diff --git a/api/video_codecs/BUILD.gn b/api/video_codecs/BUILD.gn
index 6167c1fafa..a36bf442e6 100644
--- a/api/video_codecs/BUILD.gn
+++ b/api/video_codecs/BUILD.gn
@@ -342,6 +342,7 @@ rtc_library("simple_encoder_wrapper") {
   absl_deps = [
     "//third_party/abseil-cpp/absl/algorithm:container",
     "//third_party/abseil-cpp/absl/functional:any_invocable",
+    "//third_party/abseil-cpp/absl/types:variant",
   ]
 }
 
@@ -397,6 +398,8 @@ rtc_library("libaom_av1_encoder_factory_test") {
     "../../test:test_support",
     "../../test:video_test_support",
   ]
+
+  absl_deps = [ "//third_party/abseil-cpp/absl/types:variant" ]
 }
 
 rtc_library("vp8_temporal_layers_factory") {
diff --git a/api/video_codecs/libaom_av1_encoder_factory.cc b/api/video_codecs/libaom_av1_encoder_factory.cc
index 52bf5d64aa..7e3c583c7f 100644
--- a/api/video_codecs/libaom_av1_encoder_factory.cc
+++ b/api/video_codecs/libaom_av1_encoder_factory.cc
@@ -27,7 +27,7 @@
 #define SET_OR_DO_ERROR_CALLBACK_AND_RETURN(param_id, param_value)    \
   do {                                                                \
     if (!SetEncoderControlParameters(&ctx_, param_id, param_value)) { \
-      encode_result_callback({});                                     \
+      DoErrorCallback(frame_settings);                                \
       return;                                                         \
     }                                                                 \
   } while (0)
@@ -41,8 +41,9 @@
 
 namespace webrtc {
 
-using Cbr = VideoEncoderInterface::FrameEncodeSettings::Cbr;
-using Cqp = VideoEncoderInterface::FrameEncodeSettings::Cqp;
+using FrameEncodeSettings = VideoEncoderInterface::FrameEncodeSettings;
+using Cbr = FrameEncodeSettings::Cbr;
+using Cqp = FrameEncodeSettings::Cqp;
 using aom_img_ptr = std::unique_ptr<aom_image_t, decltype(&aom_img_free)>;
 
 namespace {
@@ -87,8 +88,7 @@ class LibaomAv1Encoder : public VideoEncoderInterface {
 
   void Encode(rtc::scoped_refptr<webrtc::VideoFrameBuffer> frame_buffer,
               const TemporalUnitSettings& tu_settings,
-              const std::vector<FrameEncodeSettings>& frame_settings,
-              EncodeResultCallback encode_result_callback) override;
+              std::vector<FrameEncodeSettings> frame_settings) override;
 
  private:
   aom_img_ptr image_to_encode_ = aom_img_ptr(nullptr, aom_img_free);
@@ -276,6 +276,11 @@ bool ValidateEncodeParams(
     const VideoEncoderInterface::FrameEncodeSettings& settings =
         frame_settings[i];
 
+    if (!settings.result_callback) {
+      RTC_LOG(LS_ERROR) << "No result callback function provided.";
+      return false;
+    }
+
     if (!in_range(0, kMaxSpatialLayersWtf, settings.spatial_id)) {
       RTC_LOG(LS_ERROR) << "invalid spatial id " << settings.spatial_id;
       return false;
@@ -611,14 +616,23 @@ aom_svc_params_t GetSvcParams(
   return svc_params;
 }
 
+void DoErrorCallback(std::vector<FrameEncodeSettings>& frame_settings) {
+  for (FrameEncodeSettings& settings : frame_settings) {
+    if (settings.result_callback) {
+      settings.result_callback({});
+      // To avoid invoking any callback more than once.
+      settings.result_callback = {};
+    }
+  }
+}
+
 void LibaomAv1Encoder::Encode(
     rtc::scoped_refptr<webrtc::VideoFrameBuffer> frame_buffer,
     const TemporalUnitSettings& tu_settings,
-    const std::vector<FrameEncodeSettings>& frame_settings,
-    EncodeResultCallback encode_result_callback) {
+    std::vector<FrameEncodeSettings> frame_settings) {
   if (!ValidateEncodeParams(*frame_buffer, tu_settings, frame_settings,
                             last_resolution_in_buffer_, cfg_.rc_end_usage)) {
-    encode_result_callback({});
+    DoErrorCallback(frame_settings);
     return;
   }
 
@@ -681,7 +695,7 @@ void LibaomAv1Encoder::Encode(
   if (aom_codec_err_t ret = aom_codec_enc_config_set(&ctx_, &cfg_);
       ret != AOM_CODEC_OK) {
     RTC_LOG(LS_ERROR) << "aom_codec_enc_config_set returned " << ret;
-    encode_result_callback({});
+    DoErrorCallback(frame_settings);
     return;
   }
   aom_svc_params_t svc_params = GetSvcParams(*frame_buffer, frame_settings);
@@ -689,20 +703,20 @@ void LibaomAv1Encoder::Encode(
 
   // The libaom AV1 encoder requires that `aom_codec_encode` is called for
   // every spatial layer, even if no frame should be encoded for that layer.
-  std::array<const FrameEncodeSettings*, kMaxSpatialLayersWtf>
+  std::array<FrameEncodeSettings*, kMaxSpatialLayersWtf>
       settings_for_spatial_id;
   settings_for_spatial_id.fill(nullptr);
   FrameEncodeSettings settings_for_unused_layer;
-  for (const FrameEncodeSettings& settings : frame_settings) {
+  for (FrameEncodeSettings& settings : frame_settings) {
     settings_for_spatial_id[settings.spatial_id] = &settings;
   }
 
   for (int sid = frame_settings[0].spatial_id;
        sid < svc_params.number_spatial_layers; ++sid) {
     const bool layer_enabled = settings_for_spatial_id[sid] != nullptr;
-    const FrameEncodeSettings& settings = layer_enabled
-                                              ? *settings_for_spatial_id[sid]
-                                              : settings_for_unused_layer;
+    FrameEncodeSettings& settings = layer_enabled
+                                        ? *settings_for_spatial_id[sid]
+                                        : settings_for_unused_layer;
 
     aom_svc_layer_id_t layer_id = {
         .spatial_layer_id = sid,
@@ -713,7 +727,6 @@ void LibaomAv1Encoder::Encode(
     SET_OR_DO_ERROR_CALLBACK_AND_RETURN(AV1E_SET_SVC_REF_FRAME_CONFIG,
                                         &ref_config);
 
-    // TD: Why does the libaom have both `encode_timestamp_` and `duration`?
     // TD: Duration can't be zero, what does it matter when the layer is
     // not being encoded?
     TimeDelta duration = TimeDelta::Millis(1);
@@ -738,7 +751,7 @@ void LibaomAv1Encoder::Encode(
         settings.frame_type == FrameType::kKeyframe ? AOM_EFLAG_FORCE_KF : 0);
     if (ret != AOM_CODEC_OK) {
       RTC_LOG(LS_WARNING) << "aom_codec_encode returned " << ret;
-      encode_result_callback({});
+      DoErrorCallback(frame_settings);
       return;
     }
 
@@ -766,17 +779,18 @@ void LibaomAv1Encoder::Encode(
                                 : FrameType::kDeltaFrame;
         result.bitstream_data = EncodedImageBuffer::Create(
             static_cast<uint8_t*>(pkt->data.frame.buf), pkt->data.frame.sz);
-        result.spatial_id = sid;
         break;
       }
     }
 
     if (result.bitstream_data == nullptr) {
-      // TD: How should error callbacks be handled, only call once?
-      encode_result_callback({});
+      DoErrorCallback(frame_settings);
       return;
     } else {
-      encode_result_callback(result);
+      RTC_CHECK(settings.result_callback);
+      settings.result_callback(result);
+      // To avoid invoking any callback more than once.
+      settings.result_callback = {};
     }
   }
 }
@@ -786,7 +800,6 @@ std::string LibaomAv1EncoderFactory::CodecName() const {
   return "AV1";
 }
 
-// TD: it should also possible to expose SW/HW/driver version.
 std::string LibaomAv1EncoderFactory::ImplementationName() const {
   return "Libaom";
 }
diff --git a/api/video_codecs/libaom_av1_encoder_factory_test.cc b/api/video_codecs/libaom_av1_encoder_factory_test.cc
index eacb5a7a85..deb03aad62 100644
--- a/api/video_codecs/libaom_av1_encoder_factory_test.cc
+++ b/api/video_codecs/libaom_av1_encoder_factory_test.cc
@@ -14,6 +14,7 @@
 #include <utility>
 #include <vector>
 
+#include "absl/types/variant.h"
 #include "api/video/i420_buffer.h"
 #include "api/video_codecs/video_decoder.h"
 #include "api/video_codecs/video_encoder_interface.h"
@@ -59,7 +60,7 @@ std::string OutPath() {
 
 class EncodeResults {
  public:
-  EncodeResultCallback CallBack() {
+  EncodeResultCallback Cb() {
     return [&](const EncodeResult& result) { results_.push_back(result); };
   }
 
@@ -68,7 +69,7 @@ class EncodeResults {
       RTC_CHECK(false);
       return nullptr;
     }
-    return std::get_if<EncodedData>(&results_[index]);
+    return absl::get_if<EncodedData>(&results_[index]);
   }
 
  private:
@@ -172,8 +173,13 @@ class FrameEncoderSettingsBuilder {
     return *this;
   }
 
-  VideoEncoderInterface::FrameEncodeSettings Build() {
-    return frame_encode_settings_;
+  FrameEncoderSettingsBuilder& Cb(EncodeResultCallback cb) {
+    frame_encode_settings_.result_callback = std::move(cb);
+    return *this;
+  }
+
+  operator VideoEncoderInterface::FrameEncodeSettings&&() {
+    return std::move(frame_encode_settings_);
   }
 
  private:
@@ -182,6 +188,16 @@ class FrameEncoderSettingsBuilder {
 
 using Fb = FrameEncoderSettingsBuilder;
 
+// Since FrameEncodeSettings is move only, initalizer-list initialization won't
+// work, so instead a C-style array can be used to do aggregate initialization.
+template <int N>
+std::vector<VideoEncoderInterface::FrameEncodeSettings> ToVec(
+    VideoEncoderInterface::FrameEncodeSettings (&&settings)[N]) {
+  return std::vector<VideoEncoderInterface::FrameEncodeSettings>(
+      std::make_move_iterator(std::begin(settings)),
+      std::make_move_iterator(std::end(settings)));
+}
+
 // For reasonable debug printout when an EXPECT fail.
 struct Resolution {
   explicit Resolution(const VideoFrame& frame)
@@ -253,15 +269,14 @@ TEST(LibaomAv1Encoder, KeyframeUpdatesSpecifiedBuffer) {
   auto raw_delta = frame_reader->PullFrame();
 
   enc->Encode(raw_key, {.presentation_timestamp = Timestamp::Millis(0)},
-              {Fb().Rate(kCbr).Res(640, 360).Upd(5).Key().Build()},
-              res.CallBack());
+              ToVec({Fb().Rate(kCbr).Res(640, 360).Upd(5).Key().Cb(res.Cb())}));
   ASSERT_THAT(res.FrameAt(0), NotNull());
   VideoFrame decoded_key = dec.Decode(*res.FrameAt(0));
   EXPECT_THAT(Resolution(decoded_key), ResolutionIs(640, 360));
   EXPECT_THAT(Psnr(raw_key, decoded_key), Gt(40));
 
   enc->Encode(raw_delta, {.presentation_timestamp = Timestamp::Millis(100)},
-              {Fb().Rate(kCbr).Res(640, 360).Ref({0}).Build()}, res.CallBack());
+              ToVec({Fb().Rate(kCbr).Res(640, 360).Ref({0}).Cb(res.Cb())}));
   ASSERT_THAT(res.FrameAt(1), Eq(nullptr));
 }
 
@@ -271,20 +286,20 @@ TEST(LibaomAv1Encoder, MidTemporalUnitKeyframeResetsBuffers) {
   EncodeResults res;
   Av1Decoder dec;
 
-  enc->Encode(frame_reader->PullFrame(),
-              {.presentation_timestamp = Timestamp::Millis(0)},
-              {Fb().Rate(kCbr).Res(160, 90).S(0).Upd(0).Key().Build(),
-               Fb().Rate(kCbr).Res(320, 180).S(1).Ref({0}).Build(),
-               Fb().Rate(kCbr).Res(640, 360).S(2).Ref({0}).Build()},
-              res.CallBack());
+  enc->Encode(
+      frame_reader->PullFrame(),
+      {.presentation_timestamp = Timestamp::Millis(0)},
+      ToVec({Fb().Rate(kCbr).Res(160, 90).S(0).Upd(0).Key().Cb(res.Cb()),
+             Fb().Rate(kCbr).Res(320, 180).S(1).Ref({0}).Cb(res.Cb()),
+             Fb().Rate(kCbr).Res(640, 360).S(2).Ref({0}).Cb(res.Cb())}));
   ASSERT_THAT(res.FrameAt(2), NotNull());
 
-  enc->Encode(frame_reader->PullFrame(),
-              {.presentation_timestamp = Timestamp::Millis(100)},
-              {Fb().Rate(kCbr).Res(160, 90).S(0).Upd(0).Ref({0}).Build(),
-               Fb().Rate(kCbr).Res(320, 180).S(1).Upd(1).Key().Build(),
-               Fb().Rate(kCbr).Res(640, 360).S(2).Ref({0}).Build()},
-              res.CallBack());
+  enc->Encode(
+      frame_reader->PullFrame(),
+      {.presentation_timestamp = Timestamp::Millis(100)},
+      ToVec({Fb().Rate(kCbr).Res(160, 90).S(0).Upd(0).Ref({0}).Cb(res.Cb()),
+             Fb().Rate(kCbr).Res(320, 180).S(1).Upd(1).Key().Cb(res.Cb()),
+             Fb().Rate(kCbr).Res(640, 360).S(2).Ref({0}).Cb(res.Cb())}));
   ASSERT_THAT(res.FrameAt(3), Eq(nullptr));
 }
 
@@ -295,20 +310,15 @@ TEST(LibaomAv1Encoder, ResolutionSwitching) {
 
   rtc::scoped_refptr<I420Buffer> in0 = frame_reader->PullFrame();
   enc->Encode(in0, {.presentation_timestamp = Timestamp::Millis(0)},
-              {Fb().Rate(kCbr).Res(320, 180).Upd(0).Key().Build()},
-              res.CallBack());
+              ToVec({Fb().Rate(kCbr).Res(320, 180).Upd(0).Key().Cb(res.Cb())}));
 
   rtc::scoped_refptr<I420Buffer> in1 = frame_reader->PullFrame();
   enc->Encode(in1, {.presentation_timestamp = Timestamp::Millis(100)},
-              {Fb().Rate(kCbr).Res(640, 360).Ref({0}).Build()}, res.CallBack());
+              ToVec({Fb().Rate(kCbr).Res(640, 360).Ref({0}).Cb(res.Cb())}));
 
   rtc::scoped_refptr<I420Buffer> in2 = frame_reader->PullFrame();
   enc->Encode(in2, {.presentation_timestamp = Timestamp::Millis(200)},
-              {Fb().Rate(kCbr).Res(160, 90).Ref({0}).Build()}, res.CallBack());
-
-  EXPECT_THAT(res.FrameAt(0), Field(&EncodedData::spatial_id, 0));
-  EXPECT_THAT(res.FrameAt(1), Field(&EncodedData::spatial_id, 0));
-  EXPECT_THAT(res.FrameAt(2), Field(&EncodedData::spatial_id, 0));
+              ToVec({Fb().Rate(kCbr).Res(160, 90).Ref({0}).Cb(res.Cb())}));
 
   Av1Decoder dec;
   VideoFrame f0 = dec.Decode(*res.FrameAt(0));
@@ -333,26 +343,21 @@ TEST(LibaomAv1Encoder, InputResolutionSwitching) {
 
   rtc::scoped_refptr<I420Buffer> in0 = frame_reader->PullFrame();
   enc->Encode(in0, {.presentation_timestamp = Timestamp::Millis(0)},
-              {Fb().Rate(kCbr).Res(160, 90).Upd(0).Key().Build()},
-              res.CallBack());
+              ToVec({Fb().Rate(kCbr).Res(160, 90).Upd(0).Key().Cb(res.Cb())}));
 
   rtc::scoped_refptr<I420Buffer> in1 = frame_reader->PullFrame(
       /*frame_num=*/nullptr,
       /*resolution=*/{320, 180},
       /*framerate_scale=*/{1, 1});
   enc->Encode(in1, {.presentation_timestamp = Timestamp::Millis(100)},
-              {Fb().Rate(kCbr).Res(160, 90).Ref({0}).Build()}, res.CallBack());
+              ToVec({Fb().Rate(kCbr).Res(160, 90).Ref({0}).Cb(res.Cb())}));
 
   rtc::scoped_refptr<I420Buffer> in2 = frame_reader->PullFrame(
       /*frame_num=*/nullptr,
       /*resolution=*/{160, 90},
       /*framerate_scale=*/{1, 1});
   enc->Encode(in2, {.presentation_timestamp = Timestamp::Millis(200)},
-              {Fb().Rate(kCbr).Res(160, 90).Ref({0}).Build()}, res.CallBack());
-
-  EXPECT_THAT(res.FrameAt(0), Field(&EncodedData::spatial_id, 0));
-  EXPECT_THAT(res.FrameAt(1), Field(&EncodedData::spatial_id, 0));
-  EXPECT_THAT(res.FrameAt(2), Field(&EncodedData::spatial_id, 0));
+              ToVec({Fb().Rate(kCbr).Res(160, 90).Ref({0}).Cb(res.Cb())}));
 
   Av1Decoder dec;
   VideoFrame f0 = dec.Decode(*res.FrameAt(0));
@@ -380,24 +385,27 @@ TEST(LibaomAv1Encoder, TempoSpatial) {
   const Cbr k20Fps{.duration = TimeDelta::Millis(50),
                    .target_bitrate = DataRate::KilobitsPerSec(500)};
 
-  enc->Encode(frame_reader->PullFrame(),
-              {.presentation_timestamp = Timestamp::Millis(0)},
-              {Fb().Rate(k10Fps).Res(160, 90).S(0).Upd(0).Key().Build(),
-               Fb().Rate(k10Fps).Res(320, 180).S(1).Ref({0}).Upd(1).Build(),
-               Fb().Rate(k20Fps).Res(640, 360).S(2).Ref({1}).Upd(2).Build()},
-              res.CallBack());
+  enc->Encode(
+      frame_reader->PullFrame(),
+      {.presentation_timestamp = Timestamp::Millis(0)},
+      ToVec(
+          {Fb().Rate(k10Fps).Res(160, 90).S(0).Upd(0).Key().Cb(res.Cb()),
+           Fb().Rate(k10Fps).Res(320, 180).S(1).Ref({0}).Upd(1).Cb(res.Cb()),
+           Fb().Rate(k20Fps).Res(640, 360).S(2).Ref({1}).Upd(2).Cb(res.Cb())}));
 
   enc->Encode(frame_reader->PullFrame(),
               {.presentation_timestamp = Timestamp::Millis(50)},
-              {Fb().Rate(k20Fps).Res(640, 360).S(2).Ref({2}).Upd(2).Build()},
-              res.CallBack());
+              ToVec({Fb().Rate(k20Fps).Res(640, 360).S(2).Ref({2}).Upd(2).Cb(
+                  res.Cb())}));
 
   rtc::scoped_refptr<I420Buffer> frame = frame_reader->PullFrame();
-  enc->Encode(frame, {.presentation_timestamp = Timestamp::Millis(100)},
-              {Fb().Rate(k10Fps).Res(160, 90).S(0).Ref({0}).Upd(0).Build(),
-               Fb().Rate(k10Fps).Res(320, 180).S(1).Ref({0, 1}).Upd(1).Build(),
-               Fb().Rate(k20Fps).Res(640, 360).S(2).Ref({1, 2}).Upd(2).Build()},
-              res.CallBack());
+  enc->Encode(
+      frame, {.presentation_timestamp = Timestamp::Millis(100)},
+      ToVec(
+          {Fb().Rate(k10Fps).Res(160, 90).S(0).Ref({0}).Upd(0).Cb(res.Cb()),
+           Fb().Rate(k10Fps).Res(320, 180).S(1).Ref({0, 1}).Upd(1).Cb(res.Cb()),
+           Fb().Rate(k20Fps).Res(640, 360).S(2).Ref({1, 2}).Upd(2).Cb(
+               res.Cb())}));
 
   Av1Decoder dec;
   EXPECT_THAT(Resolution(dec.Decode(*res.FrameAt(0))), ResolutionIs(160, 90));
@@ -418,22 +426,23 @@ TEST(DISABLED_LibaomAv1Encoder, InvertedTempoSpatial) {
   auto enc = LibaomAv1EncoderFactory().CreateEncoder(kCbrEncoderSettings, {});
   EncodeResults res;
 
-  enc->Encode(frame_reader->PullFrame(),
-              {.presentation_timestamp = Timestamp::Millis(0)},
-              {Fb().Rate(kCbr).Res(320, 180).S(0).Upd(0).Key().Build(),
-               Fb().Rate(kCbr).Res(640, 360).S(1).Ref({0}).Upd(1).Build()},
-              res.CallBack());
+  enc->Encode(
+      frame_reader->PullFrame(),
+      {.presentation_timestamp = Timestamp::Millis(0)},
+      ToVec({Fb().Rate(kCbr).Res(320, 180).S(0).Upd(0).Key().Cb(res.Cb()),
+             Fb().Rate(kCbr).Res(640, 360).S(1).Ref({0}).Upd(1).Cb(res.Cb())}));
 
-  enc->Encode(frame_reader->PullFrame(),
-              {.presentation_timestamp = Timestamp::Millis(100)},
-              {Fb().Rate(kCbr).Res(320, 180).S(0).Ref({0}).Upd(0).Build()},
-              res.CallBack());
+  enc->Encode(
+      frame_reader->PullFrame(),
+      {.presentation_timestamp = Timestamp::Millis(100)},
+      ToVec({Fb().Rate(kCbr).Res(320, 180).S(0).Ref({0}).Upd(0).Cb(res.Cb())}));
 
   rtc::scoped_refptr<I420Buffer> frame = frame_reader->PullFrame();
-  enc->Encode(frame, {.presentation_timestamp = Timestamp::Millis(200)},
-              {Fb().Rate(kCbr).Res(320, 180).S(0).Ref({0}).Upd(0).Build(),
-               Fb().Rate(kCbr).Res(640, 360).S(1).Ref({1, 0}).Upd(1).Build()},
-              res.CallBack());
+  enc->Encode(
+      frame, {.presentation_timestamp = Timestamp::Millis(200)},
+      ToVec({Fb().Rate(kCbr).Res(320, 180).S(0).Ref({0}).Upd(0).Cb(res.Cb()),
+             Fb().Rate(kCbr).Res(640, 360).S(1).Ref({1, 0}).Upd(1).Cb(
+                 res.Cb())}));
 
   Av1Decoder dec;
   EXPECT_THAT(Resolution(dec.Decode(*res.FrameAt(0))), ResolutionIs(320, 180));
@@ -448,25 +457,26 @@ TEST(LibaomAv1Encoder, SkipMidLayer) {
   auto enc = LibaomAv1EncoderFactory().CreateEncoder(kCbrEncoderSettings, {});
   EncodeResults res;
 
-  enc->Encode(frame_reader->PullFrame(),
-              {.presentation_timestamp = Timestamp::Millis(0)},
-              {Fb().Rate(kCbr).Res(160, 90).S(0).Upd(0).Key().Build(),
-               Fb().Rate(kCbr).Res(320, 180).S(1).Ref({0}).Upd(1).Build(),
-               Fb().Rate(kCbr).Res(640, 360).S(2).Ref({1}).Upd(2).Build()},
-              res.CallBack());
+  enc->Encode(
+      frame_reader->PullFrame(),
+      {.presentation_timestamp = Timestamp::Millis(0)},
+      ToVec({Fb().Rate(kCbr).Res(160, 90).S(0).Upd(0).Key().Cb(res.Cb()),
+             Fb().Rate(kCbr).Res(320, 180).S(1).Ref({0}).Upd(1).Cb(res.Cb()),
+             Fb().Rate(kCbr).Res(640, 360).S(2).Ref({1}).Upd(2).Cb(res.Cb())}));
 
-  enc->Encode(frame_reader->PullFrame(),
-              {.presentation_timestamp = Timestamp::Millis(100)},
-              {Fb().Rate(kCbr).Res(160, 90).S(0).Ref({0}).Upd(0).Build(),
-               Fb().Rate(kCbr).Res(640, 360).S(2).Ref({2}).Upd(2).Build()},
-              res.CallBack());
+  enc->Encode(
+      frame_reader->PullFrame(),
+      {.presentation_timestamp = Timestamp::Millis(100)},
+      ToVec({Fb().Rate(kCbr).Res(160, 90).S(0).Ref({0}).Upd(0).Cb(res.Cb()),
+             Fb().Rate(kCbr).Res(640, 360).S(2).Ref({2}).Upd(2).Cb(res.Cb())}));
 
   rtc::scoped_refptr<I420Buffer> frame = frame_reader->PullFrame();
-  enc->Encode(frame, {.presentation_timestamp = Timestamp::Millis(200)},
-              {Fb().Rate(kCbr).Res(160, 90).S(0).Ref({0}).Upd(0).Build(),
-               Fb().Rate(kCbr).Res(320, 180).S(1).Ref({0, 1}).Upd(1).Build(),
-               Fb().Rate(kCbr).Res(640, 360).S(2).Ref({1, 2}).Upd(2).Build()},
-              res.CallBack());
+  enc->Encode(
+      frame, {.presentation_timestamp = Timestamp::Millis(200)},
+      ToVec({Fb().Rate(kCbr).Res(160, 90).S(0).Ref({0}).Upd(0).Cb(res.Cb()),
+             Fb().Rate(kCbr).Res(320, 180).S(1).Ref({0, 1}).Upd(1).Cb(res.Cb()),
+             Fb().Rate(kCbr).Res(640, 360).S(2).Ref({1, 2}).Upd(2).Cb(
+                 res.Cb())}));
 
   Av1Decoder dec;
   EXPECT_THAT(Resolution(dec.Decode(*res.FrameAt(0))), ResolutionIs(160, 90));
@@ -486,26 +496,26 @@ TEST(LibaomAv1Encoder, L3T1) {
   auto frame_reader = CreateFrameReader();
   auto enc = LibaomAv1EncoderFactory().CreateEncoder(kCbrEncoderSettings, {});
   EncodeResults res;
-
   Av1Decoder dec;
 
-  enc->Encode(frame_reader->PullFrame(),
-              {.presentation_timestamp = Timestamp::Millis(0)},
-              {Fb().Rate(kCbr).Res(160, 90).S(0).Upd(0).Key().Build(),
-               Fb().Rate(kCbr).Res(320, 180).S(1).Ref({0}).Upd(1).Build(),
-               Fb().Rate(kCbr).Res(640, 360).S(2).Ref({1}).Upd(2).Build()},
-              res.CallBack());
+  enc->Encode(
+      frame_reader->PullFrame(),
+      {.presentation_timestamp = Timestamp::Millis(0)},
+      ToVec({Fb().Rate(kCbr).Res(160, 90).S(0).Upd(0).Key().Cb(res.Cb()),
+             Fb().Rate(kCbr).Res(320, 180).S(1).Ref({0}).Upd(1).Cb(res.Cb()),
+             Fb().Rate(kCbr).Res(640, 360).S(2).Ref({1}).Upd(2).Cb(res.Cb())}));
 
   EXPECT_THAT(Resolution(dec.Decode(*res.FrameAt(0))), ResolutionIs(160, 90));
   EXPECT_THAT(Resolution(dec.Decode(*res.FrameAt(1))), ResolutionIs(320, 180));
   EXPECT_THAT(Resolution(dec.Decode(*res.FrameAt(2))), ResolutionIs(640, 360));
 
   auto tu1_frame = frame_reader->PullFrame();
-  enc->Encode(tu1_frame, {.presentation_timestamp = Timestamp::Millis(100)},
-              {Fb().Rate(kCbr).Res(160, 90).S(0).Ref({0}).Upd(0).Build(),
-               Fb().Rate(kCbr).Res(320, 180).S(1).Ref({1, 0}).Upd(1).Build(),
-               Fb().Rate(kCbr).Res(640, 360).S(2).Ref({2, 1}).Upd(2).Build()},
-              res.CallBack());
+  enc->Encode(
+      tu1_frame, {.presentation_timestamp = Timestamp::Millis(100)},
+      ToVec({Fb().Rate(kCbr).Res(160, 90).S(0).Ref({0}).Upd(0).Cb(res.Cb()),
+             Fb().Rate(kCbr).Res(320, 180).S(1).Ref({1, 0}).Upd(1).Cb(res.Cb()),
+             Fb().Rate(kCbr).Res(640, 360).S(2).Ref({2, 1}).Upd(2).Cb(
+                 res.Cb())}));
 
   EXPECT_THAT(Resolution(dec.Decode(*res.FrameAt(3))), ResolutionIs(160, 90));
   EXPECT_THAT(Resolution(dec.Decode(*res.FrameAt(4))), ResolutionIs(320, 180));
@@ -515,11 +525,12 @@ TEST(LibaomAv1Encoder, L3T1) {
   EXPECT_THAT(Psnr(tu1_frame, f_tu1), Gt(40));
 
   auto tu2_frame = frame_reader->PullFrame();
-  enc->Encode(tu2_frame, {.presentation_timestamp = Timestamp::Millis(200)},
-              {Fb().Rate(kCbr).Res(160, 90).S(0).Ref({0}).Upd(0).Build(),
-               Fb().Rate(kCbr).Res(320, 180).S(1).Ref({1, 0}).Upd(1).Build(),
-               Fb().Rate(kCbr).Res(640, 360).S(2).Ref({2, 1}).Upd(2).Build()},
-              res.CallBack());
+  enc->Encode(
+      tu2_frame, {.presentation_timestamp = Timestamp::Millis(200)},
+      ToVec({Fb().Rate(kCbr).Res(160, 90).S(0).Ref({0}).Upd(0).Cb(res.Cb()),
+             Fb().Rate(kCbr).Res(320, 180).S(1).Ref({1, 0}).Upd(1).Cb(res.Cb()),
+             Fb().Rate(kCbr).Res(640, 360).S(2).Ref({2, 1}).Upd(2).Cb(
+                 res.Cb())}));
 
   EXPECT_THAT(Resolution(dec.Decode(*res.FrameAt(6))), ResolutionIs(160, 90));
   EXPECT_THAT(Resolution(dec.Decode(*res.FrameAt(7))), ResolutionIs(320, 180));
@@ -538,12 +549,12 @@ TEST(LibaomAv1Encoder, L3T1_KEY) {
   Av1Decoder dec_s1;
   Av1Decoder dec_s2;
 
-  enc->Encode(frame_reader->PullFrame(),
-              {.presentation_timestamp = Timestamp::Millis(0)},
-              {Fb().Rate(kCbr).Res(160, 90).S(0).Upd(0).Key().Build(),
-               Fb().Rate(kCbr).Res(320, 180).S(1).Ref({0}).Upd(1).Build(),
-               Fb().Rate(kCbr).Res(640, 360).S(2).Ref({1}).Upd(2).Build()},
-              res.CallBack());
+  enc->Encode(
+      frame_reader->PullFrame(),
+      {.presentation_timestamp = Timestamp::Millis(0)},
+      ToVec({Fb().Rate(kCbr).Res(160, 90).S(0).Upd(0).Key().Cb(res.Cb()),
+             Fb().Rate(kCbr).Res(320, 180).S(1).Ref({0}).Upd(1).Cb(res.Cb()),
+             Fb().Rate(kCbr).Res(640, 360).S(2).Ref({1}).Upd(2).Cb(res.Cb())}));
 
   EXPECT_THAT(Resolution(dec_s0.Decode(*res.FrameAt(0))),
               ResolutionIs(160, 90));
@@ -557,12 +568,12 @@ TEST(LibaomAv1Encoder, L3T1_KEY) {
   EXPECT_THAT(Resolution(dec_s2.Decode(*res.FrameAt(2))),
               ResolutionIs(640, 360));
 
-  enc->Encode(frame_reader->PullFrame(),
-              {.presentation_timestamp = Timestamp::Millis(100)},
-              {Fb().Rate(kCbr).Res(160, 90).S(0).Ref({0}).Upd(0).Build(),
-               Fb().Rate(kCbr).Res(320, 180).S(1).Ref({1}).Upd(1).Build(),
-               Fb().Rate(kCbr).Res(640, 360).S(2).Ref({2}).Upd(2).Build()},
-              res.CallBack());
+  enc->Encode(
+      frame_reader->PullFrame(),
+      {.presentation_timestamp = Timestamp::Millis(100)},
+      ToVec({Fb().Rate(kCbr).Res(160, 90).S(0).Ref({0}).Upd(0).Cb(res.Cb()),
+             Fb().Rate(kCbr).Res(320, 180).S(1).Ref({1}).Upd(1).Cb(res.Cb()),
+             Fb().Rate(kCbr).Res(640, 360).S(2).Ref({2}).Upd(2).Cb(res.Cb())}));
 
   EXPECT_THAT(Resolution(dec_s0.Decode(*res.FrameAt(3))),
               ResolutionIs(160, 90));
@@ -571,12 +582,12 @@ TEST(LibaomAv1Encoder, L3T1_KEY) {
   EXPECT_THAT(Resolution(dec_s2.Decode(*res.FrameAt(5))),
               ResolutionIs(640, 360));
 
-  enc->Encode(frame_reader->PullFrame(),
-              {.presentation_timestamp = Timestamp::Millis(200)},
-              {Fb().Rate(kCbr).Res(160, 90).S(0).Ref({0}).Upd(0).Build(),
-               Fb().Rate(kCbr).Res(320, 180).S(1).Ref({1}).Upd(1).Build(),
-               Fb().Rate(kCbr).Res(640, 360).S(2).Ref({2}).Upd(2).Build()},
-              res.CallBack());
+  enc->Encode(
+      frame_reader->PullFrame(),
+      {.presentation_timestamp = Timestamp::Millis(200)},
+      ToVec({Fb().Rate(kCbr).Res(160, 90).S(0).Ref({0}).Upd(0).Cb(res.Cb()),
+             Fb().Rate(kCbr).Res(320, 180).S(1).Ref({1}).Upd(1).Cb(res.Cb()),
+             Fb().Rate(kCbr).Res(640, 360).S(2).Ref({2}).Upd(2).Cb(res.Cb())}));
 
   EXPECT_THAT(Resolution(dec_s0.Decode(*res.FrameAt(6))),
               ResolutionIs(160, 90));
@@ -595,12 +606,12 @@ TEST(LibaomAv1Encoder, S3T1) {
   Av1Decoder dec_s1;
   Av1Decoder dec_s2;
 
-  enc->Encode(frame_reader->PullFrame(),
-              {.presentation_timestamp = Timestamp::Millis(0)},
-              {Fb().Rate(kCbr).Res(160, 90).S(0).Start().Upd(0).Build(),
-               Fb().Rate(kCbr).Res(320, 180).S(1).Start().Upd(1).Build(),
-               Fb().Rate(kCbr).Res(640, 360).S(2).Start().Upd(2).Build()},
-              res.CallBack());
+  enc->Encode(
+      frame_reader->PullFrame(),
+      {.presentation_timestamp = Timestamp::Millis(0)},
+      ToVec({Fb().Rate(kCbr).Res(160, 90).S(0).Start().Upd(0).Cb(res.Cb()),
+             Fb().Rate(kCbr).Res(320, 180).S(1).Start().Upd(1).Cb(res.Cb()),
+             Fb().Rate(kCbr).Res(640, 360).S(2).Start().Upd(2).Cb(res.Cb())}));
   EXPECT_THAT(Resolution(dec_s0.Decode(*res.FrameAt(0))),
               ResolutionIs(160, 90));
   EXPECT_THAT(Resolution(dec_s1.Decode(*res.FrameAt(1))),
@@ -608,12 +619,12 @@ TEST(LibaomAv1Encoder, S3T1) {
   EXPECT_THAT(Resolution(dec_s2.Decode(*res.FrameAt(2))),
               ResolutionIs(640, 360));
 
-  enc->Encode(frame_reader->PullFrame(),
-              {.presentation_timestamp = Timestamp::Millis(100)},
-              {Fb().Rate(kCbr).Res(160, 90).S(0).Ref({0}).Upd(0).Build(),
-               Fb().Rate(kCbr).Res(320, 180).S(1).Ref({1}).Upd(1).Build(),
-               Fb().Rate(kCbr).Res(640, 360).S(2).Ref({2}).Upd(2).Build()},
-              res.CallBack());
+  enc->Encode(
+      frame_reader->PullFrame(),
+      {.presentation_timestamp = Timestamp::Millis(100)},
+      ToVec({Fb().Rate(kCbr).Res(160, 90).S(0).Ref({0}).Upd(0).Cb(res.Cb()),
+             Fb().Rate(kCbr).Res(320, 180).S(1).Ref({1}).Upd(1).Cb(res.Cb()),
+             Fb().Rate(kCbr).Res(640, 360).S(2).Ref({2}).Upd(2).Cb(res.Cb())}));
 
   EXPECT_THAT(Resolution(dec_s0.Decode(*res.FrameAt(3))),
               ResolutionIs(160, 90));
@@ -622,12 +633,12 @@ TEST(LibaomAv1Encoder, S3T1) {
   EXPECT_THAT(Resolution(dec_s2.Decode(*res.FrameAt(5))),
               ResolutionIs(640, 360));
 
-  enc->Encode(frame_reader->PullFrame(),
-              {.presentation_timestamp = Timestamp::Millis(200)},
-              {Fb().Rate(kCbr).Res(160, 90).S(0).Ref({0}).Upd(0).Build(),
-               Fb().Rate(kCbr).Res(320, 180).S(1).Ref({1}).Upd(1).Build(),
-               Fb().Rate(kCbr).Res(640, 360).S(2).Ref({2}).Upd(2).Build()},
-              res.CallBack());
+  enc->Encode(
+      frame_reader->PullFrame(),
+      {.presentation_timestamp = Timestamp::Millis(200)},
+      ToVec({Fb().Rate(kCbr).Res(160, 90).S(0).Ref({0}).Upd(0).Cb(res.Cb()),
+             Fb().Rate(kCbr).Res(320, 180).S(1).Ref({1}).Upd(1).Cb(res.Cb()),
+             Fb().Rate(kCbr).Res(640, 360).S(2).Ref({2}).Upd(2).Cb(res.Cb())}));
 
   EXPECT_THAT(Resolution(dec_s0.Decode(*res.FrameAt(6))),
               ResolutionIs(160, 90));
@@ -653,7 +664,7 @@ TEST(LibaomAv1Encoder, HigherEffortLevelYieldsHigherQualityFrames) {
     enc->Encode(
         frame_in,
         {.presentation_timestamp = Timestamp::Millis(0), .effort_level = i},
-        {Fb().Rate(kCbr).Res(640, 360).Upd(0).Key().Build()}, res.CallBack());
+        ToVec({Fb().Rate(kCbr).Res(640, 360).Upd(0).Key().Cb(res.Cb())}));
     double psnr = Psnr(frame_in, dec.Decode(*res.FrameAt(0)));
     EXPECT_THAT(psnr, Gt(psnr_last));
     psnr_last = psnr;
@@ -689,12 +700,12 @@ TEST(LibaomAv1Encoder, KeyframeAndStartrameAreApproximatelyEqual) {
     auto frame_in = frame_reader->PullFrame();
     enc_key->Encode(
         frame_in, {.presentation_timestamp = Timestamp::Millis(0)},
-        {Fb().Rate(kRate).Res(640, 360).S(sid).Upd(0).Key().Build()},
-        res_key.CallBack());
+        ToVec({Fb().Rate(kRate).Res(640, 360).S(sid).Upd(0).Key().Cb(
+            res_key.Cb())}));
     enc_start->Encode(
         frame_in, {.presentation_timestamp = Timestamp::Millis(0)},
-        {Fb().Rate(kRate).Res(640, 360).S(sid).Start().Upd(0).Build()},
-        res_start.CallBack());
+        ToVec({Fb().Rate(kRate).Res(640, 360).S(sid).Start().Upd(0).Cb(
+            res_start.Cb())}));
     total_size_key +=
         DataSize::Bytes(res_key.FrameAt(0)->bitstream_data->size());
     total_size_start +=
@@ -710,12 +721,12 @@ TEST(LibaomAv1Encoder, KeyframeAndStartrameAreApproximatelyEqual) {
       frame_in = frame_reader->PullFrame();
       enc_key->Encode(
           frame_in, {.presentation_timestamp = Timestamp::Millis(f * 100)},
-          {Fb().Rate(kRate).Res(640, 360).S(sid).Ref({0}).Upd(0).Build()},
-          res_key.CallBack());
+          ToVec({Fb().Rate(kRate).Res(640, 360).S(sid).Ref({0}).Upd(0).Cb(
+              res_key.Cb())}));
       enc_start->Encode(
           frame_in, {.presentation_timestamp = Timestamp::Millis(f * 100)},
-          {Fb().Rate(kRate).Res(640, 360).S(sid).Ref({0}).Upd(0).Build()},
-          res_start.CallBack());
+          ToVec({Fb().Rate(kRate).Res(640, 360).S(sid).Ref({0}).Upd(0).Cb(
+              res_start.Cb())}));
       total_size_key +=
           DataSize::Bytes(res_key.FrameAt(f)->bitstream_data->size());
       total_size_start +=
@@ -751,8 +762,8 @@ TEST(LibaomAv1Encoder, BitrateConsistentAcrossSpatialLayers) {
     EncodeResults res;
     enc->Encode(frame_reader->PullFrame(),
                 {.presentation_timestamp = Timestamp::Millis(0)},
-                {Fb().Rate(kRate).Res(640, 360).S(sid).Upd(0).Key().Build()},
-                res.CallBack());
+                ToVec({Fb().Rate(kRate).Res(640, 360).S(sid).Upd(0).Key().Cb(
+                    res.Cb())}));
     total_size += DataSize::Bytes(res.FrameAt(0)->bitstream_data->size());
     total_duration += kRate.duration;
     dec.Decode(*res.FrameAt(0));
@@ -761,8 +772,8 @@ TEST(LibaomAv1Encoder, BitrateConsistentAcrossSpatialLayers) {
       enc->Encode(
           frame_reader->PullFrame(),
           {.presentation_timestamp = Timestamp::Millis(f * 100)},
-          {Fb().Rate(kRate).Res(640, 360).S(sid).Ref({0}).Upd(0).Build()},
-          res.CallBack());
+          ToVec({Fb().Rate(kRate).Res(640, 360).S(sid).Ref({0}).Upd(0).Cb(
+              res.Cb())}));
       total_size += DataSize::Bytes(res.FrameAt(f)->bitstream_data->size());
       total_duration += kRate.duration;
       dec.Decode(*res.FrameAt(f));
@@ -791,13 +802,12 @@ TEST(LibaomAv1Encoder, ConstantQp) {
 
     enc->Encode(frame_reader->PullFrame(),
                 {.presentation_timestamp = Timestamp::Millis(0)},
-                {Fb().Rate(Cqp{.target_qp = kQp})
-                     .Res(640, 360)
-                     .S(sid)
-                     .Upd(0)
-                     .Key()
-                     .Build()},
-                res.CallBack());
+                ToVec({Fb().Rate(Cqp{.target_qp = kQp})
+                           .Res(640, 360)
+                           .S(sid)
+                           .Upd(0)
+                           .Key()
+                           .Cb(res.Cb())}));
     EXPECT_THAT(res.FrameAt(0)->encoded_qp, Eq(kQp));
     total_size += DataSize::Bytes(res.FrameAt(0)->bitstream_data->size());
     dec.Decode(*res.FrameAt(0));
@@ -805,13 +815,12 @@ TEST(LibaomAv1Encoder, ConstantQp) {
     for (int f = 1; f < 10; ++f) {
       enc->Encode(frame_reader->PullFrame(),
                   {.presentation_timestamp = Timestamp::Millis(f * 100)},
-                  {Fb().Rate(Cqp{.target_qp = kQp - f})
-                       .Res(640, 360)
-                       .S(sid)
-                       .Ref({0})
-                       .Upd(0)
-                       .Build()},
-                  res.CallBack());
+                  ToVec({Fb().Rate(Cqp{.target_qp = kQp - f})
+                             .Res(640, 360)
+                             .S(sid)
+                             .Ref({0})
+                             .Upd(0)
+                             .Cb(res.Cb())}));
       EXPECT_THAT(res.FrameAt(f)->encoded_qp, Eq(kQp - f));
       dec.Decode(*res.FrameAt(f));
     }
diff --git a/api/video_codecs/simple_encoder_wrapper.cc b/api/video_codecs/simple_encoder_wrapper.cc
index 51adfd5170..c3627e07d1 100644
--- a/api/video_codecs/simple_encoder_wrapper.cc
+++ b/api/video_codecs/simple_encoder_wrapper.cc
@@ -17,6 +17,7 @@
 #include <vector>
 
 #include "absl/algorithm/container.h"
+#include "absl/types/variant.h"
 #include "api/video_codecs/scalability_mode.h"
 #include "api/video_codecs/scalability_mode_helper.h"
 #include "api/video_codecs/video_encoder_factory_interface.h"
@@ -146,7 +147,6 @@ void SimpleEncoderWrapper::Encode(
       svc_controller_->NextFrameConfig(force_keyframe);
   std::vector<FrameEncodeSettings> encode_settings;
   std::vector<GenericFrameInfo> frame_infos;
-
   bool include_dependency_structure = false;
 
   for (size_t s = 0; s < configs.size(); ++s) {
@@ -178,38 +178,39 @@ void SimpleEncoderWrapper::Encode(
       settings.frame_type = FrameType::kKeyframe;
       include_dependency_structure = true;
     }
-  }
 
-  absl::optional<FrameDependencyStructure> dependency_structure;
-  if (include_dependency_structure) {
-    dependency_structure = svc_controller_->DependencyStructure();
-  }
+    absl::optional<FrameDependencyStructure> dependency_structure;
+    if (include_dependency_structure) {
+      dependency_structure = svc_controller_->DependencyStructure();
+    }
 
-  VideoEncoderInterface::EncodeResultCallback callback_internal =
-      [cb = std::move(callback), ds = std::move(dependency_structure),
-       infos = std::move(frame_infos)](
-          const VideoEncoderInterface::EncodeResult& result) mutable {
-        auto* data = std::get_if<VideoEncoderInterface::EncodedData>(&result);
-        EncodeResult res;
-        if (!data || data->spatial_id >= static_cast<int>(infos.size())) {
-          res.oh_no = true;
+    settings.result_callback =
+        [cb = callback, ds = std::move(dependency_structure),
+         info = std::move(frame_infos[settings.spatial_id])](
+            const VideoEncoderInterface::EncodeResult& result) mutable {
+          auto* data =
+              absl::get_if<VideoEncoderInterface::EncodedData>(&result);
+
+          EncodeResult res;
+          if (!data) {
+            res.oh_no = true;
+            cb(res);
+            return;
+          }
+
+          res.frame_type = data->frame_type;
+          res.bitstream_data = std::move(data->bitstream_data);
+          res.generic_frame_info = info;
+          if (res.frame_type == FrameType::kKeyframe) {
+            res.dependency_structure = ds;
+          }
           cb(res);
-          return;
-        }
-
-        res.frame_type = data->frame_type;
-        res.bitstream_data = std::move(data->bitstream_data);
-        res.generic_frame_info = infos[data->spatial_id];
-        if (res.frame_type == FrameType::kKeyframe) {
-          // Keyframe
-          res.dependency_structure = ds;
-        }
-        cb(res);
-      };
+        };
+  }
 
   encoder_->Encode(std::move(frame_buffer),
                    {.presentation_timestamp = presentation_timestamp_},
-                   encode_settings, std::move(callback_internal));
+                   std::move(encode_settings));
   presentation_timestamp_ += 1 / Frequency::Hertz(fps_);
 }
 
diff --git a/api/video_codecs/simple_encoder_wrapper.h b/api/video_codecs/simple_encoder_wrapper.h
index 4d11020924..cc1b94743e 100644
--- a/api/video_codecs/simple_encoder_wrapper.h
+++ b/api/video_codecs/simple_encoder_wrapper.h
@@ -33,8 +33,7 @@ class SimpleEncoderWrapper {
     absl::optional<FrameDependencyStructure> dependency_structure;
   };
 
-  using EncodeResultCallback =
-      absl::AnyInvocable<void(const EncodeResult& result)>;
+  using EncodeResultCallback = std::function<void(const EncodeResult& result)>;
 
   static std::vector<std::string> SupportedWebrtcSvcModes(
       const VideoEncoderFactoryInterface::Capabilities::PredictionConstraints&
diff --git a/api/video_codecs/simple_encoder_wrapper_unittests.cc b/api/video_codecs/simple_encoder_wrapper_unittests.cc
index 83518b6be5..3aa12b32b2 100644
--- a/api/video_codecs/simple_encoder_wrapper_unittests.cc
+++ b/api/video_codecs/simple_encoder_wrapper_unittests.cc
@@ -125,8 +125,8 @@ TEST(SimpleEncoderWrapper, SupportedSvcModesUpToL3T3KeyWithHScaling) {
           "S3T1", "S3T1h", "S3T2", "S3T2h", "S3T3", "S3T3h"));
 }
 
-// TD: The encoder wrapper shouldn't really use an actual encoder implementation
-//     for testing, but hey, this is just a PoC.
+// TD: The encoder wrapper shouldn't really use an actual encoder
+// implementation for testing, but hey, this is just a PoC.
 TEST(SimpleEncoderWrapper, EncodeL1T1) {
   auto encoder = LibaomAv1EncoderFactory().CreateEncoder(
       {.max_encode_dimensions = {1080, 720},
@@ -171,7 +171,7 @@ TEST(SimpleEncoderWrapper, EncodeL1T1) {
       });
 }
 
-TEST(SimpleEncoderWrapper, DISABLED_EncodeL2T2_KEY) {
+TEST(SimpleEncoderWrapper, EncodeL2T2_KEY) {
   auto encoder = LibaomAv1EncoderFactory().CreateEncoder(
       {.max_encode_dimensions = {1080, 720},
        .encoding_format = {.sub_sampling = EncodingFormat::k420,
@@ -231,7 +231,7 @@ TEST(SimpleEncoderWrapper, DISABLED_EncodeL2T2_KEY) {
   EXPECT_THAT(num_callbacks, Eq(4));
 }
 
-TEST(SimpleEncoderWrapper, DISABLED_EncodeL1T3ForceKeyframe) {
+TEST(SimpleEncoderWrapper, EncodeL1T3ForceKeyframe) {
   auto encoder = LibaomAv1EncoderFactory().CreateEncoder(
       {.max_encode_dimensions = {1080, 720},
        .encoding_format = {.sub_sampling = EncodingFormat::k420,
diff --git a/api/video_codecs/video_encoder_interface.h b/api/video_codecs/video_encoder_interface.h
index 4e0726436c..55ef55861c 100644
--- a/api/video_codecs/video_encoder_interface.h
+++ b/api/video_codecs/video_encoder_interface.h
@@ -13,7 +13,6 @@
 
 #include <map>
 #include <memory>
-// #include <unordered_set>
 #include <string>
 #include <utility>
 #include <vector>
@@ -44,6 +43,17 @@ class VideoEncoderInterface {
     int effort_level = 0;
   };
 
+  // Results from calling Encode. Called once for each configured frame.
+  struct EncodingError {};
+  struct EncodedData {
+    rtc::scoped_refptr<EncodedImageBufferInterface> bitstream_data;
+    FrameType frame_type;
+    int encoded_qp;
+  };
+  using EncodeResult = absl::variant<EncodingError, EncodedData>;
+  using EncodeResultCallback =
+      absl::AnyInvocable<void(const EncodeResult& result)>;
+
   struct FrameEncodeSettings {
     struct Cbr {
       TimeDelta duration;
@@ -62,26 +72,13 @@ class VideoEncoderInterface {
     Resolution resolution;
     std::vector<int> reference_buffers;
     absl::optional<int> update_buffer;
+
+    EncodeResultCallback result_callback;
   };
 
-  // Results from calling Encode. Called once for each configured frame.
-  struct EncodingError {};
-
-  struct EncodedData {
-    rtc::scoped_refptr<EncodedImageBufferInterface> bitstream_data;
-    FrameType frame_type;
-    int spatial_id;
-    int encoded_qp;
-  };
-
-  using EncodeResult = std::variant<EncodingError, EncodedData>;
-  using EncodeResultCallback =
-      absl::AnyInvocable<void(const EncodeResult& result)>;
-
   virtual void Encode(rtc::scoped_refptr<webrtc::VideoFrameBuffer> frame_buffer,
                       const TemporalUnitSettings& settings,
-                      const std::vector<FrameEncodeSettings>& frame_settings,
-                      EncodeResultCallback encode_result_callback) = 0;
+                      std::vector<FrameEncodeSettings> frame_settings) = 0;
 };
 
 }  // namespace webrtc