Video filetype check

[Hafpaf]

Verify audio if available in file format, and handle error of by lack thereof, ie. skip file processing if not video file.

Approaches:

• Check for filetype magic bytes by using a library interfacing with libmagic (preferable)
• Read file name extension.

One could make a list of accepted filetypes or simply skip SRT files

Error shown:

video file: ../videofiles/import-56124-eng-Goodbye_World_hd.mp4.srt                                                 
Traceback (most recent call last):                                                                                  
  File "/ASR_subtitles/venv/lib/python3.9/site-packages/whisper/audio.py", line 59, in load_audio   
    out = run(cmd, capture_output=True, check=True).stdout                                                          
  File "/usr/lib/python3.9/subprocess.py", line 528, in run                                                         
    raise CalledProcessError(retcode, process.args,                                                                 
subprocess.CalledProcessError: Command '['ffmpeg', '-nostdin', '-threads', '0', '-i', '../videofiles/import-56124-en
g-Goodbye_World_hd.mp4.srt', '-f', 's16le', '-ac', '1', '-acodec', 'pcm_s16le', '-ar', '16000', '-']' returned non-z
ero exit status 1.                                                                                                  
                                                                                                                    
The above exception was the direct cause of the following exception:                                                
                                                                                                                    
Traceback (most recent call last):                                                                                  
  File "/ASR_subtitles/app.py", line 38, in transcribe_audio                                            audio = whisper.load_audio(video_file_path)                                                                     
  File "/ASR_subtitles/venv/lib/python3.9/site-packages/whisper/audio.py", line 61, in load_audio       raise RuntimeError(f"Failed to load audio: {e.stderr.decode()}") from e
RuntimeError: Failed to load audio: ffmpeg version 4.2.7-0ubuntu0.1 Copyright (c) 2000-2022 the FFmpeg developers     built with gcc 9 (Ubuntu 9.4.0-1ubuntu1~20.04.1)  
...
Output file #0 does not contain any stream