On the Encoder:
  --SEIpictureDigest=1 (default) calculates and writes per-picture MD5
                       picture_digest SEI messages
  --SEIpictureDigest=0 does not calculate MD5s or write the SEI messages

On the Decoder:
  --SEIpictureDigest=1 (default) calculates per-picture MD5sums and
                       compares against any picture_digest SEI message
  --SEIpictureDigest=0 does not calculate MD5s or interpret picture_digest
                       SEI message

From: David Flynn <davidf@rd.bbc.co.uk>