Audio crackling with DVCAM and HD-Connect MI
by Vincent Tsu
on
May 10, 2007 at 8:52:07 am
So I'm trying to digitize a 480i DVCAM tape from a Sony HVR-M25U connected to an HD-Connect MI, upconverting to 1080i through a Kona 3 card in a Mac Pro. The problem is, about 30 seconds to a minute into capturing, I'll get crackling and popping noises in the embedded audio. This doesn't happen when I capture HDV tapes through the same setup. I've updated the firmware on the MI to the latest version--1.1.37--to no avail.
I suspect the problem might be a reference sync issue, but there's no Ref In on the M25U, so I can't feed the deck and the Kona 3 the same blackburst signal. Again, HDV tapes sound fine through the MI, so maybe it's not a sync problem. Any ideas what might be causing the audio crackling? I'm stumped.
Re: Audio crackling with DVCAM and HD-Connect MI by John Schell on May 10, 2007 at 2:41:51 pm
Hi Vince,
I did some testing on your issue this morning. I found that the audio does crackle after about 30 seconds, but stops crackling after about 10 seconds. The reason for the crackle is the local clock on our unit is working on changing frequency to match the clock coming from the deck. (We can't use the clock directly from the deck as it jitters too much). I had been working on optimizing the lock speed in high def, but standard def currently takes a bit longer.
A compounding issue though is that the deck does not output video when it is set to auto or DV mode. In HDV mode, it outputs video all the time. This allows our converter to lock to the incoming video stream prior to the video playing. In auto/DV mode, we can only lock when the tape is playing.
A workaround would be to pause the tape prior to capturing it. If you give the MI about 45 seconds, it should be locked and not give any more crackling audio. I believe you hear the crackling audio permanently as the capture card doesn't relock to the stream.
I'll work on a more permanent fix of speeding up the lock in standard def.
Regards,
Re: Audio crackling with DVCAM and HD-Connect MI by Vincent Tsu on May 11, 2007 at 1:43:29 am
Thanks for the tips, John! Makes total sense what you're saying. Unfortunately, I'm still getting the crackling, even after I tried pausing the deck for 45 seconds before capturing (on the fly). I even tried routing the SD-SDI through an AJA IO, and routing that to the Kona 3 with AES/EBU, hoping that the IO would somehow stabilize the embedded audio signal. No go.
You're right in that audio doesn't stop crackling after it starts. The Kona 3 must not be relocking to the stream. What capture card are you using that the audio stops crackling after 10 seconds or so?
Despite this, the HD-Connect MI is still an amazing product, and HDV material looks absolutely gorgeous going through it. Bob Zelin's review of the unit was spot on!
Re: Audio crackling with DVCAM and HD-Connect MI by John Schell on May 11, 2007 at 7:24:30 pm
Hi Vince,
Glad to hear you like the video quality!
As an interim solution, could you try unplugging the SDI and replugging the SDI after the deck has paused for a while and the MI has had a chance to lock to the video clock. That should force a relock.
I'm using a Sony Luma monitor when I hear the audio crackle and then go back to normal.
I'm working on a fix that should go into the next firmware release.
Regards,
Re: Audio crackling with DVCAM and HD-Connect MI by John Schell on May 21, 2007 at 9:22:32 pm
Hi Vincent,
We have a new beta firmware version out that speeds up the video lock in standard def among a number of other enhancements.
Could you try out the new version and see if it fixes the issues you are seeing?
To get the new version, run the HD-Connect MI controller application (available on our website if you don't have it). Goto the firmware update tab and click refresh list. Choose beta_1.1.46 from the drop down menu and restart the application to download the new version. Then update the firmware in your unit.
Let me know.
Regards,
John Schell
Convergent Design Inc.
Re: Audio crackling with DVCAM and HD-Connect MI by Vincent Tsu on May 22, 2007 at 6:42:41 am
Hey John,
Thanks for the update! Wish I could try the new firmware out, but the Sony deck and the MI box were rentals that had to be returned last week. Waiting for FCP 6 to test out mixing DVCPRO HD and regular DV on the same timeline. Probably not as clean as upconverting through the Kona, but it'd save me a lot of time!
