pour avoir les carrés, il faut mettre un sws

-sws <software scaler type> (see -vop scale option too)
    This option sets the quality (and speed, respectively) of the software scaler, with the -zoom option. For example with x11 or other outputs which lack hardware acceleration. Possible settings are:

    NOTE:
    For -sws 2 and 7, the sharpness can be set with the scaling parameter (p) of -vop scale (0 (soft) - 100 (sharp)), for -sws 9, it specifies the filter length (1 - 10).

0
    fast bilinear (default)
1
    bilinear
2
    bicubic (good quality)
3
    experimental
4
    nearest neighbour (bad quality)
5
    area
6
    luma bicubic / chroma bilinear
7
    gauss
8
    sincR
9
    lanczos
10

bicubic spline

**********************
et hop
mplayer -vo x11 -sws 4 -zoom -demuxer rawvideo -rawvideo
w=64:h=64:y8:fps=30 -vf dsize=240:240 /tmp/new3

par contre je n'arrive pas à avoir des images belles mais avec cette commande c plus stable