• John Koleszar's avatar
    Fix loopfilter delta zero transitions · b9be7a46
    John Koleszar authored
    Loopfilter deltas are initialized to zero on keyframes in the decoder.
    The values then persist from the previous frame unless an update bit
    is set in the bitstream. This data is not included in the entropy
    data saved by the 'refresh entropy' bit in the bitstream, so it is
    effectively an additional contextual element beyond the 3 ref-frames
    and the entropy data.
    The encoder was treating this delta update bit as update-if-nonzero,
    meaning that the value would be refreshed even if it hadn't changed,
    and more significantly, if the correct value for the delta changed
    to zero, the update wouldn't be sent, and the decoder would preserve
    the last (presumably non-zero) value.
    This patch updates the encoder to send an update only if the value
    has changed from the previously transmitted value. It also forces the
    value to be transmitted in error resilient mode, to account for lost
    context in the event of lost frames.
    Change-Id: I56671d5b42965d0166ac226765dbfce3e5301868