If the receiver contains the first edition of Dolby Pro Logic it will not work with Dolby 5.1. If it contains Dolby Pro Logic II or newer technology it will be backwards compatible.

If you get a nice receiver, such as a high-end Sony, you'll be able to play the Dolby Pro Logic IIx codec, as long as you have reasonable speakers.

Dolby Pro Logic is a surround sound processing technology made by, as the name suggests, Dolby Laboratories. It transforms, via encoding and decoding, ordinary soundtracks and stereo content into full-range surround sound retaining all the quality and subtleties of the original audio. It is designed to facilitate the more engaging experience of surround sound.

The AVR is an AV receiver. It was first introduced as a common soundtrack format by the Dolby Pro Logic company.

Some DVD's have a stereo 2-channel mix (Dolby Digital 2.0), but none feature a Dolby Surround or Pro Logic Surround option in the menus. This is because all DVD players can submix the 5.1 Dolby Digital track and output a Dolby Pro Logic Surround signal through the analog 2-channel outputs.