gentoo-overlay/media-sound/sox/metadata.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE pkgmetadata SYSTEM "http://www.gentoo.org/dtd/metadata.dtd">
<pkgmetadata>
  <herd>sound</herd>
  <use>
    <flag name="amr">Enables Adaptive Multi-Rate Audio support</flag>
    <flag name="id3tag">Enables ID3 tagging with id3tag library</flag>
	<flag name="opus">Enables reading Ogg Opus files.</flag>
    <flag name="twolame">Enables twolame support (MPEG Audio Layer 2 encoder)</flag>
  </use>
</pkgmetadata>