[Selur]

Use ffmpeg's interlace detection to figure out if a video has interlacing.

Problematic,..
I get:

Input #0, mpeg, from 'f:\TestClips&Co\files\interlaceAndTelecineSamples\interlaced\eis-sample.mpg':
  Duration: 00:00:59.98, start: 0.813356, bitrate: 2441 kb/s
    Stream #0:0[0x1e0]: Video: mpeg2video (Main), yuv420p(tv, top first), 480x576 [SAR 8:5 DAR 4:3], 25 fps, 25 tbr, 90k tbn, 50 tbc
    Side data:
      cpb: bitrate max/min/avg: 2350000/0/0 buffer size: 1835008 vbv_delay: N/A
    Stream #0:1[0x1c0]: Audio: mp2, 44100 Hz, stereo, s16p, 224 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (mpeg2video (native) -> rawvideo (native))
Press [q] to stop, [?] for help
Output #0, rawvideo, to 'NUL':
  Metadata:
    encoder         : Lavf58.65.100
    Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p(tv, top coded first (swapped)), 480x576 [SAR 8:5 DAR 4:3], q=2-31, 82944 kb/s, 25 fps, 25 tbn
    Metadata:
      encoder         : Lavc58.115.102 rawvideo
frame=  360 fps=0.0 q=-0.0 Lsize=  145800kB time=00:00:14.40 bitrate=82944.0kbits/s speed=79.3x
video:145800kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.000000%
[Parsed_idet_0 @ 00000292278275c0] Repeated Fields: Neither:   352 Top:     5 Bottom:     4
[Parsed_idet_0 @ 00000292278275c0] Single frame detection: TFF:   247 BFF:    47 Progressive:    16 Undetermined:    51
[Parsed_idet_0 @ 00000292278275c0] Multi frame detection: TFF:   330 BFF:    22 Progressive:     9 Undetermined:     0

for a totally tff source.
And I get for example:

Input #0, mpeg, from 'f:\TestClips&Co\files\interlaceAndTelecineSamples\telecine\mpeg2_720x480_4-3.vob':
  Duration: 00:03:18.03, start: 0.228411, bitrate: 7030 kb/s
    Stream #0:0[0x1bf]: Data: dvd_nav_packet
    Stream #0:1[0x1e0]: Video: mpeg2video (Main), yuv420p(tv, fcc/bt470bg/bt470bg, top first), 720x480 [SAR 8:9 DAR 4:3], 29.97 fps, 29.97 tbr, 90k tbn, 59.94 tbc
    Side data:
      cpb: bitrate max/min/avg: 8000000/0/0 buffer size: 1835008 vbv_delay: N/A
    Stream #0:2[0xa0]: Audio: pcm_dvd, 48000 Hz, stereo, s16, 1536 kb/s
Stream mapping:
  Stream #0:1 -> #0:0 (mpeg2video (native) -> rawvideo (native))
Press [q] to stop, [?] for help
Output #0, rawvideo, to 'NUL':
  Metadata:
    encoder         : Lavf58.65.100
    Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p(tv, fcc/bt470bg/bt470bg, top coded first (swapped)), 720x480 [SAR 8:9 DAR 4:3], q=2-31, 124291 kb/s, 29.97 fps, 29.97 tbn
    Metadata:
      encoder         : Lavc58.115.102 rawvideo
frame=  360 fps=0.0 q=-0.0 Lsize=  182250kB time=00:00:12.01 bitrate=124291.7kbits/s speed=50.2x
video:182250kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.000000%
[Parsed_idet_0 @ 000001dbffdd75c0] Repeated Fields: Neither:   359 Top:     1 Bottom:     1
[Parsed_idet_0 @ 000001dbffdd75c0] Single frame detection: TFF:   332 BFF:     0 Progressive:     0 Undetermined:    29
[Parsed_idet_0 @ 000001dbffdd75c0] Multi frame detection: TFF:   332 BFF:     0 Progressive:     0 Undetermined:    29

for a telecined source.

-> Nope, I don't know any reliable method to properly detect whether a source is interlaced/telecine/mixed/progressive/fieldblended/... other than looking at the source with human eyes.
I tried it years ago with https://github.com/Selur/MPlayerInterlaceDetection and MeGui also has some interlaced detection http://avisynth.nl/index.php/Interlace_detection, but none of these is really reliable.
Please let me know in case you find something good.

Use ffmpeg's black bar detection to find black bars

you would probably need to run the detection multiple times with different settings (on different parts of the input) and then add some boundaries evaluating the results.

Do a test noise filter. Use something like KNLMeansCL with a high strength setting to and do a comparison between input and output to see if there's a big difference. I'm thinking something like VMAF would be good. My assumption (Would this be wrong)? is that noisy videos would have lower VMAF scores than clean videos. Is that true? Would there be a better way to score noise of a video?

I doubt this works, at least I don't know a way to do this properly to differentiate between noise/details and artifacts.

Which noise filters should I be looking at?

Different noise characteristics (spatial/temporal/chroma noise,..) -> different filters

Which deinterlacing filters should I be looking at?

for the analysis steps or for the end deinterlacing?
For the analysis analying the effects of standard ivtc and bob filters is probably good enough, for the end deinterlacing as a start:
QTGMC for interlaced content
VIVTC for telecined and different pull-down sources (+ may be vinverse/vinverse2)
soft telecine -> no clue
VFM for field shifted content
QTGMC+sRestore for mixed content (not as good as manual tuning, but a quick way)

So here's my plan of attack, tell me if it's crazy.

Seeing that you need to ask about recommend filters -> It's crazy, but that doesn't mean you can't stumble over some good heuristics.
I thought about this when I started with the first versions of sx264 which later became Hybrid, sadly I couldn't figure it out back then.
Assuming your input has similar characteristics regarding noise etc. I think it's possible to do some best guesses based on some tests, but I don't see this reliably working on random sources.
(Knowing for example the source was created with video camera xy or similar I think its possible, but still lots of work.)


Cu Selur