing, it's a common artifact caused by sharpeners that I almost never seen corrected: http://screenshotcomparison.com/comparison/83809 (just a quick test, with proper masking the resulting clip could retain more of the sharpening).

I am very much in favor of heavy debanding, even at the loss of some "detail". It's really the most noticeable and distracting artifact for most anime sources.
« Last Edit: October 03, 2011, 03:41:05 am by der richter »

Offline Lillymon

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Re: Reference guide for spotting encoding problems
« Reply #17 on: October 02, 2011, 10:34:18 pm »
he suggested "double-hard telecine" for the video section. so i would rather add your images to "poor deinterlacing" in the static problems section. that is how it looks to me.
No problem by me, I'm still very much learning with regards to encoding.

Offline der richter

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Re: Reference guide for spotting encoding problems
« Reply #18 on: October 02, 2011, 10:38:13 pm »
1080p is just too huge in dimensions. nearly no one would be able to few the whole site with 1080p images. they will lose the overview. 720p its just the right size and all the problems listed can be found on releases with 720p or smaller resolution.

did you imply adding haloing to the list? if so it's already under "oversharpening/ringing". for me ringing and haloing is the same. please correct me if i'm wrong. if you want me to add your example please upload the pictures separately on a image host.

this is not the right place to discuss your fondness of heavy debanding. ^^

Offline jackoneill

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Re: Reference guide for spotting encoding problems
« Reply #19 on: October 02, 2011, 11:49:09 pm »
Quoting http://bakashots.me/guide/index.php?prob=rainbow&num=2:
Quote
What is rainbowing?
Is a discoloration on lines because of poor deinterlacing.
Wrong... :(

Deinterlacing has nothing to do with this. There is an explanation towards the end: http://searchcio-midmarket.techtarget.com/definition/S-Video

=========================

Quoting http://bakashots.me/guide/index.php?prob=deint:
Quote
What is deinterlacing?
Is the process of converting a interlaced video into a progressive form. Interlaced video is a sequence of pictures where every other frame contains only the even lines of an image, the rest contains odd lines. A sequence of two images combined is one full image.
Pretty much wrong again. :(

http://en.wikipedia.org/wiki/Interlaced_video
http://en.wikipedia.org/wiki/Deinterlacing

===========================

Also, dot crawl should appear in the static section, too, because even in stills, the checkerboard pattern can be quite obvious:
Badgood
(see the red text in the top left corner).
« Last Edit: October 03, 2011, 12:05:20 am by jackoneill »