[FFmpeg-devel] [RFC] ffmpeg/ffprobe commandline option to av_log_set_callback ?

[Hendrik Leppkes]

On Wed, Mar 20, 2013 at 2:57 PM, "René J.V. Bertin" <rjvbertin at gmail.com> wrote:
> On Mar 20, 2013, at 14:28, Nicolas George wrote:
>
>> I do not think it is possible to specify a C function pointer as a string on
>> the command line.
>
> Only if that function is listed in some lookup table together with its address ... and said address is in the appropriate space.
>
> But that's not what I had in mind. I thought more along the lines to specify a log file name or URI, with a little dedicated function that calls the standard log message format function and then sends the resulting string to the specified destination.
>>
>>
>> The -progress option of ffmpeg is designed exactly for that.
>
> I was not only thinking about progress information - that's not generated with av_log, or is it?
>
>> The log output goes to the standard error stream, you can connect this
>> stream to any kind of file descriptor you want.
>
> That would work under unix-like OSs, presuming that file descriptors are unique system-wide and not process-specific. I doubt mswin associates a file descriptor with a named pipe's HANDLE, and I also doubt that one can redirect stderr on the popen command line as under unix/linux. I have already hacked some things in the MSVC popen function, I could have a look if there's anything in there that allows to connect a process's error output to a given, open HANDLE.
>

Check this article: ("Creating a Child Process with Redirected Input
and Output")
http://msdn.microsoft.com/en-us/library/ms682499%28v=vs.71%29.aspx

In short, you have to use CreateProcess instead of popen, but it can
all be done.

- Hendrik