### Vector Correlation Calculation Setup

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/silk/sigproc_fix.rs.html

Initializes parameters for vector correlation calculation, including setting up indices and handling positive shifts.

```rust
pub fn silk_corr_vector_fix(
    x: &[i16],
    t: &[i16],
    l: usize,
    order: usize,
    xt: &mut [i32],
    rshifts: i32,
) {
    let mut ptr1_idx = order - 1;
    if rshifts > 0 {
        for xt_val in xt[..order].iter_mut() {

```

--------------------------------

### CeltEncoder::encode_with_start_band Method

Source: https://docs.rs/opus-rs/0.1.17/opus_rs/celt/struct.CeltEncoder.html

Encodes a frame of PCM audio data, specifying a starting band for encoding. Requires mutable access to self and a RangeCoder.

```rust
pub fn encode_with_start_band( &mut self, pcm: &[f32], frame_size: usize, rc: &mut RangeCoder, start_band: usize, )
```

--------------------------------

### Setup Silk Encoder Sample Rate

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/silk/control_codec.rs.html

Configures the Silk encoder's state based on the provided sample rate and packet size. It adjusts frame lengths, pitch window lengths, and other internal parameters.

```rust
use crate::silk::define::*;
use crate::silk::structs::*;
use crate::silk::tables_nlsf::*;

pub const FIND_PITCH_LPC_WIN_MS: i32 = 20 + (LA_PITCH_MS as i32 * 2);
pub const FIND_PITCH_LPC_WIN_MS_2_SF: i32 = 10 + (LA_PITCH_MS as i32 * 2);
pub const MAX_DEL_DEC_STATES: i32 = 4;
pub const LA_SHAPE_MAX: i32 = LA_SHAPE_MS as i32 * MAX_FS_KHZ as i32;
pub const SHAPE_LPC_WIN_MAX: i32 = 15 * MAX_FS_KHZ as i32;

pub const WARPING_MULTIPLIER_Q16: i32 = 983;

pub fn silk_setup_fs(ps_enc: &mut SilkEncoderState, fs_khz: i32, packet_size_ms: i32) -> i32 {
    let cmn = &mut ps_enc.s_cmn;

    if packet_size_ms <= 10 {
        cmn.n_frames_per_packet = 1;
        cmn.nb_subfr = if packet_size_ms == 10 { 2 } else { 1 };
        cmn.frame_length = packet_size_ms * fs_khz;
        cmn.pitch_lpc_win_length = FIND_PITCH_LPC_WIN_MS_2_SF * fs_khz;
    } else {
        cmn.n_frames_per_packet = packet_size_ms / MAX_FRAME_LENGTH_MS as i32;
        cmn.nb_subfr = MAX_NB_SUBFR as i32;
        cmn.frame_length = 20 * fs_khz;
        cmn.pitch_lpc_win_length = FIND_PITCH_LPC_WIN_MS * fs_khz;
    }
    cmn.packet_size_ms = packet_size_ms;

    if cmn.fs_khz != fs_khz {
        ps_enc.s_nsq = SilkNSQState::default();
        cmn.prev_nlsf_q15 = [0; MAX_LPC_ORDER];

        cmn.prev_lag = 100;
        cmn.first_frame_after_reset = 1;
        ps_enc.s_shape.last_gain_index = 10;
        ps_enc.s_nsq.lag_prev = 100;
        ps_enc.s_nsq.prev_gain_q16 = 65536;
        cmn.prev_signal_type = TYPE_NO_VOICE_ACTIVITY;

        cmn.fs_khz = fs_khz;

        if fs_khz == 8 || fs_khz == 12 {
            cmn.predict_lpc_order = MIN_LPC_ORDER as i32;
            ps_enc.ps_nlsf_cb = Some(&SILK_NLSF_CB_NB_MB);
        } else {
            cmn.predict_lpc_order = MAX_LPC_ORDER as i32;
            ps_enc.ps_nlsf_cb = Some(&SILK_NLSF_CB_WB);
        }

        cmn.subfr_length = SUB_FRAME_LENGTH_MS as i32 * fs_khz;
        cmn.frame_length = cmn.subfr_length * cmn.nb_subfr;
        cmn.ltp_mem_length = LTP_MEM_LENGTH_MS as i32 * fs_khz;
        cmn.la_pitch = LA_PITCH_MS as i32 * fs_khz;

        if cmn.nb_subfr == MAX_NB_SUBFR as i32 {
            cmn.pitch_lpc_win_length = FIND_PITCH_LPC_WIN_MS * fs_khz;
        } else {
            cmn.pitch_lpc_win_length = FIND_PITCH_LPC_WIN_MS_2_SF * fs_khz;
        }
    }

    SILK_NO_ERROR
}
```

--------------------------------

### Setup Silk Encoder State

Source: https://docs.rs/opus-rs/0.1.17/opus_rs/silk/control_codec/fn.silk_setup_fs.html

Initializes the Silk encoder state with specified sample rate and packet size. This function is used to configure the encoder before processing audio data.

```rust
pub fn silk_setup_fs(
    ps_enc: &mut SilkEncoderState,
    fs_khz: i32,
    packet_size_ms: i32,
) -> i32
```

--------------------------------

### Function silk_setup_fs

Source: https://docs.rs/opus-rs/0.1.17/opus_rs/silk/control_codec/fn.silk_setup_fs.html

Sets up the Silk encoder state with the specified sample rate and packet size.

```APIDOC
## Function silk_setup_fs

### Description
Sets up the Silk encoder state with the specified sample rate and packet size.

### Method
N/A (Rust function)

### Endpoint
N/A (Rust function)

### Parameters
#### Path Parameters
N/A

#### Query Parameters
N/A

#### Request Body
N/A

### Request Example
N/A

### Response
#### Success Response (200)
N/A

#### Response Example
N/A

### Rust Signature
```rust
pub fn silk_setup_fs(
    ps_enc: &mut SilkEncoderState,
    fs_khz: i32,
    packet_size_ms: i32,
) -> i32
```

### Parameters (Rust)
- **ps_enc** (*&mut SilkEncoderState*) - A mutable reference to the Silk encoder state.
- **fs_khz** (*i32*) - The sample rate in kHz.
- **packet_size_ms** (*i32*) - The packet size in milliseconds.

### Return Value (Rust)
- (*i32*) - An integer representing the result of the setup operation. (Specific meaning depends on implementation, typically 0 for success).
```

--------------------------------

### Get Default CeltMode

Source: https://docs.rs/opus-rs/0.1.17/opus_rs/modes/fn.default_mode.html

Returns the default CeltMode configuration. No setup or imports are required.

```rust
pub fn default_mode() -> &'static CeltMode
```

--------------------------------

### Opus Decoder - Decode with Start Band

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/celt.rs.html

Decodes a compressed audio frame into PCM data, allowing specification of the starting frequency band for decoding.

```APIDOC
## POST /decode_with_start_band

### Description
Decodes a compressed audio frame into PCM data, specifying the starting frequency band.

### Method
POST

### Endpoint
/decode_with_start_band

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
- **compressed** (bytes) - Required - The compressed audio data.
- **frame_size** (usize) - Required - The size of the audio frame to decode.
- **pcm** (f32 array) - Required - A mutable slice to store the decoded PCM data.
- **start_band** (usize) - Required - The starting frequency band for decoding.

### Request Example
```json
{
  "compressed": "base64_encoded_audio_data",
  "frame_size": 1024,
  "pcm": [],
  "start_band": 1
}
```

### Response
#### Success Response (200)
- **usize** - The number of samples decoded.

#### Response Example
```json
{
  "decoded_samples": 1024
}
```
```

--------------------------------

### Decode Audio Frame with Start Band

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/celt.rs.html

Decodes a compressed audio frame, allowing specification of the starting frequency band. Useful for multi-channel or advanced decoding scenarios.

```rust
pub fn decode_with_start_band(
        &mut self,
        compressed: &[u8],
        frame_size: usize,
        pcm: &mut [f32],
        start_band: usize,
    ) -> usize {
        self.decode_impl(compressed, frame_size, pcm, start_band, self.mode.nb_ebands)
    }
```

--------------------------------

### kiss_fft Module Overview

Source: https://docs.rs/opus-rs/0.1.17/opus_rs/kiss_fft/index.html

Overview of the kiss_fft module, its structs, constants, and functions.

```APIDOC
## Module kiss_fft

This module provides Fast Fourier Transform (FFT) functionalities, likely a port or wrapper around the kiss_fft library.

### Structs

- **KissCpx**: Represents a complex number, likely used in FFT calculations.
- **KissFftState**: Holds the state for FFT computations.

### Constants

- **MAXFACTORS**: A constant related to the maximum factors allowed in FFT computations.

### Functions

- **opus_fft**: Performs a forward Fast Fourier Transform.
- **opus_fft_impl**: An implementation detail for the FFT function.
- **opus_ifft**: Performs an inverse Fast Fourier Transform.
```

--------------------------------

### CloneToUninit Implementation (Nightly)

Source: https://docs.rs/opus-rs/0.1.17/opus_rs/celt/struct.AnalysisInfo.html

Nightly-only experimental API for copying data to uninitialized memory. Use with caution.

```rust
unsafe fn clone_to_uninit(&self, dest: *mut u8)
```

--------------------------------

### Determine Fold Start for Spectral Folding

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/bands.rs.html

Determines the starting index for spectral folding based on the effective lowband absolute position. It finds the first band whose position is less than or equal to el_abs.

```rust
let mut fold_start = lowband_offset;
while fold_start > 0 {
    fold_start -= 1;
    if m_val * (e_bands[fold_start] as usize) <= el_abs {
        break;
    }
}
```

--------------------------------

### NEON Optimized PVQ Initialization

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/pvq.rs.html

This function initializes PVQ search using NEON intrinsics for ARM architectures. It computes absolute values and sums of input vectors in parallel.

```rust
#[cfg(target_arch = "aarch64")]
#[inline(always)]
#[allow(unsafe_op_in_unsafe_fn)]
unsafe fn pvq_fast_select_init_neon(
    x: &[f32],
    n: usize,
    abs_x: &mut [MaybeUninit<f32>; MAX_PVQ_N],
    signs: &mut [MaybeUninit<i32>; MAX_PVQ_N],
) -> f32 {
    use std::arch::aarch64::*
;

    let mut sum_vec = vdupq_n_f32(0.0);
    let mut i = 0;

    while i + 16 <= n {
        let vx0 = vld1q_f32(x.as_ptr().add(i));
        let vx1 = vld1q_f32(x.as_ptr().add(i + 4));
        let vx2 = vld1q_f32(x.as_ptr().add(i + 8));
        let vx3 = vld1q_f32(x.as_ptr().add(i + 12));

        let vabs0 = vabsq_f32(vx0);
        let vabs1 = vabsq_f32(vx1);
        let vabs2 = vabsq_f32(vx2);
        let vabs3 = vabsq_f32(vx3);

        vst1q_f32(abs_x.as_mut_ptr().add(i) as *mut f32, vabs0);
        vst1q_f32(abs_x.as_mut_ptr().add(i + 4) as *mut f32, vabs1);
        vst1q_f32(abs_x.as_mut_ptr().add(i + 8) as *mut f32, vabs2);
        vst1q_f32(abs_x.as_mut_ptr().add(i + 12) as *mut f32, vabs3);

        sum_vec = vaddq_f32(sum_vec, vabs0);
        sum_vec = vaddq_f32(sum_vec, vabs1);
        sum_vec = vaddq_f32(sum_vec, vabs2);
        sum_vec = vaddq_f32(sum_vec, vabs3);

        for j in 0..16 {
            signs[i + j].write(if x[i + j] < 0.0 { -1i32 } else { 1i32 });
        }

        i += 16;
    }

    while i + 8 <= n {
        let vx0 = vld1q_f32(x.as_ptr().add(i));
        let vx1 = vld1q_f32(x.as_ptr().add(i + 4));

        let vabs0 = vabsq_f32(vx0);
        let vabs1 = vabsq_f32(vx1);

        vst1q_f32(abs_x.as_mut_ptr().add(i) as *mut f32, vabs0);
        vst1q_f32(abs_x.as_mut_ptr().add(i + 4) as *mut f32, vabs1);

        sum_vec = vaddq_f32(sum_vec, vabs0);
        sum_vec = vaddq_f32(sum_vec, vabs1);

        for j in 0..8 {
            signs[i + j].write(if x[i + j] < 0.0 { -1i32 } else { 1i32 });
        }

        i += 8;
    }

    while i + 4 <= n {
        let vx = vld1q_f32(x.as_ptr().add(i));
        let vabs = vabsq_f32(vx);
        vst1q_f32(abs_x.as_mut_ptr().add(i) as *mut f32, vabs);
        sum_vec = vaddq_f32(sum_vec, vabs);

        for j in 0..4 {
            signs[i + j].write(if x[i + j] < 0.0 { -1i32 } else { 1i32 });
        }

        i += 4;
    }

    let mut sum = vaddvq_f32(sum_vec);

    for j in i..n {
        let abs_xi = x[j].abs();
        abs_x[j].write(abs_xi);
        sum += abs_xi;

```

--------------------------------

### Get FFT Size

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/kiss_fft.rs.html

Returns the FFT size (`nfft`) for the current state.

```rust
    #[inline]
    pub fn nfft(&self) -> usize {
        self.nfft
    }

```

--------------------------------

### Get Fractional Bit Count

Source: https://docs.rs/opus-rs/0.1.17/opus_rs/range_coder/struct.RangeCoder.html

Returns the current bit count as a fractional value.

```rust
pub fn tell_frac(&self) -> i32
```

--------------------------------

### Initialize Output Buffer and Masks

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/celt.rs.html

Initializes the output audio buffer and collapse masks. The output buffer is filled with zeros, and masks are prepared for signal processing.

```rust
self.w_x[..frame_size * channels].fill(0.0);

        let x_pad_end = (frame_size * channels + STRIDE_ACCESS_PAD).min(self.w_x.len());
        let x = &mut self.w_x[..x_pad_end];
        self.w_collapse_masks[..nb_ebands * channels].fill(0);
        let collapse_masks = &mut self.w_collapse_masks[..nb_ebands * channels];
```

--------------------------------

### Create New KissFftState

Source: https://docs.rs/opus-rs/0.1.17/opus_rs/kiss_fft/struct.KissFftState.html

Initializes a new KissFftState with a specified number of FFT points (nfft). Returns None if the nfft is invalid.

```rust
pub fn new(nfft: usize) -> Option<Self>
```

--------------------------------

### Get SilkDecoder Sample Rate

Source: https://docs.rs/opus-rs/0.1.17/opus_rs/silk/dec_api/struct.SilkDecoder.html

Retrieves the configured sample rate in Hz for the SilkDecoder.

```rust
pub fn sample_rate(&self) -> i32
```

--------------------------------

### Get SilkDecoder Frame Length

Source: https://docs.rs/opus-rs/0.1.17/opus_rs/silk/dec_api/struct.SilkDecoder.html

Retrieves the current frame length in samples for the SilkDecoder.

```rust
pub fn frame_length(&self) -> i32
```

--------------------------------

### Implement PartialEq for Bandwidth

Source: https://docs.rs/opus-rs/0.1.17/opus_rs/enum.Bandwidth.html

Allows comparison of Bandwidth values for equality using the `==` and `!=` operators. The default implementation is usually sufficient.

```rust
fn eq(&self, other: &Bandwidth) -> bool
```

```rust
fn ne(&self, other: &Rhs) -> bool
```

--------------------------------

### Prepare Lowband Views for Quantization

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/bands.rs.html

Prepares the views for lowband data (left and right channels) for quantization. It handles lowband scratch and effective lowband calculations.

```rust
let (lb_x, lb_out_x) = prepare_lowband_views(
    norm,
    lowband_scratch_ptr,
    allow_lowband_scratch,
    effective_lowband,
    norm_pos,
    n,
    !last,
);
let (lb_y, lb_out_y) = prepare_lowband_views(
    norm2,
    lowband_scratch_ptr,
    allow_lowband_scratch,
    effective_lowband,
    norm_pos,
    n,
    !last,
);
```

--------------------------------

### Function get_pulses

Source: https://docs.rs/opus-rs/0.1.17/opus_rs/rate/fn.get_pulses.html

This function is part of the opus_rs::rate module and is used to get pulses.

```APIDOC
## Function get_pulses

### Description
Retrieves pulses based on the provided integer input.

### Method
N/A (This is a function signature, not an HTTP endpoint)

### Endpoint
N/A

### Parameters
#### Path Parameters
N/A

#### Query Parameters
N/A

#### Request Body
N/A

### Request Example
N/A

### Response
#### Success Response (200)
N/A

#### Response Example
N/A

```rust
pub fn get_pulses(i: i32) -> i32
```
```

--------------------------------

### Initialize Stereo and Bit Allocation Buffers

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/celt.rs.html

Initializes buffers for stereo processing, pulse coding, fine priority, and bit allocation across frequency bands. This prepares for the main allocation and quantization steps.

```rust
let mut intensity = 0;
        let mut dual_stereo_val = if channels == 2 { 1 } else { 0 };
        let mut balance = 0;
        self.w_pulses[..nb_ebands].fill(0);
        let pulses = &mut self.w_pulses[..nb_ebands];

        let ebands_stereo = if channels > 1 {
            nb_ebands * channels
        } else {
            nb_ebands
        };
        self.w_fine_priority[..ebands_stereo].fill(0);
        let fine_priority = &mut self.w_fine_priority[..ebands_stereo];
        self.w_ebits[..ebands_stereo].fill(0);
        let ebits = &mut self.w_ebits[..ebands_stereo];
```

--------------------------------

### Get NFFT from KissFftState

Source: https://docs.rs/opus-rs/0.1.17/opus_rs/kiss_fft/struct.KissFftState.html

Returns the number of FFT points (nfft) configured for this KissFftState.

```rust
pub fn nfft(&self) -> usize
```

--------------------------------

### Get Pulses Function Signature

Source: https://docs.rs/opus-rs/0.1.17/opus_rs/rate/fn.get_pulses.html

This is the function signature for get_pulses. It takes an i32 and returns an i32.

```rust
pub fn get_pulses(i: i32) -> i32
```

--------------------------------

### Implement Default for SilkNSQState

Source: https://docs.rs/opus-rs/0.1.17/opus_rs/silk/structs/struct.SilkNSQState.html

Provides the `default` method for SilkNSQState, enabling the creation of a SilkNSQState instance with default values.

```rust
impl Default for SilkNSQState
Source
#### fn default() -> Self
Returns the “default value” for a type. Read more
Source
```

--------------------------------

### fn type_id(&self) -> TypeId

Source: https://docs.rs/opus-rs/0.1.17/opus_rs/bands/struct.SplitCtx.html

Gets the TypeId of the current object. This is part of the Any trait implementation.

```rust
fn type_id(&self) -> TypeId
```

--------------------------------

### SilkResampler Initialization

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/silk/resampler.rs.html

Initializes the SilkResampler with input and output sample rates.

```APIDOC
## POST /silkresampler/init

### Description
Initializes the SilkResampler with the specified input and output sample rates.

### Method
POST

### Endpoint
/silkresampler/init

### Parameters
#### Query Parameters
- **fs_hz_in** (integer) - Required - Input sample rate in Hz.
- **fs_hz_out** (integer) - Required - Output sample rate in Hz.

### Request Body
This endpoint does not require a request body.

### Response
#### Success Response (200)
- **status** (integer) - 0 on success, -1 on error.

#### Response Example
```json
{
  "status": 0
}
```
```

--------------------------------

### SilkDecoder Initialization and Configuration

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/silk/dec_api.rs.html

Provides methods for creating, initializing, and configuring the SilkDecoder for audio processing.

```APIDOC
## SilkDecoder::new()

### Description
Creates and initializes a new `SilkDecoder` instance with default settings.

### Method
`new`

### Endpoint
N/A (Struct method)

### Parameters
None

### Request Example
```rust
let mut decoder = SilkDecoder::new();
```

### Response
#### Success Response (Instance)
- **SilkDecoder** (struct) - An initialized SilkDecoder instance.

#### Response Example
```rust
// Returns a SilkDecoder instance
```

## SilkDecoder::init()

### Description
Initializes the Silk decoder with a specified sample rate and number of channels.

### Method
`init`

### Endpoint
N/A (Struct method)

### Parameters
- **sample_rate_hz** (i32) - Required - The target audio sample rate in Hz.
- **channels** (i32) - Required - The number of audio channels (1 for mono, 2 for stereo).

### Request Example
```rust
let mut decoder = SilkDecoder::new();
let result = decoder.init(16000, 1); // Initialize for 16kHz mono
```

### Response
#### Success Response (0)
- **0** (i32) - Indicates successful initialization.
#### Error Response (-1 or other negative value)
- **i32** - An error code indicating failure during initialization.

#### Response Example
```rust
// Returns 0 on success, or a negative error code on failure.
```
```

--------------------------------

### Get Scaling Factor

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/kiss_fft.rs.html

Returns the scaling factor applied to the FFT output, which is typically 1.0 / nfft.

```rust
    #[inline]
    pub fn scale(&self) -> f32 {
        self.scale
    }
}

```

--------------------------------

### Initialize PVQ Search Fast Select (Non-NEON)

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/pvq.rs.html

Initializes absolute values and signs for PVQ search when NEON is not available. Calculates the sum of absolute values.

```rust
let mut s = 0.0f32;
for i in 0..n {
    abs_x_mu[i].write(x[i].abs());
    signs_mu[i].write(if x[i] < 0.0 { -1i32 } else { 1i32 });
    s += unsafe { abs_x_mu[i].assume_init() };
}
s
```

--------------------------------

### Get Current Frame Length

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/silk/dec_api.rs.html

Retrieves the current frame length of the decoder, which is determined by the audio configuration.

```rust
pub fn frame_length(&self) -> i32 {
    self.channel_state[0].frame_length
}
```

--------------------------------

### CeltEncoder::encode_with_start_band

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/celt.rs.html

Encodes an audio frame with a specified starting band, allowing for more granular control over the encoding process.

```APIDOC
## CeltEncoder::encode_with_start_band

### Description
Encodes a PCM audio frame using the Celt encoder, starting the encoding process from a specific frequency band.

### Method
`encode_with_start_band`

### Parameters
- **pcm** (`&[f32]`) - Slice of PCM audio samples to encode.
- **frame_size** (`usize`) - The number of samples in the frame.
- **rc** (`&mut RangeCoder`) - A mutable reference to the RangeCoder for entropy coding.
- **start_band** (`usize`) - The frequency band from which to start encoding.

### Request Body
This method does not take a request body in the traditional sense; it operates on the provided PCM data.
```

--------------------------------

### Initialize NLSF Conversion Polynomials

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/silk/nlsf.rs.html

Initializes the polynomial coefficients 'p' and 'q' for the a-to-NLSF conversion process.

```rust
fn silk_a2nlsf_init(a_q16: &[i32], p: &mut [i32], q: &mut [i32], dd: usize) {
    p[dd] = 1 << 16;
    q[dd] = 1 << 16;
    for k in 0..dd {
        p[k] = -a_q16[dd - k - 1] - a_q16[dd + k];
        q[k] = -a_q16[dd - k - 1] + a_q16[dd + k];
    }

    for k in (1..=dd).rev() {
        p[k - 1] -= p[k];
        q[k - 1] += q[k];
    }

    silk_a2nlsf_trans_poly(p, dd);
    silk_a2nlsf_trans_poly(q, dd);
}
```

--------------------------------

### Implement Default for NSQDelDecStruct

Source: https://docs.rs/opus-rs/0.1.17/opus_rs/silk/nsq_del_dec/struct.NSQDelDecStruct.html

Allows creating a new NSQDelDecStruct with default initial values. This is convenient for setting up the structure before its first use.

```rust
impl Default for NSQDelDecStruct
```

--------------------------------

### Get Scale Factor from KissFftState

Source: https://docs.rs/opus-rs/0.1.17/opus_rs/kiss_fft/struct.KissFftState.html

Retrieves the scaling factor associated with this KissFftState. This is often used in FFT computations.

```rust
pub fn scale(&self) -> f32
```

--------------------------------

### Initialize SilkResampler

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/silk/resampler.rs.html

Initializes the SilkResampler with input and output sample rates. It sets up internal parameters, determines the resampling mode, and calculates the inverse ratio for resampling.

```rust
pub fn init(&mut self, fs_hz_in: i32, fs_hz_out: i32) -> i32 {
    *self = Self::default();

    let in_id = rate_id(fs_hz_in);
    let out_id = rate_id(fs_hz_out);

    if in_id > 2 || out_id > 5 {
        return -1;
    }

    self.input_delay = DELAY_MATRIX_DEC[in_id][out_id] as i32;
    self.fs_in_khz = fs_hz_in / 1000;
    self.fs_out_khz = fs_hz_out / 1000;
    self.batch_size = self.fs_in_khz * RESAMPLER_MAX_BATCH_SIZE_MS;

    if fs_hz_out == fs_hz_in {
        self.mode = ResamplerMode::Copy;
    } else if fs_hz_out == fs_hz_in * 2 {
        self.mode = ResamplerMode::Up2HQ;
    } else {
        self.mode = ResamplerMode::IirFir;
    }

    let up2x = if self.mode == ResamplerMode::IirFir {
        1
    } else {
        0
    };
    self.inv_ratio_q16 = ((((fs_hz_in as i64) << (14 + up2x)) / fs_hz_out as i64) << 2) as i32;

    while silk_smulww(self.inv_ratio_q16, fs_hz_out) < (fs_hz_in << up2x) {
        self.inv_ratio_q16 += 1;
    }

    0
}
```

--------------------------------

### Get Gains ID

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/silk/enc_api.rs.html

Retrieves the gain index based on the provided indices and number of subframes. Used in gain quantization.

```rust
silk_gains_id(&ps_enc.s_cmn.indices.gains_indices, ps_enc.s_cmn.nb_subfr);
```

--------------------------------

### CeltEncoder Initialization

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/celt.rs.html

Provides details on how to initialize a new CeltEncoder instance with a given mode and channel configuration.

```APIDOC
## CeltEncoder::new

### Description
Initializes a new `CeltEncoder` instance.

### Method
`new`

### Parameters
- **mode** (`&'static CeltMode`) - Reference to the Celt mode configuration.
- **channels** (`usize`) - The number of audio channels.

### Returns
A new `CeltEncoder` instance with initialized internal buffers and state.
```

--------------------------------

### Laplace Get Frequency 1

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/range_coder.rs.html

Helper function for Laplace encoding/decoding to calculate the frequency of the next symbol based on decay.

```rust
fn laplace_get_freq1(&self, fs0: u32, decay: i32) -> u32 {
        let ft = 32768 - (2 * 16) - fs0;
        ((ft as i32 * (16384 - decay)) >> 15) as u32
    }
```

--------------------------------

### Get Decoder Sample Rate

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/silk/dec_api.rs.html

Returns the current sample rate of the decoder in Hz, derived from the internal kHz setting.

```rust
pub fn sample_rate(&self) -> i32 {
    self.channel_state[0].fs_khz * 1000
}
```

--------------------------------

### OpusDecoder::new

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/lib.rs.html

Initializes a new OpusDecoder instance with the specified sampling rate and number of channels.

```APIDOC
## OpusDecoder::new

### Description
Initializes a new OpusDecoder instance. It validates the sampling rate and channel count, then sets up the internal CELT and SILK decoders.

### Method
`pub fn new(sampling_rate: i32, channels: usize) -> Result<Self, &'static str>`

### Parameters
*   **sampling_rate** (i32) - The desired sampling rate for the audio output. Must be one of 8000, 12000, 16000, 24000, or 48000 Hz.
*   **channels** (usize) - The number of audio channels. Must be 1 (mono) or 2 (stereo).

### Response
#### Success Response (Ok)
Returns an `Ok` variant containing a new `OpusDecoder` instance if initialization is successful.

#### Error Response (Err)
Returns an `Err` variant with a static string describing the error if the sampling rate or channel count is invalid.

### Request Example
```rust
let decoder = OpusDecoder::new(48000, 2);
```

### Response Example
```rust
// On success:
// Ok(OpusDecoder { ... })

// On failure:
// Err("Invalid sampling rate")
// Err("Invalid number of channels")
```
```

--------------------------------

### Get Total Bit Count

Source: https://docs.rs/opus-rs/0.1.17/opus_rs/range_coder/struct.RangeCoder.html

Returns the total number of bits encoded or decoded, matching C's `ec_tell()`.

```rust
pub fn tell(&self) -> i32
```

--------------------------------

### SilkResampler Initialization and Processing

Source: https://docs.rs/opus-rs/0.1.17/opus_rs/silk/resampler/struct.SilkResampler.html

Methods for initializing and processing audio data with the SilkResampler.

```APIDOC
## impl SilkResampler

### pub fn init(&mut self, fs_hz_in: i32, fs_hz_out: i32) -> i32

#### Description
Initializes the SilkResampler with the input and output sample rates.

#### Parameters
- **fs_hz_in** (i32) - Required - The input sample rate in Hz.
- **fs_hz_out** (i32) - Required - The output sample rate in Hz.

#### Returns
- (i32) - An integer indicating the success or failure of the initialization. A non-zero value typically indicates an error.

### pub fn process(&mut self, out: &mut [i16], input: &[i16], in_len: i32) -> i32

#### Description
Processes a chunk of audio data, resampling it from the input rate to the output rate.

#### Parameters
- **out** (&mut [i16]) - Required - A mutable slice to store the resampled output audio data.
- **input** (&[i16]) - Required - A slice containing the input audio data to be resampled.
- **in_len** (i32) - Required - The number of samples in the input slice.

#### Returns
- (i32) - The number of samples written to the `out` buffer. A negative value typically indicates an error.
```

--------------------------------

### Quantization Partition Logic

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/bands.rs.html

Handles the partitioning and quantization of audio data based on bit allocation and band splitting. It includes logic for both mid and side channels, with optional lowband processing.

```rust
let mut sbits = b_mut - mbits;
        let mut mbits = mbits;

        let mut rebalance = ctx.remaining_bits;
        let mut cm;

        if mbits >= sbits {
            if let Some(lb) = lowband {
                let (lb_mid, lb_side) = lb.split_at_mut(mid);
                cm = quant_partition(
                    ctx,
                    x_mid,
                    mid,
                    mbits,
                    b_blocks,
                    Some(lb_mid),
                    lm,
                    gain * (sctx.imid as f32 / 32768.0),
                    fill_mut,
                );
                rebalance = mbits - (rebalance - ctx.remaining_bits);
                if rebalance > (3 << 3) && sctx.itheta != 0 {
                    sbits += rebalance - (3 << 3);
                }
                cm |= quant_partition(
                    ctx,
                    x_side,
                    mid,
                    sbits,
                    b_blocks,
                    Some(lb_side),
                    lm,
                    gain * (sctx.iside as f32 / 32768.0),
                    fill_mut >> b_blocks,
                ) << (b0 >> 1);
            } else {
                cm = quant_partition(
                    ctx,
                    x_mid,
                    mid,
                    mbits,
                    b_blocks,
                    None,
                    lm,
                    gain * (sctx.imid as f32 / 32768.0),
                    fill_mut,
                );
                rebalance = mbits - (rebalance - ctx.remaining_bits);
                if rebalance > (3 << 3) && sctx.itheta != 0 {
                    sbits += rebalance - (3 << 3);
                }
                cm |= quant_partition(
                    ctx,
                    x_side,
                    mid,
                    sbits,
                    b_blocks,
                    None,
                    lm,
                    gain * (sctx.iside as f32 / 32768.0),
                    fill_mut >> b_blocks,
                ) << (b0 >> 1);
            }
        } else if let Some(lb) = lowband {
            let (lb_mid, lb_side) = lb.split_at_mut(mid);
            cm = quant_partition(
                ctx,
                x_side,
                mid,
                sbits,
                b_blocks,
                Some(lb_side),
                lm,
                gain * (sctx.iside as f32 / 32768.0),
                fill_mut >> b_blocks,
            ) << (b0 >> 1);
            rebalance = sbits - (rebalance - ctx.remaining_bits);
            if rebalance > (3 << 3) && sctx.itheta != 16384 {
                mbits += rebalance - (3 << 3);
            }
            cm |= quant_partition(
                ctx,
                x_mid,
                mid,
                mbits,
                b_blocks,
                Some(lb_mid),
                lm,
                gain * (sctx.imid as f32 / 32768.0),
                fill_mut,
            );
        } else {
            cm = quant_partition(
                ctx,
                x_side,
                mid,
                sbits,
                b_blocks,
                None,
                lm,
                gain * (sctx.iside as f32 / 32768.0),
                fill_mut >> b_blocks,
            ) << (b0 >> 1);
            rebalance = sbits - (rebalance - ctx.remaining_bits);
            if rebalance > (3 << 3) && sctx.itheta != 16384 {
                mbits += rebalance - (3 << 3);
            }
            cm |= quant_partition(
                ctx,
                x_mid,
                mid,
                mbits,
                b_blocks,
                None,
                lm,
                gain * (sctx.imid as f32 / 32768.0),
                fill_mut,
            );
        }
        cm
```

--------------------------------

### Get Fast Bit Count

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/range_coder.rs.html

Provides a fast approximation of the bit count by returning the total number of bits accumulated so far.

```rust
pub fn tell_fast(&self) -> i32 {
        self.nbits_total
    }
```

--------------------------------

### Implement CloneToUninit for Clone types (Nightly)

Source: https://docs.rs/opus-rs/0.1.17/opus_rs/silk/structs/struct.SideInfoIndices.html

An experimental nightly-only API that performs copy-assignment from self to a raw pointer destination. Requires the type to implement Clone.

```rust
impl<T> CloneToUninit for T
where T: Clone
```

--------------------------------

### Prepare Input Buffer for Silk Encoding

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/silk/enc_api.rs.html

Prepares the input buffer for Silk encoding by copying stereo mid-values and resampler output.

```rust
let mut input_buf = [0i16; MAX_FRAME_LENGTH + 2];
input_buf[0] = ps_enc.stereo.s_mid[0];
input_buf[1] = ps_enc.stereo.s_mid[1];
input_buf[2..2 + n].copy_from_slice(&resampler_out[..n]);
```

--------------------------------

### Define MAX_LOOK_AHEAD Constant

Source: https://docs.rs/opus-rs/0.1.17/opus_rs/silk/define/constant.MAX_LOOK_AHEAD.html

This constant represents the maximum look-ahead in samples for SILK mode. It is a fixed value and does not require any special setup.

```rust
pub const MAX_LOOK_AHEAD: usize = _; // 112usize
```

--------------------------------

### Declare BETA_COEF Constant

Source: https://docs.rs/opus-rs/0.1.17/opus_rs/quant_bands/constant.BETA_COEF.html

This constant is an array of f32 values used in quantization bands. No specific usage examples are provided in the source.

```rust
pub const BETA_COEF: [f32; 4];
```

--------------------------------

### Test FFT Roundtrip with 120 points

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/kiss_fft.rs.html

Verifies the accuracy of FFT and IFFT by transforming a sine wave and checking if the output matches the original input within a tolerance. Requires the KissFftState for initialization.

```rust
    #[test]
    fn test_fft_roundtrip_120() {
        let nfft = 120;
        let st = KissFftState::new(nfft).unwrap();

        let mut fin = vec![KissCpx::default(); nfft];
        let mut fout = vec![KissCpx::default(); nfft];
        let mut finv = vec![KissCpx::default(); nfft];

        for i in 0..nfft {
            fin[i] = KissCpx::new((2.0 * PI * 3.0 * i as f32 / nfft as f32).sin(), 0.0);
        }

        opus_fft(&st, &fin, &mut fout);
        opus_ifft(&st, &fout, &mut finv);

        for i in 0..nfft {
            assert!(
                cpx_almost_equal(&finv[i], &fin[i], 1e-4),
                "Roundtrip failed at index {}: got ({}, {}), expected ({}, {})",
                i,
                finv[i].r,
                finv[i].i,
                fin[i].r,
                fin[i].i
            );
        }
    }
```

--------------------------------

### Implement Default for SideInfoIndices

Source: https://docs.rs/opus-rs/0.1.17/opus_rs/silk/structs/struct.SideInfoIndices.html

Allows creating a SideInfoIndices instance with default values. This is often used for initialization or when a sensible starting state is needed.

```rust
impl Default for SideInfoIndices
Source
```

--------------------------------

### Prepare Lowband Views

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/bands.rs.html

Prepares views for lowband audio data. This function is a precursor to further processing of low-frequency components.

```rust
fn prepare_lowband_views(
    norm: &mut [f32],

```

--------------------------------

### Get Minimum of Two Integers

Source: https://docs.rs/opus-rs/0.1.17/opus_rs/silk/macros/fn.silk_min_int.html

Use this function to find the smaller of two i32 integers. It is part of the opus_rs::silk::macros module.

```rust
pub fn silk_min_int(a: i32, b: i32) -> i32
```

--------------------------------

### Compute Quantization Noise (compute_qn)

Source: https://docs.rs/opus-rs/0.1.17/opus_rs/bands/fn.compute_qn.html

Use this function to compute quantization noise. It takes several parameters related to audio band processing and stereo configuration.

```rust
pub fn compute_qn(
    n: usize,
    b: i32,
    offset: i32,
    pulse_cap: i32,
    stereo: bool,
) -> i32
```

--------------------------------

### PVQ Fast Select Logic (Non-NEON)

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/pvq.rs.html

Implements the core PVQ fast select logic for non-NEON architectures. It calculates initial values for y, yy, and xy, and adjusts them based on k and sum.

```rust
let rcp = (k as f32 + 0.8) / sum;

let abs_x_ptr = abs_x.as_ptr();
let y_ptr = y.as_mut_ptr();
unsafe {
    for i in 0..n {
        let yi = (*abs_x_ptr.add(i) * rcp) as i32;
        *y_ptr.add(i) = yi;
        let yf = yi as f32;
        yy += yf * yf;
        xy += yf * *abs_x_ptr.add(i);
        k -= yi;
    }
}

if k > n as i32 + 3 {
    let tmp = k as f32;
    unsafe {
        yy += tmp * tmp + tmp * *y_ptr as f32;
        *y_ptr += k;
    }
    k = 0;
}
```

--------------------------------

### Update Balance Value with Tell Fraction

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/bands.rs.html

Updates the balance value by subtracting the tell fraction, which represents a portion of the data. Used when not at the start of a sequence.

```rust
let tell = tell_frac_inline!(rc);
if i != start {
    balance_val -= tell;
}
```

--------------------------------

### Create New FFT State

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/kiss_fft.rs.html

Constructor for `KissFftState`. It takes the FFT size `nfft`, factorizes it, computes the bit-reversal table, and generates twiddle factors. Returns `None` if the `nfft` is not factorizable.

```rust
impl KissFftState {
    pub fn new(nfft: usize) -> Option<Self> {
        let mut factors = [0i16; 2 * MAXFACTORS];
        if !kf_factor(nfft, &mut factors) {
            return None;
        }

        let scale = 1.0 / nfft as f32;
        let twiddles = compute_twiddles(nfft);

        let mut bitrev = vec![0i16; nfft];
        compute_bitrev_table(0, &mut bitrev, 1, 1, &factors);

        Some(Self {
            nfft,
            scale,
            shift: -1,
            factors,
            bitrev,
            twiddles,
        })
    }

```

--------------------------------

### Opus Decoder - Decode from Range Coder with Band Range

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/celt.rs.html

Decodes audio data from a RangeCoder, specifying both the start and end frequency bands for decoding.

```APIDOC
## POST /decode_from_range_coder_with_band_range

### Description
Decodes audio data from a RangeCoder, specifying both the start and end frequency bands.

### Method
POST

### Endpoint
/decode_from_range_coder_with_band_range

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
- **rc** (RangeCoder) - Required - The RangeCoder object containing the compressed data.
- **total_bits** (i32) - Required - The total number of bits in the compressed data.
- **frame_size** (usize) - Required - The size of the audio frame to decode.
- **pcm** (f32 array) - Required - A mutable slice to store the decoded PCM data.
- **start_band** (usize) - Required - The starting frequency band for decoding.
- **end_band** (usize) - Required - The ending frequency band for decoding.

### Request Example
```json
{
  "rc": "range_coder_object_representation",
  "total_bits": 8192,
  "frame_size": 1024,
  "pcm": [],
  "start_band": 0,
  "end_band": 60
}
```

### Response
#### Success Response (200)
- **usize** - The number of samples decoded.

#### Response Example
```json
{
  "decoded_samples": 1024
}
```
```

--------------------------------

### Define SILK_TRANSITION_LP_B_Q28

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/silk/tables.rs.html

Defines the SILK_TRANSITION_LP_B_Q28 constant array, likely for low-pass filter transition coefficients in Silk audio processing, with Q28 precision.

```rust
pub const SILK_TRANSITION_LP_B_Q28: [[i32; TRANSITION_NB]; TRANSITION_INT_NUM] = [
    [250767114, 501534038, 250767114],
    [209867381, 419732057, 209867381],
    [170987846, 341967853, 170987846],
    [131531482, 263046905, 131531482],
    [89306658, 178584282, 89306658],
];
```

--------------------------------

### CeltDecoder::decode_with_start_band

Source: https://docs.rs/opus-rs/0.1.17/opus_rs/celt/struct.CeltDecoder.html

Decodes a compressed audio frame, starting decoding from a specific frequency band. Useful for controlling the frequency resolution of the decoded audio.

```rust
pub fn decode_with_start_band( &mut self, compressed: &[u8], frame_size: usize, pcm: &mut [f32], start_band: usize, ) -> usize
```

--------------------------------

### Define SILK_TRANSITION_LP_A_Q28

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/silk/tables.rs.html

Defines the SILK_TRANSITION_LP_A_Q28 constant array, likely for low-pass filter transition coefficients in Silk audio processing, with Q28 precision.

```rust
pub const SILK_TRANSITION_LP_A_Q28: [[i32; TRANSITION_NA]; TRANSITION_INT_NUM] = [
    [506393414, 239854379],
    [411067935, 169683996],
    [306733530, 116694253],
    [185807084, 77959395],
    [35497197, 57401098],
];
```

--------------------------------

### silk_vad_init Function

Source: https://docs.rs/opus-rs/0.1.17/opus_rs/silk/vad/fn.silk_vad_init.html

Initializes the SILK VAD (Voice Activity Detection) state.

```APIDOC
## silk_vad_init

### Description
Initializes the SILK VAD state.

### Method
Rust Function

### Endpoint
opus_rs::silk::vad

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
- **s_vad** (SilkVADState) - Required - A mutable reference to the SilkVADState to be initialized.

### Request Example
```rust
let mut vad_state = SilkVADState::new(); // Assuming SilkVADState has a ::new() constructor
silk_vad_init(&mut vad_state);
```

### Response
#### Success Response (0)
- **Return Value** (i32) - Returns 0 on success.

#### Response Example
```rust
0
```

#### Error Response
- **Return Value** (i32) - Returns a negative value on error. Specific error codes are not detailed here.
```

--------------------------------

### Get Trigonometric Values for MDCT

Source: https://docs.rs/opus-rs/0.1.17/src/opus_rs/mdct.rs.html

Retrieves a slice of pre-calculated trigonometric values (cosines) and the corresponding FFT size for a given shift. Used internally by the MDCT.

```rust
fn get_trig(&self, shift: usize) -> (&[f32], usize) {
        let mut offset = 0;
        let mut curr_n = self.n;
        for _ in 0..shift {
            offset += curr_n / 2;
            curr_n >>= 1;
        }
        (&self.trig[offset..offset + curr_n / 2], curr_n / 4)
    }
```

--------------------------------

### silk_sqrt_approx Function Signature

Source: https://docs.rs/opus-rs/0.1.17/opus_rs/silk/macros/fn.silk_sqrt_approx.html

This is the function signature for silk_sqrt_approx, which approximates the square root of an i32 integer. No specific setup or imports are required to use this function signature.

```rust
pub fn silk_sqrt_approx(x: i32) -> i32
```

--------------------------------

### Initialize SilkResampler

Source: https://docs.rs/opus-rs/0.1.17/opus_rs/silk/resampler/struct.SilkResampler.html

Initializes the SilkResampler with input and output sample rates. Returns an i32 status code.

```rust
pub fn init(&mut self, fs_hz_in: i32, fs_hz_out: i32) -> i32
```