Add volmeter audio volume level

Author: upgradeQ

README.md

@@ -34,7 +34,9 @@ Also check out [issues](https://github.com/upgradeQ/OBS-Studio-Python-Scripting-
 - [Play sound](#play-sound)
 - [Read and write private data from scripts or plugins](#read-and-write-private-data-from-scripts-or-plugins)
 - [Browser source interaction](#browser-source-interaction)
+- [Acess source dB volume level](#access-source-db-volume-level)
 - [Debug](#debug)
+- [Security](#security)
 - [Docs and code examples](#docs-and-code-examples)
 - [Links](#links)
 - [Contribute](#contribute)
@@ -671,10 +673,39 @@ def press_shift_tab(*p):
 ```
 - [Full example read](src/browser_source_interaction.py)
 
+# Acess source dB volume level
+There is FFI `ctypes` module in Python to wrap native `obs` lib.
+However,to run it on GNU/Linux you must start obs with `LD_PRELOAD`.
+```bash
+ubsdrive3@usbdrive3:~$ LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libpython3.9.so obs
+```
+It might be in different directory, use `find /usr -name 'libpython*' ` to
+find exact location.
+
+```python
+volmeter_callback_t = CFUNCTYPE(
+    None, c_void_p, POINTER(c_float), POINTER(c_float), POINTER(c_float)
+)
+...
+wrap(
+    "obs_volmeter_add_callback",
+    None,
+    argtypes=[POINTER(Volmeter), volmeter_callback_t, c_void_p],
+)
+...
+@volmeter_callback_t
+def volmeter_callback(data, mag, peak, input):
+    G.noise = float(peak[0])
+```
+
+- [Full example read](src/volmeter_via_ffi.py)
+
 # Debug
 There is no stdin therefore you can't use pdb , options are:
 - using `print`
+- using generated log file (contains information about memory leaks)
 - using pycharm remote debugging (localhost)
+- using threading 
 - using [vscode](https://code.visualstudio.com/docs/python/debugging) attach to the process:
     - Load python extension
     - open script file , `pip install debugpy` , place  `debugpy.breakpoint()` somewhere
@@ -685,9 +716,21 @@ There is no stdin therefore you can't use pdb , options are:
 
 ![screenshot](src/assets/debug.png)  
 
+# Security
+- "Calling home" - see [`#4044`](https://github.com/obsproject/obs-studio/issues/4044)
+- On GNU/Linux there is handy program called `tcpdump`, to run a check against OBS Studio - use this command (it is active on 443 port on start and on end)
+```bash
+# tcpdump -i <your_interface_e_g_wifi_or_wire> 'port 443'
+```
+- Avoid using `sudo` or admin, check hashsums, do backups, do updates, etc...
+- There is no confirmation for loading Lua or Python scripts - they can be added/overwritten via .json key
+- Also solutions for Python source code obfuscation & loading from shared (compiled) library do exist.Applying that will make it a bit harder to reverse-engineer your code.
+
 # Docs and code examples
 
-[Generated export.md](src/export.md) contains all variables and functions available in `obspython` formatted with markdown. Table consist of links to appropriate search terms in OBS Studio repository, and obswebsocket,links to scripts in `obspython` and `obslua` with each script within github code search.`gs_*` and `matrix_*` functions exluded from that table.   
+- [`Generated export.md`](src/export.md)
+
+contains all variables and functions available in `obspython` formatted with markdown. Table consist of links to appropriate search terms in OBS Studio repository and obswebsocket,links to scripts in `obspython` and `obslua` with each script within github code search.`gs_*` and `matrix_*` functions exluded from that table.   
 [Full example](src/export_md.py)  
 `Note` : starting from 2020.12.17 Github Code Search no longer works as it was, see also this [thread](https://github.community/t/feedback-on-changes-to-code-search-indexing/150660)  
 
@@ -696,7 +739,7 @@ There is no stdin therefore you can't use pdb , options are:
 - [Scripts forum](https://obsproject.com/forum/resources/categories/scripts.5/) , [Github topic `obs-scripts`](https://github.com/topics/obs-scripts) , [Github topic `obs-script`](https://github.com/topics/obs-script)
 - [OBS Studio Repo](https://github.com/obsproject/obs-studio) , [obs-scripting-python.c](https://github.com/obsproject/obs-studio/blob/master/deps/obs-scripting/obs-scripting-python.c)
 - [Docs](https://obsproject.com/docs/) , [Docs/scripting](https://obsproject.com/docs/scripting.html) , [Docs/plugins](https://obsproject.com/docs/plugins.html) , [Docs index](https://obsproject.com/docs/genindex.html)
-- obspython [Gist](https://gist.github.com/search?l=Python&q=obspython) , [Github](https://github.com/search?l=Python&o=desc&q=obspython&s=indexed&type=Code) , [grep.app](https://grep.app/search?q=obspython&filter[lang][0]=Python)
+- obspython [Gist](https://gist.github.com/search?l=Python&q=obspython&s=updated) , [Github](https://github.com/search?l=Python&o=desc&q=obspython&s=indexed&type=Code) , [grep.app](https://grep.app/search?q=obspython&filter[lang][0]=Python)
 - obslua [Gist](https://gist.github.com/search?l=Lua&o=desc&q=obslua&s=updated) , [Github](https://github.com/search?l=Lua&o=desc&q=obslua&s=indexed&type=Code) , [grep.app](https://grep.app/search?q=obslua&filter[lang][0]=Lua)
 - [A Python bundle for integration with OBS scripting](https://github.com/zooba/obs-python)
 - [Lua tips and tricks](https://obsproject.com/forum/threads/tips-and-tricks-for-lua-scripts.132256/)

src/volmeter_via_ffi.py

@@ -0,0 +1,101 @@
+import obspython as S  # studio
+from types import SimpleNamespace
+from ctypes import *
+from ctypes.util import find_library
+
+obsffi = CDLL(find_library("obs"))
+G = SimpleNamespace()
+
+
+def wrap(funcname, restype, argtypes):
+    """Simplify wrapping ctypes functions in obsffi"""
+    func = getattr(obsffi, funcname)
+    func.restype = restype
+    func.argtypes = argtypes
+    globals()["g_" + funcname] = func
+
+
+class Source(Structure):
+    pass
+
+
+class Volmeter(Structure):
+    pass
+
+
+volmeter_callback_t = CFUNCTYPE(
+    None, c_void_p, POINTER(c_float), POINTER(c_float), POINTER(c_float)
+)
+wrap("obs_get_source_by_name", POINTER(Source), argtypes=[c_char_p])
+wrap("obs_source_release", None, argtypes=[POINTER(Source)])
+wrap("obs_volmeter_create", POINTER(Volmeter), argtypes=[c_int])
+wrap("obs_volmeter_destroy", None, argtypes=[POINTER(Volmeter)])
+wrap(
+    "obs_volmeter_add_callback",
+    None,
+    argtypes=[POINTER(Volmeter), volmeter_callback_t, c_void_p],
+)
+wrap(
+    "obs_volmeter_remove_callback",
+    None,
+    argtypes=[POINTER(Volmeter), volmeter_callback_t, c_void_p],
+)
+wrap(
+    "obs_volmeter_attach_source",
+    c_bool,
+    argtypes=[POINTER(Volmeter), POINTER(Source)],
+)
+
+
+@volmeter_callback_t
+def volmeter_callback(data, mag, peak, input):
+    G.noise = float(peak[0])
+
+
+def output_to_file(volume):
+    with open("current_db_volume_of_source_status.txt", "w", encoding="utf-8") as f:
+        f.write(str(volume))
+
+
+OBS_FADER_LOG = 2
+G.lock = False
+G.start_delay = 3
+G.duration = 0
+G.noise = 999
+G.tick = 16
+G.tick_mili = G.tick * 0.001
+G.interval_sec = 0.05
+G.tick_acc = 0
+G.source_name = "Media Source"
+G.volmeter = "not yet initialized volmeter instance"
+G.callback = output_to_file
+
+
+def event_loop():
+    """wait n seconds, then execute callback with db volume level within interval"""
+    if G.duration > G.start_delay:
+        if not G.lock:
+            print("setting volmeter")
+            source = g_obs_get_source_by_name(G.source_name.encode("utf-8"))
+            G.volmeter = g_obs_volmeter_create(OBS_FADER_LOG)
+            g_obs_volmeter_add_callback(G.volmeter, volmeter_callback, None)
+            if g_obs_volmeter_attach_source(G.volmeter, source):
+                g_obs_source_release(source)
+                G.lock = True
+                print("Attached to source")
+                return
+        G.tick_acc += G.tick_mili
+        if G.tick_acc > G.interval_sec:
+            G.callback(G.noise)
+            G.tick_acc = 0
+    else:
+        G.duration += G.tick_mili
+
+
+def script_unload():
+    g_obs_volmeter_remove_callback(G.volmeter, volmeter_callback, None)
+    g_obs_volmeter_destroy(G.volmeter)
+    print("Removed volmeter & volmeter_callback")
+
+
+S.timer_add(event_loop, G.tick)