Blackmagic Production 4K Audio Tests

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Chris Hocking

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Blackmagic Production 4K Audio Tests

PostThu Feb 13, 2014 10:40 pm

Hi Everyone,

As regular forum visitors will know, I've done a lot of audio tests since the release of the original BMCC, to check the differences between the various firmware releases. I've tried to keep these tests as "real world" as possible by using the type of gear that regular visitors of this forum tend to use. Despite the occasional complaint, these tests have been mostly well received, and hopefully some of this information has been helpful in making decisions about whether or not to purchase one of Blackmagic's cameras - and when you do, how best to tackle audio.

We received our Blackmagic Production 4K Camera earlier this week, so I thought I'd better do some more quick tests to see how the new camera fares.

Good news - it seems to have fixed a lot of the issues with the original BMCC! It seems someone at Blackmagic IS actually listening!

Disclaimer:
I'm not a full time sound recordist or an audio technician. I'm a filmmaker that occasionally has to jump on sound when required. I'm certainly not an expert by any stretch of the imagination - however, I have worked as a sound recordist on countless projects from short films to feature films - and have also won several awards for Best Sound Design in various short film competitions over the years. I've done these tests for our own internal purposes (as we use these cameras on a daily basis on jobs ranging from massive commercial budgets to no-budget shorts) - and have only shared this information in good faith for educational purposes. Take it as a grain of salt, and make your own mind up as to the performance of these cameras - don't trust or blame me!

Gear:
- You can learn more about the Sound Devices 552 here.
- You can learn more about the Sennheiser ME66 here.
- You can learn more about the Rode NT3 here.

General Notes:
- All of the below tests were done using the latest 1.6.1 firmware on both the BMCC and BMP4K.
- Unfortunately our Pocket Camera is currently overseas, so I couldn't test it out. Based on previous tests though, I doubt much has changed since it's original release.
- When a Microphone was connected to the Sound Devices 552, I was using Phantom Power off the 552.
- When a Microphone was connected directly to the camera, I was using batteries in the microphones.
- During the tests the cameras were using their internal batteries, with no SDI monitors connected.
- The Sound Devices 552 was powered off it's internal AA batteries.
- On the BMCC, I always recorded RAW - the files below are directly from the camera.
- On the BMP4K, I always recorded ProRes HD, and used Audition to create WAV files.
- I am going XLR out of 552 and using a custom-build snake cable to balanced jacks into the camera (with a headphone return).
- I recorded to 48kHz MP3 on the 552 just to keep file sizes down. The files below are directly off the recorder.

Calibration:
- When connecting the 552 to the BMCC and BMP4K I always used Line Level 100% on the camera.
- The Tone Frequency is set to 1000 Hz, and Tone Level set to 0dBu on the 552.
- Test Tone from 522 to BMCC in UltraScope.
- Test Tone from 522 to BMCC in Media Express.
- Test Tone from 522 to BMCC in Audition.
- Test Tone from 522 to BMP4K in UltraScope.
- Test Tone from 522 to BMP4K in Media Express.
- Test Tone from 522 to BMP4K in Audition.
- When connecting microphones directly to the cameras, I always used Mic Level 100% (regardless of whether this made the audio clip or not).

For the first test, I downloaded a whole heap of test tones/sounds from the good folks at AudioCheck.net, put them together into one long file in Adobe Audition, then exported out a 48kHz 24bit 320k MP3. I've then put this MP3 onto a Sound Devices 552 for playback into the BMCC and BMP4K.

- You can download the test track here.
- You can view the test track in Adobe Audition here.
- You can result from the BMCC here.
- You can view the result in Adobe Audition from the BMCC here.
- You can result from the BMP4K here.
- You can view the result in Adobe Audition from the BMP4K here.

Next up, I recorded some some dialogue on both the BMCC and a Sound Devices 552 for comparison.

- Sennheiser ME66 connected to 552 connected to BMCC
- Sennheiser ME66 connected to 552
- Rode NT connected to 552 connected to BMCC
- Rode NT connected to 552

Here are the same tests on the BMP4K:

- Sennheiser ME66 connected to 552 connected to BMP4K
- Sennheiser ME66 connected to 552
- Rode NT connected to 552 connected to BMP4K
- Rode NT connected to 552

Here are some tests with microphones connected directly to the BMCC and BMP4K:

- ME66 & Rode NT3 connected to BMCC
- ME66 & Rode NT3 connected to BMP4K

Summary:
- The frequency response issues on the BMP4K seems to be resolved. Whether this is fixed in hardware or software remains to be seen. If I get a chance, I'll open up both cameras at some stage and compare their internals.
- The headphone output on the BMP4K seems to have a really strange delay/reverb that doesn't exist on the BMCC. It makes monitoring off the BMP4K pretty impossible, or at least, very frustrating. There seems to be slightly more level and a TINY bit less noise on the BMP4K's headphone output compared to the BMCC. It's still very noisy though - and your ears will still start bleeding if you had to listen to it all day. Unless BMD can fix the delay/reverb in software - I'd say the BMCC has a more useful headphone output than the BMP4K at this stage.
- The frequency response issue seems to still exist on the BMCC. Sadly it doesn't look like anything has changed between the 1.5 and 1.6 firmware releases.
- When using Mic Levels, the gain structure seems different between the BMP4K and BMCC - you can definitely get more level out of the BMP4K than you can on the BMCC when connecting microphones directly to the camera (which is great news for a lot of people). I'm not sure if this is a software or firmware change.

Overall, the BMP4K seems to be a big improvement on the BMCC audio wise. It's not perfect by any stretch of the imagination - and I would still ALWAYS RECOMMEND using an external audio recorder - but if you have to use on-board recording (which happens - we do it all the time for a variety of reasons), then the fact that the frequency response issue has been addressed (although you will still want to tweak the EQ slightly), will be a big time saver and make life easier for everyone in post.

I'm still hopeful that BMD will release a firmware update for the BMCC that will address the frequency response issue, and that the developers will continue to try and improve the headphone performance across the whole camera range. I am also hopeful that they will revamp the Audio Settings, and scrap the percentage levels for something a bit more logical and sensible. I doubt we'll ever see audio meters - but this doesn't bother me in the slightest, as I can easily calibrate via UltraScopes.

Hopefully this information is helpful. Any questions or feedback let me know!

Onwards & Upwards!

Best Regards, Chris!
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CaptainHook

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Re: Blackmagic Production 4K Audio Tests

PostThu Feb 13, 2014 10:57 pm

I wonder if the latency on the audio headphone path is related to the general 'lag' of the camera?

I "measured" the lag on the back LCD of the BM4K to be around 3-4 frames, where as the BMCC is 0-1.
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Chris Hocking

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Re: Blackmagic Production 4K Audio Tests

PostThu Feb 13, 2014 11:11 pm

CaptainHook wrote:I wonder if the latency on the audio headphone path is related to the general 'lag' of the camera?


Yes, I'd say you're spot on. Curious... Does the SDI output have a delay as well? Have you tried the audio feed from an SDI display?
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CaptainHook

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Re: Blackmagic Production 4K Audio Tests

PostThu Feb 13, 2014 11:17 pm

SDI out has an additional 0-1 frame lag from my crude testing.. but that could be the actual external monitor processing presenting most of that delay. Either way, still gonna be 4 frames lag roughly from SDI out, so audio should follow that (not that i've tested it but still).
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Peter J. DeCrescenzo

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Re: Blackmagic Production 4K Audio Tests

PostThu Feb 13, 2014 11:19 pm

Chris Hocking wrote:...
- All of the below tests were done using the latest 1.6.1 firmware on both the BMCC and BMP4K. ...


Hi Chris: Thank you very much for doing these tests … you are my hero!

Very interesting results. I often use a ME64 (and I also have a ME66), so your test gives me a good idea what to expect.

I'll be using a Sound Devices MixPre (original version w. bal. line level outputs only) with my BMPC-4K, so I'll primarily rely on the MixPre preamps and headphone amp. The cam's headphone output can be connected to the mixer's "tape return", for easy switching back & forth for confidence checks while recording. Not ideal, but probably workable.

Thanks again!

-
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Chris Hocking

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Re: Blackmagic Production 4K Audio Tests

PostThu Feb 13, 2014 11:50 pm

Peter J. DeCrescenzo wrote:Thank you very much for doing these tests … you are my hero!


My pleasure mate. Happy to help!

Peter J. DeCrescenzo wrote:I'll be using a Sound Devices MixPre (original version w. bal. line level outputs only) with my BMPC-4K, so I'll primarily rely on the MixPre preamps and headphone amp. The cam's headphone output can be connected to the mixer's "tape return", for easy switching back & forth for confidence checks while recording. Not ideal, but probably workable.


I think that'll be fine. We regularly send out the original BMCC with a Sound Devices 302 and it works great. We always monitor off the 302, and use the return for confidence checks. There's no way I'd be happy to monitor off the camera for more than a few seconds though - as it's painfully noisy. Obviously, using an external audio recorder would achieve much better results (even on the BMP4K) - however, if you have mission critical jobs you can always just take feed off the MixPre onto an additional recorder. So yes - definitely workable. Whether or not it's recommended depends on whether you're talking to a sound recordist or a producer!
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Re: Blackmagic Production 4K Audio Tests

PostFri Feb 14, 2014 12:23 am

Hello Chris. Very interesting. Thanks for sharing.
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Re: Blackmagic Production 4K Audio Tests

PostFri Feb 14, 2014 2:45 am

Thanks Chris! This is awesome news!
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Re: Blackmagic Production 4K Audio Tests

PostFri Feb 14, 2014 7:52 am

thank you Chris for taking the time to do this indepth test, really appreciate it. Id say the 4K doesent sound bad.
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Re: Blackmagic Production 4K Audio Tests

PostFri Feb 14, 2014 8:17 am

Much appreciate your review on 4k BMPC audio.
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imac5k i7 32gb 2017 video assist 4k mbp mid 2015 r9 370x phase one 645df/p40+,ursa mini4.6 ef bmcc ef bmpcc micro panel ronin mx dji phantom 2 hero 3 black zenmuse 3d...sleepless nites...
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sean mclennan

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Re: Blackmagic Production 4K Audio Tests

PostFri Feb 14, 2014 4:36 pm

Great news on the audio, crappy news about the delay.

I wonder why that is? Strange for the camera's own monitor to have such a delay.
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CaptainHook

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Re: Blackmagic Production 4K Audio Tests

PostFri Feb 14, 2014 8:12 pm

It's because there's 4 times as much data to push around the camera.
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Theodore Prentice

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Re: Blackmagic Production 4K Audio Tests

PostFri Feb 14, 2014 8:50 pm

CaptainHook wrote:It's because there's 4 times as much data to push around the camera.



Isnt the BMCC pushing around just under half as much data as the 4k?
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Re: Blackmagic Production 4K Audio Tests

PostFri Feb 14, 2014 8:59 pm

True i was thinking HD vs UHD there which is 4 times.
But BMCC Raw to UHD is still basically 2.5 times as many pixels. That's a lot more processing to do.
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Re: Blackmagic Production 4K Audio Tests

PostFri Feb 14, 2014 9:03 pm

CaptainHook wrote:It's because there's 4 times as much data to push around the camera.


Good point I guess, but there isn't such a delay on the Scarlet's monitor.

4-5 fps isn't the end of the world for monitoring, but it would "feel" off to me. I imagine it would be more detrimental for some applications over others.
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Re: Blackmagic Production 4K Audio Tests

PostSat Feb 15, 2014 7:59 am

It's really more like 3-4 to an SDI monitor consistently.. but yeah it's still enough that lip-sync to a music vid while shooting looks very off.

I guess the Scarlet has beefier processors to get the data around quicker? Just assumptions here, but there's probably gonna be trade-offs for a UHD camera at $3K !
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Re: Blackmagic Production 4K Audio Tests

PostSat Feb 15, 2014 1:45 pm

I'm sure that can be corrected with some sort of pre-roll for audio in camera? For headphone monitoring I mean..
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Re: Blackmagic Production 4K Audio Tests

PostSat Feb 15, 2014 3:02 pm

CaptainHook wrote:It's really more like 3-4 to an SDI monitor consistently.. but yeah it's still enough that lip-sync to a music vid while shooting looks very off.


sounds bad, makes it pretty hard to follow action....
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Re: Blackmagic Production 4K Audio Tests

PostSun Feb 16, 2014 11:37 am

Blien wrote:I'm sure that can be corrected with some sort of pre-roll for audio in camera? For headphone monitoring I mean..

Preroll does not capture sound earlier then expected. Preroll just starts at an earlier point in case you forgot to roll or miss something important.
We have used delay units to match monitoring to picture for a long time.
My tool of choice is zaxcom ERX200tcd where not only you can delay the sound but also make timing adjustments to the time code.
Rado Stefanov

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