GH4 BlackMagic Video Assist Firmware 1.1 (Nov 2015)

Bern Caughey

Bern Caughey

Veteran
Been assigned a series of dual-cam interviews that will be filmed over two days with the final cut delivered on the following day. There will be an editor on-set working in FCP 7, & as there's no time to transcode, the footage must be recorded in 1080/24p ProRes. Given the option I'd rent the extension back, &/or Odessey 7Q, for my FS7 (or better yet just grab an AMIRA), but they prefer to use the GH4(s), & record on their (brand new) BlackMagic Video Assist(s). I'll be running some tests next week, but wonder if any users have insight into the GH4/BMVA combo, especially with the Video Assist's recent firmware update (v1.1).

Production is thinking of fitting the A-Cam with a YAGH so it can be fed sync audio from the SoundPerson via XLR but I'm hoping to test this against my Wooden Camera 'A-Box' XLR adapter. I've shot a lot with the GH4(s), but always dual sound which was synced in post, & don't know if the YAGH yields any better results than the A-Box, especially as I won't be riding the YAGH's pots.

http://woodencamera.com/A-Box-DSLR.html

I'd love to ditch the YAGH due to the added complexity of rigging/wiring/powering, & increased chance of part of the chain breaking, but not sure if I'll need it for triggering (&/or audio). BlackMagic' manual states the Video Assist can be triggered by '‘SDI start/stop’, or 'Record Run' timecode, but not sure which, if any, works with the GH4. If the GH4's timecode triggers the Video Assist over HDMI that's another nail in the YAGH's coffin.

I avoid recorders like the plague, especially connected via HDMI, so hope to backup with internal recording. AKAIK this will limit both recordings to 8-bit, & I'm willing to pay that price, but am unsure of the details. Would it be better to feed the Video Assist 8-bit UHD (only available via SDI) & have it down-convert to faux 10-bit 4:2:2 HD? Will the GH4 still record internally? Is there any way to send a 10-bit, &/or 4:2:2, image out of the GH4, & record internally (I think not)?

Any, & all, feedback is most appreciated! There's a chance only one, hopefully none, of the cameras will be fitted with a YAGH so I'm interested in both SDI, & HDMI, interoperability.

Thanks,
Bern
 
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Note that to get an Ultra HD (2160p24 or 2160p30) signal into the Video Assist, I believe it has to be over a 6G SDI connection (the Video Assist currently maxes out at 1080p60 over HDMI according to the manual). The YAGH doesn't output a 6G SDI signal, but instead dual 3G SDI or quad HD SDI (1.5G SDI). This is because the 6G SDI format Blackmagic uses isn't officially an SMPTE standard yet, so a lot of manufacturers have been reluctant to support it.

If you did want to get an Ultra HD signal from the GH4 into the Video Assist, you will probably need a converter of some sort. The easiest option would probably be to use the HDMI out of the GH4 into a Blackmagic HDMI to SDI 4K converter into the Video Assist. A second option might be to take the dual link 3G SDI output of the YAGH into a Blackmagic Mini Converter SDI Multiplex 4K, to convert it to a 6G SDI signal the Video Assist can accept.

If neither of these options sounds great, you might just try letting the GH4 do the downconversion internally, by setting it to output a 1080p signal over HDMI. Granted this would limit you to an 8-bit recorded signal (if you are setting the GH4 to record internally). But if you are shooting interviews with controlled lighting, you might not notice a huge difference in quality between the GH4's downconversion and that done by an external recorder anyway.
 
Thanks Dave!

Definitely won't be adding any converter boxes to the chain, & will test the other options. These are indeed controlled lighting interviews, & I'm not worried about the GH4's 8-bit 4:2:0 FHD internal, however the GH4>Video Assist's ProRes is still in question.

Anyone have an opinion on the YAGH's audio? AFAIK it doesn't enhance the GH4's recording.

Best,
Bern
 
Not much help - regarding your questions about BMVA - but I'd really push for the FS7 / external recorder ProRes options - especially if the dual cams aren't drastically diff angles. Shoot UHD - allowing two shots / reframing for post. (and I'm with you on normally avoiding the external recorders like the plague.. but in this case it could be an instant "back-up" to record internally while also ProRes externally).
 
Thanks Mark!

The camera angles are at least 30* different & there will be a second operator. Been instructed to not hand over any UHD footage to the DIT, & what the Editor ingests must be 1080/24p ProRes.

I'll be comparing the the FS7 side-by-side the GH4/VideoAssist kludge, but depending on the schedule, may not have a ProRes option for the FS7 available during the first round. Sort of defeats testing it, but still offers Production the chance to compare profiles in similar lighting.

Best,
Bern
 
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Hi

I've been looking at this exact combination myself recently and was running some tests before the HDMI port on my GH4 failed - I'll continue when it gets back from repair and my Lockport arrives!

1) The GH4 won't trigger the BMDVA when outputting 10bit 4:2:2, but it will in 8bit.
2) The GH4 4K -> FHD downscaling over HDMI is actually pretty good.
3) You can output 8bit UHD over HDMI - SDI isn't needed - the camera will downscale to FHD. The BMDVA will only downconvert from an SDI input.
4) I guess you already know this, but if you output 10bit over HDMI internal recording is stopped.

Hope I've been of some help.
 
I had the HDMI t/c output set and it didn't trigger. Put a card in, without changing any settings, and it worked. Out of interest - does the Pix E5 trigger over HDMI when the GH4 is outputting 10 bit? I imagine the issues are connected.
 
Yes Pix-e5 does trigger in 10bit. A little HDMI rec shows up on the GH4 LCD that goes from pause to circle record when you hit record on the camera. It's tied to the timecode output over HDMI setting. Haven't tried without a card in the GH4 but in this mode, I am only recording to the pix-e5 and not the internal card. It has been reliable as long as you don't jostle the HDMI cable.
 
Interesting - my Ninja 2 triggered fine on 10bit output too but the BMDVA doesn't. (Interesting = rather annoying).
 
Hey ho - so I found a couple of other 'quirks' regarding the GH4 and the BMDVA.

I thought there was something amiss with the HDMI inout on the VA, but a perusal of the BMD forums tells me that, at present, it won't recognise the GH4's signal when the camera is set to PAL or C4K frequencies - so it has to be set for NSTC. Apparently the issue is being worked on.
 
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