libavcodec/mjpegdec.c:801: error: Uninitialized Value
  The value read from linesize[_] was never initialized.

libavcodec/mjpegdec.c:801:25: 
799.                         (h * mb_x + x) * 8) >> s->avctx->lowres);
800.                     if(s->interlaced && s->bottom_field)
801.                         ptr += linesize[c] >> 1;
                             ^
802.                     if(!s->progressive) {
803.                         s->dsp.clear_block(s->block);
