Gear / Technical Help => Recording Gear => Topic started by: Ozpeter on November 10, 2020, 05:50:47 AM

Title: Slighty O.T but bear with me - DJI Pocket 2
Post by: Ozpeter on November 10, 2020, 05:50:47 AM
Due to present circumstances, it seems kind of quiet in here at the moment, so perhaps I might be forgiven for mentioning a device which could have relevance to run and gun location sound recording - even though it's a video and stills camera.

I'm talking about the DJI Pocket 2 gimbal camera.  Check it out online and you'll see it has a handle containing a small screen, and at the top is a gimbal head for the actual camera part.  If you wanted to make an informal video of a live event, it has some advantages over a mobile phone because the gimbal mechanism keeps the head pointing in one direction even if your hand wobbles about, and it's not so conspicuous as a phone, nor so irritating to the people behind.  Nor will it ring in the middle of the event. 

But that's not really what I'm posting about.  In the handle there are 4 mics - left, right, front, back.  They are just the pinhole kind, and I imagine they must therefore be omni capsules in there.  Four closely-spaced omni capsules wouldn't normally be the slightest good for creating a wide stereo soundfield.  Sony M10, I'm looking at you (only had 2 of course).

But... somehow they are getting an excellent, almost binaural sound from this arrangement.  And they are even rotating it according to which way the gimbal head points, presumably using some kind of pseudo-ambisonic technique.  Bass extension is, as far as i can tell from the YouTube videos I have seen, very good.  High frequencies?  Noise?  Don't ask me, my ears are too shot now to tell.  Younger readers might tell me.

But all in all, I could imagine getting a very servicable run-and-gun concert recording out of this, together with 4K60 video thrown in, for a very modest price - subject to how well it handles high SPL levels.  There are only four sound input levels to choose from but that needs not to be a problem if noise level is acceptable.  I'm trying to find out what the spec is in that respect. 

But there's more.  If you buy the 'creator kit' version for a bit more money, it comes with an extension to the handle into which you can connect a stereo external mic.  And it comes with a wireless transmitter with its own mono mic, and that too has a (mono) mic input for a lav mic, and a remote start/stop button.  When you turn on the transmitter, it automatically switches the input from the built in mics to the radio mic.  Could be interesting if you wanted to have the device in front of a band recording from its own mics, then from a distance turn on the radio mic to speak some commentary in between songs.   And the handle provides a wireless link to a phone app which gives full control over the camera, including panning and tilt and (digital) zoom.  Very unusually, the mic socket is also a headphone socket for checking playback.  Apparently there's an impedence sensor which makes sure you don't play back into a mic.  I shall test that with a mic I don't mind destroying... 

Mine is on order, and in due course I will see whether I can illustrate its potential usefulness as an audio recorder myself.  Meanwhile here are some YouTube examples if you are interested.

Ambient sound - https://youtu.be/WAqeed_b5Qs

More ambient sound - note that this is a comparison of the new model with the old and the sound switches between the mono sound of the old and the stereo sound of the new - https://youtu.be/w5mPe0Pc8-0

And yet more - with some music towards the end.  https://youtu.be/mLEfc6vVR_s

This one is just some test footage using the built in mic array in someone's home at night (but indicates what video performance might be like in low light eg jazz club).  There's a TV in the room.  Notice how accurately the location of the TV is pinpointed in the stereo soundfield as the camera turns in different directions.  Right at the very end there's a very low drum (?) beat from the TV which show bass extension - https://youtu.be/0qhqBPC-rDw

I'd love to get this in front of a string quartet... that would probably be revealing.
Title: Re: Slighty O.T but bear with me - DJI Pocket 2
Post by: Ozpeter on November 17, 2020, 04:30:22 AM
At last my Pocket 2 has arrived, and I've put together a tutorial for other users to explain its sound options.  There's some ambient sound examples in parkland and urban environments at 10'47" of the video.  See https://youtu.be/j2nZPGsBJtI

The way that the soundfield is rotated to match the rotation of the gimbal head is very well executed.  If used for a run and gun recording of a band, it's possible to lock the gimbal pointing towards the stage, and then if you move the handle around a bit, the stereo image won't be disturbed even though the mics are in that handle.  Initial tests with an external stereo mic indicate that input sensitivity is relatively low, thus suiting use in loud environments.  But I've got a fair bit more testing to do.  Sadly, not much prospect of trying it at a live gig for some time... ::)
Title: Re: Slighty O.T but bear with me - DJI Pocket 2
Post by: ol' dirty taper on November 17, 2020, 08:35:39 PM
I'm jealous, I picked up a NIB osmo pocket 1 a few months back. It's been a fun toy to play with while waiting to use it for shows. Might upgrade if there is enough of a difference in the performance, I am not concerned over audio since I'll be running mics separately for music. I did notice it picks up wind pretty bad.

The freewell filters make a really nice difference in image quality.
Title: Re: Slighty O.T but bear with me - DJI Pocket 2
Post by: Ozpeter on November 18, 2020, 07:23:06 AM
I've been doing some tests of the audio of the device, with mixed results.  Running a gliding test tone into the device directly and scanning it into a frequency display (Audition) shows that the input's frequency response is pretty flat.  But looking at the spectral display - and listening - reveals that there's substantial distortions happening.  For instance, as the tone glides up, you hear spurious tones gliding down - stuff like that.  In many uses I don't think it would be noticable, as real life sounds and test tones are kind of different, but I was alerted to the problem when doing the key jangle test, where you jangle a bunch of keys in a circular motion fairly close to a stereo mic.  Playing that back sounded nothing like keys jangling!  Hence the subsequent testing.

Testing the frequency response of the built in mics is difficult without an anechoic chamber etc, but a crude test showed that their response is pretty wide and without anything obviously nasty.  In comparison with Zoom H1n mics, their HF response seems more extended.

Still a very interesting device, so long as the distortion doesn't rear its ugly head!
Title: Re: Slighty O.T but bear with me - DJI Pocket 2
Post by: Ozpeter on November 24, 2020, 05:51:03 AM
And finally - location recording of passing trains, one of which usefully sounded its horn as the driver didn't like how close I was.  Also, for contrast, there's footsteps, birds, and passing bicycles.