Update README.md

README.md

@@ -51,4 +51,8 @@ Example:
 
 In this case we got the PSSH value of `AAAAV3Bzc2gAAAAA7e+LqXnWSs6jyCfc1R0h7QAAADcIARIQFi99MmzyT229Exm8Vyu8FRoLYnV5ZHJta2V5b3MiEBYvfTJs8k9tvRMZvFcrvBUqAkhE`
 
-Congrats, you have the PSSH!
+Congrats, you have the PSSH!
+
+4) Using init files
+
+You can use [this tool](https://cdm-project.com/CDM-Tools/Obtaining-PSSH/src/branch/main/get_pssh_from_init.py "this tool") to obtain the PSSH from an init file

get_pssh_from_init.py

@@ -0,0 +1,29 @@
+import base64
+
+import requests
+import xmltodict
+
+
+def read_pssh_from_bytes(bytes: bytes):
+    pssh_offset = bytes.rfind(b"pssh")
+    _start = pssh_offset - 4
+    _end = pssh_offset - 4 + bytes[pssh_offset - 1]
+    pssh = bytes[_start:_end]
+    return pssh
+
+
+url = input("Enter Init segment url: ")
+headers = {
+    # "Range": "bytes=0-962",
+}
+print("Downloading...")
+
+res = requests.get(url, headers=headers)
+if not res.ok:
+    print(f"Could not download init segment: {res.text}")
+
+pssh = read_pssh_from_bytes(res.content)
+if pssh is not None:
+    print(f"PSSH: {base64.b64encode(pssh).decode('utf8')}")
+else:
+    print("Failed to extract PSSH!")