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Expr

Expr - expression language and expression evaluation for Go.

  • language definition - takes best from JS, Python, Jinja2 syntax
  • your expression should return a link of any supported source
  • expression supports multiple operation, but:
    • all operations must be separated by a semicolon
    • all operations, except the last one, must declare a new variable (let s = "abc";)
    • the last operation should return a string
  • go2rtc supports additional functions:
    • fetch - JS-like HTTP requests
    • match - JS-like RegExp queries

Examples

Two way audio for Dahua VTO

streams:
  dahua_vto: |
    expr: let host = "admin:[email protected]";
    fetch("http://"+host+"/cgi-bin/configManager.cgi?action=setConfig&Encode[0].MainFormat[0].Audio.Compression=G.711A&Encode[0].MainFormat[0].Audio.Frequency=8000").ok
        ? "rtsp://"+host+"/cam/realmonitor?channel=1&subtype=0&unicast=true&proto=Onvif" : ""

dom.ru

You can get credentials via:

streams:
  dom_ru: |
    expr: let camera = "99999999"; let token = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"; let operator = 99;
    fetch("https://myhome.novotelecom.ru/rest/v1/forpost/cameras/"+camera+"/video", {
      headers: {Authorization: "Bearer "+token, Operator: operator}
    }).json().data.URL

Parse HLS files from Apple

Same example in two languages - python and expr.

streams:
  example_python: |
    echo:python -c 'from urllib.request import urlopen; import re

    # url1 = "https://devstreaming-cdn.apple.com/videos/streaming/examples/bipbop_16x9/bipbop_16x9_variant.m3u8"
    html1 = urlopen("https://developer.apple.com/streaming/examples/basic-stream-osx-ios5.html").read().decode("utf-8")
    url1 = re.search(r"https.+?m3u8", html1)[0]

    # url2 = "gear1/prog_index.m3u8"
    html2 = urlopen(url1).read().decode("utf-8")
    url2 = re.search(r"^[a-z0-1/_]+\.m3u8$", html2, flags=re.MULTILINE)[0]

    # url3 = "https://devstreaming-cdn.apple.com/videos/streaming/examples/bipbop_16x9/gear1/prog_index.m3u8"
    url3 = url1[:url1.rindex("/")+1] + url2

    print("ffmpeg:" + url3 + "#video=copy")'

  example_expr: |
    expr:

    let html1 = fetch("https://developer.apple.com/streaming/examples/basic-stream-osx-ios5.html").text;
    let url1 = match(html1, "https.+?m3u8")[0];

    let html2 = fetch(url1).text;
    let url2 = match(html2, "^[a-z0-1/_]+\\.m3u8$", "m")[0];

    let url3 = url1[:lastIndexOf(url1, "/")+1] + url2;

    "ffmpeg:" + url3 + "#video=copy"

Comparsion

expr python js
let x = 1; x = 1 let x = 1
{a: 1, b: 2} {"a": 1, "b": 2} {a: 1, b: 2}
let r = fetch(url, {method}) r = request(method, url) r = await fetch(url, {method})
r.ok r.ok r.ok
r.status r.status_code r.status
r.text r.text await r.text()
r.json() r.json() await r.json()
r.headers r.headers r.headers
let m = match(text, "abc") m = re.search("abc", text) let m = text.match(/abc/)