Move default tune setting earlier in codec_aom.c

src/codec_aom.c

@@ -420,6 +420,10 @@ static avifBool avifImageUsesTuneIq(const avifCodec * codec, avifBool alpha)
         }
     }
 
+    // In practice this function should also return true if avifEncoderSetCodecSpecificOption("tune", "iq")
+    // was called for a previous frame and not called (or called with NULL) for this frame, because the tune
+    // option persists across frames in libaom. However AOM_TUNE_IQ is only supported with still images in
+    // libavif and libaom as of today, so there is no need to remember this option across frames.
     return ret;
 }
 
@@ -648,10 +652,21 @@ static avifResult aomCodecEncodeImage(avifCodec * codec,
                                       avifAddImageFlags addImageFlags,
                                       avifCodecEncodeOutput * output)
 {
+    avifBool useLibavifDefaultTuneMetric = AVIF_FALSE;        // If true, override libaom's default tune option.
+    aom_tune_metric libavifDefaultTuneMetric = AOM_TUNE_PSNR; // Meaningless unless useLibavifDefaultTuneMetric.
+    if (quality != AVIF_QUALITY_LOSSLESS && !avifAOMOptionsContainExplicitTuning(codec, alpha)) {
+        useLibavifDefaultTuneMetric = AVIF_TRUE;
+        libavifDefaultTuneMetric = AOM_TUNE_SSIM;
+    }
+
     struct aom_codec_enc_cfg * cfg = &codec->internal->cfg;
     avifBool quantizerUpdated = AVIF_FALSE;
-    const avifBool tuneIq = avifImageUsesTuneIq(codec, alpha);
-    const int quantizer = aomQualityToQuantizer(quality, tuneIq);
+    // True if libavif knows that tune=iq is used, either by default by libavif, or explicitly set by the user.
+    // False otherwise (including if libaom uses tune=iq by default, which is not the case as of v1.13.1 and earlier versions).
+    // This is only accurate for the first frame but tune=iq is only supported for still images in libavif and
+    // for all-intra coding in libaom (at least up to v1.13.1) anyway.
+    const avifBool useTuneIq = useLibavifDefaultTuneMetric ? libavifDefaultTuneMetric == AOM_TUNE_IQ : avifImageUsesTuneIq(codec, alpha);
+    const int quantizer = aomQualityToQuantizer(quality, useTuneIq);
 
     // For encoder->scalingMode.horizontal and encoder->scalingMode.vertical to take effect in AOM
     // encoder, config should be applied for each frame, so we don't care about changes on these
@@ -990,10 +1005,9 @@ static avifResult aomCodecEncodeImage(avifCodec * codec,
         }
 #endif
 
-        if (!avifAOMOptionsContainExplicitTuning(codec, alpha)) {
-            if (aom_codec_control(&codec->internal->encoder, AOME_SET_TUNING, AOM_TUNE_SSIM) != AOM_CODEC_OK) {
-                return AVIF_RESULT_UNKNOWN_ERROR;
-            }
+        if (useLibavifDefaultTuneMetric &&
+            aom_codec_control(&codec->internal->encoder, AOME_SET_TUNING, libavifDefaultTuneMetric) != AOM_CODEC_OK) {
+            return AVIF_RESULT_UNKNOWN_ERROR;
         }
         if (!avifProcessAOMOptionsPostInit(codec, alpha)) {
             return AVIF_RESULT_INVALID_CODEC_SPECIFIC_OPTION;
@@ -1074,6 +1088,8 @@ static avifResult aomCodecEncodeImage(avifCodec * codec,
             aom_codec_control(&codec->internal->encoder, AV1E_SET_LOSSLESS, lossless);
         }
         if (encoderChanges & AVIF_ENCODER_CHANGE_CODEC_SPECIFIC) {
+            // Do not apply libavifDefaultTuneMetric even if useLibavifDefaultTuneMetric is true:
+            // codec-specific settings persist on the libaom side, so keep the same behavior for tune.
             if (!avifProcessAOMOptionsPostInit(codec, alpha)) {
                 return AVIF_RESULT_INVALID_CODEC_SPECIFIC_OPTION;
             }

tests/gtest/aviftunetest.cc

@@ -112,6 +112,126 @@ TEST(AomSharpnessTest, GenerateDifferentBitstreams) {
   }
 }
 
+constexpr uint64_t kDuration = 1;
+
+void EncodeAnimation(const char* key, const char* value_before_first_frame,
+                     const char* value_after_first_frame,
+                     const char* value_before_second_frame,
+                     std::vector<uint8_t>& encoded_bitstream) {
+  // Generate an animation with two different frames.
+  const ImagePtr first_frame =
+      testutil::ReadImage(data_path, "paris_exif_xmp_icc.jpg");
+  ASSERT_NE(first_frame, nullptr);
+  // Speed up the test.
+  first_frame->width = 64;
+  first_frame->height = 64;
+  const ImagePtr second_frame(avifImageCreateEmpty());
+  ASSERT_NE(second_frame, nullptr);
+  ASSERT_EQ(
+      avifImageCopy(second_frame.get(), first_frame.get(), AVIF_PLANES_ALL),
+      AVIF_RESULT_OK);
+  testutil::FillImageGradient(first_frame.get());
+
+  EncoderPtr encoder(avifEncoderCreate());
+  ASSERT_NE(encoder, nullptr);
+  encoder->codecChoice = AVIF_CODEC_CHOICE_AOM;
+  encoder->creationTime = encoder->modificationTime = 1;  // Deterministic.
+  const avifAddImageFlag flag = AVIF_ADD_IMAGE_FLAG_FORCE_KEYFRAME;
+
+  // First frame.
+  ASSERT_EQ(avifEncoderSetCodecSpecificOption(encoder.get(), key,
+                                              value_before_first_frame),
+            AVIF_RESULT_OK);
+  ASSERT_EQ(
+      avifEncoderAddImage(encoder.get(), first_frame.get(), kDuration, flag),
+      AVIF_RESULT_OK);
+  ASSERT_EQ(avifEncoderSetCodecSpecificOption(encoder.get(), key,
+                                              value_after_first_frame),
+            AVIF_RESULT_OK);
+
+  // Second frame.
+  ASSERT_EQ(avifEncoderSetCodecSpecificOption(encoder.get(), key,
+                                              value_before_second_frame),
+            AVIF_RESULT_OK);
+  ASSERT_EQ(
+      avifEncoderAddImage(encoder.get(), second_frame.get(), kDuration, flag),
+      AVIF_RESULT_OK);
+
+  testutil::AvifRwData encoded;
+  ASSERT_EQ(avifEncoderFinish(encoder.get(), &encoded), AVIF_RESULT_OK);
+
+  // Make sure it decodes fine, even if unrelated to the current test.
+  DecoderPtr decoder(avifDecoderCreate());
+  ASSERT_NE(decoder, nullptr);
+  ASSERT_EQ(avifDecoderSetIOMemory(decoder.get(), encoded.data, encoded.size),
+            AVIF_RESULT_OK);
+  ASSERT_EQ(avifDecoderParse(decoder.get()), AVIF_RESULT_OK);
+  ASSERT_EQ(avifDecoderNextImage(decoder.get()), AVIF_RESULT_OK);
+  ASSERT_GT(testutil::GetPsnr(*first_frame, *decoder->image), 32.0);
+  ASSERT_EQ(avifDecoderNextImage(decoder.get()), AVIF_RESULT_OK);
+  ASSERT_GT(testutil::GetPsnr(*second_frame, *decoder->image), 32.0);
+
+  encoded_bitstream = std::vector(encoded.data, encoded.data + encoded.size);
+}
+
+TEST(AomTuneMetricTest, TuneOptionHasSameBehaviorAsOtherCodecSpecificOptions) {
+  if (avifCodecName(AVIF_CODEC_CHOICE_AOM, AVIF_CODEC_FLAG_CAN_ENCODE) ==
+      nullptr) {
+    GTEST_SKIP() << "Codec unavailable, skip test.";
+  }
+  std::vector<uint8_t> a, b;
+
+  EncodeAnimation("tune", nullptr, nullptr, nullptr, a);
+  EncodeAnimation("tune", nullptr, nullptr, nullptr, b);
+  // Make sure the comparison works as intended for identical input.
+  EXPECT_EQ(a, b);
+
+  EncodeAnimation("tune", "psnr", nullptr, nullptr, a);
+  EncodeAnimation("tune", nullptr, nullptr, nullptr, b);
+  // AOM_TUNE_PSNR is not the default.
+  EXPECT_NE(a, b);
+
+  EncodeAnimation("tune", nullptr, nullptr, nullptr, a);
+  EncodeAnimation("tune", nullptr, nullptr, "psnr", b);
+  // The second frame differs.
+  EXPECT_NE(a, b);
+
+  EncodeAnimation("tune", nullptr, "ssim", "psnr", a);
+  EncodeAnimation("tune", nullptr, nullptr, "psnr", b);
+  // The option is overwritten successfully.
+  EXPECT_EQ(a, b);
+
+  EncodeAnimation("tune", nullptr, nullptr, nullptr, a);
+  EncodeAnimation("tune", nullptr, "psnr", nullptr, b);
+  // The pending key is successfully deleted.
+  EXPECT_EQ(a, b);
+
+  EncodeAnimation("tune", "psnr", "psnr", "psnr", a);
+  EncodeAnimation("tune", "psnr", nullptr, nullptr, b);
+  // avifEncoderSetCodecSpecificOption(NULL) only deletes the *pending* key.
+  EXPECT_EQ(a, b);
+}
+
+TEST(AomTuneMetricTest, TuneIqOnlySupportsAllIntra) {
+  if (avifCodecName(AVIF_CODEC_CHOICE_AOM, AVIF_CODEC_FLAG_CAN_ENCODE) ==
+      nullptr) {
+    GTEST_SKIP() << "Codec unavailable, skip test.";
+  }
+
+  const ImagePtr image =
+      testutil::ReadImage(data_path, "paris_exif_xmp_icc.jpg");
+  ASSERT_NE(image, nullptr);
+
+  EncoderPtr encoder(avifEncoderCreate());
+  ASSERT_NE(encoder, nullptr);
+  encoder->codecChoice = AVIF_CODEC_CHOICE_AOM;
+  ASSERT_EQ(avifEncoderSetCodecSpecificOption(encoder.get(), "tune", "iq"),
+            AVIF_RESULT_OK);
+  ASSERT_EQ(avifEncoderAddImage(encoder.get(), image.get(), kDuration,
+                                AVIF_ADD_IMAGE_FLAG_NONE),
+            AVIF_RESULT_INVALID_CODEC_SPECIFIC_OPTION);
+}
+
 //------------------------------------------------------------------------------
 
 }  // namespace