Yeah, I don't know about other channels but wrt Sports HD channels, Sun Direct is the best wrt picture quality. Star Sports HD channels also not much. But have personally experienced a significant difference in Sony Sports HD channels. Think Airtel is also using HEVC technology only. But don't know the reason.
@chandu1192, still you can check if HDR is turned off in Xstream STB. Many say HDR is not stable. Also observe other channels. If the quality is less on all, might be the problem is with STB.