I'm using the following command to convert FLV to WMV: ffmpeg -y -i ./gta4.flv -vcodec wmv2 -acodec wmav2 -ar 44100 -ab 128k -b 1500k ./test.wmv FFmpeg version SVN-r8551, Copyright (c) 2000-2007 Fabrice Bellard, et al. configuration: --enable-shared --enable-xvid --enable-libvorbis --enable-libogg --enable-libmp3lame --enable-gpl --enable-libfaad --enable-libfaac --enable-liba52 --enable-x264 --enable-amr_nb --enable-pp libavutil version: 49.4.0 libavcodec version: 51.40.2 libavformat version: 51.11.0 built on Mar 30 2007 11:28:36, gcc: 3.3.5 (Debian 1:3.3.5-13) Seems stream 0 codec frame rate differs from container frame rate: 1000.00 (1000/1) -> 59.94 (60000/1001) Input #0, flv, from './gta4.flv': Duration: 00:01:03.7, start: 0.000000, bitrate: 128 kb/s Stream #0.0: Video: vp6f, yuv420p, 640x360, 59.94 fps(r) Stream #0.1: Audio: mp3, 44100 Hz, stereo, 128 kb/s Output #0, asf, to './test.wmv': Stream #0.0: Video: wmv2, yuv420p, 640x360, q=2-31, 1500 kb/s, 59.94 fps(c) Stream #0.1: Audio: wmav2, 44100 Hz, stereo, 128 kb/s Stream mapping: Stream #0.0 -> #0.0 Stream #0.1 -> #0.1 Press [q] to stop encoding Compiler did not align stack variables. Libavcodec has been miscompiled and may be very slow or crash. This is not a bug in libavcodec, but in the compiler. Do not report crashes to FFmpeg developers. frame= 3821 fps=120 q=2.0 Lsize= 1kB time=63.7 bitrate= 0.1kbits/s video:10683kB audio:996kB global headers:0kB muxing overhead -99.994992% Everything seems to be fine, but when watching the video you see some parts with big blocks for a few seconds. You can watch the video here (at about 23 seconds you see the scrambled bit) : http://217.67.230.176/test.wmv I've seen these blocks before, but in this movie there are just too much of them... What is causing this and more important, how can I fix it? Please note that the output must be WMV format. Thanks