Hello Robert:
After researching and talking with some others there is a way to make
ffmpeg thread safe but you need to add a call back via the lock
register api found in libavcodec and compile ffmpeg with thread
support enabled. Internally they use the lock callback to allow for
global synchronization access to the libavcodec library. I am going
to try and test this out this week.
Take care
Garrett
On Jan 5, 2010, at 5:10 AM, Robert Osfield wrote:
Hi Garret,
Thanks for reporting this issue, I'm afraid I can't add anything to
the mix as I'm not too familiar with ffmpeg. However, it does sounds
like we'll also need to protect some or all of ffmpeg calls. I'll
have a look through the ffmpeg and have a think about how to tackle
this is a manageable way.
Cheers,
Robert.
On Thu, Dec 31, 2009 at 3:03 PM, Garrett Potts <[email protected]>
wrote:
Hello All:
Just recently I have been testing ffmpeg library (Not OSG's ffmpeg
plugin)
use within some tools we are doing. Over the past couple of days
we have
been hammering video in a multi threaded environment and it has
come to our
attention that ffmpeg is not thread safe. I have not locked down
where in
ffmpeg it uses global structures besides the registerall calls. In
our code
we had to do a shared mutex lock on all calls to the ffmpeg
library. So for
instance a call to avcodec_open could fail if you are doing a code
decode at
the same time.
Example:
When we were grabbing a frame from one file and opening another
file the
open could fail which gave strong indication of shared global data
within
ffmpeg. After lock down with a comon critical section mutex we
were able to
use the ffmpeg in a multi threaded environment.
I wanted to pass this along because I have seen the ffmpeg plugin
added to
OSG.
If anyone knows the exact API calls or found docs specifying the
exact calls
in ffmpeg library that is not thread safe please pass it along.
For now, I
have just wrapped all calls as critical and everything works
robustly in a
multi threaded environment.
Take care
Garrett
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