AC3 to HDCAM

[Craig F]

I know we can lay an AC3 file from Pro Tools to a HDCAM (or other digital tape ) by putting it in DATA mode

If one was to hand an AC3 wave file back to picture could they put it on tape from MC when they do there tape out?

[JeromeOD]

Nope. It's not video-frame accurate.

[tom_lowe]

I believe Paul Neyrinck makes a plug-in for this very reason.
It will encode the AC-3 as what appears to be a normal WAV file with timecode. Of course it wouldn't play unless through an AC-3 decoder.

This wouldn't be suitable for broadcast, they'd want Dolby E for 5.1 delivery on HDCAM, but some theatres have AC-3 decoders attached to HDCAM and other tape formats.

Best to check with whoever will receive the tape.

[quadraphonics]

This isn't entirely accurate. There are a few broadcasters that we deal with that still require AC-3 laybacks to tape instead of Dolby-E.
You could create a .WAV that is AC-3 encoded to give to video to output, but the question then becomes who checks to make sure that the layback to tape is correct and that the video people didn't ruin the data when they output it. Remember that they won't have any way to really check it.

Randall

Originally Posted by tom_lowe

I believe Paul Neyrinck makes a plug-in for this very reason.
It will encode the AC-3 as what appears to be a normal WAV file with timecode. Of course it wouldn't play unless through an AC-3 decoder.

This wouldn't be suitable for broadcast, they'd want Dolby E for 5.1 delivery on HDCAM, but some theatres have AC-3 decoders attached to HDCAM and other tape formats.

Best to check with whoever will receive the tape.

[tom_lowe]

Originally Posted by quadraphonics

This isn't entirely accurate. There are a few broadcasters that we deal with that still require AC-3 laybacks to tape instead of Dolby-E.
You could create a .WAV that is AC-3 encoded to give to video to output, but the question then becomes who checks to make sure that the layback to tape is correct and that the video people didn't ruin the data when they output it. Remember that they won't have any way to really check it.

Randall

Sorry, I was talking from a UK perspective, where to the best of my knowledge no one accepts AC-3 for deliverables.

[Postman]

Nope. It's not video-frame accurate.

To clarify this, in case someone doesn't know what you mean.

The decoded sound is frame and sample accurate. There is a very short, fixed encode and decode delay of a few milliseconds. Because it is small and fixed (dependent only on sample rate), the delay is easlily compensated for and often does not matter.

It is not editable in a typical video system because there is no reliable way to punch into it. I think that is what the above quote means to say. AC3 is a continuous data stream that cannot be edited or modified. If you edit or punch in on an AC3 stream, like you would on video tape, there will be a glitch. It is intended for delivery of final mixes, not of material that requires later editing or processing.

[JeromeOD]

Thanks Postman, that is the detailed answer to the one-bottle-of-wine-down one I blithered yesterday. :)