oximedia-codec 0.1.7

Video codec implementations for OxiMedia
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149

//! VP8L pixel arithmetic helpers.
//!
//! Pure helper functions for ARGB pixel manipulation used by the VP8L
//! lossless decoder's spatial prediction transforms.

/// Add two ARGB pixels component-wise (mod 256 per channel).
#[inline]
pub(crate) fn add_pixels(a: u32, b: u32) -> u32 {
    let a0 = (a >> 24) & 0xFF;
    let a1 = (a >> 16) & 0xFF;
    let a2 = (a >> 8) & 0xFF;
    let a3 = a & 0xFF;

    let b0 = (b >> 24) & 0xFF;
    let b1 = (b >> 16) & 0xFF;
    let b2 = (b >> 8) & 0xFF;
    let b3 = b & 0xFF;

    (((a0 + b0) & 0xFF) << 24)
        | (((a1 + b1) & 0xFF) << 16)
        | (((a2 + b2) & 0xFF) << 8)
        | ((a3 + b3) & 0xFF)
}

/// Average two bytes (component-wise).
#[inline]
fn average2_byte(a: u8, b: u8) -> u8 {
    ((u16::from(a) + u16::from(b)) / 2) as u8
}

/// Average two ARGB pixels component-wise.
#[inline]
pub(crate) fn average2(a: u32, b: u32) -> u32 {
    let a_ch = pixel_channels(a);
    let b_ch = pixel_channels(b);
    channels_to_pixel([
        average2_byte(a_ch[0], b_ch[0]),
        average2_byte(a_ch[1], b_ch[1]),
        average2_byte(a_ch[2], b_ch[2]),
        average2_byte(a_ch[3], b_ch[3]),
    ])
}

/// Extract ARGB channels as [A, R, G, B].
#[inline]
pub(crate) fn pixel_channels(p: u32) -> [u8; 4] {
    [
        ((p >> 24) & 0xFF) as u8,
        ((p >> 16) & 0xFF) as u8,
        ((p >> 8) & 0xFF) as u8,
        (p & 0xFF) as u8,
    ]
}

/// Pack [A, R, G, B] channels into a pixel.
#[inline]
pub(crate) fn channels_to_pixel(ch: [u8; 4]) -> u32 {
    (u32::from(ch[0]) << 24) | (u32::from(ch[1]) << 16) | (u32::from(ch[2]) << 8) | u32::from(ch[3])
}

/// Clamp a value to [0, 255].
#[inline]
fn clamp_byte(v: i32) -> u8 {
    v.clamp(0, 255) as u8
}

/// Select predictor: choose L or T based on Manhattan distance to TL.
#[inline]
pub(crate) fn select(left: u32, top: u32, top_left: u32) -> u32 {
    let l = pixel_channels(left);
    let t = pixel_channels(top);
    let tl = pixel_channels(top_left);

    let predict_l: i32 = (0..4)
        .map(|i| (i32::from(t[i]) - i32::from(tl[i])).abs())
        .sum();
    let predict_t: i32 = (0..4)
        .map(|i| (i32::from(l[i]) - i32::from(tl[i])).abs())
        .sum();

    if predict_l < predict_t {
        left
    } else {
        top
    }
}

/// ClampAddSubtractFull: L + T - TL, clamped per channel.
#[inline]
pub(crate) fn clamp_add_subtract_full(left: u32, top: u32, top_left: u32) -> u32 {
    let l = pixel_channels(left);
    let t = pixel_channels(top);
    let tl = pixel_channels(top_left);
    channels_to_pixel([
        clamp_byte(i32::from(l[0]) + i32::from(t[0]) - i32::from(tl[0])),
        clamp_byte(i32::from(l[1]) + i32::from(t[1]) - i32::from(tl[1])),
        clamp_byte(i32::from(l[2]) + i32::from(t[2]) - i32::from(tl[2])),
        clamp_byte(i32::from(l[3]) + i32::from(t[3]) - i32::from(tl[3])),
    ])
}

/// ClampAddSubtractHalf: avg + (avg - other) / 2, clamped.
#[inline]
pub(crate) fn clamp_add_subtract_half(avg: u32, other: u32) -> u32 {
    let a = pixel_channels(avg);
    let o = pixel_channels(other);
    channels_to_pixel([
        clamp_byte(i32::from(a[0]) + (i32::from(a[0]) - i32::from(o[0])) / 2),
        clamp_byte(i32::from(a[1]) + (i32::from(a[1]) - i32::from(o[1])) / 2),
        clamp_byte(i32::from(a[2]) + (i32::from(a[2]) - i32::from(o[2])) / 2),
        clamp_byte(i32::from(a[3]) + (i32::from(a[3]) - i32::from(o[3])) / 2),
    ])
}

/// Color transform delta.
#[inline]
#[allow(clippy::cast_possible_truncation)]
pub(crate) fn color_transform_delta(multiplier: i32, channel: i32) -> i32 {
    // The spec defines: (multiplier * channel) >> 5
    // but the multiplier is a signed byte interpreted as i8.
    ((multiplier as i8 as i32) * (channel as i8 as i32)) >> 5
}

/// Predict a pixel using one of the 14 predictor modes.
pub(crate) fn predict(mode: u8, left: u32, top: u32, top_left: u32, top_right: u32) -> u32 {
    match mode {
        0 => 0xFF00_0000, // black with opaque alpha
        1 => left,
        2 => top,
        3 => top_right,
        4 => top_left,
        5 => average2(average2(left, top_right), top),
        6 => average2(left, top_left),
        7 => average2(left, top),
        8 => average2(top_left, top),
        9 => average2(top, top_right),
        10 => average2(average2(left, top_left), average2(top, top_right)),
        11 => select(left, top, top_left),
        12 => clamp_add_subtract_full(left, top, top_left),
        13 => clamp_add_subtract_half(average2(left, top), top_left),
        _ => 0xFF00_0000, // fallback
    }
}

/// Integer division rounding up.
#[inline]
pub(crate) fn div_round_up(a: u32, b: u32) -> u32 {
    (a + b - 1) / b
}