How can I make an iPhone video recording convert mono USB-C input to stereo?

I see tons of people running into the same issue I am and I'm desperate for a solution. I have high-quality audio gear (microphone, pre-amp, etc) and I simply want to send a mono audio signal from my vocal mic over USB-C to the iPhone, to be used for recording videos. When the input is mono like this, I assume there should be way to convert to stereo instead of dumping the mono signal into the left channel.


What I've tried so far: I read that on iPhone, Settings->Camera->Record Stereo should be turned off. That doesn't fix the problem for me though. The input mono signal (from my Scarlett Claret 4x4 USB gen 3) is dumped into the left channel, regardless of the "Record Stereo" setting being on or off.

iPhone 15 Pro

Posted on Feb 12, 2025 10:17 PM

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Feb 12, 2025 10:41 PM in response to eraoul

If you're only hearing sound in one channel (left or right), it's likely due to poor recording quality caused by faulty cables or subpar instruments.


Let us understand Mono and Stereo closely.


  1. Mono vs. Stereo Audio:
    1. Mono (Monaural) Audio: A single audio channel where the same sound is sent to both the left and right speakers (or ears) at the same frequency and intensity. There’s no spatial differentiation in the sound.
    2. Stereo Audio: Two distinct channels (left and right) capture and play different sounds, allowing for a perception of directionality and space. This creates a more immersive experience.
  2. How Stereo Recording Works on an iPhone:
    1. iPhones with stereo recording capability (like recent Pro models) use multiple microphones to capture sound from different directions.
    2. Sounds coming from the left side of the iPhone are primarily recorded in the left channel, and sounds from the right side are recorded in the right channel.
    3. This separation creates a stereo effect when played back through stereo speakers or headphones, making it feel like sounds are positioned in a 3D space.
  3. For True Stereo Effects:
    1. You must record in stereo (using a stereo microphone setup).
    2. You must transmit in stereo (the file must preserve the left and right channel separation).
    3. You must playback in stereo (using stereo speakers or headphones that can reproduce the left and right channels separately).
  4. Why Listening on a Single Speaker is Still Mono:
    1. If you listen to a stereo recording through only one speaker, you lose the directional separation, and the audio effectively becomes mono again.
    2. Even if the stereo signal is combined into one channel, it no longer has spatial positioning, making it indistinguishable from mono-playback.


Practical Example:

  • If you record a street scene in stereo, footsteps on the left should sound more dominant in the left channel, and cars on the right should be more dominant in the right channel.
  • If you listen with two stereo speakers, you’ll perceive the depth and separation.
  • If you listen with only one speaker, both channels are mixed, and it sounds like a flat mono recording.


This is why stereo sound requires the full chain—recording, transmission, and playback in stereo—to retain the stereo effect.


If you're only hearing sound in one channel (left or right), it’s typically a result of issues during the recording process. This can be caused by poor-quality cables, faulty connections, or low-grade instruments that do not properly transmit a balanced audio signal. Ensuring high-quality recording equipment and checking for secure connections can help prevent this issue.


if a recording is only playing on one channel (left or right), there are several ways to correct it after recording using third-party apps or software. This cannot be corrected on an iPhone.

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How can I make an iPhone video recording convert mono USB-C input to stereo?

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