I used mencoder, but it never re-ncode the quality, I can get out of the HB.
complete nonsense and misinformation. Handbrake and Mencoder both use the same encoder, x264.
Fact: You will get bit-bit identical files encoded with mencoder,handbrake,ffmpeg...etc with same x264 settings and same x264 revision.
Also handbrake/mencoder/libav/ffmpeg/super/megaipodvideoconverter And any other h264 encoder gui in existence supports threaded encoding... because they all call libx264
which has both frame based and slice based threading...