[GRASS-dev] OSX FFMPEG build instructions available

[Glynn Clements]

Hamish wrote:

> > > > I finally got back to FFMPEG on OSX.  It went fairly smooth this  
> > > > time.  I added build instructions to the GRASS OSX readme.  My
> > > > future OSX builds will now have ffmpeg support, yay!
> > > > 
> > > > Question: what is the minimum needed in the ffmpeg libraries for  
> > > > GRASS?  I'm thinking of disabling codecs and formats that GRASS
> > > > can't use to reduce the library size (a basic universal build
> > > > without debug symbols added ~6.5MB to libgrass_ogsf!).  Or can
> > > > GRASS use any codec available in ffmpeg?
> > > 
> > > It only uses MPEG-1. There's a compile-time option to use XviD, but
> > > that gives you a "raw" XviD stream (no AVI etc container), which isn't
> > > much use.
> > > 
> > 
> > I have attached a patch for gsd_img_mpeg.c (ogsf) which is based on the
> > later releases of ffmpeg (output_example.c). This uses a function
> > guess_format to guess the format based upon the file extension given. If
> > the format is unknown it reverts to mpeg1. With this patch you can save
> > to any (almost) format supported by ffmpeg. For example you can save to
> > asf, avi, flv, swf, etc. To use this with nviz the auto name extension
> > in panel_kanimator.tcl will have to be commented out ...
> > 
> > #       if { [string compare $fnameExt ".mpg"] != 0  &&
> > #               [string compare $fnameExt ".mpeg"] != 0 } then {
> > #           append keyanimBaseName ".mpg"
> > #       }
> > 
> > The patch needs testing, etc. 
> > 
> > Let me know if you have any questions.
> 
> I have applied this patch now in 6.3-cvs.

This patch causes NVIZ compilation to fail.

It causes the OGSF library to depend upon libavformat, but nothing in
the patch adds -lavformat to the link command for libogsf.

I managed to work around the problem by hardcoding -lavformat into
lib/ogsf/Makefile, but this should be done via configure and
Platform.make, either by adding the relevant switch(es) to FFMPEGLIB
or by adding a new variable.

-- 
Glynn Clements <glynn at gclements.plus.com>