interlaced video: unpredictable quality

[benoitvm]

when I launch an interlaced (50i) DXV3 clip, playback quality is unpredictable and seems completely random: sometimes it plays smoothly as expected from 50i video (i.e. smooth and fluid on external TV set) while sometimes it looks like its ignoring the interlaced mode (e.g. crawling text is very rough/fuzzy, sometimes with combed edges). Restarting, or pausing the clip does not help (50% chances it restarts/resumes "good" and 50% 'bad").
I have tried setting the comp speed to auto, 25 and 50 fps with no apparent change, except that there are never combed edges in 25 fps (but still unacceptable stuttering). I tried with 50i MP4 instead of DVX3, no change.
The PC is Win10, 6 core i7 8th gen, dual GPU, with a Intel UHD 630 and a nVidia Quadro P2000 (this is the GPU used by Resolume)
The external monitor is a consumer TV connected via HDMI, the corresponding HDMI port is configured as 1080/50i.

Obviously, interlaced video works, but how can I make sure it will work predictably, and not just randomly ?
I tried changing the Quadro GPU vertical sync settings, but that doesn't help.
I have a live show in 2 weeks with 60 sq. m screen and full HD projector ! Help !

More generally, even with progressive video, smooth playback seems very irregular (and I could not correlate with anything - the system is far from being overloaded): sometimes it's (almost) as good as real video, sometimes its pretty stuttering

[benoitvm]

Anyone ?

[Zoltán]

DXV doesn't support interlacing. How did you create the file?

Can you send us one of these interlaced DXV files you have issues with?
Thanks!

[benoitvm]

for a number of practical reasons I create my DXV files using TMPGEnc Video Mastering Works -> Quicktime -> framerate 25 (interlaced) -> DXV3

Shall I send a link to such a file to your email ?

[Zoltán]

I can't think of any good reason to make videos interlaced in 2019.
Every display I have seen in the last five years does progressive. If you have a TV with a HDMI input, I'm quite sure it's not a CRT, and runs it's display panel progressive.

Anyhow, you can send the file or a link to the file to mail@resolume.com, we'll take a look.

[benoitvm]

Unfortunately our show uses a complex mix of hardware, including an "old" HD videomixer which is HD TV compliant, i.e. 1080i or 720p. So for fluidity (50i) and other reasons we decided to set our show using the common denominator 1080i (the PC running Avenue is not the last device in the chain).
Will send you a link to a 50i DXV3 file
Tx

[Zoltán]

Thanks,
The file you sent is 25p.
I can see the artifacts in the file, but it's definitely not encoded interlaced. As I said DXV doesn't support Interlaced.

I guess you go from Resolume into your mixer, then to the TV right?

Resolume will render and display every frame as a whole (progressive), you should use progressive files.
If you use interlaced files, Resolume decodes the odd and even lines separately into successive, progressive frames. If you connect this to your mixer, it can happen that you see flickering output on your mixer, because the even/odd line render input might not be in sync with the even/odd line mixer output.

With the files you already have, you'd get a better result switching the mixer to 720p50.

[benoitvm]

Thanks for the suggestions

Actually the file I sent you was indeed progressive - sorry (resending a new one right now)
I agree with your explanations; when 50i playback is 'smooth' (see discussion below), pausing playback freezes on a frame containing the two merged fields, with nice comb edges...

My understanding is as follows:
feeding 'traditional' video to a computer display is never as good as sending it through a real chain of video devices, where frame sync is guaranteed from star-to-end, whereas computer displays (or video displays connected like a computer display, e.g. to the HDMI of the computer rather than a I/O device) are async with the video stream (except perhaps for some specific GPUs). This is not specific to Avenue of course, most software video players have this problem (symptoms range from occasional hiccups in e.g. panning shots, to visible tearing).
I'd say that using interlaced video (with double framerate 50i vs. 25p) simply makes the problem worse.

The only thing that bothers me in this topic is that sometimes it works just fine, sometimes not; even with 25p (50p) DXV3, sometimes playback is almost as smooth as 'traditional' video on a TV or similar device, while sometimes, without apparent reason, playback is more stuttering, like if frame sync is really random....
Even pausing/restarting the currently playing video can often toggle between these two 'states'...
This is why 720p50 isn't much better than 1080i50 in this case (and unfortunately, the videomixer we use can't mix resolutions: all input devices must be set on the same res/framerate)

Waiting for further hints based on the real interlaced DXV3 I just sent

[Zoltán]

The new file you sent is also 25p. DXV doesn't support interlaced. Really.

pausing playback freezes on a frame containing the two merged fields, with nice comb edges...

Comb edges are nice?
The fields were merged when encoding, it's not Resolume who's merging the fields.

I think you have a general issue with stuttering on your machine.
This usually comes from a bottleneck in the system, could be a background task that's running and eating up resources, or wrong config.
Check the system monitors on what this could be.
A search for "stutter" on the forums could give some topics that could help you diagnose.

[benoitvm]

The new file you sent is also 25p. DXV doesn't support interlaced. Really.

Indeed, the DXV doesn't say it is interlaced, arguably because it just ignores that (has no support for it).

Comb edges are nice?
The fields were merged when encoding, it's not Resolume who's merging the fields.

Indeed, that is what I meant with 'nice comb edges': it's not a desired effect, it's just a symptom I use to try understanding what's happening; comb artefacts (especially when freezing) just show that fields are merged without any deinterlacing processing during encoding or diplay.
However, and this is the puzzling part, when playback is ok (about 50% of the time), the interlaced-content aware display (TV set) really sees interlaced content, and fast moves or panning in the video plays smooth like real 50 frames/s or fields/s, definitely NOT 25 fps (did you see that on the crawling text in my sample file?): this somewhat contradicts the above idea that the interlace source was encoded 'as is' into a 25p DXV3 stream (in this case, my display would not recognize interlaced video, and hence, not properly display it fluidly like 50 fields/s TV, correct? Unless my dumb TV would blindly deinterlace when it sees combing artefacts, not when it sees 'interlaced content' signaled????Unlikely to me)

I think you have a general issue with stuttering on your machine.
This usually comes from a bottleneck in the system, could be a background task that's running and eating up resources, or wrong config.
Check the system monitors on what this could be.
A search for "stutter" on the forums could give some topics that could help you diagnose.

I understand that, but have no clue; when playing video, even with multiple layers, none of the system counters (Win Task Manager) report any resource being bottlenecked (GPU, CPU, RAM, disk,...are all below 25% utilization)
Remains the issue of lack of sync between the GPU (Quadro P2000) and the display...tried already tweaking a bit the 3D processing settings in the nVidia CP, but so far without success.
Will try researching further
Thx