Blackmagic Forum

I have spent the past night trying to figure this out, and am ready to pull my hair out, so if anyone has any insight on this it would be greatly appreciated!

I am using Resolve 14 Beta (just downloaded it, was using 12.5ish Free). I am trying to export a video with a transparent background that I can use as a transition on my Twitch stream. I have found a video on YouTube showing how to do it on Adobe After Effects, but no luck with Resolve (just search "How to Make Video Transitions with Transparency in OBS " on YouTube, if it helps).

The whole video is 5 seconds of some PNG files coming off screen, joining together on screen to block the whole screen, then they all go back off screen. I just need the background to be transparent when I export, but can't figure out how to do that. All of my PNG files do have transparent backgrounds, so I have that figured out.

I completely understand if this is just not possible with Resolve, I just figured I would pick the minds of the forum before completely giving up.

It works fine for me in DR 14 beta, but in ProRes 4444, uncompressed RGBA or image sequences only.

Which format are you trying? DNxHR/HD seems not ready yet.

Jeffrey, this is indeed easily possible if your codec deals with alpha channel. Best example : ProRes 4444.
Also have a look on youtube and/or in the manual to see how to add an alpha output in the node tree.

Thank you both for your replies!

I'm not sure if I am overlooking it or its just not available in the free version, but I dont see prores 4444... Is it under QuickTime? I exported as uncompressed argh but vlc and media player classic dont seem to have thr natural codec to play it, do you have any suggestions on any codec packs I should download to play it?

Alpha output in the node! I bet thats my problem. I'll try to search when I get off work and post what I find out. Thank you!

ProRes is not available under Windows in Resolve, only in Fusion 9, that may be the problem (but I don't remember if you wrote about your system).
Otherwise, codecs with "a" (argb for ex.) mean they deal with the alpha channel. Therefore you could try animation or uncompressed argb

On the PC you don't have much of an option yet for more than 8 bit, other than image sequences.
"Animation" or uncompressed should work, but with huge files and limited bit depth.

Let's hope that BM soon fixes the DNxHD/HR output.

Yes, I am using Windows.

So I played around with it a bit more and realized what I needed to do to create an alpha background; I had to right click the node tree, click "add alpha output", then link the nodes, then make sure to click the individual files and Export Alpha options when rendering. BUT I am now having a problem with most programs using the exports. VLC and OBS (my streaming program) seems to hate all the exports I've tried (Grass Valley, Uncompressed ARGB/BGRA, I even went back to 12.5 and tried DNxHD), even Quicktime sometimes won't play them. I don't see a Quicktime animation option, where would that be at? I understand this isn't a forum for VLC or OBS, but does anyone have any suggestions on why they wouldn't play the video files?

On Mac OSX the DNxHD 1080p codec exports ok with alpha channels. You do need to add an alpha output on the Color Page or there will be no alpha (or full raster alpha) in the output file.

Thanks, Peter,
need to try that, DNxHR didn't work for me, even if it offers an alpha channel.

Peter Cave wrote:On Mac OSX the DNxHD 1080p codec exports ok with alpha channels. You do need to add an alpha output on the Color Page or there will be no alpha (or full raster alpha) in the output file.

Just for me to know because I understand you're writing it to make it clear about the codec, but how come anyone on OSX could prefer it to ProRes 4444 ?

Teamwork, maybe?

Sam Steti wrote:

Peter Cave wrote:On Mac OSX the DNxHD 1080p codec exports ok with alpha channels. You do need to add an alpha output on the Color Page or there will be no alpha (or full raster alpha) in the output file.

Just for me to know because I understand you're writing it to make it clear about the codec, but how come anyone on OSX could prefer it to ProRes 4444 ?

DNxHD is the native Avid codec. Using Avid round trip grading workflows with Resolve, DNxHD is an easier format to use and does not have some of the interchange issues that ProRes can exhibit. I prefer ProRes if NOT working with Avid systems. Some of my clients only work with Avid codecs and will not accept ProRes.

Yep of course, Avid codecs are crossplatorm, Uli also rang the bell about collaborations made on exports.
It's my fault, I haven't seen a macuser on Avid for a while (I'm talking about Media Composer), most of them are on FCPX, Premiere, FCP7 and Resolve... Itend to behave as if it was the whole world

Just as an update: No luck using resolve; I ended up trying some other video programs and it works pretty easily using Hitfilm Express, using some basic settings.

Is this nonsense getting sorted in 15? Just spent the last hour trying to get an alpha out of Resolve on Windows to no avail. The only codec options with alpha seem to be DNxHR which don't seem to work. I can see video layer 1 underneath layer 2 which is the layer I want to export in both the edit and colour page with with my external matte plugged into the alpha output in the node graph. Set to render individual clips with Export Alpha ticked. Do I get an alpha? No. I seem to remember having more success under 12.5. Is this a codec issue? Why do TIFF, DPX and EXR not have an Export Alpha tickbox option?

What if you don't render individual clips? This may be your problem.

BMD's Peter (or some else ?) had finally answered this in the meantime in another thread : try rendering a single clip instead of individual ones from your same TL (put and i and o for the test purpose if needed)

Nope, no difference. Here's Jeff.



No difference with an external matte added, you can still see the video layer 1 underneath. It shouldn't need one anyway as it is carried in the source clip I just tried it as it wasn't working without. As far as I can tell my render settings are correct. Turning video layer 1 off when rendering for a timeline render also does not work.

Also not the way that I have to stack and offset my parallel node stack even though I am working on UDH monitor... 150% GUI scaling anyone??

Exporting ProRes 4444 from a Mac works so the problem seems to be with the DNxHR implementation. This leads me to my earlier point, why is there no alpha option with TIFF, DPX or EXR?

I just played around with this and am also stumped. On Windows (no Prores 4444). From what I understand, DNxHR 444 supports alpha so I wonder what the deal is. Would be nice if someone from BMD chimed in...

Cheers

Here no problem.

A TIFF => Fusion TAB => Luma Keyer (without adding Alpha option ... with even simpler option )
Color TAB => add Alpha Output
Delivery => Quicktime => DnxHD 444

Reimport delivery:
Clip Attribute => Alpha Mode Premultiplied

Result

I've just tried rendering a Quicktime DNxHR 444 12bit as opposed to an MXF and Resolve sees the alpha when reimporting. However After Effects does not see the alpha. Who's to blame I don't know but I'm no better off. Need TIFF, DPX etc....

I gave this a shot and it sort of works. I tried adding a blur to a text object and the premultiplication looks a bit odd when I bring the media back into Resolve.

I also tried another test where I put a circular window over my footage (in a node on the color page) and added an alpha output channel - connected the windowed node to the alpha output channel and then generated the output media on the delivery page - that also works but there is something off regarding the edge of the softened circle.

So - I'm not quite there - missing some key knowledge I guess...

The output file is an DNxHR 444 10-bit but I tried with DNxHD 444 and DNxHR 444 12-bit and got the same odd edge behavior.

I am not a smart man, miss jenny...

Is it possible that DNxXX 444 expects alpha as premultiplied white whereas Resolve expects premultiplied black (or vise-versa)?

I ask because Media Composer offers to treat alpha in one of three ways (straight, premultiplied white and premultiplied black) because Avid historically treats premultiplied different than Adobe (IIRC). Given that Resolve does not offer this option, is it possible that this is causing problems with DNxXX 444 and the alpha generated from within Resolve.

Bear in mind that I don't know what I'm talking about, lol.

Steve Alexander wrote:Is it possible that DNxXX 444 expects alpha as premultiplied white whereas Resolve expects premultiplied black (or vise-versa)?

I ask because Media Composer offers to treat alpha in one of three ways (straight, premultiplied white and premultiplied black) because Avid historically treats premultiplied different than Adobe (IIRC). Given that Resolve does not offer this option, is it possible that this is causing problems with DNxXX 444 and the alpha generated from within Resolve.

Bear in mind that I don't know what I'm talking about, lol.

Hi Steve,

You should try in MC (we can reverse in MC: OK )
Fusion Tab => invert Luma


result

Thanks Jean Claude -

I did pretty much that and found that it worked well unless I introduced a softened edge to the hole - then the resulting alpha didn't look right. Not sure what's going on there.

Also - I couldn't bring this back into MC to see the alpha so I've definitely done something wrong...

You know that alpha only gets rendered if you set Deliver to individual clips, do you?

Then I have it backwards - I thought it was the other way around - single clip renders alpha... I'll keep playing with this... that could be my whole problem. If I ever figure this out I'll do a tutorial covering the workflow.

That's what I told you 2 days ago

Not really, Sam - This is what you said:

"BMD's Peter (or some else ?) had finally answered this in the meantime in another thread : try rendering a single clip instead of individual ones from your same TL (put and i and o for the test purpose if needed)"

This is incorrect - in order to make use of Alpha for DNxHR 444 10-bit and 12-bit you must select the 'Individual clips' mode. I'm not sure if you posted the reverse of what you meant but I was following your advice (which didn't work for me) and now I see that if I select individual clips that I get an addition option to 'Export Alpha' for DNxHR 444 10-bit and 12-bit. The 'Export Alpha' option is not available when selecting the 'Single clip' option.

I have now successfully exported a short timeline with a power-window applied in the CC panel with an alpha output and that seems to work just fine (bringing it back into Resolve - the alpha is perfect). I haven't tried bringing it into Media Composer yet - but I will.

I also tried (separately) to use a mask in Fusion to see if I could also delivery a DNxHR with alpha but I don't seem to be able to get that working correctly.

Tiny steps, Ellie...

Tried using the file in Media Composer and received a core consistency check failure. Nothing is easy - lol.

Yep sorry Steve, I didn't post the reverse of what I meant on puprose, I admit I just made a mistake

No problem, Sam - I didn't think there was any malevolence involved - lol

Yes it seems Resolve can export an alpha channel from Windows using DNxHR MOVs but only Resolve can see the alpha. So pretty useless. We had to resort to exporting the project to an old iMac and rendering some prores at about 2fps.

Peter, is this getting sorted??

Sorry,

For the moment it is still a V15.BETA: if it is possible it is to call in VFX connnect or in Standalone Fusion Studio (on PC) and RENDER in PRORES4444. AVID immediately recognizes ALPHA

In Davinci Resole : ALPHA is 'Strainght'

Hey, so from this thread it seems I can't export an .EXR or a 16bit LZW .TIFF with alpha?

My only option is DNxHR or uncompressed DPX? And I can't choose between premult & straight?

That's sad - I was hoping for a nice clean workflow doing some work that we traditionally do in Nuke in Resolve / Fusion then piping work back and forth with the Nuke artists.

Feature request for Resolve 16, I guess!

Of course the ideal would be where you could export and input multiple named mattes as channels in the EXR. And have those come in as separate layers.

That way you could pass separate, named matte channels for separate elements etc between artists, roto, 3d tracking, etc as we often do in Nuke.

Bruce Allen
Senior Theatrical Designer & TD - mOcean

Hmm, just tried DNxHR 444 12bit with Export Alpha checked and it doesn't show up in After Effects...

Yes, with all of the power Resolve has with Fusion etc it's going to be used a heck of a lot as the center of a VFX workflow, so I hope they get this all sorted out!

Bruce Allen
Senior Theatrical Designer & TD - mOcean

I figured out how to render a fusion title sequence so that I can use it in VMIX at least.

Just create a fusion title sequence with transparent background, by dropping a text + title on the timeline, select the title clip and open fusion tab, add whatever elements you want including animations.

(**EDITED** Then at edit tab create new compound clip from fusion clip)

Next go to render tab select Individual Clips, 1080p output or 720 whatever, then QuickTime, uncompressed, BGRA 8 Bit. Once these are selected the render alpha box pops up, check the box and you can render a .mov sequence that can be used in vmix or OBS as an overlay animated title.

This worked great for me as I don't currently have after effects and I enjoy creating animations in Davinci Resolve.

After hours of trying to find a combination which gets a clip with transparency (alpha) from Fusion/Resolve to MC and encountering all the problems described above (BMD DNxHR alpha export yields corrupt file, ProRes 4444 works but AMA is super slow to the point of unusable, DPX doesn't support alpha, TIFF sequences not recognized by MC, ...) I've finally landed on a workable solution.

Instead of looking for that one file that does it all, split the color and the alpha into two files. It can be either two DPX sequences or even a plain old ProRes 422HQ files (which renders faster). Import them separately. Then put the RGB file on track 1 and the Alpha file on track 2, add the matte effect to the Alpha clip and invert the key and it all works. A few extra steps, but few headaches.

One note, when exporting DPX from Resolve there is the option to export an 8bit Alpha. That doesn't work because Resolve marks the color space as 'A' in the header and MC doesn't know what to do with that. Instead the Alpha channel has to be mapped to RGB. In Fusion in the export tab there's a option 'Save Alpha To Color' that does that. Haven't worked out yet the equivalent for Resolve, but assume this can be done with a node in the color tab.