[GRASS-dev] Re: Nviz animation wish

[Helena Mitasova]

On Jan 25, 2007, at 6:22 PM, Hamish wrote:

> William Kyngesburye wrote:
>>> Michael - there is a file sequencing tool for that in nviz - I have
>>> been doing it for years (I also had some of it at your workshop),
>>> just check my website. My slides for the lausanne workshop should
>>> have a description how to do it along with a sample data set. I need
>>> to run now but I can write you more later.
>>> It may be broken in the latest CVS but it worked well in 6.1
>
> A link to that should be added to the animations help page on the  
> wiki.
>   http://grass.gdf-hannover.de/wiki/Movies
> (please)

I just put it there, Helena
>
>
> [slight change of topic]
>> As an alternative to directly in nviz, there is the r.out.mpeg
>> module.  You could create the ppms in nviz, then run those thru
>> r.out.mpeg.
>
> No, that is much more than is needed. Create series of PPM images with
> NVIZ keyframe animator, then use mencoder (or similar [transcode?]) to
> create the MPEG. see Maris's example:
>  http://grass.ibiblio.org/grass63/manuals/html63_user/nviz/ 
> nviz_panel_kanim.html
>
> If less than 100 frames an animated GIF or PNG(MNG) might be a
> preferable option.
>
>> But that has a similar problem - no Mac binaries for the mpeg-encode
>> program that it uses.  And ancient code - I haven't tried building it
>> yet, but I expect problems.
>
> Again, not needed. r.out.mpeg will work fine with "ppmtompeg" which
> comes with NetPBM tools. AFAIK this comes with MacOSX already.
> ppmtompeg is mpeg-encode renamed; r.out.mpeg should work out of
> the box, ie without ffmpeg.
>
>> A possibility would be to rewrite the r.out.mpeg module to use the
>> ffmpeg program or other mpeg encoder, which has readily available
>> binaries.  Or just run them manually thru ffmpeg.
>
> IMO it would be much better to de-emphasise r.out.mpeg and rewrite  
> as a
> shell/python/perl script depending on mencoder (or similar FFMPEG  
> tool).
> Most of that module deals with creating the MPEG-1 encode spec file,
> which is not needed with newer encoders.
>
> Certainly MPEG-1 is too cruddy to consider using for new development.
> What it has going for it is a (the only?) truly patent-safe encoder
> and widespread codec use. The movies it makes are huge and of poor
> quality.
>
>> A question about the ffmpeg support - is it limited to just the
>> mpeg-1 output, or can it use any format supported by ffmpeg?
>
> Glynn:
>> There is a compile-time option (USE_XVID) to use XviD instead. It
>> should be straightforward to allow the user to specify the codec by
>> name; there is already some (commented-out) code which attempts to do
>> this, although it should be using avcodec_find_encoder_by_name().
>> See lib/ogsf/gsd_img_ppm.c for details.
>
> WRT the USE_XVID option -- I didn't finish that, it only writes the  
> raw
> stream and the output seems to be missing some header info. As such  
> the
> only player I found that would play the result was mplayer, which is
> more forgiving. TODO: test with "mplayer -forceidx" & attempt fix with
> mencoder (see -forceidx help in mplayer man page). Help appreciated.
>
>
> Hamish
>
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