HD-SDI vs SDTI

[Ramona Howard]

Today, SDI (SMPTE 259M) is in widespread use as the method to transfer uncompressed digital audio and video signals between digital devices in broadcast and post-production facilities. The advent of compressed video formats such as DVCPRO, DVCPRO 50, Betacam SX, Digital-S, DVCAM, and MPEG-2 brought about the need to transfer compressed audio and video streams between devices. SDI has been used to meet this need, but signals must be uncompressed at the output of a device and recompressed at the input of the target device. Repeated compression/ decompression passes degrade the signal unnecessarily. SDTI was built on the SDI base to provide a mechanism for exchanging digital audio and video signals in their native compressed formats.

SDTI was built on the SDI base to provide a mechanism for exchanging digital audio and video signals in their native compressed formats.

Hope this helps,
Ramona

[Sean Oneil]

This is like asking if a strawberry milkshake is better than fresh strawberries. Clients should not be giving technical advice to editors. Just my $.02.

Uncompressed video is the best quality you can get. Period. HD-SDI is uncompressed. It can’t get any better. So if you’re mastering to D5 (which you should be if your client is this picky), then it makes absolutely no difference whatsoever because D5 is an uncompressed format.

SDTI is similar to DV over firewire. You can capture the native HDCam codec without decompressing it. Of course decompressing it is fine and 100% lossless (in this case at least). But if you master to HDCam after doing this, the deck will recompress it to the HDcam codec which is 3:1 or something like that.

The advantage of SDTI, aside from using less disk space, is that you can avoid this re-compression for cuts-only frames. It’s just like DV over firewire. Any frames that are part of a transition, anthing with color correction applied, any frame with any effect or filter whatsoever will still have to be recompressed and thus, not be able to take advantage of this.

More importantly, you can’t even capture HDCam natively over SDTI with anything other than Sony’s xpri non-linear editing system. Sony has decided to exercise what in my opinion is ethically unsound. They own the pro tape formats w/ strong market penetration, and they own a movie studio – so they decided to exploit this by only allowing their own NLE to have this capability, hoping that people will find themselves in your situation and feel pressure to switch to their system. Panasonic on the other hand, allows Apple and Avid to use their DVCPro formats.

A D5 deck is probably cheaper than an xpri, and you’ll get a lot more use out of it. But if you do go HD-SDI back to HDCam, the loss is minimal and visually non-existent. It’s what just about everyone does because they have to. Very similar to Digibeta in the SD realm.

[Shane Sokolosky]

Matrox has a pretty good document on it (https://www.matrox.com/video/press/papers/sdti.cfm) , the only time I’ve ever seen it used is with Sony’s XPRI system connected to an MPEG IMX VTR to do faster than real time transfers of data.
From what I’ve seen on it, it just looks like a signal that carries all of the digital information that is on the tape for making direct dubs or copys.

Besides if it were really better quality (or if SDI was missing something) wouldn’t we see it on the HDCAM SR series of decks?

Shane Sokolosky

SAN Product Manager
ProMax Systems inc.
16 Technology Dr. Ste.106
Irvine, CA. 92618

Office (949) 727-3977 x108
Toll free (877) 776-6292
Fax (949) 727-7002
Website-https://www.Promax.com
shane.sokolosky@promax.com

[Marco Pulvirenti]

Thanks for your feedback guys. All your info has been a great help.

_______________________________

marco pulvirenti

http://www.rhubarb.tv

durban, south africa

[Lars Vassenden]

Hi

Does anyone know if the Pansonic AJ-HD1700 support HD over SDTI? It does not have a firewire connector, so HD over SDTI would be charming.

What kind of systems would support this?

Lars Vassenden
lars@vassenden.no

[Sean Oneil]

No it does not. DVCProHD uses firewire for native transfers. You need the AJ-1200.

[Lars Vassenden]

So the SDTI is actually for DVCPRO50/25?

[Sean Oneil]

Not sure. It probably works for tape to tape transfers. I think Avid might support it, but I don’t know if it works for HD. You can’t use SDTI on a FCP system, you need Firewire.

Sean