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# NIP-5E
## Censorship Resistant Live Streams
`draft` `optional`
Describes a way to distribute live video streams via nostr.
**"Live Video" in this context implies segmented video streams like HLS or DASH**
## N94 Stream
A new `kind: 1053` event lists a single live stream.
Example:
```jsonc
{
"kind": 1053,
"tags": [
["title", "<name of the event>"],
["summary", "<description>"],
["image", "<preview image url>"],
[
"variant",
"dim 1920x1080",
"bitrate 5000000",
"m video/mp2t",
"d 1080p"
],
[
"variant",
"dim 1280x720",
"bitrate 3000000",
"m video/mp2t",
"d 720p"
],
[
"variant",
"dim 1920x1080",
"bitrate 6000000",
"m video/mp4",
"d 1080p-fmp4"
],
["t", "hashtag"]
["starts", "<unix timestamp in seconds>"],
["ends", "<unix timestamp in seconds>"],
["relays", "wss://one.com", "wss://two.com", /*...*/],
["pinned", "<event id of pinned live chat message>"],
],
"content": "",
// other fields...
}
```
The `variant` tag works like `imeta` tag from [NIP-92](92.md) and defines a variant stream.
The `d` entry of the `variant` tag is used in the NIP-94 segment event for variant following.
## N94 Segment
Each segment of the stream is a [NIP-94](94.md) event which describes where the file can be found and its hash.
```jsonc
{
"kind": 1063,
"tags": [
["d", "1080p"]
["e", "<id-of-kind-1053>"],
["x", "<sha256>"],
["m", "video/mp2t"],
["dim", "1920x1080"],
["duration", "2.033"],
["index", "1234"],
["url", "https://example.com/1234.ts"],
["fallback", "https://another.com/1234.ts"],
["service", "blossom"],
...
]
// other fields...
}
```
Aside from the standard NIP-94 tags:
- `d`: Variant stream tag.
- `index`: Segment index, a simple counter. Used of ordering.
`service` tag should be used for extended censorship resitance by looking up the appropriate server list (Blossom) of the uploader and checking for files on alternate servers.
## Implementors
### Consumers
Clients wishing to implement a player should use [MSE](https://developer.mozilla.org/en-US/docs/Web/API/Media_Source_Extensions_API) or similar technologies which allow appending data to the player buffer.
Other services MAY provide a compatability layer with [NIP-53](53.md) live streams by producing HLS playlists over a N94 Stream.
Clients SHOULD follow only a single variant by using a filter like this:
`{"kinds":[1063],"#e":["<id-of-kind-5053>"],"#d":["1080p"],"limit":10}`
Leaving the subscription open will allow clients to be notified immediately as segments are published and can fetch those segments and append them to the player buffer.
### Producers
Segment length SHOULD be carefully considered as a trade off between stream delay and total number of NIP-94 events / segment files.
Using `expiration` tags on N94 segments and deleting segment files from servers SHOULD be used to cleanup streams which don't want to persist after the stream is finished.
## Example implementations:
### Player
[zap.stream](https://github.com/v0l/zap.stream/blob/main/src/element/stream/n94-player.tsx)
### Producer
[zap-stream-core](https://github.com/v0l/zap-stream-core/blob/ccb2add6073e5bb68191c42613c34f66583e34fc/crates/zap-stream/src/overseer.rs#L340-L380)
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