[FFmpeg-user] Differences between ffmpeg mpeg2 codec and the official mpeg2 tm5 codec

[Fernando Silva]

i'm comparing ffmpeg with official mpeg2 tm5 implementations and i´m getting
some differences in PSNR measurement (tm5 indicades 4 to 5 dB less than ffmpeg).
Is there some explanation for this? A post or pre-processing perhaps?

Any thoughts would be helpful.