I was using Nero Infotool to look at some DVD-Rs I made. Under the "disc" tab the video format is being shown as NTSC 4:3 Mpeg-1 720x480

However, when I look at the same disc in TMPEGEnc DVD author, it identifies the video input format as MPEG-2, 720x480 29.97 fps (4:3) NTSC, 4610kbps. Audio is shown as Dolby Digital, 4800Hz stereo, 256kbps.

Any idea what is going on here?

MPeg-1 or Mpeg-2?