Trying to Setup a Round-trip Digital to Analog Workflow

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rddight

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Trying to Setup a Round-trip Digital to Analog Workflow

PostMon Feb 12, 2018 9:47 pm

Hi there!

I'm trying to figure out the simplest and budget friendly workflow for a sort of unusual post-process I'm trying to implement in my work. I want to convert SD/1080p material I'm working with in OSX to an Analog signal, run it through a video mixer, and bring it out of the mixer to then be captured on the same or another OSX based computer. It would be incredible if I could find a way to preserve an Alpha channel from start to finish as I'm working with animation assets that I'd like to manipulate in isolation.

I'm assuming I would use an NLE like Premiere, Final Cut X or Resolve to send out the signal and also re-capture it. I'm not sure which NLE would be the best fit or if I might be able to manage this whole process inside of another software. Any suggestions or information would be super appreciated.

I'm also assuming I'd need at minimum a a device like the Ultra Studio Mini but I'm not sure if i'll need something else. My Analog Video Mixer has BNC connectors for input and output, so it seems like the SDI inputs/outputs on the Ultra Studio Mini should work well.

I'm not sure if an additional analog to SDI converter will be necessary or not, and I'm not sure if I can manage a round-trip like this on one device. I have a full spec'd 2017 Macbook Pro and a hackintosh desktop that is roughly as powerful. If I could manage this setup on one machine, that would defintely be ideal. My goal is to have the least amount of connections possible and keep the hardware expense below $750.

Any advice or thoughts would be super super appreciated. Happy to provide more details if necessary, just ask! I'm still very much learning the nuances this type of workflow and not sure what's relevant.
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Peter Cave

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Re: Trying to Setup a Round-trip Digital to Analog Workflow

PostTue Feb 13, 2018 6:13 am

SD and 1080 SDI formats are different so you may need to downrez to SD for your vision mixer. You will probably need 2 computers to do this. Alpha channels don't exist in analog video so you need to patch seperate 'key channel' source to the vision mixer & output seperate 'key channel' mixer output to the recording computer. You will need capture & playback devices with seperate 'key & fill' inputs/outputs.

Good luck. Personally I would run a mile from trying such a difficult setup. Very few modern editing programs support simultaneous key & fill outputs or inputs. Analog signals are also interlaced which can add an extra layer of fun!
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Dave Johnstone

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Re: Trying to Setup a Round-trip Digital to Analog Workflow

PostTue Feb 13, 2018 11:04 am

To use key/fill (alpha channel) simultaneously you will probably need an "Extreme" card which will use up all of your budget. If you only need up to HD, older cards (HD Extreme3D) will be sufficient if you can source them but you'd need 2 as these cards can only input OR output. The Extreme cards have analogue inputs and outputs so would save the converters but I'm not sure they can do key/fill in analogue, so you will likely need a DAC and ADC for key.

For playout you can use GStreamer as recent versions of this now support alpha output on the 'B' channel.

I'm not sure what can ingest key/fill but maybe setting Media Express to 3D mode will work, certainly worth a try.

Regards,

Dave.
Freelance Television Broadcast Engineer
and Software Programmer.
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rddight

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Re: Trying to Setup a Round-trip Digital to Analog Workflow

PostTue Feb 13, 2018 1:21 pm

Peter Cave wrote:SD and 1080 SDI formats are different so you may need to downrez to SD for your vision mixer. You will probably need 2 computers to do this. Alpha channels don't exist in analog video so you need to patch seperate 'key channel' source to the vision mixer & output seperate 'key channel' mixer output to the recording computer. You will need capture & playback devices with seperate 'key & fill' inputs/outputs.


Really appreciate the insight, had a feeling maintaining an Alpha channel would make this significantly more complicated. While this is defintely good to know for the future, lets say for now I could live without the alpha channel.

Do you think I would still need two machines for playback and capture? Would I need any other hardware than the Ultra Studio Mini?

Thanks, and again I really appreciate your response.

-Ryan
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rddight

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Re: Trying to Setup a Round-trip Digital to Analog Workflow

PostTue Feb 13, 2018 1:37 pm

Dave Johnstone wrote:To use key/fill (alpha channel) simultaneously you will probably need an "Extreme" card which will use up all of your budget. If you only need up to HD, older cards (HD Extreme3D) will be sufficient if you can source them but you'd need 2 as these cards can only input OR output. The Extreme cards have analogue inputs and outputs so would save the converters but I'm not sure they can do key/fill in analogue, so you will likely need a DAC and ADC for key.

For playout you can use GStreamer as recent versions of this now support alpha output on the 'B' channel.

I'm not sure what can ingest key/fill but maybe setting Media Express to 3D mode will work, certainly worth a try.

Regards,

Dave.


Wow this is awesome info. Curious as to why you're specifically recommending the PCI-E cards, do they generally handle capture better? Would either "Extreme" card potentially work as a complete solution (allowing for playback and capture at a single source)?

Its awesome to know that it might be possible to preserve an alpha round-trip, and I think this is defintely a setup to work up to.

If I were to compromise on the alpha channel for now and I was just trying to playback from one computer into the mixer and capture the signal would you still recommend the same setup? I was initially thinking it'd be nice to have an external device that I could also have the option to travel with and utilize for client work outside my studio. Is there an external capture/playback device you'd recommend in addition to the "Extreme" card?

Thanks again, I really appreciate you taking the time to share your thoughts.

-Ryan
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Peter Cave

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Re: Trying to Setup a Round-trip Digital to Analog Workflow

PostWed Feb 14, 2018 3:11 am

Can you explain the purpose of your intended setup? There may be a better way if we know what you are trying to achieve.
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Scott Smith

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Re: Trying to Setup a Round-trip Digital to Analog Workflow

PostWed Feb 14, 2018 4:50 pm

Agree with Peter. Why are you needing to convert to analog? Is there another way to do what you want and stay digital?
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rddight

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Re: Trying to Setup a Round-trip Digital to Analog Workflow

PostWed Feb 14, 2018 4:55 pm

Good point Peter,

The main thing I'm trying to do is experiment with a workflow where I can start to utilize analog textures (beyond DV, VHS, and HI 8), analog effects work and analog synthesizers in my visual effects work. Interlacing/blemishes wouldn't necessarily be problematic because I'm not trying to get a crystal clear image, really just trying to get a richer color space from my sources because right now DV, Hi8 and VHS are super limited.

Right now I can only capture and re-capture material to those sources, but I'd like to preserve the color-space as much as possible while still capturing the warmth of an analog signal. Not entirely sure what thats going to look like, and maybe this is a bit of a wild goose chase but I'm interested in the experiment.

The visual synthesizer will make things more complicated, as its manipulating the signal by design. Not sure if capture will work without putting it through something like an external time-base corrector. Currently my workflow is to capture footage to a dv tape, display it off a CRT screen and film the screen.

Sort of secondary to this but I'm also trying to gradually build a gear kit that would position myself to ultimately take on more DIT work in a production environment, and potentially some freelance technician work for live events. Thats why the external devices are a bit more appealing to me, because it seems like they would be valuable to have on set to establish a pretty robust video village and could potentially be used to capture a live stream or presentation.

I know the later bit sort of complicates things, but I'm trying to make this investment with that in mind. I understand there are other more expensive devices that might be better suited and check all these boxes , would defintely be open to hearing thoughts and recommendations to that end as well.

Apologize for the long winded response but I'm hoping that helps. Thanks again for taking the time to share your thoughts!
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Scott Smith

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Re: Trying to Setup a Round-trip Digital to Analog Workflow

PostWed Feb 14, 2018 9:13 pm

So, crazy artsy stuff. Got it. Sounds to me like you might still benefit from using digital signals and a mixer/switcher like an ATEM. There, you can do partial dissolves and/or keying, do them live, and record the output. But, you know best the direction your creativity needs to go.

But I will say that I am not so sure I agree with this whole "warmth of an analog signal" concept. Maybe, I see a "warmth of film look" concept, if you went film. Maybe. Not that much anymore. But analog video....not so much. (Oh, and you do realize DV is digital, right? And i imagine your "Visual synthesizer" might also be digital.) But that "warmth" is a subjective quality you are chasing, and up to your creative side to figure out. In video, "warmth" is usually found in the color grading, effects, lenses/focal length, and lighting, far more than in the analog/digital nature of the signal. "Analog Video on a CRT" is no "Vinyl Album played through a tube amp" in it's "warmth" factor in my personal opinion. (Enough quote marks? I get "paid" by the quotation mark.)

But continue on. You are going into a realm of little ability to make concrete recommendations.

Just remember, external signals does not equal analog. SDI and HDMI are digital signals, and external.
Scott R Smith
BMD Stuff I use: ATEM 2-M/E, 4 x ATEM PS 4K, Broadcast Videohub, 6 Hyperdeck Pros, 4 Hyperdeck Shuttles, Multidock, Smartscope Duo, Smartview, Intensity Extreme, Decklink Studio, and lots of Miniconverters and Open Gear Converters.
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Andrew Kolakowski

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Re: Trying to Setup a Round-trip Digital to Analog Workflow

PostWed Feb 14, 2018 9:35 pm

When high end advert needs VHS effect it's done as described above as simulated methods look crap and cheap.

I don't get this analog bit, but I understand a use of analog equipment to achieve some desired effects. It just doesn't need a whole "analog" bit. As mentioned example- put through VHS to make it "real VHS" and capture as digital.
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rddight

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Re: Trying to Setup a Round-trip Digital to Analog Workflow

PostWed Feb 14, 2018 10:12 pm

Thanks Scott!

I understand that I'd need a signal converter in order to convert SDI (or HDMI) to an analog signal, I guess I'm asking if there is a device that facilitates that conversion process (Digital signal to analog, then analog back to digital) AND facilitates the capture or monitoring processes. From what you've described so far it seems as if in most cases thats unnecessary, because a lot of these devices can read digital signals just fine.

As you mentioned something like an ATEM or a similar device would just be mixing a digital signal correct? I have an old Sony FXE-120 that I think facilitates the same process. The "visual synthesizer" I'm using currently is a circuit bent Archer Video Processor with composite connections. I think originally these devices were intended to "clean up" the signal out of a VHS player but I don't really know. I'm not 100% sure if that classifies it as an analog or digital device, would love to be educated on that though if anyone knows.

Really I'm just trying to send a signal to the FXE-120 and this Archer Video Processor, then capture it directly to the computer, bypassing any other capture devices.

It sounds like converting that signal to be truly analog would be an entirely seperate process. If thats the case, would the most budget friendly way be to experiment with analog signal be to get two mini-converters (sdi to analog and vice versa)?

Again, thanks so much to everyone who has responded!
Last edited by rddight on Thu Feb 15, 2018 3:53 pm, edited 1 time in total.
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rddight

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Re: Trying to Setup a Round-trip Digital to Analog Workflow

PostWed Feb 14, 2018 10:22 pm

Andrew Kolakowski wrote:When high end advert needs VHS effect it's done as described above as simulated methods look crap and cheap.

I don't get this analog bit, but I understand a use of analog equipment to achieve some desired effects. It just doesn't need a whole "analog" bit. As mentioned example- put through VHS to make it "real VHS" and capture as digital.



Defintely get this, and I can do this currently by recording the contents of a vhs tape to a dv tape.

I'm looking for a monitor/recorder setup that removes that additional step from the process.

The analog bit is seperate. That has less to do with medium emulation and more to do with experimentation. I believe the archer video processor sends an analog signal out. You can see the effect here


Not sure if it would need to be converted or not, like I said I've never been able to capture it directly. The effects don't show up when its recorded to a VHS tape or a DV tape I believe because it lacks the bit depth??
Last edited by rddight on Thu Feb 15, 2018 3:54 pm, edited 1 time in total.
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Peter Cave

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Re: Trying to Setup a Round-trip Digital to Analog Workflow

PostThu Feb 15, 2018 6:08 am

I think you should research the video formats you plan to use. VHS is analog video as is Hi8. DV is digital. They are all standard definition. Modern capture devices are (mostly) High Definition digital. There are line frequency differences and frame size & aspect differences. Analog signals may need a TBC for reliable capture. You will also need to deal with NTSC vs PAL format (both 4:3 and 16:9 anamorphic aspect ratios) with analog devices as not all analog gear can switch between the two formats.

IMO and from your post you will need a fair bit more knowledge of the technical side to be able to ensure you don't end up with incompatible equipment.

BTW I have been editing professionally for nearly 40 years starting with SD analog and progressing with each format change as it happened. It's a bit more involved than you may think!

I would suggest you try to find an older BMD Decklink Duo 2 PCI capture card as they will offer both SDI & Analog inputs & outputs. It also has video deck control for capture from RS422 serial protocol like older Sony VCRs. Try and find an older SD professional VCR (BetacamSP is good) so you can play out your modern material from Premiere (FCPX won't work) and record it. Then play it through the video mixer, add effects and re-capture on the computer using the BMD Decklink card. If you have two computers you may be able to do it all at once, but it gets inefficient pretty quickly! Also some decks won't play the video through to the output in real time (EE mode) without recording. The advantage of a pro deck is that they have TBCs built-in.

The whole "warmth of analog" thing is mostly just talk by people who don't understand the underlying technology. Analog and digital SD colour spaces are almost identical due to the original intention of the SMPTE engineering teams to keep consumer display (television sets) compatibility issues to a minimum. I spent a couple of years making MTV promos on high end linear digital equipment (Digital Betacam, huge programable Sony vision mixers Abekas A57 effects etc) where we simulated funky degraded analog video (and film) on a daily basis. Shooting from monitors was standard practice. However, format changes from SD to HD in real time is where most of the technical issues are. If I were you I would produce everything in SD and then uprez the SD final result to HD.

From the Decklink PDF:

Blackmagic Design - DeckLink Duo is the world's most popular video capture cards. The DeckLink capture card
eliminate all compromises by giving you the highest video quality, so you can connect to virtuality any deck,
monitor or camera available.
Blackmagic Design Decklink Duo is ideal for those who need two SDI inputs and two SDI outputs. The user can
utilise the two independent video capture and video playback streams. A tri-sync/blackburst reference also adds
to this highly useful PCI Express card. The Decklink Duo appears as two independent SDI cards to the computer
but only uses a single PCI Express slot. Therefore it is perfect for servers with simultaneous video capture and
video playback per system or multiple streams. It is also extremely compatible working with Mac OS X, Windows
and Linux.
Blackmagic Design - DeckLink Duo is a product that you can use to connect and to capture and playback SDI,
HDMI, analog component, S-Video and composite to your windows, mac or Linux computer. Includes Media
Express software for capture and playback of AVI, QuickTime and DPX files.

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rddight

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Re: Trying to Setup a Round-trip Digital to Analog Workflow

PostThu Feb 15, 2018 3:52 pm

This is all really great advice, thanks everyone. I apologize for having no idea what I'm talking about and appreciate everyones insight, this has been super helpful.

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