Vivo H.263

• FOURCCs: viv2
• Company: Vivo Software
• Samples: http://samples.mplayerhq.hu/vivo/

This is a variant of H.263 with such features as AIC and PB-frames but with quantisation approach closer to MPEG-4 ASP.

Picture header

Vivo 1/2 picture header is almost the same as H.263 but with some subtle changes.

 22 bits - syncword (0x000020)
  8 bits - TR
  1 bit  - marker
  1 bit  - should be zero
  1 bit  - split screen indicator?
  1 bit  - document camera indicator?
  1 bit  - freeze picture release?
  3 bits - source format (0 - illegal, 6 - extended)
  1 bit  - inter frame
  1 bit  - UMV
  1 bit  - SAC?
  1 bit  - APM
  1 bit  - is PB-frame
  if source format == 6 {
    3 bits - actual source format (0 and 6 are illegal ones)
    1 bit  - AIC
    1 bit  - deblocking
    1 bit  - unknown
    1 bit  - unknown
    1 bit  - unknown
    1 bit  - unknown
    1 bit  - PB plus mode
    1 bit  - unknown
    1 bit  - interlaced mode
    1 bit  - unknown
    1 bit  - unknown
  }
  5 bits - quantiser
  1 bit  - should be zero
  if PB-frame {
     3 bits - TRB
     2 bits - DBQUANT
  }
  1-n bits - PEI

Notable differences:

• in AIC mode coefficient prediction is done before quantisation
• deblocking is performed on all edges using (3 * (p1 - q1) + 8 * (q0 - p0)) >> 4 as delta.

Interlacing does not affect bitstream decoding, just reconstruction of the image.