Add ffmpeg arguments to make HDTC-2US streams work with Roku 2

[ricardoanguiano]

Hello,

I made two changes here in the ffmpeg invocation:

1. mp3 audio codec.
2. hls_flags delete_segments.

My Roku 2 would not pick up any audio from ply from my HDTC-2US unless I transcoded audio to mp3 in ply's invocation of ffmpeg. Setting acodec to aac or copy resulted in silence. I don't have a Roku 3 mentioned in your readme.md, so I can't test this setup on your original configuration. If this new acodec argument does not work for newer Roku maybe there should be a configuration file where you enter your model number and ply does the right thing.

Once I got audio working, I noticed that static/streams started filling with ts segments, slowly filling the ply server disk for as long as I was watching the stream on the Roku. Adding the hls_flags delete_segments argument caused ffmpeg to delete the older ts segments resulting in a small rolling window of segments that did not fill the disk but kept the stream watchable.

I am using ffmpeg git g1212e34 built on 20160924.

Thanks, -R