AGC code is affected by wow/flutter

[happycube]

@Gamnn found an issue where the two fields luma didn't match up after the AGC change. Oops.

[toynbeeidea]

Yeah, I think I got one too, if you need a further example. Testing the new build now.

[happycube]

If it's not fixed, that'd be nice, thanks!

[toynbeeidea]

Ah, yeah. I'm afraid I'm still having an issue:

https://drive.google.com/open?id=1KO0f3-ysRatvxDON7b-_B0EsSWdErvk_

Clip is a little longer than I intended, see issue #495. I meant to just show the cloud section after the "Garrrr Video" screen.

[Gamnn]

frame 393, timecode 00:47:48.01 does appear affected.

be sure the trailing _ is in the URL if you have trouble downloading toynbeeidea's sample.

[happycube]

Thanks for the tip about the _, that got me just now...

Going to look at two changes: Changing the AGC on first fields only, and keeping a running average (which should cover wow/flutter on CLV disks as well)

[toynbeeidea]

I ran the entire video through last night. Seems better now as of 9ed93a0. There's a bit of a luma spike or something during the cloud sequence, but I'm inclined to write it off as a flaw in the source. Going to leave this open for the moment, as I gather that this is a partial fix?

[Gamnn]

Sounds like it's due to the wow/flutter affecting the first field on one frame, causing the AGC to adjust both fields just for that frame.

In cases where there's a lot of frames like that, might be best to use the --noAGC option, until AGC is a little smarter. (maybe a rolling average, ramping up if it changes rather than spiking on single errant frames)

This is also something that might be fixed with a TBC-based AGC in once VITS is better worked out. #326 #490

[toynbeeidea]

Ran it through with --noAGC, and yeah, no more luma spike - thanks!

[Gamnn]

Frame 393 seems to be due to a dropout in the hsync, more examples on issue 503.

[Gamnn]

Here's another interesting case. A frame goes bright with no obvious dropouts. A decode in April had an audible pop here, but no problem in the audio in the current commit. Wow/flutter related I'm guessing?

pop.ldf.zip

[happycube]

Can you recheck this? It should be better now.

[happycube]

Checked pop.ldf.zip - doesn't sound great, but no pops, so closing