Nicolas Hanson September 28, 2016 Share September 28, 2016 The audio is perfectly in sync when playback on both Avid and DaVinci but the desktop audio is out of sync. Any ideas? Link to comment Share on other sites
Bruno Mansi September 30, 2016 Share September 30, 2016 I'm not sure quite what you mean... When you say "playback on Avid and Resolve" do you mean when you're looking at the viewers inside the software with the computer monitor(s)? And when you say " desktop audio is out of sync" are you referring to the output of your Decklink to an external grading/client monitor and speakers? If the above is true then the probable reason is due to the external monitor. Virtually all modern LCD,LED, OLED monitors have a delay. It's a function of the fact that due to the way the picture is processed by frame buffers, there's typically a 1 to 2 frame delay in the picture being displayed. CRT displays, (being essentially analogue in nature) didn't have this problem. So in a typical setup with an external display and external loudspeakers, you would need to introduce a delay box in the audio signal chain. Manufacturers of domestic LCD/LED televisions build this into their products so that the sound coming from the TV speakers is in sync. What's slightly confusing about the title of your post is that you say you're having an audio lag. In the situation I've described, it would be the picture that lagged behind the audio. 1 Link to comment Share on other sites
Nicolas Hanson September 30, 2016 Author Share September 30, 2016 10 hours ago, Bruno Mansi said: I'm not sure quite what you mean... When you say "playback on Avid and Resolve" do you mean when you're looking at the viewers inside the software with the computer monitor(s)? #Yes And when you say " desktop audio is out of sync" are you referring to the output of your Decklink to an external grading/client monitor and speakers? #Output on the Decklink when looking at YouTube or playing a video on desktop. If the above is true then the probable reason is due to the external monitor. Virtually all modern LCD,LED, OLED monitors have a delay. It's a function of the fact that due to the way the picture is processed by frame buffers, there's typically a 1 to 2 frame delay in the picture being displayed. CRT displays, (being essentially analogue in nature) didn't have this problem. So in a typical setup with an external display and external loudspeakers, you would need to introduce a delay box in the audio signal chain. Manufacturers of domestic LCD/LED televisions build this into their products so that the sound coming from the TV speakers is in sync. What's slightly confusing about the title of your post is that you say you're having an audio lag. In the situation I've described, it would be the picture that lagged behind the audio. Link to comment Share on other sites
Bruno Mansi October 1, 2016 Share October 1, 2016 12 hours ago, Nicolas Hanson said: #Output on the Decklink when looking at YouTube or playing a video on desktop. OK, so when you're watching using quicktime player or VLC for example. I'm trying to remember if the Blackmagic Desktop Video software has any settings that would control the video or audio timing to your Decklink - I don't remember seeing any. I have a Decklink card in one of my workstations and will try a test to see if I have the same problem. Are you using the latest version of this software? Looking at the Blackmagic site I see that it's up to version 10.8. I know that VLC has the ability to alter the timing of the audio signal. It's under Tools/Track Syncronization, but this isn't going to help you with YouTube videos. 1 Link to comment Share on other sites
Nicolas Hanson October 2, 2016 Author Share October 2, 2016 Thank you Bruno, that is really nice of you! I'm using the latest version. Link to comment Share on other sites
Bruno Mansi October 4, 2016 Share October 4, 2016 OK, I had a go at looking at the output of my Decklink card. To get a file to play through the card from the desktop I had to use Blackmagic's Media Express software. I used a test file from http://www.sync-one2.co.uk/support/test-files/ This is a series of 1 frame bleep/flashes. I fed the HDSDI output from the card through a Leader waveform monitor to both a CRT monitor and a Dreamcolor LED display. The audio was de-embedded from the SDI by the Leader and fed as AES digital audio to a TSL monitoring unit & speakers. This is done to make sure there's as little difference as possible in the audio & video cable lengths, and everything's kept digital for as long as possible. Running the test file and watching the CRT monitor, the sync looked spot-on to me. As I previously mentioned, the Dreamcolor display showed the expected video delay (compared with the CRT) of a frame or two. I did notice that I'm running quite an old version of the Blackmagic Desktop video software (10.5.4). Never did upgrade as I remember there were problems when 10.6 was released, and I'm a firm believer that if everything works, leave well alone! Link to comment Share on other sites
