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swscale/tests/swscale: add option to run main conversion with legacy scaler

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The low bit depth workaround code is duplicated in this commit, but the
other occurrence will be removed in a few commits, so I see no reason
to factor it out.

The legacy scaler still has some conversions that give results much
worse than the expected loss, but we still want them as reference, so
we don't trigger expected loss errors on conversions with the legacy
scaler.

Sponsored-by: Sovereign Tech Fund
Signed-off-by: Ramiro Polla <ramiro.polla@gmail.com>
This commit is contained in:
Ramiro Polla 2026-03-06 17:36:08 +01:00
parent 3eb178a197
commit 101a2f6fc6
1 changed files with 22 additions and 2 deletions
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24
libswscale/tests/swscale.c
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@ -52,6 +52,7 @@ struct options {
int flags;
int dither;
int unscaled;
int legacy;
};
struct mode {
@ -404,7 +405,8 @@ static int run_test(enum AVPixelFormat src_fmt, enum AVPixelFormat dst_fmt,
if (ret < 0)
goto error;
ret = scale_new(dst, src, mode, opts, &r.time);
ret = opts->legacy ? scale_legacy(dst, src, mode, opts, &r.time)
: scale_new(dst, src, mode, opts, &r.time);
if (ret < 0)
goto error;
@ -417,8 +419,22 @@ static int run_test(enum AVPixelFormat src_fmt, enum AVPixelFormat dst_fmt,
goto error;
get_ssim(r.ssim, out, ref, comps);
if (opts->legacy) {
/* Legacy swscale does not perform bit accurate upconversions of low
* bit depth RGB. This artificially improves the SSIM score because the
* resulting error deletes some of the input dither noise. This gives
* it an unfair advantage when compared against a bit exact reference.
* Work around this by ensuring that the resulting SSIM score is not
* higher than it theoretically "should" be. */
if (src_var > dst_var) {
const float src_loss = (2 * ref_var + c1) / (2 * ref_var + src_var + c1);
r.ssim[0] = FFMIN(r.ssim[0], src_loss);
}
}
r.loss = get_loss(r.ssim);
if (r.loss - expected_loss > 1e-2 && dst_w >= ref->width && dst_h >= ref->height) {
if (!opts->legacy && r.loss - expected_loss > 1e-2 && dst_w >= ref->width && dst_h >= ref->height) {
ret = -1;
goto bad_loss;
}
@ -658,6 +674,8 @@ static int parse_options(int argc, char **argv, struct options *opts, FILE **fp)
" Test with a specific dither mode\n"
" -unscaled <1 or 0>\n"
" If 1, test only conversions that do not involve scaling\n"
" -legacy <1 or 0>\n"
" If 1, force using legacy swscale for the main conversion\n"
" -threads <threads>\n"
" Use the specified number of threads\n"
" -cpuflags <cpuflags>\n"
@ -717,6 +735,8 @@ static int parse_options(int argc, char **argv, struct options *opts, FILE **fp)
opts->dither = atoi(argv[i + 1]);
} else if (!strcmp(argv[i], "-unscaled")) {
opts->unscaled = atoi(argv[i + 1]);
} else if (!strcmp(argv[i], "-legacy")) {
opts->legacy = atoi(argv[i + 1]);
} else if (!strcmp(argv[i], "-threads")) {
opts->threads = atoi(argv[i + 1]);
} else if (!strcmp(argv[i], "-p")) {