Up Down Cross HD low quality deinterlacing

Further to my discovery that the ATEM Mini Pro appears to deinterlace 1080/50i native interlaced sources to 540/25p and then upscales and frame doubles to get to 1080/50p, I thought I'd see if an Up Down Cross HD Mini Converter would improve things and solve my issue of being able to use 1080/50i native interlaced content with an ATEM Mini Pro at 1080/50p without major quality issues.

Well the Up Down Cross HD also seems to deinterlace 50i to 25p, not 50p, even when configured to 50p output, it just repeats the 1080/25p frames...

I've recorded the 1080/50p 3G-SDI output when feeding it a 1080/50i source with native interlaced motion (a recording of an entertainment show shot interlaced). Sadly although the video output format was 1080/50p - the content of it showed it was a deinterlace from 1080/50i to 1080/25p followed by a frame double to get to 1080/50p.

When I captured the 1080/50p output of the Up Down Cross HD and scrubbed through it in Resolve and QuickTime Player a frame at a time, every frame was repeated.

Not quite what I'd expect for a device that is advertised as being "a full standards converter that lets you convert any SD or HD video format to any other SD or HD video format using high quality Teranex algorithms!"

This certainly isn't converting 1080/50i to 1080/50p - it's converting it to 1080/25p and then frame doubling it with 2:2 pull-down... Not something I'd describe as high quality.

Can anyone recommend a BMD or other device that does an acceptable 1080/50i to 1080/50p deinterlace without halving the motion, and will deinterlace with full 50Hz motion?

(If anyone is using this in their archive workflow for upconversion - be very aware of its limitations. It's a great 'get out of jail' converter to let you plug in any HDMI or SDI/HD-SDI/3G-SDI source and get a fixed, known-compatible, signal out of it - but it's not anything you want near interlaced sources if you want a quality conversion, Teranex algorithms or not)

It is even worse the other way around.
The UDC converts 50p to 50i by dropping each second frame to 25p intermediate with frame doubling.
Instead of just removing half of the lines of each frame frames to get clean fields.

Als long as this is not fixed BMD UDCs are not usable for any production with motion.

BMD Teranex Express does a much better job.
Also Decimator devices support much better conversion results.

It is even worse the other way around.
The UDC converts 50p to 50i by dropping each second frame to 25p intermediate with frame doubling.
Instead of just removing half of the lines of each frame frames to get clean fields.

OK - so the UDC is really designed for 1080/30p and less sources and/or outputs, unless you are going 50p to 50p or 59.94p to 59.94p (say 720/50p up to 1080/50p, or 1080/59.94p down to 720/59.94p)

If you start or finish with 50i (or 59.94i) then it goes via 25p (or 29.97p) on the way and frame doubles :

• 1080/50i->1080/25p (losing 50Hz motion) then frame doubles->1080/50p
• 1080/50p->1080/25p (dropping alternate frames)->1080/50i with 2:2 pull-down (aka 1080/25psf)

Als long as this is not fixed BMD UDCs are not usable for any production with motion.

As the product has been out for 6 years, this feels baked in. Such a pity - and poor for it not to be noted on the product page. Blackmagic is usually excellent in detailing their products' performance. This feels a bit shabby.

When you see a product say it does 50i->50p or 50p->50i conversion you wouldn't expect a 25p intermediate to be used halving the motion rate...

This feels like it's purely designed for people with 1080/25psf or 1080/29.97psf sources to handle, or who are running 30fps or lower for their entire workflow.

BMD Teranex Express does a much better job.
Also Decimator devices support much better conversion results.

Looks like I'll be returning my UDC and going for a Decimator... The Teranex is over-specified for my 50i->50p conversion requirement...

It is even worse the other way around.
The UDC converts 50p to 50i by dropping each second frame to 25p intermediate with frame doubling.
Instead of just removing half of the lines of each frame frames to get clean fields.

Als long as this is not fixed BMD UDCs are not usable for any production with motion.

BMD Teranex Express does a much better job.
Also Decimator devices support much better conversion results.

Before I return my BMD UDC I thought I'd test it with some 50p and 50i source media - including content with 50fps timecode burned in.

My first test was a clip with alternate frames of a large black number 1 or 2 on a white background. In 50p this gives alternate frames that are clearly different, in 50i (interlaced on Resolve export) this gives alternate fields that are clearly different.

Clips were exported from Resolve in ProRes HQ in 1080/50p or 1080/50i and played from SD card on a Hyperdeck Studio Mini into a UDC configured to output 1080/50p or 1080/50i - and then captured losslessly in v210 uncompressed by an Ultrastudio Mini 4K (SDI In, SDI Out)

As expected this confirms that 50p to 50i is done by discarding every other 50p frame to create a 25p sequence, with these 25p frames then interlaced to 50i (with no intra-frame motion as a result). This halves the 50Hz motion to 25Hz.

With my 50fps test clip of alternate numbers 1 & 2 each frame with 50 frame/second timecode, I get an interlaced output just showing a single number (1 in this case) from my source (all the 2s on the alternate frames have been discarded). In timecode terms you just see every other source frame number in both interlaced fields.

In an ideal world the 50p frames should be interlaced to 50i fields - so each field is different, there is intra-frame motion - and you get 50Hz motion preserved. (Ideally you'd see the large black 1 and 2 in alternate fields in each frame, and the 50fps frame timecode differ in each field too)

If you run 50i to 50p (with field-based 50field/second timecode and ak large black 1 in field 1 and large black 2 in field 2) there is deinterlacing going on to 25p and then frame repeating to get to 50p - but with some awareness of INTER-frame motion by the look of it.

The timecode at the bottom of frame is cleanly showing the timecode number from a single field, repeated across two 50p frames, (so it's deinterlacing to 25p from a single field - i.e. bobbing and line doubling) but the overall image shows a combed 1 and 2 simultaneously (which I assume it sees as static information as there is no difference between the fields in successive frames so for this content it weaves assuming it's static vertical detail) So there is some motion adaptation going on at the pixel/block level - but instead of deinterlacing 50i to 50p it's deinterlacing 50i to 25p and then frame doubling to 50p.

NB this is an improvement on the way the Frame Rate converters on the Atem Mini Pro work, as at least information from both fields is being used... On the Atem Mini Pro you just get one 50i field, line doubled and repeated to get to 50p. (i.e. half the vertical resolution on static content). If you fed an Atem Mini Pro 1080/25psf you'd end up with 540/25p upscaled to 1080/50p quality...

thats really bad