Multimedia_AAC_Project/source/level_1/tests/test_SSC.py

import numpy as np
import pytest

# Adjust the import based on package/module layout.
from level_1.level_1 import SSC

# Helper "fixtures" for SSC
# -----------------------------------------------------------------------------

def _next_frame_no_attack() -> np.ndarray:
    """
    Build a next_frame_T that should NOT trigger ESH detection.

    Uses exact zeros so all s2l are zero and the ESH condition (s2l > 1e-3) cannot hold.
    """
    return np.zeros((2048, 2), dtype=np.float64)


def _next_frame_strong_attack(
    *,
    attack_left: bool,
    attack_right: bool,
    segment_l: int = 4,
    baseline: float = 1e-6,
    burst_amp: float = 1.0,
) -> np.ndarray:
    """
    Build a next_frame_T (2048x2) that should trigger ESH detection on selected channels.

    Spec: ESH if exists l in {1..7} with s2l > 1e-3 AND ds2l > 10.
    We create:
      - small baseline energy in all samples (avoids division by zero in ds2l),
      - a strong burst inside one 128-sample segment l in 1..7.
    """
    assert 1 <= segment_l <= 7
    x = np.full((2048, 2), baseline, dtype=np.float64)

    a = segment_l * 128
    b = (segment_l + 1) * 128

    if attack_left:
        x[a:b, 0] += burst_amp
    if attack_right:
        x[a:b, 1] += burst_amp

    return x


def _next_frame_below_s2l_threshold(
    *,
    left: bool,
    right: bool,
    segment_l: int = 4,
    impulse_amp: float = 0.01,
) -> np.ndarray:
    """
    Construct a next_frame_T where s2l is below 1e-3, so ESH must NOT be triggered,
    even if ds2l could be large.

    Put a single impulse of amplitude 'impulse_amp' inside a segment.
    Energy in the 128-sample segment: s2l ~= impulse_amp^2.
    With impulse_amp=0.01 => s2l ~= 1e-4 < 1e-3.
    """
    assert 1 <= segment_l <= 7
    x = np.zeros((2048, 2), dtype=np.float64)

    idx = segment_l * 128 + 10  # inside segment
    if left:
        x[idx, 0] = impulse_amp
    if right:
        x[idx, 1] = impulse_amp

    return x


# ---------------------------------------------------------------------
# 1) Fixed/mandatory cases (prev frame type forces current type)
# ---------------------------------------------------------------------

def test_ssc_fixed_cases_prev_lss_and_lps() -> None:
    """
    Spec: if prev was:
      - LSS => current MUST be ESH
      - LPS => current MUST be OLS
    independent of next frame check.
    """
    frame_t = np.zeros((2048, 2), dtype=np.float64)

    # Even if next frame has a strong attack, LSS must force ESH.
    next_attack = _next_frame_strong_attack(attack_left=True, attack_right=True)
    out1 = SSC(frame_t, next_attack, "LSS")
    assert out1 == "ESH"

    # Even if next frame has a strong attack, LPS must force OLS.
    out2 = SSC(frame_t, next_attack, "LPS")
    assert out2 == "OLS"


# ---------------------------------------------------------------------
# 2) Cases requiring next-frame ESH prediction (energy/attack computation)
# ---------------------------------------------------------------------

def test_prev_ols_next_not_esh_returns_ols() -> None:
    """
    Spec: if prev=OLS, current is OLS or LSS.
    Choose LSS iff (i+1) predicted ESH, else OLS.
    """
    frame_t = np.zeros((2048, 2), dtype=np.float64)
    next_t = _next_frame_no_attack()

    out = SSC(frame_t, next_t, "OLS")
    assert out == "OLS"


def test_prev_ols_next_esh_both_channels_returns_lss() -> None:
    """
    prev=OLS, next predicted ESH (both channels) => per-channel decisions are LSS and LSS
    and merge table keeps LSS.
    """
    frame_t = np.zeros((2048, 2), dtype=np.float64)
    next_t = _next_frame_strong_attack(attack_left=True, attack_right=True)

    out = SSC(frame_t, next_t, "OLS")
    assert out == "LSS"


def test_prev_ols_next_esh_one_channel_returns_lss() -> None:
    """
    prev=OLS:
      - one channel predicts ESH => LSS
      - other channel predicts not ESH => OLS
    Merge table: OLS + LSS => LSS.
    """
    frame_t = np.zeros((2048, 2), dtype=np.float64)

    next1_t = _next_frame_strong_attack(attack_left=True, attack_right=False)
    out1 = SSC(frame_t, next1_t, "OLS")
    assert out1 == "LSS"

    next2_t = _next_frame_strong_attack(attack_left=False, attack_right=True)
    out2 = SSC(frame_t, next2_t, "OLS")
    assert out2 == "LSS"


def test_prev_esh_next_esh_both_channels_returns_esh() -> None:
    """
    prev=ESH:
      - next predicted ESH => current ESH (per-channel)
    Merge table: ESH + ESH => ESH.
    """
    frame_t = np.zeros((2048, 2), dtype=np.float64)
    next_t = _next_frame_strong_attack(attack_left=True, attack_right=True)

    out = SSC(frame_t, next_t, "ESH")
    assert out == "ESH"


def test_prev_esh_next_not_esh_both_channels_returns_lps() -> None:
    """
    prev=ESH:
      - next not predicted ESH => current LPS (per-channel)
    Merge table: LPS + LPS => LPS.
    """
    frame_t = np.zeros((2048, 2), dtype=np.float64)
    next_t = _next_frame_no_attack()

    out = SSC(frame_t, next_t, "ESH")
    assert out == "LPS"


def test_prev_esh_next_esh_one_channel_merged_is_esh() -> None:
    """
    prev=ESH:
      - one channel predicts ESH => ESH
      - other channel predicts not ESH => LPS
    Merge table: ESH + LPS => ESH.
    """
    frame_t = np.zeros((2048, 2), dtype=np.float64)

    next1_t = _next_frame_strong_attack(attack_left=True, attack_right=False)
    out1 = SSC(frame_t, next1_t, "ESH")
    assert out1 == "ESH"

    next2_t = _next_frame_strong_attack(attack_left=True, attack_right=False)
    out2 = SSC(frame_t, next2_t, "ESH")
    assert out2 == "ESH"

def test_threshold_s2l_must_exceed_1e_3() -> None:
    """
    Spec: next frame is ESH only if s2l > 1e-3 AND ds2l > 10 for some l in 1..7.
    This test checks the necessity of the s2l threshold:
      - Create a frame with s2l ~= 1e-4 < 1e-3 (single impulse with amp 0.01).
      - Expect: not classified as ESH -> for prev=OLS return OLS.
    """
    frame_t = np.zeros((2048, 2), dtype=np.float64)
    next_t = _next_frame_below_s2l_threshold(left=True, right=True, impulse_amp=0.01)

    out = SSC(frame_t, next_t, "OLS")
    assert out == "OLS"