Windows version and audio output types

[dinkypumpkin]

On 06/09/2011 18:59, dinkypumpkin wrote:
> I think FFmpeg reports the latter (need to check), but other tools like
> iTunes report the former.

I deserver an extra dollop of shame for not remembering this earlier, 
but there are some extra bits (frame headers for streaming) that are 
stripped out of the intermediate AAC file during conversion to M4A, so 
probably accounts for most of the difference.  The amount of "extra 
bits" will be proportional to the length of the programme, thus the 
variance you mentioned.