Converting from NTSC to PAL

[zoopido]

Hi, I'm quite a novice, so please excuse my lack of knowledge. Currently I have many NTSC Mpeg-4 AVC clips encoded with Ateme. However my player (setup box) does not support NTSC. What is the easiest way to convert my existing NTSC clips to PAL. Would it be possible without having to re-encode each clip from original source?

Thanks in advance!

[Skelsgard]

Is it a NTSC 29.970 or IVTC´ed 23.976, progressive or interlaced, etc?
If it´s progresive 23.976, one of the easiest ways (without jerkiness) would be to change the FPS to 25.000 and accelerate the audio on a ~ 4% (25 is 4.2% faster than 23.976). This way u won´t have to reencode the video but still need to treat the audio.