video recording requires pulseaudio support. Otherwise following error
happens:
```
Phase 2: mpegize -- /home/mobian/Videos/VID20250331075934.mkv
Traceback (most recent call last):
File "/app/libexec/megapixels//mpegize.py", line 546, in <module>
m.run(sys.argv)
File "/app/libexec/megapixels//mpegize.py", line 462, in run
gst_convert(m.base, argv[3], ext=="dng")
File "/app/libexec/megapixels//mpegize.py", line 260, in gst_convert
t2 = audio.get_time()
^^^^^^^^^^^^^^^^
File "/app/libexec/megapixels//mpegize.py", line 102, in get_time
s = s[:-m.slen]
~^^^^^^^^^^
TypeError: 'NoneType' object is not subscriptable
```
