[FFmpeg-user] Codec "same" as opposed to "copy"?

[Claudiu Rad]

On 11/20/2014 11:47 AM, Carl Eugen Hoyos wrote:
>> My source's audio codec will typically be either
>> pcm_s16le or pcm_s24le, but ideally I don't want to care
>> and want to say "use the same codec as the source."
> This is not implemented, patch (or enhancement request)
> welcome.

without trying to hijack the thread, sorry if i force it a bit but it is 
quite related:

is there a possibility (or is anything foreseen) in ffmpeg to 
*conditionally* copy the stream?
an example would be that in a batch process, i would only want to 
convert audio to aac if it is not already aac.
are there any workarounds on this other than first ffmpeg -i <source>, 
parse the output, try to detect what you have there and if it is not 
what you want convert, otherwise copy?
this workaround is reasonable for some sources, but for others where 
seeking is problematic or a large portion of the file must be read for 
detection it raises many problems.

-- 
Claudiu