BMCC 6K - 4 channel audio. Possible? Feature request

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ricforster

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BMCC 6K - 4 channel audio. Possible? Feature request

PostTue Jun 11, 2024 2:31 am

Hey BM team -

Is it possible to add 4 channel audio recording to the BMCC 6K in a firmware update? Or on a future revision to the camera?

I produce feature films - often with very small crews (3 people or less!) - and would love to be able to record 4 channels audio directly into camera. This would allow the use of 3 lav mics and a boom, without having to carry a mixer, and avoids having to sync all the audio in post.

The BMCC 6K has dual mini XLR audio inputs, and a stereo 3.5mm input. Is there a hardware limitation preventing 4 channel simultaneous recording? Patent problem?

Notable that the new Panasonic cams (S5ii, GH7) are enabling 4 channel with an XLR add-on unit. For me it's a killer feature. My old Sony FS7 is also capable, but the image quality doesn't hold up.

FYI I recently shot a feature film solo (no crew, just me as director/DOP/sound recordist). Shot on the Ursa Mini Pro 4.6K. Now up on Amazon.

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Robert Niessner

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Re: BMCC 6K - 4 channel audio. Possible? Feature request

PostTue Jun 11, 2024 9:14 am

I'd also like to have optional 4 channel audio and several people have suggested this to BMD over the years since the first UM46k was released. UMP G1 even had a grayed out menu for channel 3+4. But alas that feature never saw the light of day.

I don't know if it is a hardware restriction or just lack of implementation.
Saying "Thx for help!" is not a crime.
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Steve Fishwick

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Re: BMCC 6K - 4 channel audio. Possible? Feature request

PostTue Jun 11, 2024 2:14 pm

Robert Niessner wrote:I don't know if it is a hardware restriction or just lack of implementation.


I very much doubt the hardware was ever there, except perhaps via AES on the Ursas. On Eng cameras there would be at least an extra front XLR for the camera mic and provision for wireless radio mic caddies. The legacy monitoring switches are still there so I'm sure it was an idea once.
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Robert Niessner

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Re: BMCC 6K - 4 channel audio. Possible? Feature request

PostTue Jun 11, 2024 6:05 pm

Steve Fishwick wrote:
Robert Niessner wrote:I don't know if it is a hardware restriction or just lack of implementation.


I very much doubt the hardware was ever there, except perhaps via AES on the Ursas. On Eng cameras there would be at least an extra front XLR for the camera mic and provision for wireless radio mic caddies. The legacy monitoring switches are still there so I'm sure it was an idea once.


That you can feed Timecode sync into the 3.5 mm port and at the same time use both XLR inputs for recording, should provide some evidence that at least from start of the signal processing the ports do not get switched off. And the bridging of the audio is quite flexible. So I wonder if it is really the hardware...
Saying "Thx for help!" is not a crime.
--------------------------------
Robert Niessner
LAUFBILDkommission
Graz / Austria
--------------------------------
Blackmagic Camera Blog (German):
http://laufbildkommission.wordpress.com

Read the blog in English via Google Translate:
http://tinyurl.com/pjf6a3m
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Steve Fishwick

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Re: BMCC 6K - 4 channel audio. Possible? Feature request

PostTue Jun 11, 2024 6:34 pm

Robert Niessner wrote:That you can feed Timecode sync into the 3.5 mm port and at the same time use both XLR inputs for recording, should provide some evidence that at least from start of the signal processing the ports do not get switched off. And the bridging of the audio is quite flexible. So I wonder if it is really the hardware...


Not necessarily, it is more likely the 3.5mm stereo in and XLRs share the same pre-amp and ADC; just one being unbalanced and the other balanced. Normally LTC is 0db and requires no pre-amp at all. In any case the Ursas have no such hardware analogue alternative; and if the Pockets had 4 channels and they didn't that would be odd indeed.

It could be that in the case of the Ursas, since they were closely modelled on existing ENG cameras in many ways, the original intention had been to offer a radio mic unit between the V-lock battery and body, a la Sony; hence the switches and some legacy references to it.
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Robert Niessner

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Re: BMCC 6K - 4 channel audio. Possible? Feature request

PostWed Jun 12, 2024 6:22 am

Steve Fishwick wrote:Not necessarily, it is more likely the 3.5mm stereo in and XLRs share the same pre-amp and ADC; just one being unbalanced and the other balanced. Normally LTC is 0db and requires no pre-amp at all. In any case the Ursas have no such hardware analogue alternative; and if the Pockets had 4 channels and they didn't that would be odd indeed.

It could be that in the case of the Ursas, since they were closely modelled on existing ENG cameras in many ways, the original intention had been to offer a radio mic unit between the V-lock battery and body, a la Sony; hence the switches and some legacy references to it.


With the first UM46k you could set your audio either to camera mic or to XLR inputs. BMD changed that with the UMP where you could record cam mic and XLR at the same time on separate channels. With the PCC4k you could interchange cam mic L or R or L+R to Mono, 3.5mm input L+R and XLR. And also mic / line levels.

So the more I think about this, the more I'd speculate that at least beginning with the PCC4k model and newer - the hardware could be already there, but BMD didn't have the resources or priorities to implement multi-channel recording into the system.
Saying "Thx for help!" is not a crime.
--------------------------------
Robert Niessner
LAUFBILDkommission
Graz / Austria
--------------------------------
Blackmagic Camera Blog (German):
http://laufbildkommission.wordpress.com

Read the blog in English via Google Translate:
http://tinyurl.com/pjf6a3m
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Steve Fishwick

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Re: BMCC 6K - 4 channel audio. Possible? Feature request

PostWed Jun 12, 2024 1:07 pm

Robert Niessner wrote:With the first UM46k you could set your audio either to camera mic or to XLR inputs. BMD changed that with the UMP where you could record cam mic and XLR at the same time on separate channels. With the PCC4k you could interchange cam mic L or R or L+R to Mono, 3.5mm input L+R and XLR. And also mic / line levels.


Robert, that's not possible on my Ursa Broadcast G2, which is identical in audio features to all the other Ursas - there is only channel 1 and 2; you have to choose between Internal mics, XLRs line/Mic. Having different inputs does not imply more channels, they are merely switched. That it's possible to have 4 or more channels on the recording is not in doubt, but the hardware to be able to do that separately is not necessarily there and probably not fixable now through a firmware upgrade; or I'm sure it would have been done by now.

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