Am I capturing at the right fps?

[ChibiBoi]

OK, so this is not how I would normally capture HDTV if I was still running on a Windows and also had money to pay for real HDTV, but as of now, I'm using a SlingTV subscription and using OBS to capture through my Apple TV gen 3.

So my issue is, through my TV app (without AppleTV), I can set my TV's statistics to show me what fps the video is natively playing through the SlingTV app, which is 29.970fps (though I'm not sure if that's interlaced or progressive).

However, when I'm capturing, obviously I'm using the SlingTV app on my Apple TV device. So I've tried setting my Apple TV device to play video at 1080p 29.97Hz, hooked it up to my MacBook through Elgato HD 60X, and capturing via OBS at 29.970fps.

What I'm noticing though is capturing at 29.970fps results in choppy motion with dropped frames.

SO I went back and changed my Apple TV settings to 1080p 59.94Hz and changed my OBS to capture at 59.940fps. The motion is much smoother, however there's obviously a lot of duplicate frames. However, it's not the same pattern you'd expect.

With 23.976 -> 29.970 you get a duplicate frame every 5 frames (ABCDD) so doubling that to 59.940 fps, I was expecting a pattern of AABBCCDDDD. However that's not the case.

Anyway, can someone help me figure out how to adjust my settings so I'm not getting any dropped frames or duplicate frames?

[jagabo]

Yes, the source material was 24 fps. Sling is probably streaming this at 30 fps with a duplicate every 5th frame. Then your AppleTV is converting to 60p (by duplicating each frame) for output.

Your 30p capture has both duplicates and missing frames -- and not in a consistent pattern. The 60p capture has lots of duplicates, again not in a consistent pattern. The latter can be decimated back to 24p but the usual "M in N" decimation doesn't work perfectly with the inconsistent pattern. AviSynth:

TDecimate(Cycle=10, CycleR=6) #remove 6 duplicates from every group of 10 frames

Sample attached. Ignore the file name -- the source was the 60p video.

Larger cycles like TDecimate(Cycle=20, CycleR=12) work a little better.

[ChibiBoi]

Yes, the source material was 24 fps. Sling is probably streaming this at 30 fps with a duplicate every 5th frame. Then your AppleTV is converting to 60p (by duplicating each frame) for output.

Your 30p capture has both duplicates and missing frames -- and not in a consistent pattern. The 60p capture has lots of duplicates, again not in a consistent pattern. The latter can be decimated back to 24p but the usual "M in N" decimation doesn't work perfectly with the inconsistent pattern. AviSynth:

TDecimate(Cycle=10, CycleR=6) #remove 6 duplicates from every group of 10 frames

Sample attached. Ignore the file name -- the source was the 60p video.

Larger cycles like TDecimate(Cycle=20, CycleR=12) work a little better.

Thank you! 10 or 20 was my count too when I first tried counting. But then I went back to double check and I kept losing my spot lol. Do you know what could be causing this inconsistency? Should I try setting my Apple TV to 60fps even instead of 59.94?

[jagabo]

My guess is that sling is probably encoding and streaming the video at 30p. So four film frames (A B C D) becomes 5 digital frames before streaming:

A B C D -> A B C D D

Then your AppleTV is doubling each of those frames to make 60p:

A B C D D -> A A B B C C D D D D

Then your capture device is missing some of the frames at random intervals and adding duplicates of others to make up for them.

I would try setting the Apple TV to output 30p, then capture at 30p (so the capture device can keep up, use faster compression settings if possible -- AVC instead of HEVC, for example). Hopefully you'll end up with the A B C D D pattern which can be easily and cleanly decimated.

I'm using rounded whole numbers for the frame rates but they are probably really 29.97 (24000/1001) and 59.94 (60000/1001).

[ChibiBoi]

My guess is that sling is probably encoding and streaming the video at 30p. So four film frames (A B C D) becomes 5 digital frames before streaming:

A B C D -> A B C D D

Then your AppleTV is doubling each of those frames to make 60p:

A B C D D -> A A B B C C D D D D

Then your capture device is missing some of the frames at random intervals and adding duplicates of others to make up for them.

I would try setting the Apple TV to output 30p, then capture at 30p (so the capture device can keep up, use faster compression settings if possible -- AVC instead of HEVC, for example). Hopefully you'll end up with the A B C D D pattern which can be easily and cleanly decimated.

I'm using rounded whole numbers for the frame rates but they are probably really 29.97 (24000/1001) and 59.94 (60000/1001).

Yeah the 30fps sample is with the AppleTV set to 29.970 and OBS also set at 29.970, which seems to have hella dropped frames. But OBS always reported 0 dropped frames every time I captured. So I’m not sure why. Maybe it’s my capture card? I wonder if Apple TV is actually giving me interlaced feed and my capture card is doing some weird deinterlacing.

EDIT:
I've played around with my Apple TV settings. I've changed the resolution to 1080p 59.94Hz but set content frame rate on, and captured with OBS at 29.970fps to make it easier to see what's going on. I've found at every 20 frames, the frame that's duplicated will swap.

For example:
ABCDDABCDDABCDDABCDA and the 21st frame will be a duplicate of frame 20, and this pattern repeats:
ABCDDABCDDABCDDABCDAABCDDABCDDABCDDABCDA

Maybe that's just how SlingTV does telecine? But that's consistent with your assessment of cycle=20