More precise duration for audio

More precise duration for audio is using 'seconds' rather than 'duration' for audio.
But value for duration and seconds in video are same.

```xml
rx  <message from="64675643077300-1407855840@g.us" id="1414990734-5" participant="64675643077300@s.whatsapp.net" offline="0" type="media" t="1414991768" notify="Ardian">
rx    <media type="audio" encoding="raw" url="https://mmv24.whatsapp.net/d/n7RoNgPmiLj0YbxNAgBP1RXD5gABQbtcblmgQ/AhLgfvThafZBJVDQPTQYWSReQz54nw1jwDnrGKqERj0y.mp3" file="AhLgfvThafZBJVDQPTQYWSReQz54nw1jwDnrGKqERj0y.mp3" size="3846158" seconds="954" ip="19.1.212.5" mimetype="audio/mpeg" filehash="1c/Lr6XvllWlh5scD2cNHlWXL4vTRk3HdyCxRbDwBFA=" duration="962" acodec="mp3" asampfreq="22050" asampfmt="s16" abitrate="32"></media>
rx  </message>
```