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AC3 in Sony Vegas Pro

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Ross Stark
AC3 in Sony Vegas Pro
on Jan 29, 2016 at 9:29:56 pm

So, I can render files in AC3 (for audio output), but I can't open those AC3 files in Vegas??? What gives? I've only recently had the need to do this, but man... this might be a large problem for me when I need to reach back in the archives. Anyone else had this issue/know how to fix it?


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Aaron Star
Re: AC3 in Sony Vegas Pro
on Jan 29, 2016 at 11:07:03 pm

Its probably not Vegas, its probably a Dolby deal. Vegas has to ability to render to AC3 for import into DVDA, but not for editing reasons. The Dolby license probably limits certain abilities unless the Sony were to pay for the full CODEC.

You need an AC3 decoder like the one at http://www.ac3filter.net/
This decoder works well but gives me the creeps since I believe its RU ware.


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Glenn Cowan
Re: AC3 in Sony Vegas Pro
on Jan 29, 2016 at 11:21:39 pm

You should always save an uncompressed audio file for archival. AC3 should be considered an endgame file for presentation only (DVD etc). I discovered this in the 2000s.

Indie Filmmaker


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Richard Jones
Re: AC3 in Sony Vegas Pro
on Jan 30, 2016 at 11:52:16 am

Yes, I understand this is a copyright related issue at the Dolby end of things. Glenn's advice is spot on.

Richard


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Ross Stark
Re: AC3 in Sony Vegas Pro
on Feb 4, 2016 at 12:14:12 am

I appreciate the feedback. With all of the above in mind, what do you recommend for archival? Almost all of my delivery is currently from SVP to DVDA and to DVD. I render DVDA MPEG and AC3 (Dolby Pro). Should I render all as HD MP4s (audio included)? What do you guys do?


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Mike Kujbida
Re: AC3 in Sony Vegas Pro
on Feb 4, 2016 at 12:21:02 am

I save my HD work in MXF format. From that I can render to any format desired.


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Ross Stark
Re: AC3 in Sony Vegas Pro
on Feb 4, 2016 at 4:23:34 pm

Thanks, Mike. Obviously you prefer the MXF over the MP4. Can you explain to a codec-ignorant person like myself the whys and hows behind your decision?


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Ross Stark
Re: AC3 in Sony Vegas Pro
on Feb 6, 2016 at 1:48:49 am

Mike, I'm looking into this mxf thing. Do you use the VBR or CBR version?


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Aaron Star
Re: AC3 in Sony Vegas Pro
on Feb 6, 2016 at 3:50:19 am

There are three separate components to a video file.

One is a container or wrapper: These formats are like .mxf, .mov, .avi, or .mp4, .mkv, wmv or wma. Mp4's container was a poor naming choice, due to confusion with Mpeg4 the codec. Containers align information in a way video and audio can be read back at the same time. Containers can hold multiple video tracks, audio tracks, and data like CC, and timecode. Only certain containers are able to hold large amounts of tracks and things like embedded CC.


Two is the video codec:
Mpeg1
M-jpeg
Mpeg2
Wmv/VC-1
mpeg4-L1/VC-1,L2,L3
mpeg4-L4/h.264/AVC/vp8
mpeg4-visual/dnxhd/prores
mpeg4-L5/xavc/dnxhr/prores-4k
h.265/HEVC/vp9
Uncompressed
Wavlet/jpeg2000


Three is the the audio codec:

PCM/WAV/CD-Audio format/uncompressed
Mpeg1,MP2,MP3,MP4/AAC
Dolby AC3 is basically MP3 with a multitrack ability, hence 5.1 or 7.1. WMA professional can do at least 7.1+ and handle things like vbr, zip like compression (lossless), and uncompressed.
The container specifies how many tracks can be held and IO'ed at one time.


Formats like DNxHD, prores, hdcam, xdcam, and cineform are marketing names for manufacturer created "standards". These standards are created so that hardware, that is less flexible than software, can read and write the information. Professional workflows tend to use the mxf container due to its wide range of information it can hold. Where as Mp4 is much more constrained to audio and video, but no data or CC.


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Mike Kujbida
Re: AC3 in Sony Vegas Pro
on Feb 6, 2016 at 1:41:55 pm

[Ross Stark] "Mike, I'm looking into this mxf thing. Do you use the VBR or CBR version?"

Ross, sorry for the delay in getting back to you.
I use the MXF HD EX 1920x1080-60i template and it only has a VBR option.
If you use the MXF HD422 1920x1080-60i 50 Mbps template then you get CBR but at a higher bitrate.
Some folks use the XAVC option but that results in an even larger file size.
The first MXF option has always worked just fine for me so I stick to it.
Try a few different renders and see which one you like best. The final choice is yours.


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Ross Stark
Re: AC3 in Sony Vegas Pro
on Feb 13, 2016 at 12:40:35 am

Thanks, Mike.

I now have the task of working through my archives... I will be glad I did it, though.

Another question: do you leave it as "upper field first"?


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Mike Kujbida
Re: AC3 in Sony Vegas Pro
on Feb 13, 2016 at 1:30:32 am

Ross, yes to leaving it at upper field first.
Good luck with your projects :)


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