Can't things like ffmpeg do reasonable deinterlacing?

Yadif x2 seems to be a well regarded filter (as far as my knowledge of these things goes)
The Intel GPUs do some good Motion Adaptive and Motion Compensation filters in hardware. I assume nvidia would have some too, but not sure if they're supported via something like ffmpeg though.

Reason I know this is that I still watch TV at home via Tvheadend and Kodi. TVH feeds the broadcast video to Kodi which is interlaced, and Kodi does the deinterlacing. Usually requires an OK CPU or GPU hardware support.

Yes, and I've used ffmpeg with yadif 1 and 2x plenty of times. I generally use it with Hybrid because although I have a stack of batch commands ready made in a big text file, I'm inclined to fiddle with the settings and Hybrid just makes it easier. The problem is that many of the files I play with are very poor quality to begin with: 70s and 80s TV series, even some from the 90s and later, taken from DVD. Somewhere, and I have much too little knowledge to say where, the transcoding process knocks just enough quality off to be counterproductive. I suspect if I was working with a decent quality 576i or 1080i original, it would be fine - but then I probably wouldn't bother deinterlacing anyway since most hardware decoders in TVs do a better job anyway and I wouldn't be looking to improve the quality.

I'm sure it's possible, but I've tried avidemux, avisynth, ffmpeg plus a whole load of free and commercial  deinterlacers and enhancers and I almost always end up with a large number of hours expended and a result that isn't a significant improvement on the original, if at all.

The really annoying part is that whereas I can buy absolute crap movies and series in every format up to including 4K (and maybe 8K soon) many of the classics of the big and small screens aren't available at all, and when they are it's in shitty DVDs, poorly produced. The BBC release of the Singing Detective isn't bad, it's just meh... a grainy, overcompressed, 576i. Potter wanted contrast between video inside shots of the hospital and film (some b&w) of outside and historical content. In the end it was all shot on film, so a decent remastering would be possible, always assuming the BBC haven't extended their usual level of tlc to the film, in which case it's probably rotted away somewhere. It won't happen. Potter's last couple of plays aren't even available new.

The good news, is that Topaz has a "basic" deinterlace/enhance profile that doesn't appear to change the video length and it's also faster: 11-12 hours per hour of video as opposed to 16 plus, with audio in sync. I ran the first episode through and it's very impressive, so I've just fired off a batch job with all 6 episodes. I'll post a couple of comparative samples when it's finished. A minor issue is that for some reason Topaz has decided to compress the audio to 96K max which may be a pain for some videos. No idea why they don't just pass it through as is and remux at the end. Still, it wouldn't take long to remux the output with the original audio myself.

I guess with an already poor source you want to avoid multi stage compression to retain as much quality as possible

Exactly. 

Couple of clips from the Singing Detective. I realised after I'd cut the bits out that I'd picked an area of better quality source video, but I think the difference/improvement is obvious.

Clip straight from the DVD

Clip after Topaz processing

That's actually quite interesting. I paused both at a similar frame and it was fairly impressive that her badge has gone from pretty much totally impossible to read, to maybe possible to read. Significantly clearer and sharper

I think some of the problems people have had with Topaz involve expectations. In essence each profile is just a type of filter, only with an enormously greater number of "if thens" than a standard "unsharp" or "denoise" etc. If you overdo a filter then not only do you overwrite real information with fake but cosmetically preferable information, you risk producing cosmetically undesirable results: ridiculously sharp edges where they shouldn't be, shiny, waxy, skin tones and loads of false detail. I saw an interesting blog where a photographer pushed an old landscape photo up to 4K using a Topaz photographic filter. The results were quite good, but looking closer, a road sign now had totally meaningless but clear and sharp "marks" where the words had previously been completely blurred. 

I stopped the processing at 1080P and also increased the default grain filter to add some noise back in. So Joanne Whalley's badge says "Miss C Mills Enrolled Nurse". I have a feeling that at 4K that might actually deteriorate. I'm pleased with that and will probably stop there, because it has enough clarity to look good on a big(ish) flatscreen telly. 

I have seen people online who are determined to get their ropey home-filmed VHS holiday epics up to 4K. That's quite literally true. It seems that if every single bit of the image isn't pin sharp then its unwatchable.

Trying the same settings on the DVD box set of Porterhouse Blue. This is a truly shabby Channel 4/Acorn DVD production. It was briefly released as a 2 DVD box set with 2 episodes per disk. This is now unavailable and the present production squashes everything onto 1 disk. Unbelievably, there are a couple of "library club" editions which are even worse. I managed to find the original 2 disk release on sale in Norway.

Ensemble cast of British character actors, Tom Sharpe novel with Malcolm Bradbury screen play, great cinematography and production values for broadcast, all shat on by Acorn DVD. Clumsy mastering, shaky, noisy, and way over-compressed.

Finding that the results aren't quite so good here. Because the source is so bad, I'm getting areas that look great, clear, sharp, faces for instance, in a sea of not-so-clear detail. Which doesn't look right. May have to redo them at 720P.

Weird user forum, by the way. Looks to be custom made, although it's fairly normal at first glance. You don't join the forum*, you gain membership by using it. Sounds reasonable but since there are no obvious instructions it's really confusing. The categories for posting are muddled up in different places and although you aren't told when you start using the forum, you can't post to it straight away. It seems that, without exception, people waste their first hours trying to find what the fuck's going on. People turn up having spent £100s on the various products and feel as though they're being treated like shit. 

I spent ages wondering what I was doing wrong because although, for some reason, I could post in a section on photographic filters (where I had nothing to say and no particular interest) the new post button for Video enhancement was (is) greyed out.

I found a bundle of posts in a general section which basically asked WTF? Somebody said they'd finally realised that they had to post stuff where they could, to be allowed to post where they actually wanted to. I (was able to) comment on this that it seemed a bizarre idea, to have to comment on stuff I had no interest in or knowledge about. This was pounced on by a "moderator" with a patronizing reply:
 

And there's the main issue. Very enthusiastic mods. At least one, apparently, has fun deleting and editing posts he doesn't like. I've been using online forums since they were known as bulletin boards and I've never seen one quite so badly thought through.

*they use the account set up when you get a download of a product

> It may be inconvenient for you but works for the site.

I think that sums up the ethos Apple/Google/etc have brought - so much software isn't about the users any more, it boils down to being another mechanism of control.

> Weird user forum, by the way. Looks to be custom made, although it's fairly normal at first glance.
> You don't join the forum*, you gain membership by using it. Sounds reasonable but since there are
> no obvious instructions it's really confusing. The categories for posting are muddled up in different
> places and although you aren't told when you start using the forum, you can't post to it straight away

That had me thinking "I bet they're using Discourse", and I was right.

Discourse is what you get when the imbeciles behind StackOverflow think they know what they're doing, instead of realising their success there was mostly due to being less shit than Experts Exchange, and in spite off all the dumb hurdles they added, not because of them.

You're 100% right. That's probably why there are lively active threads on "why the forum is so bad" (so long as the particular mod I mentioned allows them to continue) and so few on the software itself.



 

I suspect a lot of the activity is down to performative busywork by really bored, underemployed it hacks.

I suspect you're right. It's not exactly a bustling hub of enthusiasm anyway. It should be, considering that Topaz products have created quite a stir in photographic and video circles in the last year, but I think the forum software is really stifling discussion. Plus, any time things kick off, the arsehole mod steps in, declares the discussion "off topic" or "not relevant" and either edits posts or cancels the thread altogether.

The video categories, in particular, are dire. It's a product that is clearly designed for high-end NVIDIA GPUs. It will run (just) on a very high-end CPU but may take multiple times longer. Yet the discussion has far too many posts along the lines of "it takes 60 hours to do 10 minutes of vid on my Matrox Mystique, what's wrong?" and "will this work on my Atom-powered notepad?"