ffmpeg command to convert mpeg2 with ac3 audio codec to audible H264/ ProResHQ?
Use

ffmpeg -i 1.mpg -c:v libx264 -c:a ac3 -b:a 192k 1.mov


in order to convert to a MOV file containing H.264 video and AC3 audio. I've used 192kb/s as bitrate for the audio and the H.264 encoding will use the defaults of CRF 23 and preset 'medium'.

To convert only video, and strip out audio, use

ffmpeg -i 1.mpg -c:v libx264 -an 1.mov