Masking without re-encoding

[rds11]

I have the Hauppauge HD-PVR which I use to record tv shows. I can only record to m2ts, ts or mp4 files. I would like to mask the bottom of the video with a black bar, but without re-encoding the whole video. Can this be done ? I know I can mask using Virtualdub, but not under directstream, so I can only save the file in avi format, which means re-encoding to get back to m2ts.

Is there a software that can mask in m2ts format and do not need to re-encode the whole file ?

[jagabo]

Any time you change a video the process involves decompressing the video, making the changes, then recompressing. So no, you cannot mask the bottom of the frame without re-encoding.