This paper introduces a new technique for TV standards conversion called "adaptive intra-frame line interpolation". The configuration and the performance of a digital converter developed by using the technique are also described. In the present converter, an input picture is divided into still and moving areas by measuring frame difference signals, and suitable interpolation parameters are adaptively chosen for each area. This method brings good results to both areas. Especially, the converter has enabled the converted picture to recover high vertical resolution of more than 350 TV lines in still pictures, which has never been obtained by any conventional intra-field line interpolation.