Requirements for GStreamer encoder elements

== ElementFactory Class ==

 * Must contain at least "Codec/Encoder"
 * If you operate on raw audio, must also include "Audio"
 * If you operate on raw video, must also include "Video"
 * Quid of other formats ?

== Pad Templates ==

 * Both pad templates must have an availability of ALWAYS
 * The sink pad template caps *MUST* specify the exact range of accepted formats
  * For video,
   * the width/height range
   * the colorspaces supported
   * If the codec stores the framerate, the supported framerate(s) or range
  * For audio,
   * the supported rate(s), channels, depth, width, endianness