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swscale: provide a default scaler if none is set

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Lanczos for general case, sinc for upscaling, Gaussian for
downscaling. According to current literature these scalers
should be the best quality-wise algorithms for each case.

Inspired from a patch by wm4 <nfxjfg@googlemail.com>

Signed-off-by: Luca Barbato <lu_zero@gentoo.org>
This commit is contained in:
Vittorio Giovara 2013-10-01 19:11:00 +02:00 committed by Luca Barbato
parent 258414d077
commit 6b3ff6f91a
1 changed files with 11 additions and 1 deletions
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12
libswscale/utils.c
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@ -914,7 +914,17 @@ av_cold int sws_init_context(SwsContext *c, SwsFilter *srcFilter,
SWS_SINC |
SWS_SPLINE |
SWS_BICUBLIN);
if (!i || (i & (i - 1))) {
/* 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;
} else if (i & (i - 1)) {
av_log(c, AV_LOG_ERROR,
"Exactly one scaler algorithm must be chosen\n");
return AVERROR(EINVAL);