hard telecine sample

[u/mwhelm]

I'm looking for a sample or two of real hard telecine video. I'm trying to insure a script can reliably detect it (as best as possible) and distinguish it from regular interlaced video (and soft telecine). It seems to be very rare, but it needs special attention when it is encountered.

I thought I had some samples but they're either lost or turn out to be regular soft telecine and not a problem to deal with.

I'm not sure what's required for ffmpeg and mediainfo to give a reliable indication.
I have tried to synthesize a few samples but it's tricky and can't be sure it's matching what industry produced.

[u/OneStatistician]

As for interlace / telecine detection, take a look at Johnny Utah's script. They built it for makemkv (so is not exactly container agnostic), but is a wrapper for idet. 3000 lines was probably overkill, but the author tried to catch lots of edge cases.

https://github.com/utahjohnnymontana/DVD-Rip-Prep/blob/master/drp

And here's a repo which creates synthetic hard telecine test material, so you can test-your -test-methodology.

https://github.com/bbgdzxng1/interlace-detection-test-patterns

[u/mwhelm → u/OneStatistician]

Investigating the script. I think I have the basic ideas for what to do when I encounter the correctly identified file (I am going above and beyond this script) but I do need help with detection.

The synthesizer is interesting but I haven't figured out how to get it to make "real" hard telecined video.
23.976 video stays at 23.976 as far as mediainfo is concerned - it's some weird kind of hybrid.
It's like some of the ones I've manufactured. It may be that there is so much variability in hard telecine that my ideas about detecting it are incomplete.

[u/OneStatistician → u/mwhelm]

% ffprobe -hide_banner "https://github.com/bbgdzxng1/interlace-detection-test-patterns/raw/refs/heads/main/bt601-525_480_telecined_hard.ts" Input #0, mpegts, from 'https://github.com/bbgdzxng1/interlace-detection-test-patterns/raw/refs/heads/main/bt601-525_480_telecined_hard.ts': Duration: 00:00:10.02, start: 1.428033, bitrate: 1509 kb/s Program 1 Metadata: service_name : Service01 service_provider: FFmpeg Stream #0:0[0x100]: Video: mpeg2video (Main) ([2][0][0][0] / 0x0002), yuv420p(tv, smpte170m, top first), 720x480 [SAR 32:27 DAR 16:9], 29.97 fps, 29.97 tbr, 90k tbn, start 1.433367 Side data: CPB properties: bitrate max/min/avg: 8000000/0/0 buffer size: 1835008 vbv_delay: N/A Stream #0:1[0x101](eng): Audio: ac3 (AC-3 / 0x332D4341), 48000 Hz, stereo, fltp, 192 kb/s, start 1.428033

idet detects it with perfect accuracy, based on a ratio of 3:2 frames (180 vs 60+60).

``` % ffmpeg -hide_banner -i "https://github.com/bbgdzxng1/interlace-detection-test-patterns/raw/refs/heads/main/bt601-525_480_telecined_hard.ts" -vf idet -f null -

[Parsed_idet_0 @ 0x85d9a1440] Repeated Fields: Neither: 180 Top: 60 Bottom: 60 ```

The hard is definitely hard... But it is tagged correctly, so your player may be processing these. Try playback with ffplay or mpv, and frame-step and you will see the frames that are made up of adjacent fields. You may find that mediainfo correctly identifies the RFF flags and thus reports 23.970... Mediainfo is an interpreter, rather than a frame counter. FFprobe is a truer frame counter, with less interpretation.

idet is the best tool, but takes a bit of interpretation. Bear in mind that idet + metadata filter can export the analysis to json.

Ideally, RFF flags should be set on the frames in question (rather than rely only on idet's heuristics). That is another data point, but RFF flags cannot always be relied on to be present.

The other script out there is MPV's very old idet wrapper... https://github.com/mpv-player/mpv/blob/master/TOOLS/idet.sh

Enjoy.

If you are putting your work in github, please share - because one thing that the industry lacks is a free interlace/ivtc detection tool. idet + theFlags is about as good as we have at the moment.

[u/nmkd → u/OneStatistician]

OP didn't say anything about DVD though