mirror of
https://github.com/AlexxIT/go2rtc.git
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92 lines
3.7 KiB
Markdown
92 lines
3.7 KiB
Markdown
# Expr
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[Expr](https://github.com/antonmedv/expr) - expression language and expression evaluation for Go.
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- [language definition](https://expr.medv.io/docs/Language-Definition) - takes best from JS, Python, Jinja2 syntax
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- your expression should return a link of any supported source
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- expression supports multiple operation, but:
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- all operations must be separated by a semicolon
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- all operations, except the last one, must declare a new variable (`let s = "abc";`)
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- the last operation should return a string
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- go2rtc supports additional functions:
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- `fetch` - JS-like HTTP requests
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- `match` - JS-like RegExp queries
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## Examples
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**Two way audio for Dahua VTO**
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```yaml
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streams:
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dahua_vto: |
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expr: let host = "admin:password@192.168.1.123";
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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
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? "rtsp://"+host+"/cam/realmonitor?channel=1&subtype=0&unicast=true&proto=Onvif" : ""
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```
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**dom.ru**
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You can get credentials via:
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- https://github.com/alexmorbo/domru (file `/share/domru/accounts`)
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- https://github.com/ad/domru
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```yaml
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streams:
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dom_ru: |
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expr: let camera = "99999999"; let token = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"; let operator = 99;
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fetch("https://myhome.novotelecom.ru/rest/v1/forpost/cameras/"+camera+"/video", {
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headers: {Authorization: "Bearer "+token, Operator: operator}
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}).json().data.URL
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```
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**Parse HLS files from Apple**
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Same example in two languages - python and expr.
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```yaml
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streams:
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example_python: |
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echo:python -c 'from urllib.request import urlopen; import re
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# url1 = "https://devstreaming-cdn.apple.com/videos/streaming/examples/bipbop_16x9/bipbop_16x9_variant.m3u8"
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html1 = urlopen("https://developer.apple.com/streaming/examples/basic-stream-osx-ios5.html").read().decode("utf-8")
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url1 = re.search(r"https.+?m3u8", html1)[0]
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# url2 = "gear1/prog_index.m3u8"
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html2 = urlopen(url1).read().decode("utf-8")
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url2 = re.search(r"^[a-z0-1/_]+\.m3u8$", html2, flags=re.MULTILINE)[0]
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# url3 = "https://devstreaming-cdn.apple.com/videos/streaming/examples/bipbop_16x9/gear1/prog_index.m3u8"
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url3 = url1[:url1.rindex("/")+1] + url2
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print("ffmpeg:" + url3 + "#video=copy")'
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example_expr: |
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expr:
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let html1 = fetch("https://developer.apple.com/streaming/examples/basic-stream-osx-ios5.html").text;
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let url1 = match(html1, "https.+?m3u8")[0];
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let html2 = fetch(url1).text;
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let url2 = match(html2, "^[a-z0-1/_]+\\.m3u8$", "m")[0];
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let url3 = url1[:lastIndexOf(url1, "/")+1] + url2;
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"ffmpeg:" + url3 + "#video=copy"
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```
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## Comparsion
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| expr | python | js |
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|------------------------------|----------------------------|--------------------------------|
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| let x = 1; | x = 1 | let x = 1 |
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| {a: 1, b: 2} | {"a": 1, "b": 2} | {a: 1, b: 2} |
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| let r = fetch(url, {method}) | r = request(method, url) | r = await fetch(url, {method}) |
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| r.ok | r.ok | r.ok |
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| r.status | r.status_code | r.status |
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| r.text | r.text | await r.text() |
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| r.json() | r.json() | await r.json() |
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| r.headers | r.headers | r.headers |
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| let m = match(text, "abc") | m = re.search("abc", text) | let m = text.match(/abc/) |
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