avformat/hls: do not call ffurl_seek/ffurl_size on crypto protocol

ffurl_seek() will not work even when it should be a no-op, so do not
call it on crypto protocol.

Also replace use of ffurl_size() for the same reason.

Reported-by: Michael Schenk <Michael.Schenk@albistechnologies.com>
Signed-off-by: Anssi Hannula <anssi.hannula@iki.fi>
avcodec/mpegaudioenc_template: default to 384k bitrate as default

If 384k is too high for the samplerate, choose the closest
possible

Idea to increase the bitrate from: 46439e156219d27f059cf687743ba5aacf238b87
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>