HDMI vs SDI?

A

antonyoung

Active member
A couple of accessories I've been looking at, including the SmallHD Dp6, have HDMI and SDI versions. SDI versions cost $4-500 more. I'm moving up from a 7D, this is my first real video camera, so I've been reading avidly here and elsewhere trying to educate myself. From what I gather, people prefer the SDI connectors to the HDMI ones, and SDI is capable of longer cable runs. As neither of those would be worth $4-500 to me, are there other advantages I'm missing? And with the AF100, HDMI connection would still allow me to use both camera LCD and EVF, whereas SDI would not, correct?
 
With the Dp6 the HDMI version would also be compatible with your 7D, for that matter. And the Dp6 has some special functions to punch in on the wierd signal Canon uses on the 7d.

There are some market options that have both HD-SDI and HDMI.

Personally, I love HD-SDI. Locking durable connectors is a big deal to me. I've had PAs trip over cords and damage ports on cameras before (to this day the component out on my EX1 is broke), and HDMI is far more prone to this than BNC.

HDMI is going to work well not only with the AF100 but also a lot of consumer gear and some newer prosumer gear.

HD-SDI can be used with tons of high end pro gear.

Really depends on how you work, although it sounds like your situation suits HDMI.
 
For me, if your ONLY use of the monitor is on a camera rig for keeping an eye no your shot, (meaning a short cable, and attached to the camera, shoulder mount, etc), I wouldn't spend the extra money. Very little danger there of cable issues. Then you can use that cash for something else.

If you plan on using the monitor for remote viewing, using longer cables that can get under foot, or if you need timecode spend the extra cash.
 
It also depends on how future proof you need to be.

I'll soon be in the market for a small HD monitor. I like saving money, but getting a monitor with the HD-SDI option means I can use it on pro cameras that lack HDMI. It'll only take a few days of rental to make up the difference, and is guaranteed to work on any camera I purchase in the future.
 
I cases where I have to run a long HDMI cable from the camera to a director's monitor or video village, I use a short HDMI cable from the camera and zip tie the end of the cable to the tripod or dolly. I then use a female to female HDMI coupler to connect the long HDMI cable. If it gets kicked or tripped on, the long cable just pulls out of the coupler and doesn't tip over the camera or damage the camera's connector.
 
Basically they are, buuuuut:

SDI: SMPTE 259M, 270 MB/s
HD-SDI: SMPTE 292M, 1.45 GB/s
Dual Link: SMPTE 372M, 2.23 GB/s (2 coax connections)
Single Link 3G SMPTE 424M, 2.97 Gbit/s

Advantages are low jitter & superior signal integrity as well as higher data rates.
SDI can (and does in many professional installations) carry 4 full bandwidth (48khz) AES channels. HDSDI can actually carry 16.

SDI is a true unbalanced serial interface needing only a sigle wire and a return wire - coax.

HDMI is not fully serial in the same sense. While the individual data channels, Y,pB,pR rae serial streams, there are three of them along with a clock. These four signals are balanced LVDS signals.
So HDMI is also a PARALLEL interface in a sense. The problem is data skew. On a long cable it's not possible to make the four pairs exactly the same physical length. At some point this delay causes data skew. At worst case a data pair may actually be delayed into the next clock pulse resulting in visual chaos.

SDI is far more robust than HDMI. It can travel much greater distances over inexpensive cable.

Frank
 
Jim Brennan said:
I'm curious about this statement. Is the video signal through HDMI different than through HD-SDI? I though they were the same.
Click to expand...

I don't think it's accurate, but it is typically correct.

In my experience, monitoring through HDMI is good for composition & focus, but not colors. I have a feeling this is because anytime I'm monitoring via HDMI, it is a consumer monitor or television. Whereas when I'm looking at something via HD-SDI signal, it is on a (calibrated) professional monitor.

It's my understanding that HDMI and SDI signals are the same quality, but you have to consider what type of monitor you're viewing and its intended consumer/professional application.
 
Jim Brennan said:
I'm curious about this statement. Is the video signal through HDMI different than through HD-SDI? I though they were the same.
Click to expand...

They are the same, but if you think about it since HDMI is a consumer cable it works with lots of monitors and most are consumer monitors. So it's my guess that is what he is referring to. A $200 low end consumer HDMI monitor would be less accurate than a $800 or higher SDI monitor.
 
One big difference is that SDI carries TC. HDMI does not. BNC cables are easy to make and a lot less expensive than HDMI cables, and they lock.
 
Last edited:
Well, I get all of that, but in my original post I was pretty specific about a short cable to an on-camera monitor. I recommended HD-SDI for longer runs and to a video village. Would the colors be as accurate over a 3' or 6' cable to an HDMI, calibrated monitor?
 
For just monitoring it´s fine.

I would just not record from HDMI if I could have SDI though.

Frank
 
Basically you will have a more secure connection with the SDI BNC cable.

As far as pic quality goes there will not be any real difference you can see on a small monitor.

HDMI cables are not secure and less flexible, but they work fine, until you bend them to hard or knock into the jack hard. They are far more complex than BNC connectors. And as I stated earlier BNC cables are very easy to make and rarely go bad.

It is up to the individual to decide. With DSLR's you don't have a choice. But with the AF100 you do. It is great that if you have a HDMI monitor available you can use it. But personally I would always get a HD-SDI monitor over a HDMI one, even though it is more money.
 
You must log in or register to reply here.
Back
Top