[GRASS-user] buffer on granular polygon... it fails

[G. Allegri]

I'm having a problem trying to execute a buffer of 150m on a polygon
generated from a raster with resolution 5x5.
The polygon is a single area, constituted of 1576 vertices (highly granular).
v.buffer generates 32633 vertices, the it get "mad" building the
topology: it tries to remove intersections, duplicates, etc. giving
the following final result:

 Topology was built.
 Number of nodes     :   32633
 Number of primitives:   65264
 Number of points    :   0
 Number of lines     :   0
 Number of boundaries:   65264
 Number of centroids :   0
 Number of areas     :   32632
 Number of isles     :   1
 Number of areas without centroid :   32632

The vector is not readable...

I don.t know if the problems is due to the buffer algorithm, which
fails because of the pixelated polygon (figure below)

 ____
      |                          _______
      |_______             |            |
                   |            |            |
                   |_______|            |_______

I've tried to generilze it, but I get no reduction of the number of
vertices. I can't figure out why!

 v.generalize input=grd0_MASKED output=grd0_MASKED_Gen type=area
 method=douglas_reduction threshold=50 reduction=50

 Any advice?
 Giovanni