Merge pull request #16 from macaodha/fix/GH-15-spectrogram-features-computation

Fix/gh 15 spectrogram features computation

.gitignore

@@ -65,7 +65,7 @@ ipython_config.py
 #   pdm stores project-wide configurations in .pdm.toml, but it is recommended to not include it
 #   in version control.
 #   https://pdm.fming.dev/#use-with-ide
-.pdm.toml
+.pdm-python
 
 # PEP 582; used by e.g. github.com/David-OConnor/pyflow and github.com/pdm-project/pdm
 __pypackages__/

batdetect2/detector/compute_features.py

@@ -1,22 +1,27 @@
+"""Functions to compute features from predictions."""
+from typing import Dict, Optional
+
 import numpy as np
 
+from batdetect2 import types
+from batdetect2.detector.parameters import MAX_FREQ_HZ, MIN_FREQ_HZ
+
 
 def convert_int_to_freq(spec_ind, spec_height, min_freq, max_freq):
+    """Convert spectrogram index to frequency in Hz.""" ""
     spec_ind = spec_height - spec_ind
     return round(
         (spec_ind / float(spec_height)) * (max_freq - min_freq) + min_freq, 2
     )
 
 
-def extract_spec_slices(spec, pred_nms, params):
-    """
-    Extracts spectrogram slices from spectrogram based on detected call locations.
-    """
+def extract_spec_slices(spec, pred_nms):
+    """Extract spectrogram slices from spectrogram.
 
+    The slices are extracted based on detected call locations.
+    """
     x_pos = pred_nms["x_pos"]
-    y_pos = pred_nms["y_pos"]
     bb_width = pred_nms["bb_width"]
-    bb_height = pred_nms["bb_height"]
     slices = []
 
     # add 20% padding either side of call
@@ -35,100 +40,273 @@ def extract_spec_slices(spec, pred_nms, params):
     return slices
 
 
-def get_feature_names():
-    feature_names = [
-        "duration",
-        "low_freq_bb",
-        "high_freq_bb",
-        "bandwidth",
-        "max_power_bb",
-        "max_power",
-        "max_power_first",
-        "max_power_second",
-        "call_interval",
-    ]
-    return feature_names
+def compute_duration(
+    prediction: types.Prediction,
+    **_,
+) -> float:
+    """Compute duration of call in seconds."""
+    return round(prediction["end_time"] - prediction["start_time"], 5)
 
 
-def get_feats(spec, pred_nms, params):
+def compute_low_freq(
+    prediction: types.Prediction,
+    **_,
+) -> float:
+    """Compute lowest frequency in call in Hz."""
+    return int(prediction["low_freq"])
+
+
+def compute_high_freq(
+    prediction: types.Prediction,
+    **_,
+) -> float:
+    """Compute highest frequency in call in Hz."""
+    return int(prediction["high_freq"])
+
+
+def compute_bandwidth(
+    prediction: types.Prediction,
+    **_,
+) -> float:
+    """Compute bandwidth of call in Hz."""
+    return int(prediction["high_freq"] - prediction["low_freq"])
+
+
+def compute_max_power_bb(
+    prediction: types.Prediction,
+    spec: Optional[np.ndarray] = None,
+    min_freq: int = MIN_FREQ_HZ,
+    max_freq: int = MAX_FREQ_HZ,
+    **_,
+) -> float:
+    """Compute frequency with maximum power in call in Hz.
+
+    This is the frequency with the maximum power in the bounding box of the
+    call.
     """
-    Extracts features from spectrogram based on detected call locations.
-    Condsider re-extracting spectrogram for this to get better temporal resolution.
+    if spec is None:
+        return np.nan
+
+    x_start = max(0, prediction["x_pos"])
+    x_end = min(
+        spec.shape[1] - 1, prediction["x_pos"] + prediction["bb_width"]
+    )
+
+    # y low is the lowest freq but it will have a higher value due to array
+    # starting at 0 at top
+    y_low = min(spec.shape[0] - 1, prediction["y_pos"])
+    y_high = max(0, prediction["y_pos"] - prediction["bb_height"])
+
+    spec_bb = spec[y_high:y_low, x_start:x_end]
+    power_per_freq_band = np.sum(spec_bb, axis=1)
+
+    try:
+        max_power_ind = np.argmax(power_per_freq_band)
+    except ValueError:
+        # If the call is too short, the bounding box might be empty.
+        # In this case, return NaN.
+        return np.nan
+
+    return int(
+        convert_int_to_freq(
+            y_high + max_power_ind,
+            spec.shape[0],
+            min_freq,
+            max_freq,
+        )
+    )
+
+
+def compute_max_power(
+    prediction: types.Prediction,
+    spec: Optional[np.ndarray] = None,
+    min_freq: int = MIN_FREQ_HZ,
+    max_freq: int = MAX_FREQ_HZ,
+    **_,
+) -> float:
+    """Compute frequency with maximum power in during the call in Hz."""
+    if spec is None:
+        return np.nan
+
+    x_start = max(0, prediction["x_pos"])
+    x_end = min(
+        spec.shape[1] - 1, prediction["x_pos"] + prediction["bb_width"]
+    )
+    spec_call = spec[:, x_start:x_end]
+    power_per_freq_band = np.sum(spec_call, axis=1)
+    max_power_ind = np.argmax(power_per_freq_band)
+    return int(
+        convert_int_to_freq(
+            max_power_ind,
+            spec.shape[0],
+            min_freq,
+            max_freq,
+        )
+    )
+
+
+def compute_max_power_first(
+    prediction: types.Prediction,
+    spec: Optional[np.ndarray] = None,
+    min_freq: int = MIN_FREQ_HZ,
+    max_freq: int = MAX_FREQ_HZ,
+    **_,
+) -> float:
+    """Compute frequency with maximum power in first half of call in Hz."""
+    if spec is None:
+        return np.nan
+
+    x_start = max(0, prediction["x_pos"])
+    x_end = min(
+        spec.shape[1] - 1, prediction["x_pos"] + prediction["bb_width"]
+    )
+    spec_call = spec[:, x_start:x_end]
+    first_half = spec_call[:, : int(spec_call.shape[1] / 2)]
+    power_per_freq_band = np.sum(first_half, axis=1)
+    max_power_ind = np.argmax(power_per_freq_band)
+    return int(
+        convert_int_to_freq(
+            max_power_ind,
+            spec.shape[0],
+            min_freq,
+            max_freq,
+        )
+    )
+
+
+def compute_max_power_second(
+    prediction: types.Prediction,
+    spec: Optional[np.ndarray] = None,
+    min_freq: int = MIN_FREQ_HZ,
+    max_freq: int = MAX_FREQ_HZ,
+    **_,
+) -> float:
+    """Compute frequency with maximum power in second half of call in Hz."""
+    if spec is None:
+        return np.nan
+
+    x_start = max(0, prediction["x_pos"])
+    x_end = min(
+        spec.shape[1] - 1, prediction["x_pos"] + prediction["bb_width"]
+    )
+    spec_call = spec[:, x_start:x_end]
+    second_half = spec_call[:, int(spec_call.shape[1] / 2) :]
+    power_per_freq_band = np.sum(second_half, axis=1)
+    max_power_ind = np.argmax(power_per_freq_band)
+    return int(
+        convert_int_to_freq(
+            max_power_ind,
+            spec.shape[0],
+            min_freq,
+            max_freq,
+        )
+    )
+
+
+def compute_call_interval(
+    prediction: types.Prediction,
+    previous: Optional[types.Prediction] = None,
+    **_,
+) -> float:
+    """Compute time between this call and the previous call in seconds."""
+    if previous is None:
+        return np.nan
+    return round(prediction["start_time"] - previous["end_time"], 5)
+
+
+# NOTE: The order of the features in this dictionary is important. The
+# features are extracted in this order and the order of the columns in the
+# output csv file is determined by this order. In order to avoid breaking
+# changes in the output csv file, new features should be added to the end of
+# this dictionary.
+FEATURES: Dict[str, types.FeatureExtractor] = {
+    "duration": compute_duration,
+    "low_freq_bb": compute_low_freq,
+    "high_freq_bb": compute_high_freq,
+    "bandwidth": compute_bandwidth,
+    "max_power_bb": compute_max_power_bb,
+    "max_power": compute_max_power,
+    "max_power_first": compute_max_power_first,
+    "max_power_second": compute_max_power_second,
+    "call_interval": compute_call_interval,
+}
+
+
+def get_feats(
+    spec: np.ndarray,
+    pred_nms: types.PredictionResults,
+    params: types.FeatureExtractionParameters,
+):
+    """Extract features from spectrogram based on detected call locations.
+
+    The features extracted are:
+
+    - duration: duration of call in seconds
+    - low_freq: lowest frequency in call in kHz
+    - high_freq: highest frequency in call in kHz
+    - bandwidth: high_freq - low_freq
+    - max_power_bb: frequency with maximum power in call in kHz
+    - max_power: frequency with maximum power in spectrogram in kHz
+    - max_power_first: frequency with maximum power in first half of call in
+    kHz.
+    - max_power_second: frequency with maximum power in second half of call in
+    kHz.
+    - call_interval: time between this call and the previous call in seconds
+
+    Consider re-extracting spectrogram for this to get better temporal
+    resolution.
 
     For more possible features check out:
     https://github.com/YvesBas/Tadarida-D/blob/master/Manual_Tadarida-D.odt
+
+    Parameters
+    ----------
+    spec : np.ndarray
+        Spectrogram from which to extract features.
+
+    pred_nms : types.PredictionResults
+        Information about detected calls from which to extract features.
+
+    params : types.FeatureExtractionParameters
+        Parameters for feature extraction.
+
+    Returns
+    -------
+    features : np.ndarray
+        Extracted features for each detected call. Shape is
+        (num_detections, num_features).
     """
-
-    x_pos = pred_nms["x_pos"]
-    y_pos = pred_nms["y_pos"]
-    bb_width = pred_nms["bb_width"]
-    bb_height = pred_nms["bb_height"]
-
-    feature_names = get_feature_names()
     num_detections = len(pred_nms["det_probs"])
-    features = (
-        np.ones((num_detections, len(feature_names)), dtype=np.float32) * -1
-    )
+    features = np.empty((num_detections, len(FEATURES)), dtype=np.float32)
+    previous = None
 
-    for ff in range(num_detections):
-        x_start = int(np.maximum(0, x_pos[ff]))
-        x_end = int(
-            np.minimum(spec.shape[1] - 1, np.round(x_pos[ff] + bb_width[ff]))
-        )
-        # y low is the lowest freq but it will have a higher value due to array starting at 0 at top
-        y_low = int(np.minimum(spec.shape[0] - 1, y_pos[ff]))
-        y_high = int(np.maximum(0, np.round(y_pos[ff] - bb_height[ff])))
-        spec_slice = spec[:, x_start:x_end]
+    for row in range(num_detections):
+        prediction: types.Prediction = {
+            "det_prob": float(pred_nms["det_probs"][row]),
+            "class_prob": pred_nms["class_probs"][:, row],
+            "start_time": float(pred_nms["start_times"][row]),
+            "end_time": float(pred_nms["end_times"][row]),
+            "low_freq": float(pred_nms["low_freqs"][row]),
+            "high_freq": float(pred_nms["high_freqs"][row]),
+            "x_pos": int(pred_nms["x_pos"][row]),
+            "y_pos": int(pred_nms["y_pos"][row]),
+            "bb_width": int(pred_nms["bb_width"][row]),
+            "bb_height": int(pred_nms["bb_height"][row]),
+        }
 
-        if spec_slice.shape[1] > 1:
-            features[ff, 0] = round(
-                pred_nms["end_times"][ff] - pred_nms["start_times"][ff], 5
-            )
-            features[ff, 1] = int(pred_nms["low_freqs"][ff])
-            features[ff, 2] = int(pred_nms["high_freqs"][ff])
-            features[ff, 3] = int(
-                pred_nms["high_freqs"][ff] - pred_nms["low_freqs"][ff]
-            )
-            features[ff, 4] = int(
-                convert_int_to_freq(
-                    y_high + spec_slice[y_high:y_low, :].sum(1).argmax(),
-                    spec.shape[0],
-                    params["min_freq"],
-                    params["max_freq"],
-                )
-            )
-            features[ff, 5] = int(
-                convert_int_to_freq(
-                    spec_slice.sum(1).argmax(),
-                    spec.shape[0],
-                    params["min_freq"],
-                    params["max_freq"],
-                )
-            )
-            hlf_val = spec_slice.shape[1] // 2
-
-            features[ff, 6] = int(
-                convert_int_to_freq(
-                    spec_slice[:, :hlf_val].sum(1).argmax(),
-                    spec.shape[0],
-                    params["min_freq"],
-                    params["max_freq"],
-                )
-            )
-            features[ff, 7] = int(
-                convert_int_to_freq(
-                    spec_slice[:, hlf_val:].sum(1).argmax(),
-                    spec.shape[0],
-                    params["min_freq"],
-                    params["max_freq"],
-                )
+        for col, feature in enumerate(FEATURES.values()):
+            features[row, col] = feature(
+                prediction,
+                previous=previous,
+                spec=spec,
+                **params,
             )
 
-            if ff > 0:
-                features[ff, 8] = round(
-                    pred_nms["start_times"][ff]
-                    - pred_nms["start_times"][ff - 1],
-                    5,
-                )
+        previous = prediction
 
     return features
+
+
+def get_feature_names():
+    """Get names of features in the order they are extracted."""
+    return list(FEATURES.keys())

batdetect2/types.py

@@ -1,5 +1,5 @@
 """Types used in the code base."""
-from typing import List, NamedTuple, Optional
+from typing import List, NamedTuple, Optional, Union
 
 import numpy as np
 import torch
@@ -25,10 +25,13 @@ except ImportError:
 __all__ = [
     "Annotation",
     "DetectionModel",
+    "FeatureExtractionParameters",
+    "FeatureExtractor",
     "FileAnnotations",
     "ModelOutput",
     "ModelParameters",
     "NonMaximumSuppressionConfig",
+    "Prediction",
     "PredictionResults",
     "ProcessingConfiguration",
     "ResultParams",
@@ -312,6 +315,40 @@ class ModelOutput(NamedTuple):
     """Tensor with intermediate features."""
 
 
+class Prediction(TypedDict):
+    """Singe prediction."""
+
+    det_prob: float
+    """Detection probability."""
+
+    x_pos: int
+    """X position of the detection in pixels."""
+
+    y_pos: int
+    """Y position of the detection in pixels."""
+
+    bb_width: int
+    """Width of the detection in pixels."""
+
+    bb_height: int
+    """Height of the detection in pixels."""
+
+    start_time: float
+    """Start time of the detection in seconds."""
+
+    end_time: float
+    """End time of the detection in seconds."""
+
+    low_freq: float
+    """Low frequency of the detection in Hz."""
+
+    high_freq: float
+    """High frequency of the detection in Hz."""
+
+    class_prob: np.ndarray
+    """Vector holding the probability of each class."""
+
+
 class PredictionResults(TypedDict):
     """Results of the prediction.
 
@@ -418,6 +455,16 @@ class NonMaximumSuppressionConfig(TypedDict):
     """Threshold for detection probability."""
 
 
+class FeatureExtractionParameters(TypedDict):
+    """Parameters that control the feature extraction function."""
+
+    min_freq: int
+    """Minimum frequency to consider in Hz."""
+
+    max_freq: int
+    """Maximum frequency to consider in Hz."""
+
+
 class HeatmapParameters(TypedDict):
     """Parameters that control the heatmap generation function."""
 
@@ -473,3 +520,11 @@ class AnnotationGroup(TypedDict):
 
     y_inds: NotRequired[np.ndarray]
     """Y coordinate of the annotations in the spectrogram."""
+
+
+class FeatureExtractor(Protocol):
+    """Protocol for feature extractors."""
+
+    def __call__(self, prediction: Prediction, **kwargs) -> Union[float, int]:
+        """Extract features from a prediction."""
+        ...

batdetect2/utils/detector_utils.py

@@ -773,7 +773,7 @@ def process_file(
         )
 
         # convert to numpy
-        spec_np = spec.detach().cpu().numpy()
+        spec_np = spec.detach().cpu().numpy().squeeze()
 
         # add chunk time to start and end times
         pred_nms["start_times"] += chunk_time
@@ -794,7 +794,7 @@ def process_file(
         if config["spec_slices"]:
             # FIX: This is not currently working. Returns empty slices
             spec_slices.extend(
-                feats.extract_spec_slices(spec_np, pred_nms, config)
+                feats.extract_spec_slices(spec_np, pred_nms)
             )
 
     # Merge results from chunks

pyproject.toml

@@ -56,7 +56,7 @@ build-backend = "pdm.pep517.api"
 batdetect2 = "batdetect2.cli:cli"
 
 [tool.black]
-line-length = 80
+line-length = 79
 
 [[tool.mypy.overrides]]
 module = [

tests/test_cli.py

@@ -1,5 +1,7 @@
 """Test the command line interface."""
+from pathlib import Path
 from click.testing import CliRunner
+import pandas as pd
 
 from batdetect2.cli import cli
 
@@ -67,3 +69,42 @@ def test_cli_detect_command_with_non_trivial_time_expansion(tmp_path):
 
     assert result.exit_code == 0
     assert 'Time Expansion Factor: 10' in result.stdout
+
+
+
+def test_cli_detect_command_with_the_spec_feature_flag(tmp_path: Path):
+    """Test the detect command with the spec feature flag."""
+    results_dir = tmp_path / "results"
+
+    # Remove results dir if it exists
+    if results_dir.exists():
+        results_dir.rmdir()
+
+    runner = CliRunner()
+    result = runner.invoke(
+        cli,
+        [
+            "detect",
+            "example_data/audio",
+            str(results_dir),
+            "0.3",
+            "--spec_features",
+        ],
+    )
+    assert result.exit_code == 0
+    assert results_dir.exists()
+
+
+    csv_files = [path.name for path in results_dir.glob("*.csv")]
+
+    expected_files = [
+        "20170701_213954-MYOMYS-LR_0_0.5.wav_spec_features.csv",
+        "20180530_213516-EPTSER-LR_0_0.5.wav_spec_features.csv",
+        "20180627_215323-RHIFER-LR_0_0.5.wav_spec_features.csv"
+    ]
+
+    for expected_file in expected_files:
+        assert expected_file in csv_files
+
+        df = pd.read_csv(results_dir / expected_file)
+        assert not (df.duration == -1).any()

tests/test_features.py

@@ -0,0 +1,291 @@
+"""Test suite for feature extraction functions."""
+
+import logging
+
+import librosa
+import numpy as np
+import pytest
+
+import batdetect2.detector.compute_features as feats
+from batdetect2 import api, types
+from batdetect2.utils import audio_utils as au
+
+numba_logger = logging.getLogger("numba")
+numba_logger.setLevel(logging.WARNING)
+
+
+def index_to_freq(
+    index: int,
+    spec_height: int,
+    min_freq: int,
+    max_freq: int,
+) -> float:
+    """Convert spectrogram index to frequency in Hz."""
+    index = spec_height - index
+    return round(
+        (index / float(spec_height)) * (max_freq - min_freq) + min_freq, 2
+    )
+
+
+def index_to_time(
+    index: int,
+    spec_width: int,
+    spec_duration: float,
+) -> float:
+    """Convert spectrogram index to time in seconds."""
+    return round((index / float(spec_width)) * spec_duration, 2)
+
+
+def test_get_feats_function_with_empty_spectrogram():
+    """Test get_feats function with empty spectrogram.
+
+    This tests that the overall flow of the function works, even if the
+    spectrogram is empty.
+    """
+    spec_duration = 3
+    spec_width = 100
+    spec_height = 100
+    min_freq = 10_000
+    max_freq = 120_000
+    spectrogram = np.zeros((spec_height, spec_width))
+
+    x_pos = 20
+    y_pos = 80
+    bb_width = 20
+    bb_height = 20
+
+    start_time = index_to_time(x_pos, spec_width, spec_duration)
+    end_time = index_to_time(x_pos + bb_width, spec_width, spec_duration)
+    low_freq = index_to_freq(y_pos, spec_height, min_freq, max_freq)
+    high_freq = index_to_freq(
+        y_pos - bb_height, spec_height, min_freq, max_freq
+    )
+
+    pred_nms: types.PredictionResults = {
+        "det_probs": np.array([1]),
+        "class_probs": np.array([[1]]),
+        "x_pos": np.array([x_pos]),
+        "y_pos": np.array([y_pos]),
+        "bb_width": np.array([bb_width]),
+        "bb_height": np.array([bb_height]),
+        "start_times": np.array([start_time]),
+        "end_times": np.array([end_time]),
+        "low_freqs": np.array([low_freq]),
+        "high_freqs": np.array([high_freq]),
+    }
+
+    params: types.FeatureExtractionParameters = {
+        "min_freq": min_freq,
+        "max_freq": max_freq,
+    }
+
+    features = feats.get_feats(spectrogram, pred_nms, params)
+    assert low_freq < high_freq
+    assert isinstance(features, np.ndarray)
+    assert features.shape == (len(pred_nms["det_probs"]), 9)
+    assert np.isclose(
+        features[0],
+        np.array(
+            [
+                end_time - start_time,
+                low_freq,
+                high_freq,
+                high_freq - low_freq,
+                high_freq,
+                max_freq,
+                max_freq,
+                max_freq,
+                np.nan,
+            ]
+        ),
+        equal_nan=True,
+    ).all()
+
+
+@pytest.mark.parametrize(
+    "max_power",
+    [
+        30_000,
+        31_000,
+        32_000,
+        33_000,
+        34_000,
+        35_000,
+        36_000,
+        37_000,
+        38_000,
+        39_000,
+        40_000,
+    ],
+)
+def test_compute_max_power_bb(max_power: int):
+    """Test compute_max_power_bb function."""
+    duration = 1
+    samplerate = 256_000
+    min_freq = 0
+    max_freq = 128_000
+
+    start_time = 0.3
+    end_time = 0.6
+    low_freq = 30_000
+    high_freq = 40_000
+
+    audio = np.zeros((int(duration * samplerate),))
+
+    # Add a signal during the time and frequency range of interest
+    audio[
+        int(start_time * samplerate) : int(end_time * samplerate)
+    ] = 0.5 * librosa.tone(
+        max_power, sr=samplerate, duration=end_time - start_time
+    )
+
+    # Add a more powerful signal outside frequency range of interest
+    audio[
+        int(start_time * samplerate) : int(end_time * samplerate)
+    ] += 2 * librosa.tone(
+        80_000, sr=samplerate, duration=end_time - start_time
+    )
+
+    params = api.get_config(
+        min_freq=min_freq,
+        max_freq=max_freq,
+        target_samp_rate=samplerate,
+    )
+
+    spec, _ = au.generate_spectrogram(
+        audio,
+        samplerate,
+        params,
+    )
+
+    x_start = int(
+        au.time_to_x_coords(
+            start_time,
+            samplerate,
+            params["fft_win_length"],
+            params["fft_overlap"],
+        )
+    )
+
+    x_end = int(
+        au.time_to_x_coords(
+            end_time,
+            samplerate,
+            params["fft_win_length"],
+            params["fft_overlap"],
+        )
+    )
+
+    num_freq_bins = spec.shape[0]
+    y_low = num_freq_bins - int(num_freq_bins * low_freq / max_freq)
+    y_high = num_freq_bins - int(num_freq_bins * high_freq / max_freq)
+
+    prediction: types.Prediction = {
+        "det_prob": 1,
+        "class_prob": np.ones((1,)),
+        "x_pos": x_start,
+        "y_pos": int(y_low),
+        "bb_width": int(x_end - x_start),
+        "bb_height": int(y_low - y_high),
+        "start_time": start_time,
+        "end_time": end_time,
+        "low_freq": low_freq,
+        "high_freq": high_freq,
+    }
+
+    print(prediction)
+
+    max_power_bb = feats.compute_max_power_bb(
+        prediction,
+        spec,
+        min_freq=min_freq,
+        max_freq=max_freq,
+    )
+
+    assert abs(max_power_bb - max_power) <= 500
+
+
+def test_compute_max_power():
+    """Test compute_max_power_bb function."""
+    duration = 3
+    samplerate = 16_000
+    min_freq = 0
+    max_freq = 8_000
+
+    start_time = 1
+    end_time = 2
+    low_freq = 3_000
+    high_freq = 4_000
+    max_power = 5_000
+
+    audio = np.zeros((int(duration * samplerate),))
+
+    # Add a signal during the time and frequency range of interest
+    audio[
+        int(start_time * samplerate) : int(end_time * samplerate)
+    ] = 0.5 * librosa.tone(
+        3_500, sr=samplerate, duration=end_time - start_time
+    )
+
+    # Add a more powerful signal outside frequency range of interest
+    audio[
+        int(start_time * samplerate) : int(end_time * samplerate)
+    ] += 2 * librosa.tone(
+        max_power, sr=samplerate, duration=end_time - start_time
+    )
+
+    params = api.get_config(
+        min_freq=min_freq,
+        max_freq=max_freq,
+        target_samp_rate=samplerate,
+    )
+
+    spec, _ = au.generate_spectrogram(
+        audio,
+        samplerate,
+        params,
+    )
+
+    x_start = int(
+        au.time_to_x_coords(
+            start_time,
+            samplerate,
+            params["fft_win_length"],
+            params["fft_overlap"],
+        )
+    )
+
+    x_end = int(
+        au.time_to_x_coords(
+            end_time,
+            samplerate,
+            params["fft_win_length"],
+            params["fft_overlap"],
+        )
+    )
+
+    num_freq_bins = spec.shape[0]
+    y_low = int(num_freq_bins * low_freq / max_freq)
+    y_high = int(num_freq_bins * high_freq / max_freq)
+
+    prediction: types.Prediction = {
+        "det_prob": 1,
+        "class_prob": np.ones((1,)),
+        "x_pos": x_start,
+        "y_pos": int(y_high),
+        "bb_width": int(x_end - x_start),
+        "bb_height": int(y_high - y_low),
+        "start_time": start_time,
+        "end_time": end_time,
+        "low_freq": low_freq,
+        "high_freq": high_freq,
+    }
+
+    computed_max_power = feats.compute_max_power(
+        prediction,
+        spec,
+        min_freq=min_freq,
+        max_freq=max_freq,
+    )
+
+    assert abs(computed_max_power - max_power) < 100