Newbie question on aspect ratio

[vicfred]

Well im tryin to set the default aspect ratio of an 704x480 video to 16:9 it should be done through the x264 cli or avisynth?

[vicfred]

*solved*
well i found this formula to calculate the sar and set it on x264 cli
SAR_x DAR_x * height
----- = --------------
SAR_y DAR_y * width

[Brother John]

You don’t need a formula. You just need a table:
http://encodingwissen.de/video/anamorph-quelle.html#mpeg4par
Feed the appropriate number to the --sar switch (with a : instead of a /) and you’re fine.