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TOPIC: HDMI Monitoring

HDMI Monitoring 20 Dec 2013 13:03 #36669

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So is the HDMI out port available for true broadcast video monitoring like a AJA T-Tap would provide or merely a display port doing full screen preview? Will it show up as a device for Avid and Premiere? What are the drawbacks for using HDMI vs SDI for color correction provided your broadcast monitor has both?

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HDMI Monitoring 20 Dec 2013 13:43 #36676

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From the FCP page:
For the first time, Final Cut Pro supports external monitoring at resolutions up to 4K. Use the HDMI port on the new Mac Pro to connect directly to a high-quality display. Or use third‑party I/O devices for gorgeous 10-bit video monitoring via Thunderbolt 2.*

So I would say it is a full screen preview.

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HDMI Monitoring 20 Dec 2013 14:00 #36681

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HDMI is a two way communication connection that negotiates things, so the image may not be a 100% true, raw image. HDMI is not "for" true broadcast monitoring.

SDI does that, so for color grading and QA, SDI is the way to go for real broadcast and theater projection systems.

But HDMI can be used on a budget fairly well.

What specific broadcast monitor are you using?

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Last edit: by BenB.

HDMI Monitoring 20 Dec 2013 15:26 #36706

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I use a Kona 3, but was helping a friend set up a BM Mini Monitor. We couldn't get SDI to work with his Sony Broadcast Monitor, and reverted to HDMI. I was trying to explain that HDMI wasn't the best way of monitoring for color correction, but might be "good enough" for what he's doing (corporate and short form). I was just curious how the HDMI out on the MP works and if it is "true." The way Apple describes it on the page and suggests other products, I think it's not.

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HDMI Monitoring 20 Dec 2013 18:52 #36742

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It is a true 4K image, but an HDMI image. The Mini Monitor should work, that's the one that is T'bolt, right? I'd contact BMD and get it working correctly. Be sure you've got the latest versions of their software installed, too.

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HDMI Monitoring 20 Dec 2013 21:50 #36775

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Why all the poo-pooing on HDMI? It'll give a much better image than you'll receive over any broadcast. Broadcast compression destroys the image into a nearly unwatchable mess. There's only one standard in broadcast these days: Low quality and limited bandwidth.

Are broadcast legal levels still a thing in this digital age? If so, why?

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Last edit: by Redifer.

HDMI Monitoring 21 Dec 2013 07:45 #36830

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Broadcast legal is still very important. It applies to film, also. First of all, it gives a much higher quality image. But if you submit to a broadcast station, they still test it. One of my students submitted a digital file for film transfer by the production company who hired her, and they rejected it due to illegal broadcast levels. It is still a simple, effective method of QA.

But broadcast safe levels are not the issue here. And we're not talking about broadcast signals. We're talking about the raw image, un-tainted by compression or downgraded by two way negotiating data communication protocols, which is necessary for professional level color grading and QA work. As I said, HDMI works well, but it isn't a 100% replacement for SDI.

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Last edit: by BenB.

HDMI Monitoring 23 Dec 2013 00:57 #37008

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I don't think that most broadcast stations care what they get. I often see commercials in SD letterboxed for 16:9 and they are presented in a tiny little box onscreen. They aren't even deinterlaced properly, giving us 240p-style visuals. Some commercials are squished, some look like they didn't know what the hell they were doing on the video levels, others have very visible noise/white lines at the edge of the screen (as in sourced from an analog tape) which are NOT supposed to be seen, etc. I haven't seen anything professional come over a broadcast since they went digital.

Anyway HDMI is not compressed from what I understand. And how is it "tainted" or downgraded by two-way communication? What visible difference is there, if any? As I understand digital is either there or it isn't. Interference would cause macro-blocking somewhere in the image.

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Last edit: by Redifer.

HDMI Monitoring 23 Dec 2013 04:51 #37026

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SDI is a very solid industry standard. When you use SDI, no matter what product, it is SDI. SDI carries TC, and is a very durable connection.

HDMI can vary between cheap consumer to very professional. Flimsy, cheap HDMI cables can corrupt data, and the data correction on the receiving end may degrade the image to compensate. HDMI is not a very robust connection, and if you get good quality thick cables, the little connector may be stressed. Common HDMI screens like plasma need to be calibrated often, and are as accurate as a true SDI broadcast monitor. Not timecode in the signal.

Digital is not a there or not-there proposition. Look at the macro-blocking you mention. That is "partial data", so it is partly there and partly not. Both MPEG-2 and Uncompressed are digital, but one would never state that MPEG-2 is the same quality as Uncompressed, simply because they're digital.

More and more pro level HDMI equipment is starting to emerge on the market, which is a very good thing. So if you do broadcast of film work, and want to go the HDMI route, you'll have to do some homework to make sure the equipment you're buying is pro level enough for color correction and QA work. Meaning that once it gets a signal, it processes it properly. The big drawback of HDMI is in how the hardware handing the data processes it. This can vary widely.

Just because two cameras use the exact same CMOS sensor to capture the light, doesn't mean they're going to produce the same quality picture. How they're processes can vary greatly. May not be the best analogy, but it has been a very long, very busy, very tiring weekend. Where as SDI is a pretty solid standard, and when you get SDI hardware, it is rare you get crappy processing. It has just been around a lot longer for professional use.

MOST video is not shot for broadcast nor theater projections, so a true broadcast monitor is not really vital. If it is only going to be seen on computer screens, kiosks, digital signage systems, the web, then a good HDTV is perfectly fine.

The founder of Flanders Scientific, Inc (sadly deceased, he was a rare and wonderful human being) gave a presentation for our FCPUG a few years ago. It was fantastic. I wish FSI would put that info in a video and post it online. Great info about different standards, signals, processing, and how different monitor technologies work, pros/cons, etc.

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HDMI Monitoring 23 Dec 2013 09:06 #37043

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OK so basically you're saying that the drawbacks of HDMI is the physical format itself (which I certainly agree with) and not the actual image itself. SDI just sends the data and doesn't have to worry about other stuff and has a much better connection (BNC from what I've usually experienced).

What I meant by the "there or not" thing about digital wasn't the entire picture being there or no picture at all. Basically I was referring to interference. It's VERY noticeable in the digital realm ie: macro blocking. But in analog you can get added noise or color-shifting or what have you. I'm basically inferring that the video image transmitted through an SDI cable and an HDMI cable is exactly the same, provided that they reach their destination without problems. It's up to the display to show it properly, but an HDMI image is all there (provided to problems that you mentioned, none of which I've experienced). You said it may not be the 100% true raw image. I say it is. Yeah HDMI cables and jacks suck, but the image itself is fine.

One other thing I am curious about though is how can HDMI transfer a 4K image? I know with anything over, say 1920 x 1200 I need a dual link DVI cable. I thought HDMI and DVI were pretty much the same as far as the image data goes. You probably haven't noticed but the new Mac Pro and the new FCPX can do 4K. I know this may come as a surprise to everyone here because Apple has been really quiet, subtle and shy about mentioning the 4K thing.

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Last edit: by Redifer.

HDMI Monitoring 23 Dec 2013 14:55 #37078

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HDMI by itself is an uncompressed electronic signal, the devices on each end can actually compress themselves. Just because that HDMI signal hits the device uncompressed, there are consumer level devices that will compress that HDMI signal right away for processing internally. That is the huge gottcha in HDMI.

Only 3 of the 4 DVI types are compatible with HDMI, and none at all if the HDMI signal is component color space. And DVI does not support audio data. They are electronically similar, but not "the same".

HDMI comes in versoins, just like USB and other transport protocols. Version 1.4b introduced support for 1080p video. That latest version, 2.0 (released this past Sept) which Apple is using, increases bandwidth to 6 Bbit/s per channel, increases to 6 channels (4 audio, 2 video) and supports 4k at 60fps, plus YCbCr 4:2:0 color sub-sampling, 21:9 aspect ratio, etc.

So, HDMI comes in various versions, with various specs, and "what" data is put through it can be manipulated between devices. If a device devices to compress internally to MPEG-2, not matter what you send down that HDMI cable, you still only have the MPEG-2 quality. Thus the consumer level vs pro level HDMI equipment issue. No one makes a consumer level SDI (too expensive, another plus for HDMI).

That said, what is called "Clean HDMI" is a professional level of HDMI, which more and more devices are coming to market. HDMI could someday totally replace SDI. But for now, SDI is more reliable and trusted in the broadcast industry. So if you're working on broadcast for film, be sure your HDMI equipment is "Clean HDMI".

SDI cables are much less pron to interference. It supports 4:2:2 color sub-sampling, and the new 3G version supports 4:4:4 YCbCr sampling. It is only a matter of time until "Clean HDMI" will support these specs, be more standardized, and SDI (aside from more durable hardware for field use) could be on the way out.

Point is, if I buy SDI equipment, I know exactly what I'm getting. If I buy HDMI equipment, I need to do some homework to verify the quality of that specific device is what I need.

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Last edit: by BenB.

HDMI Monitoring 24 Dec 2013 01:24 #37122

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Understood, but I've never heard of anything sending MPEG2 (or anything other than uncompressed video) down the HDMI pipe.

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HDMI Monitoring 01 Feb 2014 08:46 #40305

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I just got my 6-core today, and even while I have a Blackmagic Minimonitor (Thunderbolt), I tried hooking up my OLED via HDMI to see what gives.

The HDMI port in FCPX is recognized in the video out pulldown in preferences just like an AJA or BM product.

The HDMI output matches my Minimonitor output exactly. The waveform on my broadcast monitor bears this out. How nice. too bad it won't work in Resolve, but I won't pick nits. Awful convenient.

Built-in HDMI monitoring in an NLE in the past was bogus because it was always another Desktop output. A Desktop output that was color managed by the system to who knows what ends, so it was inherently untrustable, especially from a broadcast legal/scopes point of view.

For just broadcast monitoring, there's nothing keeping HDMI from doing the job, as long as the software between your video files and the HDMI port is pumping out the video without modification. That's all AJA and BM do. And it appears that's what FCPX is doing as well, because Apple realizes people aren't going to be using the HDMI port on a $7K MacPro to watch pirated movies via VLC. The HDMI port needs to have real video production use, and it now appears it does. All it took was software.

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HDMI Monitoring 01 Feb 2014 12:42 #40319

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Just beware of the monitor you're using. HDTVs will actually alter the image themselves. There is no substitute for a real broadcast monitor.

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HDMI Monitoring 01 Feb 2014 17:04 #40333

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BenB wrote: Just beware of the monitor you're using. HDTVs will actually alter the image themselves. There is no substitute for a real broadcast monitor.


Well aware. I'm heavily invested in Sony PVM OLED. But it is a good warning to anybody just getting into it.

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HDMI Monitoring 01 Feb 2014 20:35 #40349

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One more note from my HDMI goofing around in FCPX on the new Mac Pro:

In FCPX, that output has zero latency. The Blackmagic MiniMonitor is nice and fast, and definitely prior to seeing this I was happy with any lag it displayed while scrubbing around, if I switch the monitoring output to HDMI it's absolutely zero.

Video below is Sony 4K XAVC footage from F55, in a 3840x2160 timeline. Output is via built-in HDMI. Machine is new Mac Pro 6-core, with D700 graphics. Footage is running off internal SSD.

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Last edit: by Direktor.
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