how to interpret motion vector values in h.264 output
netraju
I,ve downloaded a h.264 codec. Once I run it on a video file, i'm
getting somm values as motion vectors and residuals. What do they
represent? some values are negative , some are positive.They are in
2x2 matrix output per macro block. Please xplain.
Thanx in Advance
Sanjay
Bernhard Agthe
Motion vectors point to an area in a different frame, that has roughly
the same pattern as the area they are calculated for. This may or may
not be related to "motion" - though "motion" is where the concept is
coming from: the football was just a bit further left in the previous
frame, so instead of re-encoding it, a "motion vector" is coded. But the
perceived motion may be a result of the football moving, the camera
moving or it might be a second football that is lying just next to the
original one and is perceived by the encoder to be a "good guess" ;-)
Actually in H.264, a macroblock is usually 16x16 and may be divided into
blocks of 4x4. The 2x2 matrix you get does not seem to be related to
anything else than chroma components, but they are derived from luma
components and should either be shown separately or not at all. Please
do check, what you are shown.
Ciao...
.