libavcodec/vp56.c:622: error: Uninitialized Value
  The value read from alpha_offset was never initialized.

libavcodec/vp56.c:622:13: 
620.             FFSWAP(AVFrame *, s->framep[VP56_FRAME_GOLDEN],
621.                               s->framep[VP56_FRAME_GOLDEN2]);
622.             buf += alpha_offset;
                 ^
623.             remaining_buf_size -= alpha_offset;
624.         }
