vorbis suffers from the same sign flip issue as wma (so this lame workaround, though it arguably doesnt matter much where the sign is fliped back)

Originally committed as revision 7873 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/vorbis_enc.c

@@ -906,7 +906,7 @@ static int apply_window_and_mdct(venc_context_t * venc, signed short * audio, in
             float * offset = venc->samples + channel*window_len*2 + window_len;
             j = channel;
             for (i = 0; i < samples; i++, j += venc->channels)
-                offset[i] = audio[j] / 32768. / n * win[window_len - i - 1];
+                offset[i] = -audio[j] / 32768. / n * win[window_len - i - 1]; //FIXME find out why the sign has to be fliped
         }
     } else {
         for (channel = 0; channel < venc->channels; channel++) {
@@ -923,7 +923,7 @@ static int apply_window_and_mdct(venc_context_t * venc, signed short * audio, in
             float * offset = venc->saved + channel*window_len;
             j = channel;
             for (i = 0; i < samples; i++, j += venc->channels)
-                offset[i] = audio[j] / 32768. / n * win[i];
+                offset[i] = -audio[j] / 32768. / n * win[i]; //FIXME find out why the sign has to be fliped
         }
         venc->have_saved = 1;
     } else {