I'm trying to burn a dvd on a mac with an external (firewire-connected) dvd drive. I'm checking the size of the iso thus:

DVD-4:dvd_files macbook$ ls -l /tmp/hybrid.iso 
-rw-r--r--  1 macbook  wheel  8700884992 Aug 22 10:57 /tmp/hybrid.iso
DVD-4:dvd_files macbook$ ls -lh /tmp/hybrid.iso 
-rw-r--r--  1 macbook  wheel   8.1G Aug 22 10:57 /tmp/hybrid.iso

The "human-readable" size is 8.1 Gig but when i try to burn, onto an 8.4G dual-layer dvd, it says "Media does not have enough free space"

The definition of a "Gigabyte" according to Wikipedia is 1 billion bytes, so the iso size should actually be 8.7 Gig according to this definition, in which case the disk definitely isn't big enough, and it's just that the -h option to ls is misleading.

Is the discrepancy just due to the ls command using a different definition of "G" (eg 1024 Meg aka 1.07 Gig? This comes out as 8.103 which fits what ls is displaying)