Random access decoding start points (audio frame headers) for AMR-type files are found by sequential elimination of types of file points from consideration for a block of file points following a random access selected point. Chaining of file points according to frame header format interpretation gives paths of points through the block, and selection of maximal path(s) includes sums of weights of the points of a path. The next-to-initial points of such a maximal path provides a decoding start point.