In xDecodeSlice function, there is the following code copying slice info and setting slice index:

  m_apcSlicePilot->setSliceIdx(m_uiSliceIdx);
  if (!m_bFirstSliceInPicture)
  {
    m_apcSlicePilot->copySliceInfo( pcPic->getPicSym()->getSlice(m_uiSliceIdx-1) );
  }

However, in the multi slices case, it will assign the slice index from the previous slice through the copying. So, for example, in two slices case, both slices will have index 0.

Probably, the order should be swapped as follows:

  if (!m_bFirstSliceInPicture)
  {
    m_apcSlicePilot->copySliceInfo( pcPic->getPicSym()->getSlice(m_uiSliceIdx-1) );
  }
  m_apcSlicePilot->setSliceIdx(m_uiSliceIdx);