[FFmpeg-devel] [PATCH] What is missing for working AVFMT_FLAG_NONBLOCK?

Nicolas George nicolas.george
Tue Mar 3 19:50:13 CET 2009

Le tridi 13 vent?se, an CCXVII, Michael Niedermayer a ?crit?:
> The kernel knows excatly what we polled in the last timeslice when we
> called sched_yield() it could (in theory) just give us the cpu again
> if one of the polled things became available.
> IMHO this would be alot nicer for (some) applications than having to
> explicitly collect things (where its possible at all) and run select()
> and then deal with all the special case about signals.

That would be nice indeed, but that is not possible with current Unix APIs,
and that is definitely not what sched_yield does.

The nearest to what you describe would be signal-driven IO: enabling O_ASYNC
on the file descriptors and then using pause() to wait for a SIGIO.

Unfortunately this is not portable: this is BSD and never made it into POSIX
or Single Unix; furthermore, it is made for sockets, there is no guarantee
that it would be implemented for devices.

I really think that the only reliable and portable way to deal with blocking
inputs is threads.


  Nicolas George
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