How to calculate delay between image and sound on monitor?

[dominiquegreffard]

Hi all,

Did some search and couldn t come up with any suitable answer.

Video monitoring creates a delay between sound and image that makes judging proper lipsync on music video challenging when looking at monitor.

I ve used simple technique to guesstimate delay with a slate listening to my erx ifb but i d like to have a way to have a proper time measurement?

Filming fs700 hdmi to hdmi to sony monitor guesstimate gives me around 80ms.

Any ideas?

Cheers!

[Ken Wilkinson]

This is what I use to calculate video delay in the studio. Pretty standard in post houses. 

 

http://www.pharoahaudio.com/syncheckproducthomepage.html

[dominiquegreffard]

It s nice but it s 500$. I ll stick with the guesstimate untill i find a quick trick for onset applications. But thanks for the heads up!

[Ken Wilkinson]

It s nice but it s 500$. I ll stick with the guesstimate untill i find a quick trick for onset applications. But thanks for the heads up!

It's not cheap but it does it's job very well.  I learned the hard way sync might not be what you think it is in post.  Different monitors, different codecs and different video cards each have their own delay.  I was lucky enough to find mine on ebay for $0.99.  Luckily nobody else knew what it was

[pindrop]

This is what I use to calculate video delay in the studio. Pretty standard in post houses. 

 

http://www.pharoahaudio.com/syncheckproducthomepage.html

Interesting how does it work please? What does it measure against what?

[Ken Wilkinson]

You load its calibration videos into you DAW, they have  beep and a visual pop that play in sync.  You play the files back and point the device at the screen and it measures the offset between the audio and the video delay in either quarter frames or milliseconds.  Then you take those numbers and use them to delay the audio to match the video delay.

 

[pkautzsch]

...but you can't do this with a monitor on location, fed a live picture from a camera, can you?

[Ken Wilkinson]

...but you can't do this with a monitor on location, fed a live picture from a camera, can you?

 

Guess not.  Best solution I could think of

[Marc Wielage]

My advice: guess. Try 2 frames, which is usually pretty close to 80 milliseconds (assuming about 24 video frames per second). If that doesn't work, add another frame. 

 

If they're going through a downconverter and watching standard def, all bets are off. It could be anything. Keep dialing it in until it looks right. 

[Jim Feeley]

Marc's advice looks good. Perhaps this chart from a Sound Devices tech note would be handy guide. Perhaps not, but it's helped me  when setting up a PIX, so what the heck:

 

http://www.sounddevices.com/notes/pix/sync-offset/

Sync Offset When Using PIX Audio Inputs with Camera Video

 

[i cut the useful info on how to compensate for video delay when recording to a PIX]

 

"Below is a table indicating the input delay setting (milliseconds) required to compensate for different amounts of video delay. The top row (1-10) indicates the amount of video delay in frames and the left column corresponds to the frame rate being used."

 

 

[RadoStefanov]

Get a camera that shoots photos and the video camera. Point the video camera at a sound synced slate and take a picture of the actual slate and the image in the monitor...  

[JesseF]

http://quietart.co.nz/catchinsync/

 

Free app, might be what you are looking for?

[John Blankenship]

http://quietart.co.nz/catchinsync/

Free app, might be what you are looking for?

While this app may very well work fine, I'd have more confidence in the developers if they understood that it's the video that's out of sync, not the audio:

"... In almost all cases where audio and video playback passes through separate devices ... there will be advancement or delay on the audio signal, making the viewing experience unpleasant..."

Thus further perpetuating the misunderstanding and myth that the problem originates with sound.

[dominiquegreffard]

Get a camera that shoots photos and the video camera. Point the video camera at a sound synced slate and take a picture of the actual slate and the image in the monitor...

Smart!

[dominiquegreffard]

http://quietart.co.nz/catchinsync/

Free app, might be what you are looking for?

Great tip, i will most definetly try it next day on set.

[Marc Wielage]

Below is a table indicating the input delay setting (milliseconds) required to compensate for different amounts of video delay. The top row (1-10) indicates the amount of video delay in frames and the left column corresponds to the frame rate being used.

 

Note that the 33 millisecond per frame only works for 30fps video. 24fps video would be about 40 milliseconds per frame. 

 

But in the real world, nobody's gonna notice 7 milliseconds of difference. Once you get over 1/2 frame, then it becomes an issue... and it can add up at different parts of the signal path, especially in large facilities, live shoots, and other situations like that.

 

I agree with John B above that it's the video that's typically delayed by processors in the signal path, making sound fall ahead. When that happens, we have to introduce a delay for the sound to compensate. So it starts with a video problem, not a sound problem. 

[RadoStefanov]

dominiquegreffard mentioned he has an erx ifb. Erx sets delay by half frames. So no need for tables ..

[Marc Wielage]

BTW, the way we used to check sync accuracy in video post was, we'd dub off the segment to Digital Betacam, which was extremely accurate in regards to picture and sound, plus we could jog in half-frame increments. So if we jogged and saw a picture, then got the sound 1 frame late (or a frame early), it was easy to compute the additional delay necessary and fix it.

 

This is also easy with digital files, though all picture editing systems I'm aware of (like Avid, Premiere, and FCP) only jog in 1-frame increments, with no sub-frames. Any good editor can just watch the slate clap and instantly tell if it's a frame early or a frame late. A hand clap works fine. I used to use "door slam sync" frequently on shows where they forgot to slate.

 

Nothing's worse than when sound is early -- this really irritates people on a subconscious level. 

[Philip Perkins]

Sync is in the eye of the beholder, so adjust the sync until it looks good to whoever is writing the check.

 

philp

[Marc Wielage]

Sync is in the eye of the beholder, so adjust the sync until it looks good to whoever is writing the check.

 

And that is the right answer!  

 

If it's just on-set playback, it's not that big a deal. I would be much, much pickier if this were a final delivery master, where it has to be absolutely in sync.

[mikewest]

Great John

 

We do not create the delay so should not be called on to sort it

 

NMD  (not my department)

 

mike

[dominiquegreffard]

Great John

We do not create the delay so should not be called on to sort it

NMD (not my department)

mike

I get your point but if we have the ability to delay our sound to match the late picture why not just do it? They cannot get the image there any faster afaik. It s a flip of a switch on a ERX.

I don t mind helping the other departments if it gets me home faster or it simply makes a better product if it s within reason. I wouldn t drive the gripping truck but i can bring a sandbag once in a while u know.. The counter productive attitude of some technicians sometimes really bug me. Being open to help others will be returned when you will need a favor from other departments down the line.

I feel it s common sense or is it just my small set mentality. Who knows?

[studiomprd]

" I don t mind helping the other departments... "

...especially if it increases my rental income.

[mikewest]

I'm not being counter productive and I do help other departments.

 

I spend more time dealing with camera feed issues, timecode jamming and multiple headsets

than I spend on dealing with my primary focus of getting good sound.

 

Every video split system is different. Different delays, different connectors, different levels.

 

Delegation is the art of responsibility, sorting out other peoples problems is a distraction

and we all need to focus on the job we are there for.

 

mike

[Philip Perkins]

I don't mind supplying a cheap audio delay in the Comtek line if it helps the show, but as was pointed out one can easily end up in a situation with varying amounts of real or perceived delay due to the listener's proximity to the talent and the various monitors and video signal processing in play.  I have done shoots where I had to set up as many as 3 different audio delays for various monitor systems at the same time, but I made sure I was getting paid for it.  Otherwise--one delay, if any.  Most of the time it seems that people don't even notice the sync issues in on-set monitoring....weird.

 

philp