Dolby 5.1 Through SDI

[Aaron Neitz]

A real Dolby 5.1 file is an encoded stream that contains all 6 channels (typically a Dolby E mix will get laid down to channels 3/4 on an HDCAM… and it contains all the metadata and the audio data for the 6 channels therein).

If you send 6 channels straight to deck from AIFF’s, that’s all they are – 6 discreet channels without the Dolby matering, metadata, and encoding.

[Edit.one]

Thank you,

just to be precise you’re saying that if I place on FCP timeline the ‘Dolby 5.1 encoded stream’ (Dolby E mix to channels 3/4 ) it will go through the HD SDI to tape or do I need a special way to put them in HDCAM?.
can I hear them from my audio speakers in case to monitor that they are there or if everything is right?

Best,
edit.one

[Aaron Neitz]

Dolby E is an encoding method that gives you a 2 channel PCM stream which contains 6 or 8 channels of audio (16 or 20 bit depth). If you tried to listen to it, there’d be nothing… your AES to analog decoder would be stimied – you’d have to buy a purpose built Dolby E to analog decoder.

You can transport this stream over AES or SDI as long as it remains BIT for BIT accurate. So, in theory, if you digitized a Dolby E track over SDI, you could lay it off to another tape.

BUT: we never do this in our studio. We finish everything on D5 with 8 channels of regular audio and let Dolby labs or the network or the mix house deal withe the encoding. so really all my knowledge is academic and not hands on. I can’t guarantee FCP or the Kona won’t swap some bit information or do some sample rate conversion to the Dolby PCM stream. Good question for Aja tech support!

[Matt Galuszewski]

If you are intending to capture the Dolby E data stream, do some cut only editing and then output back to tape then I can tell you the following.

The AES inputs on the Kona 3 card corrupt the DOLBY E data stream whilst the embedded embedded audio does not.

Regards

[Edit.one]

How about to take the Dolby PCM stream from audio studio and without changing it to place in audio tracks of the secuence I mean just matching the start and the end point and lay on tape together with video through SDI out. will that corrupt the ‘bit by bit’ transfer of signal ?
I guess the best advise yet is to let the audio people to do the 5.1 layout or I have to take the challenge if budget will allow.

I’ll reach AJA and If I learn anything I’ll post it.

thank you for the real professional help

edit.one

[Aaron Neitz]

The slightest change in the audio stream will corrupt it. So if you’re HDCAM wasn’t at unity and added +1 DB to audio tracks – I think that’ll ruin it. So just give the final master tape to the audio house for final layoff. good luck

[Juan Salvo]

Actually just capturing it into FCP, resamples the audio… so the Dolby-E data is lost…. it will no longer be recognized by a Dolby decoder… so the short answer is no, you can’t do this.