audio delay on HDMI output

[Bob Zelin]

for now, run long audio cables from the Kona right into the Mackie – just for this test. Is it in sync ?

Bob Zelin

[Eric Hansen]

hey bob

right now the XLR outputs of the Kona are feeding the Mackie, and it’s in sync with the edit. are you suggesting a run longer cords?

e

Eric Hansen – The Audio Visual Plumber – http://www.avplumber.com

[Bob Zelin]

Boy Eric, I am not following you. When you monitor off the Kona, it’s in sync (as per what you said in your post). then exactly what is your problem ?

Bob Zelin

[Eric Hansen]

sorry about the confusion. its kind of a confusing setup

the room is a viewing and color correction theater. the editing console is towards the back of the room. there are seats in front of the editing desk for client viewing. when not using the projector for viewing, the editor uses KRK near-field monitors on the editing desk, or headphones, for audio. these are connected to a Mackie mixer which is connected to the stereo XLR output of the Kona LHi. this audio is in sync.

when the room is used as a viewing theater, the audio is routed through a Denon 7.1 surround receiver via the HDMI output on the LHi. this output can support 8 channels of audio from Final Cut, Logic, etc. the receiver feeds KEF speakers and a Velodyne sub that are arranged in a 7.1 surround setup. this audio has a delay.

AJA believes that the Denon receiver is introducing a delay, probably from processing the HDMI audio signal. but the pass though video onto the projector is not delayed. so the problem is either the Denon receiver itself, or something related to the HDMI protocol. like i said in the earlier post, i found a setting for “Lip Sync”, but it didnt do anything. but maybe its supposed to. is it common for a receiver with an HDMI in/out to have a delay?

yes we can route the stereo XLR output from the board to the receiver, but the reason for the theater was surround. we want to be able to open multi-channel mixes in FCP or Logic and listen to the output via HDMI.

i’m gonna bring in a Matrox MXO2 with my laptop and test the receiver again. i don’t think this is an AJA problem. but i’m wondering if anyone else has a similar setup and has seen this issue.

thanks

e

Eric Hansen – The Audio Visual Plumber – http://www.avplumber.com

[Gary Adcock]

[Eric Hansen] “AJA believes that the Denon receiver is introducing a delay, probably from processing the HDMI audio signal. “

Yes, I have seen this in 2 other installs.

Since you are feeding a receiver an HDMI signal with discreet audio channels from the LHI the Denon receiver is mux’ing the signal into a true 5.1 signal so that the output is correct, that process takes time if the device is not designed correctly.

gary adcock
Studio37
HD & Film Consultation
Post and Production Workflows for the Digitally Inclined
Chicago, IL

https://blogs.creativecow.net/24640

https://library.creativecow.net/articles/adcock_gary/AJAIOHD.php

[Eric Hansen]

thanks gary

we have the receiver set on its direct 7.1 mode. so internally it should just be sending each discrete channel to its designated amplifier. maybe i’m using the wrong mode. i’ll check but i’m starting to think this isnt going to work.

we’re thinking about replacing the LHi with an MXO2, which has both a 6 channel analog out and HDMI out. HDMI is our only option for video because thats the only line that was run for the projector. we’re planning on adding more edit systems in the future, so hopefully this LHi card can be used again.

thanks

e

Eric Hansen – The Audio Visual Plumber – http://www.avplumber.com

[Jeremy Garchow]

Woops, I reread and that’s what you are doing.

Changing the surround mode on the receiver sounds like your best bet so far.

What format is your timeline?

Have you checked sync at the receiver with another monitor besides the projector?

[Eric Hansen]

i spoke with Denon and they’re aware of this problem with HDMI. but they tell me it’s not just their receiver and that a lot of other receivers exhibit this too. so it looks like we need to run 6 channel analog direct to make this work.

does anyone have experience with integrating an audio interface like an M-Audio Profire 610 with a Kona card? i’ve heard of audio interfaces having latency, but i’ve never tried it. i’ve never really dealt with surround monitoring with a Final Cut system, so i’ll admit that i’m a noob in this area.

e

Eric Hansen – The Audio Visual Plumber – http://www.avplumber.com

[Eric Hansen]

ok, i spent some more time on this swapping out different HDMI monitors, and trying different frame offset settings in Final Cut. this is where i am and i want to know if i’m interpreting this stuff correctly. thanks in advance.

the frame offset feature in Final Cut seems to delay the timeline and the canvas monitor when you use higher offsets to match any delay introduced by the capture card or monitor. just to see, i set the offset to 30 frames. the cursor in the timeline and the canvas video are delayed a second after i press the space bar. during this though, the audio never changes. it does make FCP feel sluggish though, which i guess is the point.

the Flanders monitor has different delays depending on the processing setting. i got this info from FSI support. with the “Normal” processing setting, i have to set Final Cut’s frame offset to 6 to match the monitor. if i set it to “Fast” processing, i have to use a 4 frame offset in Final Cut. FSI support says that all LCD panels have an inherent delay and will never be as fast as a CRT.

all HDMI devices seem to introduce a delay of varying length. a Dell 24″ computer monitor with HDMI input needs a 1 frame delay from Final Cut. and the Denon receiver/projector combo we’re using in this theater needs a 6 frame offset.

this is where the audio delay is a problem. since the Denon/projector combo introduces a 6 frame delay, the audio through the receiver is delayed 6 frames to match the video. but, it matches the video on all points, including the FSI monitor and canvas monitor. i ran a bunch of different material through to make sure that the projector video and Denon audio were in sync. so the problem is that Final Cut doesn’t delay the audio when you use a frame offset. so the XLR analog audio out of the Kona card is 6 frames ahead of everything else. half of the time that this theater is used, the editor is either using headphones or KRK monitors running through a Mackie mixer. so i’m now thinking that i need to add an outboard audio delay between the Kona XLR outs and the Mackie mixer.

does any of this seem correct? AJA has told me that all outputs on the Kona LHi are in sync with each other. FSI has told me theres an inherent delay in their panels, and Denon has told me that all HDMI processors will have some amount of delay. what i’m trying to figure out is how the frame offset effects all this, and in the end, how to get all the different components in this theater to be in sync.

thanks. since this is now a frame offset question, i’m thinking i should have posted it in the FCP n00b forum…

e

Eric Hansen – The Audio Visual Plumber – http://www.avplumber.com

[Eric Hansen]

I was having dinner last night with a friend who’s a blogging editor like myself. he said there’s 2 things he hates when he’s researching a new product or workflow on different sites and blogs.

1. no one ever talks about the problems they encounter because it either makes the writer look dumb, or the product less awesome. he used the example of 35mm adapters for video cameras. no one wrote that they looked like jittery crap when shot handheld. since that made the footage look bad, no one wanted to post footage like that on their blogs. i think the aliasing problem on the 5D/7D is a good example of this too. the camera is so awesome, why would you want to talk about the shortcomings.

2. unanswered questions and problems on forums. i’m guilty of this for sure. when i figure out the answer to a question i posted on a forum, a lot of times i forget to update the forum post for those with the same problem in the future.

so onto my solution to my current problem.

i have a lot of different components with different internal latencies that i’m trying to play in-sync. the biggest problem is that the Denon receiver has a big processing delay on its HDMI input. since we have a Kona LHi card with HDMI out for this purpose, we wanted to find a solution without buying a new card. so:

1. Final Cut is set with a 6 frame offset. this brings the canvas and the HDMI projector into sync.
2. FSI monitor’s processing setting is “Noise Reduction” this maximizes it’s delay which matches the Denon’s 6 frame delay
3. adding a digital delay to the analog XLR outputs on the Kona LHi which feeds a Mackie Mixer for audio monitoring. since the speakers and headphone attached to the mixer will be used more than the speakers attached to the Denon receiver, getting this combo to work was critical. the digital delay is set to 206ms. yes that’s not equal to 6 frames at 23.98fps, but that my be due to differences in distance (20ft to theater speakers, 3 ft to KRK monitors). now the KRKs monitors are in sync at the editing position to the theater speakers, which are in sync to the video.

i wonder if audio delay is a bigger problem? i’ve never run into this issue on other systems that i’ve installed, but i’ve also never had to sync 2 different audio components in the same chain. most of the FCP systems i’ve installed have between 0 and 4 frame offsets. since this was 6, maybe that’s why it’s so jarring. so, onto posting about this “problem” on my blog.

thanks

e

Eric Hansen – The Audio Visual Plumber – http://www.avplumber.com