Methods and apparatus are disclosed for estimating a quality of a received data frame in a trellis decoder. The decoder utilizes a trellis diagram to depict the states and stages the decoder transitions through in search of a sequence of bits that closely resemble the received sequence. In the trellis diagram, each state at one stage is connected to a state at the next stage by a branch and a group of connected branches form a path. The decoder selects a winning path by comparing path metrics computed for each of the paths in the trellis diagram and outputs a most-likely sequence of hard bits from the winning path. A count of non-ideal branches over the winning path can be used for calculating the frame quality of the received data frame or the burst quality of a data burst in the received data frame.