Onscreen audio meters in Magic Lantern firmware

It isn't perfect by a long shot, but we're making very swift progress this holiday weekend. I found the VRAM and was able to write a small task that monitors the audio levels at 30 Hz and draws a very simple level meter on the top of the screen. It is calibrated with 5 dB tick marks, but the ballistics are bad and it isn't synced with the redraw period (causing it to flicker), but we're running real code doing real work on the camera!

I promise you this is the most boring 45 second video you will ever see, but it provides a glimpse of the promise of what we can do with this camera.

Sorry about the quality; my wife's SD400 point-and-shoot isn't quite the same as a 5D Mark 2...

EDIT: I found the calibration table for the audio device as well as some bugs in my drawing code. I've added calibrated 5 dB tick marks (-40 on the left to 0 dB on the right) and wrote some simplistic ballistics for the peak with a few second delay. The video is a new one to reflect the changes.

EDIT: I figured out how to draw into the bitmap area rather than the YUV space so that the overlay is synchronized with the video refresh. This avoids any flickering. I have also added full time 16:9 crop marks at clovenguth's suggestion and a brief commentary as to what is being shown on screen.

EDIT: Project renamed and FAQ updated.

That's awsome. Keep up the great work. Thank your wife for us. So far this 3 day weekend I have had to install a ceiling fan, put up a screen door and clean our basement. No time for camera work

If Canon can't, HUD can!

Not good video quality...
BUT it's amazingly interesting !!

Congrats for achieving that !!

Great to run your own code in real time, very impressive indeed.

When I read this, I hollered so loud my girlfriend came running from the bathroom to find out what we'd won!

Thanks so much for unlocking this thing for us. Great work!

When I read this, I hollered so loud my girlfriend came running from the bathroom to find out what we'd won!

I laughed !

It isn't perfect by a long shot . . . . . .

Fantastic stuff !!!!!

". . . . .that monitors the audio levels at 30 Hz"

I am sure you can go for much much less ! 11 khz (11.025) would be overkill for a VU/meter !!


Hudson, if you ever find yourself in London/UK, there is a pub with a bunch of people who will get you very drunk and probably much worse.



+ I realise it is all very easy for us to suggest features when you are in the middle of digging though this thing, and even more easy when you are relying on someone else (you!) to implement these ideas, but . . . .

. . . for a useable level indicator it would be great to have some (any) kind of peak hold - even if it is for half a second or so,

You are right, it's horribly boring....

BUT it's amazingly interesting !!

+1

Hudson,

Fantastic! Thanks for taking the time to record and upload the video. Really something to see it in action.

Do you plan on the first "5D Mark Free" (official now?) release to be audio based? As soon as you get it working a little better I mean.. At what point will you let us get our hands on it?

". . . . .that monitors the audio levels at 30 Hz"
I am sure you can go for much much less ! 11 khz (11.025) would be overkill for a VU/meter !!

30 Hz is way slower than 11 KHz...

. . . for a useable level indicator it would be great to have some (any) kind of peak hold - even if it is for half a second or so,

Check out the new video. I replaced the old video with one showing the calibrated meter with some simplistic ballistics that give a peak-hold/decay sort of function. I had a huge mistake in my peak calculation -- the values are signed 16-bit, so my averaging function was always returning zero. Hmm.

I've also written an o-scope mode that draws sample points across the screen. It isn't very useful for monitoring the audio during recording, but it sure works great for finding the signed value bug.

Thanks for taking the time to record and upload the video. Really something to see it in action.

Just in case there were doubters claiming the screen shot was done in Photoshop...

Do you plan on the first "5D Mark Free" (official now?) release to be audio based? As soon as you get it working a little better I mean.. At what point will you let us get our hands on it?

That's my plan. The audio stuff is the easiest to attack and one that will make a big difference for lots of folks trying to do on-camera audio. We have a decent work-around for DOF by twisting the lenses (in fact, I just shot an entire short with my 85 mm f/1.8 twisted off), but there aren't any good workarounds for the AGC and audio problems. Feeding 20 KHz into the mic doesn't seem like a good solution to me since there is already limited headroom in the AK4646.

I'll be testing next week with the Juicedlink CX231 and hope to have a stable "release" sometime by next weekend once I have verified the behaviour with good mics.