Bug#692609: ffmpeg: converting with avconv to mpeg4 makes jerking and short pauses of video

[rpnpif]

Package: ffmpeg
Version: 6:0.8.3-1~bpo60+1
Severity: normal

Converting videos with avconv/ffmpeg to mpeg4 makes jerking, short pauses 
periodically all about 5 sec.
Avidemux (not in Debian repositery) has not this issue.

avconv -i video.x output.mp4
x in wmv or mpg1 format.

-- System Information:
Debian Release: 6.0.6
  APT prefers stable
  APT policy: (500, 'stable')
Architecture: i386 (i686)

Kernel: Linux 3.2.0-0.bpo.3-rt-686-pae (SMP w/1 CPU core; PREEMPT)
Locale: LANG=fr_FR.UTF-8, LC_CTYPE=fr_FR.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

Versions of packages ffmpeg depends on:
ii  libav-tools            6:0.8.3-1~bpo60+1 Multimedia player, server, encoder
ii  libavcodec-extra-53    6:0.8.3-1~bpo60+1 Libav codec library
ii  libavdevice53          6:0.8.3-1~bpo60+1 Libav device handling library
ii  libavfilter2           6:0.8.3-1~bpo60+1 Libav video filtering library
ii  libavformat53          6:0.8.3-1~bpo60+1 Libav file format library
ii  libavutil51            6:0.8.3-1~bpo60+1 Libav utility library
ii  libc6                  2.11.3-4          Embedded GNU C Library: Shared lib
ii  libpostproc52          6:0.8.3-1~bpo60+1 Libav video postprocessing library
ii  libswscale2            6:0.8.3-1~bpo60+1 Libav video scaling library

ffmpeg recommends no packages.

ffmpeg suggests no packages.

-- no debconf information