Basic question about filters

[DisMyMac]

Do deblock, denoise, and such filters prevent artifacts, or do they remove them? I'm guessing it's the former, because what if blocky/noisy areas are supposed to be part of the video? (That would also explain why amateurs often complain that the filters don't do anything.)

This question occurred to me when I noticed the crop options in Streamclip - it lets you apply them to either the source or destination video... and of course that makes a huge difference.

 

[KeithPratt]

The prefix "de-" means "remove".

 

[DisMyMac]

The prefix "de-" means "remove".

From what? The source or the output?

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To put it another way, the new codec you're encoding with is going to introduce its own artifacts (due to limited bit rates etc). Do filters help prevent those new artifacts, or just remove them from the original video?

 

[KeithPratt]

From what? The source or the output?

It can't remove them from the output. If it did it'd then have to re-encode, meaning that wasn't the output.

 

[DisMyMac]

It can't remove them from the output. If it did it'd then have to re-encode, meaning that wasn't the output.

I'm not doubting you, but then it's a question of when the filter is applied- if you have multiple filters, are they always applied in a certain order (or does it matter)? You're right - it wouldn't be the output, but a kind of double-encode going on. I thought maybe that explains why it takes so long to encode using filters....

So if you already have artifacts in a video, then a filter may be successful in removing them. Don't just blame the encoder for introducing new artifacts. That was confusing, but this is actually good information. Thanks.

 

[arjen92]

It does matter in what order you apply filters. I believe this goes for almost any program. Here's an example (I did a really fast google search) where it's confirmed.