This paper proposes a practical content-dependent low power DCT design with tolerable quality drop. Low power issue has become more and more important, especially for portable devices. Unfortunately, low-power design always brings in significant quality drop at the same time. This work not only achieves ultra low power dissipation but also remains tolerable quality drop (about 0.1dB) in most cases. The proposed architecture is based on distributed arithmetic architecture [1] and combined with more reliable PPA classification algorithm [2]. It can accurately control bit-level calculation and avoid unnecessary calculation to save power. This characteristic is powerful and very useful in video encoder systems, since coefficients after DCT and Q become zero with high probability. This part of power can be saved without causing undesired quality drop.