[Mp4-tech] aspect_ratio_idc

[Glenn Connery]

I don't understand what the encoding of the aspect_ratio_idc means.  I've got 
a 352x240 NTSC sample, meaning it's going to be scaled up to a 4:3 720x480 
image.  In MPEG-2 the sequence header would contain an encoding for "4:3", 
but in h.264 I see the value 7 which means, according to the table in the 
spec, is 10:11 and might represent a 352x480 4:3 frame without overscan or a 
480x480 16:9 frame with horizontal overscan.  Okay, so what am I supposed to 
do with this?  How do I know the sample is 4:3?