converting for Roku

Recently I tried to play a movie on my Roku XDS.  The video played fine, but the audio was gone, and there were no subtitles.

Using "avprobe" I saw my MPEG4 movie has two audio streams.  The Roku is finding the first, 5-speaker stream and playing it, instead of my desired stereo output.

So, the proper incantation to have normal audio is to tell avconv to use the first video stream, and skip the first audio stream:

avconv -i input.mp4 -codec copy -map 0 -map -0:a:0 output.mp4

Success!  Now about those subtitles...