Let the hive mind of Engadget get that for you.
"I am looking for a device that will stream sound from one source to several recipients. For example, I want to stream sound from my TV or stereo to my phone or MP3 player that has radio and Bluetooth capabilities. I have looked into radio transmitters and they seem like a decent choice, but I can't find one that uses external power (USB or from the plug) and I would want one with a transmit range of around 50 meters. Thanks!"
They'll all be MPEG-4 for sure. And I just bought my second HR20, and sold my HR10-250 on ebay. I have to say, the Tivo interface actually looks somewhat primitive compared to the HR20 interface. True you can't combine/split OTA, but there are a lot of cities now covered. And I love watching my local sports in HD on the new receiver, which you can only do with an MPEG4-capable receiver.