Audio crackling from Blackmagic audio device

Hi all,

From DaVinci Resolve 10 (full) with a Decklink HD Extreme 2, using AES output, i get audio crackling when i play any audio source from any timeline. I use at the same time the SDI output. The problem doesn't appear with any other software (Final Cut Pro, VLC etc.). I use OS X Mavericks.

By the way, i've got an external USB sound card that can't play at all, even if it is switched to default sound audio device in OS X. Isn't there any option in Resolve to selec the audio device ?

Thank you.

see if the audio is at 23.98 and the timeline setup at 24.00 ( or vice versa)

see if the audio is at 23.98 and the timeline setup at 24.00 ( or vice versa)

I've tried with an independant stream in WAVE - PCM, no video linked.

Are you getting 24fps playback in the Edit timeline? When it's not playing at sync speed, you get audio distortion.

I have the same issues with audio in the Media & Edit areas. Try playing back from the Color or Render areas and see if its any different. For some reason, I can hear my audio properly in the Output tab, but not in the Edit or Media tabs. Its hit or miss in the Color tabs.

BM tech support has blamed this on Mavericks, but I get flawless playback in FCPX, Premiere etc, so I don't really buy it.

Thanks, i'll give a try and let you know

And what about the fact that the default soundcard in OS X can't be used for playing ? Would DaVinci Resolve force using the Blackmagic audio device within the Decklink ?

EDIT : Found the confirmation here : http://forum.blackmagicdesign.com/viewtopic.php?f=3&t=2641 locks the audio playback to the Decklink and won't allow any other soundcard output. This is a scandal !

We have a similar issue on both of our Resolve 10s.

Config: Mac Pro 16GB RAM, 10.8.5, DeckLink Extreme, Desktop 9.9.3

Audio source: -20dB 1K tone, 24bit, 48K, PCM WAV (important that it's tone in order to notice the audible pattern in the error). There is no framerate or timecode metadata in this wav file.

Create a new project. Leave default frame rates (in my case 24)
Add the media to the project. In Edit, play the audio file in the source window. Plays fine.

Create another new project. Change config to 29.97.
Add the media to the project. In Edit, play the audio file in the source window. Audio "pops". Change the playback frame rate (in the project config) and you will notice the frequency of the pops changes.

If, while playing the popping audio, I move my mouse over areas of the UI that respond to mouseovers (clip thumbnails, etc), the popping gets much worse.

that is normal.

a 24.00 fps pitched audio need a protool session to be changed to 23.98 (29.97) (it run slower...)

It is an expected behavior.

I haven't checked this in Resolve 10 yet, but Resolve 9 on Mac and Linux always had a slight sample rate error (crackle) on the embedded audio when the video monitoring format was set to HD 1080i 59.94 (using Decklink HD Extreme 3D+ card or Decklink SDI card). It does stay in sync, though, and the timecode matches. The easiest way to notice is to a play a 48k 1k wav tone with the speakers turned up (hard to notice a problem if you don't crank up the volume) and the video monitoring format set to HD 1080i 59.94. It would be very difficult to notice any crackle on normal program audio, so that's why I test with tone. Unless there happened to be a really loud high pitched sound, typical program audio should sound normal. I never worried about it much since the 48k audio wav file always played fine once in the Avid, FCP, or Premiere synced with the 1080i video tracks.

I remember when the Resolve 9 beta came out, the audio wouldn't stay in sync for a 45 min 1080i show. That was fixed, but I wonder if the subtle crackle on high pitched sounds could be related.