ffmpeg : broken pipe / debian wheezy

hello,

i can’t render using ffmpeg with 0.64.1 / 0.65.dev : render running , output file created but empty.

[code]
$>./synfig -t ffmpeg -o test.mp4 /home/…/SynfigAnimation1.sifz
synfig(4461) [09:48:41] info: Loading modules from /home/…/Sources/Synfig/synfig/install/etc/synfig_modules.cfg
/home/…/Sources/Synfig/synfig/install/bin/synfig: warning: Unable to find module “mod_magickpp” (file not found)
/home/…/Sources/Synfig/synfig/install/bin/synfig: warning: Unable to find module “mod_libavcodec” (file not found)
ffmpeg version 0.8.6-6:0.8.6-1, Copyright © 2000-2013 the Libav developers
built on Mar 24 2013 07:20:17 with gcc 4.7.2
*** THIS PROGRAM IS DEPRECATED ***
This program is only provided for compatibility and will be removed in a future release. Please use avconv instead.
/home/…/SynfigAnimation1.sifz ==> test.mp4: Line 2 of 121 – 13s
/home/…/SynfigAnimation1.sifz ==> test.mp4: Line 4 of 121 – 18s
/home/…/SynfigAnimation1.sifz ==> test.mp4: Line 6 of 121 – 19s
[image2pipe @ 0x80e2c80] Estimating duration from bitrate, this may be inaccurate
Input #0, image2pipe, from ‘pipe:’:
Duration: N/A, bitrate: N/A
Stream #0.0: Video: ppm, rgb24, 720x576, 24 fps, 24 tbr, 24 tbn, 24 tbc
Incompatible pixel format ‘rgb24’ for codec ‘mpeg1video’, auto-selecting format ‘yuv420p’
[buffer @ 0x80e5860] w:720 h:576 pixfmt:rgb24
[avsink @ 0x80e2380] auto-inserting filter ‘auto-inserted scaler 0’ between the filter ‘src’ and the filter ‘out’
[scale @ 0x80e27c0] w:720 h:576 fmt:rgb24 -> w:720 h:576 fmt:yuv420p flags:0x4
Option loop not found.
synfig(4461) [09:48:42] warning: Broken Pipe…
synfig(4461) [09:48:42] warning: Broken Pipe…

…8<…8<…8<…8<…8<…8<…8<…

synfig(4461) [09:49:07] warning: Broken Pipe…
synfig(4461) [09:49:07] warning: Broken Pipe…
synfig(4461) [09:49:07] warning: Broken Pipe…[/code]

$>avconv -version
avconv version 0.8.6-6:0.8.6-1, Copyright (c) 2000-2013 the Libav developers
  built on Mar 24 2013 07:20:17 with gcc 4.7.2
avconv 0.8.6-6:0.8.6-1
libavutil    51. 22. 1 / 51. 22. 1
libavcodec   53. 35. 0 / 53. 35. 0
libavformat  53. 21. 1 / 53. 21. 1
libavdevice  53.  2. 0 / 53.  2. 0
libavfilter   2. 15. 0 /  2. 15. 0
libswscale    2.  1. 0 /  2.  1. 0
libpostproc  52.  0. 0 / 52.  0. 0