What deinterlacing filter should I use to encode/compress a PAL MPEG-2 576i 25fps raw file?
I don't agree that the other answer is a good idea in general, because "-vf yadif" will drop half the frames, thus resulting in a poor substitute of the original footage. Here is the thing: 576i25 means that you have 50 interlaced fields per second, rendering motion of objects fluid and natural to the human eye. You can get a high speed video at 50 frames per second easily by means of this:

ffmpeg -i in.mpg -vf yadif=1 out.mp4


Please note the difference, i.e. yadif=1 is specified. If you don't give a value, the yadif filter defaults to yadif=0 which cuts the frame rate of TV footage in 2.

Some people think that, because 25 fps is close to the theatrical movie speed (24p), the resulting video should look better, right?. Big mistake. The director of any project for TV had in mind that the target medium was TV and acted accordingly, using different techniques and taking a different artistic approach, allowing for instance a lot of fast movement, pan and zoom, or a hand-held camera to give a more subjective point of view. Also, a higher shutter speed is usual in TV without producing the nasty stroboscopic look because the frame rate is high. But later, when that footage gets converted to half frame rate the result is not "cinema look" but simply bad TV footage with stroboscopic movement.