[FFmpeg-user] swScaler: Unknown format is not supported as input pixel format

[Ibrahim Abdo]

I'm developing a php youtube downloader and the original video format I get
from youtube is webm, then I want to convert it to different formats, like
avi, mp4, etc.
The command I'm using is this:
ffmpeg -i input_file.webm output_file.avi

And I receive the error:

FFmpeg version 0.6.5, Copyright (c) 2000-2010 the FFmpeg developers
  built on Jan 29 2012 23:56:18 with gcc 4.1.2 20080704 (Red Hat 4.1.2-51)
  configuration: --prefix=/usr --libdir=/usr/lib --shlibdir=/usr/lib
--mandir=/usr/share/man --incdir=/usr/include --disable-avisynth
--extra-cflags='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions
-fstack-protector --param=ssp-buffer-size=4 -m32 -march=i386 -mtune=generic
-fasynchronous-unwind-tables' --enable-avfilter --enable-avfilter-lavf
--enable-libdirac --enable-libfaac --enable-libfaad --enable-libfaadbin
--enable-libgsm --enable-libmp3lame --enable-libopencore-amrnb
--enable-libopencore-amrwb --enable-libx264 --enable-gpl --enable-nonfree
--enable-postproc --enable-pthreads --enable-shared --enable-swscale
--enable-vdpau --enable-version3 --enable-x11grab
  libavutil     50.15. 1 / 50.15. 1
  libavcodec    52.72. 2 / 52.72. 2
  libavformat   52.64. 2 / 52.64. 2
  libavdevice   52. 2. 0 / 52. 2. 0
  libavfilter    1.19. 0 /  1.19. 0
  libswscale     0.11. 0 /  0.11. 0
  libpostproc   51. 2. 0 / 51. 2. 0
[matroska @ 0x9ab4850]Estimating duration from bitrate, this may be
inaccurate

Seems stream 0 codec frame rate differs from container frame rate: 1000.00
(1000/1) -> 29.97 (30000/1001)
Input #0, matroska, from '1_yt.webm':
  Metadata:
    doctype         : webm
  Duration: 00:01:53.63, start: 0.000000, bitrate: N/A
    Stream #0.0(eng): Video: 0x0000, 1440x1080, PAR 1:1 DAR 4:3, 1k fps,
29.97 tbr, 1k tbn, 1k tbc
    Stream #0.1: Audio: vorbis, 44100 Hz, stereo, s16
swScaler: Unknown format is not supported as input pixel format
Cannot get resampling context

I'm using CentOS 5 32bit. I must say that the same php script with the same
command runs perfectly under windows 7 with ffmpeg for windows.