Despite a growing number of supported devices and its superiority over WMA, WMA Pro still has little hardware and software support. Some notable exceptions to this are the Microsoft Zune (limited to stereo),[27] Xbox 360,[28] Windows Mobile-powered devices with Windows Media Player 10 Mobile,[29] newer Toshiba Gigabeat and Motorola devices,[30][31] and devices running recent versions of the Rockbox alternative firmware.[32] In addition, WMA Pro is a requirement for the WMV HD certification program.[33] On the software side, Verizon utilizes WMA 10 Pro for its V CAST Music Service,[34] and Windows Media Player 11 has promoted the codec as an alternative to WMA for copying audio CD tracks.[35] WMA Pro is supported in Silverlight as of version 2 (though only in stereo mode). In the absence of the appropriate audio hardware, WMA Pro can automatically downmix multichannel audio to stereo or mono, and 24-bit resolution to 16-bit during playback.