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Audio rates
I have just installed my DL Extreme. My first capture with Blackmagic codec 8 bit. The audio is 24bit with 12 channels!!, but I see that the apple codec is 16 bit with 2 channels. I am used to Avid with 48k 16 bit. I am having trouble with my levels, they are totally different. With Avid I generated tone giving me ‘5’ on my PPMs. What should I be setting my reference level to with 24 bit?
Thanks
Roddy Jamieson
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3 Replies
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Hi,
The DeckLink drivers use the Apple 8-bit codec in standard definition in both DeckLink 4.x and 5.0 drivers. The easy setup in Final Cut Pro HD will mention Blackmagic but we invoke Apple’s codecs for capture and playback.
All DeckLink cards use the Television standard sample rate of 48 kHz and 24 bit. However QuickTime only supports 16 bit so any movie that you capture via DeckLink on a Mac will have audio set to 48 kHz and 16 bit. The difference between 16-bit and 24-bit is related to the quality of the audio sampling but has no relation to audio levels. You should not need to change your audio levels between the Avid and Apple systems. I’m not sure why you are seeing an audio difference. How are you transferring the movies from the Avid system to the Apple system? For example, are you rendering the Avid movies to an Apple or Blackmagic codec or are you outputting via SDI and recapturing via the DeckLink card?
The DeckLink 5.0 drivers support up to 12 channels of audio capture and playback via HD-SDI. Standard definition cards support up to 8 channels of audio capture and playback via SD-SDI. If you want to reduce the number of captured audio channels, please refer to the support note 2 channel stereo capture in Final Cut Pro HD 5.0
Regards,
Luke Maslen
Blackmagic Design -
I’m not explaining very well. Here’s my set up: I use a DSR 1500 and output 1khz tone at reference -12db. I have two PPM boxes, one monitoring the output from my input devices and the other the output from the decklink. In this direction both PPMs (input and output) read “5”. When I output tone from FCP at -12db both sets of PPMs read “7” and input to the DSR is up around approx -3 or 4db. This is exactly the same set up as my old Avid Meridien which gave me the same readings in either direction.???
I’m baffled.
Roddy Jamieson
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Probably best to ignore the meters in FCP, and rely on your ppms.
Each new sequence I create I add bars and tone to the top and adjust the level of the clip till my meters reach 4ppm (standard in the UK). I then trust my PPMs for levels.
The good news is that FCP meters show lower levels than external meters so there is no chance of clipping in FCP because your ppms would be off the scale.
Lex
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