Lacnzos for general case, sinc for upscaling, Gaussian for
downscaling. According to various literature these scalers
should be the best (quality-wise) available for each case.
Inspired from a patch by wm4 <nfx...@googlemail.com>
---
libswscale/utils.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/libswscale/utils.c b/libswscale/utils.c
index 2781985..a642710 100644
--- a/libswscale/utils.c
+++ b/libswscale/utils.c
@@ -914,6 +914,18 @@ av_cold int sws_init_context(SwsContext *c, SwsFilter
*srcFilter,
SWS_SINC |
SWS_SPLINE |
SWS_BICUBLIN);
+
+ /* provide a default scaler if not set by caller */
+ if (!i) {
+ if (dstW < srcW && dstH < srcH)
+ flags |= SWS_GAUSS;
+ else if (dstW > srcW && dstH > srcH)
+ flags |= SWS_SINC;
+ else
+ flags |= SWS_LANCZOS;
+ c->flags = flags;
+ }
+
if (!i || (i & (i - 1))) {
av_log(c, AV_LOG_ERROR,
"Exactly one scaler algorithm must be chosen\n");
--
1.7.9.5
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