STIC_PACKET_SIZE
v = i * STIC_PACKET_SIZE +
si->si_pbuf_select ^= STIC_PACKET_SIZE;
STIC_XCOMM_SIZE + STIC_PACKET_SIZE * PX_BUF_COUNT;
(STIC_PACKET_SIZE * PX_BUF_COUNT + STIC_IMGBUF_SIZE*2 + STIC_XCOMM_SIZE)
si->si_pbuf_select ^= STIC_PACKET_SIZE;
sxi->sxi_buf_imgoff = STIC_XCOMM_SIZE + STIC_PACKET_SIZE * 2;