FLACs with embedded pictures can't transcode as a stream

[graue]

The avconv utility is unable to stream any FLAC with a picture tag. It waits to encode the entire file before producing any output. By this time the connection has long since timed out so it's impossible to listen to these tracks.

I've been working around by manually deleting these picture tags since I don't use them (in favor of folder.jpg files), but a real solution would probably be to try upgrading avconv or use a different library/utility to do the conversion that doesn't have this bug.