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Fix "all|no frames are keyframes" settings.

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Documentation says: "if kmin == 0, then key-frame insertion is disabled;
and if kmax == 0, then all frames will be key-frames."
Reading this, you'd expect that if kmax == 0, then with any kmin <= 0
all frames will be key-frames. But actually the kmin <= 0 test is caught
first and you get the opposite (no keyframes but the first). You'd have
instead to set kmax == 0 and any value kmin > 0, which is absolutely
counter-intuitive (reversing order).
Moreover kmax == 1 has no valid kmin (kmin == 1 conflicts with the
`kmax > kmin` rule and kmin == 0 conflicts with `kmin >= kmax / 2 + 1`).
So it should be considered an exception too.

Instead I propose this new logic:
- kmax == 1 means that all frames are keyframes (you are explicitly
  requesting a keyframe every 1 frame at most, i.e. all frames).
- kmax == 0 means no keyframes (you ask for a keyframe every 0 frames,
  i.e. never).
This is more "logical" language-wise, and also does not involve any
conflicts about what if both kmax and kmin are 0, since now a single
property value is meaningful for the 2 exceptional cases.

Change-Id: Ia90fb963bc26904ff078d2e4ef9f74b22b13a0fd
This commit is contained in:
Jehan
2016-11-26 01:25:49 +01:00
committed by James Zern
parent 84cef16f47
commit 2dc0bdcaee
3 changed files with 13 additions and 12 deletions
Download Patch File Download Diff File Expand all files Collapse all files

9
src/mux/anim_encode.c
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@ -129,14 +129,13 @@ static void SanitizeEncoderOptions(WebPAnimEncoderOptions* const enc_options) {
DisableKeyframes(enc_options);
}
if (enc_options->kmin <= 0) {
DisableKeyframes(enc_options);
print_warning = 0;
}
if (enc_options->kmax <= 0) { // All frames will be key-frames.
if (enc_options->kmax == 1) { // All frames will be key-frames.
enc_options->kmin = 0;
enc_options->kmax = 0;
return;
} else if (enc_options->kmax <= 0) {
DisableKeyframes(enc_options);
print_warning = 0;
}
if (enc_options->kmin >= enc_options->kmax) {