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Vadim Finkov
Print to Video AC3 data stream problems
on Dec 5, 2009 at 9:25:22 pm

What i am trying to do appears not so easy as it sounds like.
Mac Pro loaded, FCP 7, AJA Kona LHi w/breakout box and Sony HDCAM HDW-M2000 tape recorder this is the equipment that is involved in my project.
DESIRED RESULT: HDCAM tape with 1080i video, audio ch.1-2 mixed stereo, ch.3-4 AC3 data stream.
For some reason I am not able to print AC3 signal to the tape. HDCAM recorder connected to my Mac Pro through AJA Kona LHi using HDSDI cable and 422 control cable. AC3 track is a Logic Pro track mastered, tested on DVD, works like a champion.

Any help will be appreciated.


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Michael Gissing
Re: Print to Video AC3 data stream problems
on Dec 6, 2009 at 9:53:11 pm


Because ac3 is not designed to be embedded in a PCM data stream, Dolby developed Dolby E. This is the only signal (apart from mpeg2 multichannel) that can be recorded on tracks 3&4 of an HDCam.

So you need to send your uncompressed 5.1 mix files (not the ac3) to a facility with HDCam and a Dolby E encoder to restripe. Even if you managed to get the ac3 stream onto the HDCam, international deliverables do not accept this format, only Dolby E.


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Vadim Finkov
Re: Print to Video AC3 data stream problems
on Dec 7, 2009 at 4:53:10 am

I am not sure that you are right.

HDCam recorder can receive AC3 data as well as Dolby E as well as any data. My problem is the workflow using nothing but what I already have. I know it can be done. For Dolby E encoding you need about $10K worth of hardware or software. Dolby Digital encoding requirements are not as expensive as Dolby E. And as long as nobody will re-print the HDCam tape sound quality of AC3 is just as good as Dolby E if not better. I am not planing to send this media anywhere, it is created for an internal use only. And as far is compatibility, I don not think I have to convince you about popularity of dolby digital format vs. dolby E.

If anybody had REAL experience of working with ANY DOLBY signal and had successfully printed this data on to HDCam tape, please share your knowledge and if it is possible the list of equipment and software that was involve in this process.

Thank You.



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Michael Gissing
Re: Print to Video AC3 data stream problems
on Dec 8, 2009 at 3:20:58 am


[Vadim Finkov] "sound quality of AC3 is just as good as Dolby E if not better"

You clearly don't know about the difference in data rate between ac3 files & Dolby E.

I was at the digital broadcast conference in Jackson, Wyoming over 12 years ago when the rep from Dolby announced the development of Dolby E. He explained the reason for the development was to enable Dolby digital data to be embedded in a 48Khz PCM data stream which you could not do reliably with ac3.

As well as running FCP for online & grading I also run a sound studio so I can tell you I have enough experience of sound deliverables and formats on nearly 800 broadcast programs to tell you again that what you are trying to do is not a deliverable standard and not recommended by Dolby or Sony.

If you want to store your 5.1 mix with the HDCam tape, then burn the PCM files to a DVDRom and put it inside the tape box.



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Vadim Finkov
Re: Print to Video AC3 data stream problems
on Dec 8, 2009 at 3:55:47 pm

I hate to school people. Please read below Sony recommendations on how to setup HDCAM VTR's for Dolby and an official Dolby format descriptions from Dolby Labs.
As far as deliverable or not, I DO NOT CARE IT IS FOR AN INTERNAL USE ONLY!
And one more thing, please do not flash your experience out, it is sounds really funny. I think you need multiply X2 your experience to be where I was 10 years ago. No disrespect!

Setting up Digital VTRs for Dolby E and Dolby Digital Compatibility
· In all cases, any audio channels used for recording either Dolby E or Dolby Digital must be in unity gain mode. Depending on the VTR, proper unity gain mode requires either selecting unity in the setup menu or physically “pressing in” the audio level knobs. Manually adjusting audio level controls to set unity gain will not work.
· Editing of Dolby E requires “cut” edits. Cross fading will cause Dolby E frames to be corrupted at the edit point.
· Editing of Dolby Digital is not supported in any mode and can cause muting.
Sony HDCAM HDW-M2000
Dolby E Compatible Yes, when in “non-audio” and “burst” modes
Dolby Digital Compatible Yes, when in “non-audio” and “continuous” modes
Channel Bit Depth 20bit
Sample Rate Conversion Yes, but offers a “data mode” for Dolby E/Dolby Digital
Audio Advance Function Yes (can only be disabled on output)
24 Frame Compatible Yes (Dolby Tri-Level Sync Adaptor required for Dolby E)
The menu settings that apply are for disabling sample rate conversion, enabling valid edits with Dolby E, selecting Dolby E or Dolby Digital compatibility, and selecting the appropriate audio/video output sync parameter according to the application.


Definitions
2.1 Dolby Digital
Dolby Digital (AC-3) is intended for the transmission of audio into the home through digital television broadcast (either high or standard definition), DVD, or other media.
Dolby Digital can carry anywhere from a single channel of audio up to a full 5.1-channel program, including metadata. In both digital television and DVD, it is commonly used for the transmission of stereo as well as full 5.1 discrete audio programs. Dolby Digital is designed for maximum fidelity and space efficiency, and should only pass through one encode/decode cycle.

2.2 Dolby E
Dolby E is specifically intended for the distribution of multichannel audio within professional production and distribution environments. Any time prior to delivery to the consumer, Dolby E is the preferred method for distribution of multichannel/multiprogram audio with video. Dolby E can carry up to eight discrete audio channels configured into any number of individual program configurations (including metadata for each) within an existing two-channel digital audio infrastructure. Unlike Dolby Digital, Dolby E can handle many encode/decode generations, and is synchronous with the video frame rate. Like Dolby Digital, Dolby E carries metadata for each individual audio program encoded within the data stream. The use of Dolby E allows the resulting audio data stream to be decoded, modified, and re-encoded with no audible degradation. As the Dolby E stream is synchronous to the video frame rate, it can be routed, switched, and edited in a professional broadcast environment.


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Michael Gissing
Re: Print to Video AC3 data stream problems
on Dec 8, 2009 at 10:46:23 pm

[Vadim Finkov] "And one more thing, please do not flash your experience out, it is sounds really funny. I think you need multiply X2 your experience to be where I was 10 years ago. No disrespect!"

Good luck vadim. I thought you came here to work out why you couldn't do something and when I explained why you tell me I don't know what I am talking about.

No disrespect? Seriously? You must think I am a total idiot. Also if you don't like to teach people, then you won't be much use to us lesser mortals on this forum. Shame to have all that experience and contribute nothing.


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