Figure 1
A two level DWT for N data. The number of data is halved after every filtering and down sampling operation. A wavelet transform is applied on output of low pass filter (h [n]) (approximation coefficients) recursively keeping the output coefficients of each high pass filtering operation (g [n]) (detailed coefficients) at each stage. The wavelet transform of a data at any level i of decomposition consists of approximation coefficients only at i th level and all detailed coefficients up to ith level.