Comcast Corp. is working with TiVo Inc. on an advertising system that will insert new, updated commercials into already-recorded programs, the company said. Comcast Chief Executive Roberts told cable executives late Monday that under such a system, programs that were recorded weeks ago on a TiVo digital video recorder would have their old commercials replaced with new ones.

The system could also take into account viewer patterns to make ads more targeted and relevant, Roberts explained.

Philadelphia-based Comcast, the country's largest cable company, announced last month it would start offering TiVo's DVRs by 2006.

The new technology could help make DVRs more palatable to TV networks, which are concerned about losing advertising opportunities because DVRs allow viewers to fast-forward past commercials in recorded shows.

Separately, TiVo and satellite broadcaster The DirecTV Group Inc. Tuesday said they have signed a deal to let both companies sell advertising for TiVo recorders. The DVRs recently began showing static images, such as company logos, when fast-forwarding some shows.