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AES / EBU audio problems...Posted by Adrian Zehn
Hi,
I have been using a KONA LH card with FCP 5.1.2. When outputting to Digibeta, using SDI for video and AES / EBU for audio (going to 4 channels) the audio is bad. While I am laying down to tape all appears ok - the green channel condition light comes on (indicating good audio), and when I monitor with headphones straight from the deck, the audio sounds fine. However, when I play back the tape later, after the first few minutes the red channel condition light starts flickering, and the audio contains distortion. I have experienced this exact problem with two different digibeta decks, and in 3 different edit suites with different MACs and different KONA LH cards and cables. Also, the macs I have used include G5s and MacPros. Consequently I must presume that the problem is either inherent in the KONA card or with FCP 5.1.2 or with some settings I have wrong somewhere. Can anyone with experience with this type of setup help? Thanks in advance, AZ
Hi Andrew,
Actually initially I tried the SDI embedded audio and had similar problems - and someone told me that I should try the AES EBU....... The only audio we can get to work properly is the analogue audio - which means that we have to do two passes to lay down all 4 tracks - not to mention the theoretical loss in audio quality.... A
Do you have a genlock signal going to your Kona card? That kind of thing happens when your video data clocks and audio data clocks are unlocked from each other. Synchronization drifts in and out during the performance. You can solve that many times by putting a stable black signal into the Kona card. Our Kona2 has a connector called REF LOOP. That's what it does. You put a black generator in one connector and terminate the other to keep it from leaking back out again.
Variations on that symphony are covered here: [www.aja.com] Koz
You say the condition lights on the deck are flickering. The Green/yellow/red condtion lights on a digibeta deck montior the data stream being recorded on tape. Things like drop outs on the tape, clean or worn out heads can cause data errors. The format is able to do some error correction and produce usable audio and video, but you get a yellow light to tell you that there is a problem. A red light means the errors are beyond the ability of the deck to recover the signal.
I am not aware of any conditions of the input signals that would cause channel condition errors. Not to say there are not signals that might do this, but I have never seen one in 10 years of dealing with digibeta. I would look more to your decks or tape stock than to the FCP system. -V
Hi All,
I looped black burst through the kona to the digibeta, changed the setting in the kona control panel to "Ref In" (from freerun) and the aes audio worked fine.....I have only layed down once so we will see if that fixes the problem permanently over time.....but so far so good.......thanks for the advice..... AZ
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