MSC3246: Audio waveform for extensible events

proposals/3246-audio-waveform.md

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+# MSC3246: Audio waveforms (extensible events)
+
+This is largely a placeholder MSC to describe how audio waveforms/events could work in an extensible
+events world.
+
+Proposals like [MSC3245 - Voice messages using extensible events](https://github.com/matrix-org/matrix-doc/pull/3245)
+would make best use of this.
+
+## Proposal
+
+A `waveform` property is added to the `m.audio` event definition as an array of numbers to denote
+amplitudes for the audio file. The array should have no less than 30 elements and no more than 120.
+Clients might have to resample for their use case, and are encouraged to only use the information
+as placeholder until the real waveform can be determined.
+
+Due to floats not being allowed in events, the waveform should be rescaled to a range of integers
+between zero and 1024, inclusive. This should allow for enough resolution to be maintained for
+preview purposes. Values larger/smaller than those should be clamped.
+
+The waveform is optional.
+
+## Potential issues
+
+TBD
+
+## Alternatives
+
+TBD
+
+## Security considerations
+
+TBD
+
+## Unstable prefix
+
+TBD (not currently needed)