How to fix “underwater” / garbled sound on the iphone

I have just purchased a Canon Legria HF-G25 camcorder as part of my business is providing website video for clients. However my first upload with it to YouTube via editing in iMovie has created a problem that I have never had before.

For some reason the audio sounds really quiet and very distorted / garbled through the iPhone speakers, yet it's fine when you use headphones (in the same iphone) and it's fine on all other computers including iPads.

I've had a search around for a fix for this but really can't find much and wondered if you had any suggestions for settings etc.?

The set up I used is: Canon LEGRIA HF G25; a Sony wireless lapel mic into a Sony receiver; a standard 3.5mm to 3.5mm jack lead from the receiver into the camera mic socket.

The camera microphone attenuator was on automatic and the audio setttings on their defaults. I edited in iMovie, rendered out to QuickTime and used Logic Pro to balance the sound levels and smooth audio edits. Finally it was re-rendered out as a .mov for upload to YouTube.

It works perfectly on all all devices expect iphone speakers! I have also used this mic before on other cameras with no problem but I have uploaded 5 videos from this shoot and, regardless of whether I use Logic Pro or go straight from iMovie up to YouTube, they all have the same problem.

— Paul, UK

Answer:
First of all, if you haven’t already watched it then I strongly recommend – pardon my ego – my video about improving sound on the G25, as the defaults really aren’t that good in fact: http://www.youtube.com/watch?v=XVHNe-6runQ

As regards your specific problem, here’s your issue: the output of the radio mic receiver is BALANCED MONO but the camcorder input is UNBALANCED STEREO. Your 3.5mm lead is the problem.

In short, your lapel mic is mono. Being a “pro” bit of kit, it uses a system called balancing to help minimise any unwanted noise pickup between the receiver and the camcorder.

In balancing, the radio mic receiver takes your mono sound and makes an equal but out of phase copy. These are sent down the Left and Right sides of the 3.5mm jack and should only be plugged into equipment that is expecting a mono, balanced signal (which the camcorder is not).

The idea is that at the camcorder end, it would re-flip the balanced side and use this to help cut out any crackles and bangs. Since the camcorder is not balanced, it doesn’t know to do this and simply records the two signals as the Left and Right halves of the stereo recording.

When you play that back on the iphone, what you are hearing is the out of phase signals being mixed together back into mono and cancelling each other out. This is because the iphone’s loudspeaker is mono.

The reason you don’t hear it in headphones or on any other device is because they play the sound back in stereo so the sounds aren’t mixed and don’t suffer the problem.

You can probably check this in Logic Pro (or on your loudspeaker amplifier, if you use one) by switching your monitoring to mono. It should exhibit the same effect.

The “proper” solution is to use a different type of lead from radio mic receiver to camcorder. What you need is one that has one (and only one) of the stereo sides – it doesn’t matter which – shorted to the ground pin. That way, only one half of the balanced audio will be recorded (it will appear in the camcorder that only one side is working but this is fine for mono, which is what your lapel mic is)

Alternatively, you can buy a balanced-to-unbalanced adapter from companies such as Beachtek or Juiced Link and this will convert the signal correctly.

The fix for your existing recordings is to mute one side (either Left or Right, it doesn’t matter which) and pan the other one so it’s in the middle of your final stereo mix.

I hope this made sense and helps!

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4 Responses

  1. Nelson Agee says:

    Hi! I am also having similar problems every time I post my videos to YouTube. When I listen to the videos on my iPhone they are always garbled however if I listen with my head phones the sound quality is excellent. I use the Focusrite Scarlett sound card that is connected to my MacBook pro. I have tried just about everything to fix the issue. Can you help??

    Nelson

    • admin says:

      The reason for the problem, and the solution, is as described in the article above. You have almost certainly recorded out-of-phase mono audio as a single stereo track in your videos. When listened to on a mono device (like an iphone) the two sides, L & R, are mixed and cancel each other out. You need to identify what part of your equipment or setup is using balanced audio and connect it properly to your camcorder so as either to take it in as balanced, or to unbalance it without simply treating it as a stereo signal (which it isn’t).

  2. Alan Langdon says:

    Lovely answer,,, I was noticing something strange all the time I was editing my “mono” sound, and when it got to an iPhone, as well as a Moto G, garbled audio! Many thanks!

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