HD-SDI Switching and Genlock/Timecode

[TheReverendDave]

My church is looking to head into the territory of IMAG. I've got a pretty good handle on how I'd like to see the flow of video, by sticking with HD-SDI. Specifically, I've got my eye on the AVHS300G to handle this.

Currently, our church is looking to upgrade from the single Panasonic DVX100 we have, and get a few great HD cams. I've really enjoyed working with Panasonic equipment, so I'm looking to the HPX170, and the HPX300/370 and using HD-SDI outs on both.

My question is this, the HPX170 does not have genlock on TC/in/out. Is this going to be a problem for switching, or recording the HDSDI streams for sync later? I guess this really leans into my lack of knowledge as to what exactly genlock/TC syncing does for a multicam shoot.

So, in summary, when switching using HDSDI, do you need to have a TC generator and cameras capable of this to be able to sync video/audio signals, either for IMAG display or HDSDI capturing?

Thanks!

[petereit]

You may get away without syncing genlock or time code. Read this thread.

[petereit]

When live-switching, the ideal situation is to align your genlock on all your video sources. The Panasonic AV-HS300G can do internal sync, but it may add a frame or two of delay. That's the way I'm running mine now and the delay is barely noticeable. I'm probably the only one who even sees it, but that's because I know it's there and I know what I'm looking for.

99% sure nobody in the congregation even notices. I don't think you'll have any problem running without genlock sync.

[tdangelo]

Originally Posted by TheReverendDave

when switching using HDSDI, do you need to have a TC generator and cameras capable of this to be able to sync video/audio signals, either for IMAG display or HDSDI capturing?

Reverend Dave,

It seems like you may be confusing the purpose of these various synchronizing signals.

Genlock, Blackburts, Sync, Bi-Level Sync, Tri-Level Sync are all used to tell the various pieces of video equipment when to blank and retrace. This is very important when switching between sources because you want a switcher's cut to occur during blanking. Otherwise the cut will look like a glitch. These timing signals also keep all video sources that are locked to them moving along at the pace. The analogy of a drum corps is a good one with everyone hitting their drum exactly on the downbeat and marching at the same pace.

Timecode does not lock any sources (itself) but rather records a unique identifier on every frame of video/audio. It just so happens that in SMPTE timecode these unique identifiers are formatted as hours, minutes, seconds and frames, but it could have just as easily been alphabetic or any other logical code. Timecode when recorded into a signal allows you to tell a VTR, VCR, DDR, ATR, ADR, computer, etc., on playback to go to a certain place in the recording and have the device understand where you mean. If all the sources have the same timecode you will be able to go to the same place in multiple signals. So, if you were never recording anything but only stream live or only project I-mag ... timecode may not be important ... but if you are recording for a future edit, timecode can be very important.

- Tom D'Angelo
NYC

[TheReverendDave]

Thanks for the replies guys.

The biggest reason I'm asking is because as a church, there is no way we can afford 3 (or more) HPX300s, and I know we need at least 3 cams to do good IMAG. I really want to stay with HDSDI, cause going with anything less seems like a waste to me. So, I'm looking to get the 300 for the main, and a 170 for the side, and depending on budget, a 300 or 170 for a wide/moving shot. Since the 170s arent genlocked, I was wondering if this could/would work.

I also would prefer to stick with Panasonic cameras/switcher because of volunteer training and equipment compatibility, as well as DVCPROHD, which I prefer to HDV. We've got good training on the DVX100 we have already. With HPX170s very similar, and the HPX300 full pro, we can have a good scaling system for volunteer training.

The lack of matching timecode shouldn't be a bother. With the Telestream Pipeline model that I'm looking into, the lack of matched timecoding shouldn't be an issue.

So I'm hearing that lack of Genlock can cause visual "issues" or imperceptable delay, but until we can afford more and better cams, the lack of Genlock should be good enough for rock and roll!

[tdangelo]

To expand further .... because the sources must be switched during blanking how do you incorporate sources that are not genlockable? You use a frame synchonizer. These can be internal to the switcher or external. The result in either case is video delay. Video delay can be worked around in a recording, a webcast, broadcast, etc., BUT CANNOT be worked around in I-mag. The more sources that are not genlockable ... the worse the delay. The smaller the venue ... the worse the delay appears. There is a very real risk the picture on the Imag screens will be out of sink with audio from PA if you rely on frame syncs. Genlocking and timing signals is always better.

- Tom D'Angelo
NYC

[zactommo]

Any reason why you need to be HD?

If money is a problem, then maybe you should be looking down the used SD broadcast quality gear. That way, your guaranteed to get genlock, and TC IN/OUT on your cameras, and you can hopefully get 3 matching cameras, which always makes life easier.

Whats your reasons behind wanting HD?

[TheReverendDave]

Right now our church has a Sunday video campus that plays video from the previous Saturday evening service at the main campus. We are planning on starting two more campuses in the next year. We've tried HD a couple times (demoing cameras), and it does seem to make a noticeable difference to picture quality. A digital tapeless workflow would be fantastic with the amount of video our church produces every week (4 different projects this week). I'm aware that HD is not "necessary", but spending alot on SD/tapes seems like a step backwards in quality as well as productivity. We are planning on doing significant amounts of green screening, and DV is not a good solution for that. This is a church that is growing fast and is aiming big, so HD seems appropriate.

I still am in the process of building a proposal, so I can shoot for the moon... Heck why not propose 3 HPX300s...

I've gotten several suggestions to have identical cams for IMAG. How necessary is this, and what are the benefits?

[tdangelo]

Originally Posted by TheReverendDave

... I'm aware that HD is not "necessary"...

Please forgive me if the response seems to ruffle feathers but there are many who struggle with the same thought.

To them I ask, "would you consider buying a black & white camera?" manufacturers still make them. They will deliver a picture. You can do I-mag, webcasting, sell DVDs, etc. People with color TVs, even fancy flat panel ones can still see your programming.

No, that would be silly ... and a poor investment. Same with SD now.

I think it is important for the church to understand that HD is not a lofty "state of the art" medium that only the highest end of broadcast networks can afford or use.

HD as we know it is already passe. 1920x1080 progressive is quickly being transplanted by 3D, 3G, 444, 4K, 5K, etc. 1080 interlace is going away. 720p is called "medium def." 480 (SD) has been dead and burried.

My point here is that there will always be "a better" technology than which you can afford. There will also always be a worse technology than that which is appropriate. I think all who are involved in church media ministry have a responsibility to produce the best product possible with the tools that are available...... but to do so good tools are certainly helpful.

My .02 cents.

- Tom D'Angelo
NYC

[tdangelo]

Originally Posted by TheReverendDave

I've gotten several suggestions to have identical cams for IMAG. How necessary is this, and what are the benefits?

Its very helpful especially if you do not have a highly trained team that knows how to "match" the look of different model cameras.

- Tom D'Angelo
NYC

[TheReverendDave]

This may seem like a dumb question, but genlock doesn't need to be on the switcher, correct? If you genlock the cams with a device and then pipe the HDSDI signal to a genlockless switcher, the cameras would still be in sync.

I'm asking cause the new Panny switcher looks great and affordable, but no genlock on it.

[tdangelo]

Genlock is the act of making sure that all components are blanking at the same time.

Sync, bi-level sync, tri-level sync, black burst, are the timing signals which can be used to time all items together.

The switcher does not need to be the origin of the timing signals, but in a system that does not use frame syncs all sources AND the switcher must be connected to the same timing signal.

- Tom D'Angelo
NYC