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Cannot properly decode Base64 string from Power Apps to audio file

I am trying to properly decode a Base64 string from Power Apps to an audio file. The point is: I do decode it and I can play it. But as soon as I try to convert it using ffmpeg or any website, all kind of errors are thrown. I have tried changing the formats too (aac, weba, m4a, wav, mp3, ogg, 3gp, caf), but none of them could be converted to another format.
PS: If I decode the string (which is too big to post here) directly using a website, then the audio file can finally be converted, indicating that the issue is in the code or even in the Python library.
===============
CODE ===============
import os
import base64
mainDir = os.path.dirname(__file__)
audioFileOGG = os.path.join(mainDir, "myAudio.ogg")
audioFile3GP = os.path.join(mainDir, "myAudio.3gp")
audioFileAAC = os.path.join(mainDir, "myAudio.aac")
binaryFileTXT = os.path.join(mainDir, 'binaryData.txt')
with open(binaryFileTXT, 'rb') as f:
audioData = f.readlines()
audioData = audioData[0]
with open(audioFileAAC, "wb") as f:
f.write(base64.b64decode(audioData))
Result: the audio file is playable, but it cannot be converted to any other format (I need *.wav).
What am I missing here?

I found the issue myself: in order to decode the Base64 string, one must remove the header first (eg.: "data:audio/webm;base64,"). Then it works!

Covert SAP XSTRING to a doc file?

I'm working in an application which has SAP RFC which returns doc files as XSTRINGs. And also there is a client application written in python that sends request to SAP RFC to get doc files. So my question is, in python, how can i convert XSTRING to a doc file?.
Response Header's content type is application/msword; and charset=utf-8

This answer was given by the OP inside his own question, so I have moved it here to fit StackOverflow principles.
Answer to my own question :
Even though SAP RFC returns a variable of type xstring, Python receives it in base64. In order to convert base64 string to doc, first I decoded base64 string and it gave me output in RTF. Then I wrote RTF bytes to a .rtf file. RTF files can be opened from most of the word processing tools. Therefore I was able to open .rtf file from word processing tools.
Following is code I wrote for conversion:
from base64 import b64decode
base64_resp = response_json['data']
bytes_rtf = b64decode(base64_resp, validate=True)
f = open(rtf_filename, 'wb')
f.write(bytes_rtf)
f.close()

Python method like File.WriteAllBytes() in .Net

There is a .net API sending the byte data as a string in JSON, I am using a python API to read it and write it in a file.
a = io.BytesIO(b"JVBERi0xLjQNJcjIyMjIyMg...")
with open('test.pdf','wb') as g:
g.write(a.getvalue())
I created a file with this code but unable to open the file.
I need another way of doing the same.

instead of using io.BytesIO use base64.
import base64
data = "strin data"
base64_data =base64.b64decode(data)
with open(filename,'wb') as f:
f.write(base64_data)

Saving uploaded binary to local file

I'm trying to upload files from a javascript webpage, to a python-based server, with websockets.
In the JS, this is how I'm transmitting the package of data over the websocket:
var json = JSON.stringify({
'name': name,
'iData': image
});
in the python, I'm decoding it like this:
noJson = json.loads(message)
fName = noJson["name"]
fData = noJson["iData"]
I know fData is in unicode format, but when I try to save the file locally is when the problems begin. Say, I'm trying to upload/save a JPG file. Looking at that file after upload I see at the beginning:
ÿØÿà^#^PJFIF
the original code should be:
<FF><D8><FF><E0>^#^PJFIF
So how do I get it to save with the codes, instead of the interpreted unicode characters?
fd = codecs.open( fName, encoding='utf-8', mode='wb' ) ## On Unix, so the 'b' might be ignored
fd.write( fData)
fd.close()
(if I don't use the "encoding=" bit, it throws a UnicodeDecodeError exception)

Use 'latin-1' encoding to save the file.
The fData that you are getting already has the characters encoded, i.e. you get the string u'\xff\xd8\xff\xe0^#^PJFIF'. The latin-1 encoding will literally convert all codepoints between U+00 and U+FF to a single char, and fail to convert any codepoint above U+FF.

Handling B64 encoded data in Python

In my Google App Engine based app, I am fetching data from a SOAP webservice.
The problem is that one of the tag contains binary 64 encoded data. I decode it using
decodedStr = base64.b64decode(str(content))
It seems that the decoding is not done correctly a I get garbage data in decodeStr. I think the problem is that the content string is falsely parsed as a unicode string instead of simple byte string
Can any Python guru tell me how to handle b64 encoded data in Python?
For now I am using this workaround
fileContent = str(fileContent)
fileContent = fileContent[3:-3]
self.response.out.write(base64.b64decode(fileContent))

You could try using base64.decodestring or if you were passed an url base64.urlsafe_b64decode.
Make sure that the data is not in base16 or base32.

Strange. If the content were not b64 encoded, the call to decode should raise a TypeError exception. I assume that's not happening?
Which would lead me to wonder how you know the resulting decodedStr is not what your after?