NIP-A0
======

Voice Messages
-----------

**Status:** Draft

This NIP defines new events `kind: 1222` for root messages and `kind: 1244` for reply messages to be used for short voice messages, typically up to 60 seconds in length.

## Specification

### Event Kind `1222` and Kind `1244`

The `kind: 1222` event is defined as follows:

-   `content`: MUST be a URL pointing directly to an audio file.
    -   The audio file SHOULD be in `audio/webm` format. Clients MAY support other common audio formats like `audio/ogg`, `audio/mp4` (m4a), or `audio/mpeg` (mp3), but `audio/webm` is recommended for broad compatibility and efficiency.
    -   The audio duration SHOULD be no longer than 60 seconds. Clients publishing `kind: 1222` events SHOULD enforce this limit or provide a clear warning to the user if exceeded.
-   `tags`:
    -   Tags MAY be included as per other NIPs (e.g., `t` for hashtags, `g` for geohash, etc.).

  The `kind: 1244` event is defined as follows:
  
-    To be used for replies, `kind: 1244` events MUST follow the structure of `NIP-22`.
-   `content`: MUST be a URL pointing directly to an audio file.
    -   The audio file SHOULD be in `audio/webm` format. Clients MAY support other common audio formats like `audio/ogg`, `audio/mp4` (m4a), or `audio/mpeg` (mp3), but `audio/webm` is recommended for broad compatibility and efficiency.
    -   The audio duration SHOULD be no longer than 60 seconds. Clients publishing `kind: 1222` events SHOULD enforce this limit or provide a clear warning to the user if exceeded.
-   `tags`:
    -   Tags MAY be included as per other NIPs (e.g., `t` for hashtags, `g` for geohash, etc.).


## Visual representation with `imeta` (NIP-92) tag (optional)

The following imeta (NIP-92) tags MAY be included so clients can render a visual preview without having to download the audio file first:

- `waveform`: amplitude values over time, space separated, less than 100 values should be enough to render a nice visual
- `duration`: audio length in seconds

## Examples

### Root Voice Message Example

```json
{
  "content": "https://blossom.primal.net/5fe7df0e46ee6b14b5a8b8b92939e84e3ca5e3950eb630299742325d5ed9891b.mp4",
  "created_at": 1752501052,
  "id": "...",
  "kind": 1222,
  "pubkey": "...",
  "sig": "...",
  "tags": [
    [
      "imeta",
      "url https://blossom.primal.net/5fe7df0e46ee6b14b5a8b8b92939e84e3ca5e3950eb630299742325d5ed9891b.mp4",
      "waveform 0 0.05 0.27 0.08 0.01 0.01 0.01 0.03 0.38 1.5 0.49 0.02 0.28 0.04 0.01 0 0 0.39 0.22 0.16 0.05 0.06 0.55 0.01 0.06 0.01 0 0 0.02 0.61 0.02 0.07 0.01 0.21 0.09 0.12 0.63 0.01 0.02 0.02 0.42 0.02 0.68 0.05 0.02 0.05 0.02 0 0 0 0",
      "duration 8"
    ]
  ]
}