I'm working my way through the BBC Technical Delivery Standards, and I came across this specification:

If mono originated sound is used, it must be recorded as dual mono, so that it may be handled exactly as stereo. It must meet all the stereo standards regarding levels, balance and phase.

As far as I understand it, 'recorded as dual mono' means that a signal from a single microphone would be fed into two channels of a recorder, set as stereo linked. Is that correct?

If so, I fail to see the point of such an exercise, or what is meant by 'so that it may be handled exactly as stereo'.

Can someone with experience in these matters please enlighten me?

  • I understand "dual mono" to mean that both the left and right channels are 100% identical, signal-wise. After a couple hours of research I am unable to find an explanation of WHY the BBC specifies dual mono for a source originating in mono. My suspicions involve achieving consistency no matter how the content is reproduced - in mono on a stereo system, summed mono on a mono system, or just a single channel on a really old cassette recorder.
    – user23353
    Mar 15, 2019 at 1:37

1 Answer 1


This is often the case where you have a single microphone feeding two channels of input. The reason for this is that it reduces the risk of a single channel of audio going to air as part of a stereo pair, resulting in left (or right) channel only - sound. If an editor, under the pump, forgets to pan a single channel of audio in the edit correctly, you will end up with this very situation going to air. Basically the request is simply to reduce downstream risk with the signal.

'so that it may be handled exactly as stereo' assumes that anything coming from downstream is going to be two-channel audio. If there is only a single mono source then there should be a reasonable assumption that it is panned centrally across a stereo pair, rather than panned hard left or right, which would require correction prior to airing.

  • I see that this might make sense in a live broadcast situation. I hadn't considered that before. Would that be what this requirement refers to? In the case of a piece of filmed material which has been carefully mixed in post-production, it still doesn't make sense to me.
    – Igid
    Mar 16, 2019 at 21:46
  • 1
    The document you refer to details "programme delivery standards". Basically they are saying that you must deliver two channels of audio. In the situation where there is only one (mono) source channel, you must still deliver two of them.
    – Mark
    Mar 17, 2019 at 4:53
  • I guess you're right, it is talking about delivery. The phrasing 'recorded as' threw me, but in this context I suppose it's synonymous with 'encoded as', and distinguished from 'originated'.
    – Igid
    Mar 18, 2019 at 21:22

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