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make the filtering process match libvpx and ffvp8

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libvpx (and ffvp8) implementations are completely skipping the deblocking
step if loop_filter_level is 0, which is _not_ equivalent to performing
the loop-filtering with a 0 value for loop_filter_level. In the latter case
(which we followed), few pixels were modified here and there and you could
observe off-by-1 errors on few places.

This patch will reconcile the 3 implementations (since the difference
is minor, skipping the deblocking step will save CPU for virtually
no visible difference).

The spec will be made clearer about the expected behaviour:
* if the global loop_filter_level is 0, turn deblocking off.
* if it's not 0 but the local loop_filter_level ends up being 0 for whatever
reason (lf_delta, mode delta, ref delta, etc.) on a particular
macroblock, skip the deblocking too.

Change-Id: I157f1f8de463b8a76caddb3f347b7fbc7bd527d2
This commit is contained in:
Pascal Massimino 2011-03-08 18:47:08 -08:00
parent dd60138d20
commit d5bc05a47b
1 changed files with 3 additions and 0 deletions
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3
src/dec/frame.c
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@ -126,6 +126,9 @@ static void DoFilter(VP8Decoder* const dec, int mb_x, int mb_y) {
const int level = mb->f_level_;
const int ilevel = mb->f_ilevel_;
const int limit = 2 * level + ilevel;
if (level == 0) {
return;
}
if (dec->filter_type_ == 1) { // simple
if (mb_x > 0) {
VP8SimpleHFilter16(y_dst, y_bps, limit + 4);