SDI inputdelay

Hello ,

we`ve upgraded our cat3.3. pro servers with sdi cards from decklink .

The delay of the input to output was up to 15 frames .

This is not really live .

Do you have any suggestions to lower the delaytime , please ?

The input delay is variable, and can be as low as 2-3 frames - it seems to depend on a bit of video voodoo. and whatever else is going on in the computer.

How many layers have you got playing back whilst using video input?

Quicktime is not optimised for live input - its optimised for recording to disc - so it buffers frames -quite a few frames - if too much is going on. i have to try and get it to stop buffering frames, but its very hard to get it to do this across the range of video input cards that are available without sacrificing portability-

There is a timer settings menu - if you click on video input settings;
You will see Timer A and Timer B shown- can you switch between this and tell me if you see a difference in the delay?

Decklink performance should be 1-2 frame delay maximum - with NTSC or PAL.

HUGH

Which decklink card did you get?

We`ve build in DeckLink Extreme.

Did you switch between timerA and timerB as shown above?
it might not look like much but it changes the way I try to get at video input frames before quicktime buffers them away

because it produces much more delay than Timer A
but i think there must be a small latency - this is not a broadcasttool just a visual effect -- got much more problems with ruckel-free textanimations .

The Decklink Extreme, whilst being versatile, does have a few issues:
The wiring loom causes an impedance mismatch with incoming SDI - especially long runs. If you are using the Extreme with a long SDI run, it is prudent to reclock the SDI before you stick it into the card.

Its worth checking that you have NO other software installed or running when you are running Catalysts. Some applications run daemons in the background which can detract from performance - video input perfomance is one area that can be effected.

The BlackMagic Decklink capture application that installs itself into applications when you install your decklink drivers is a useful diagnostic tool. If you shut down Catalyst and start up the capture application, it will show you what the card is seeing - which in turn is what Catalyst is seeing. A visible delay witnessed in the application means that the delay is from somewhere else. Remember that every bit of video equipment in the video chain - vision mixers, dve, routers/switchers, scan converters etc all add their own delays into the video signal.

I have tested most of the Blackmagic, Aurora Pipe cards with SDI, Composite, Y/C (where appropriate) and Component video in PAL and NTSC.

Best wishes,

Hugh
High End Catalyst test bloke.

I got in touch with Jan, who made the initial report.
He thinks he was getting an 8 frame delay just through the projector.
So he had delays everywhere,

It is worth pointing out, that every piece of video processing equipment will add at least one frame delay, and possibly many many more.

By the time you get out of the projectors, you can get a perceivable delay.
In rock shows however - the whole sound delay things also confuses things;

Sound travels really slowly - only 300m/second. 1 frame is only 12meters!
So you move around the concert hall and sound and picture will move in and out of sync!

I had been using the Cat 3.3 version with a Decklink SDI input.

I did notice a huge delay sometimes, i did figure out, if i use only one layer with the Video Input, and one or two layers with a STOPED Image, even a movie, but stoped, i get almost no delay, at least SYNC good enouth to you do not feel. If you play another layer, then the delay begins.... and goes slow and slow as more layers actived.

Gian

quicktime buffers all the video input frames. totally beyond my control.

so it depends on what else is going on in the computer.

sometimes the delays are from other equipment in the chain as well.

sometimes there is almost no delay. even with movies playing