moq_video/
size.rs

1use crate::Error;
2
3/// A frame resolution in pixels.
4///
5/// Names the pair that [`decode::Config::resize`](crate::decode::Config::resize)
6/// and [`Frame::resize`](crate::Frame::resize) both take, so
7/// width and height can't be swapped at a call site.
8#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Hash)]
9pub struct Size {
10	/// Width in pixels.
11	pub width: u32,
12	/// Height in pixels.
13	pub height: u32,
14}
15
16impl Size {
17	/// A size of `width` x `height` pixels.
18	pub fn new(width: u32, height: u32) -> Self {
19		Self { width, height }
20	}
21
22	/// Total pixels. Can't overflow: the widest `u32` square still fits a `u64`.
23	pub fn pixels(&self) -> u64 {
24		self.width as u64 * self.height as u64
25	}
26
27	/// Reject anything the I420 pipeline can't represent.
28	///
29	/// I420 chroma is subsampled 2x2, so every stage (encode, decode, resize)
30	/// needs even, non-zero dimensions. Checking here keeps the rule in one place
31	/// instead of re-deriving it at each boundary.
32	pub(crate) fn validate(&self, what: &str) -> Result<(), Error> {
33		self.validate_nonzero(what)?;
34		if !self.width.is_multiple_of(2) || !self.height.is_multiple_of(2) {
35			return Err(Error::Codec(anyhow::anyhow!("{what} {self}: dimensions must be even")));
36		}
37		Ok(())
38	}
39
40	/// Reject a size whose derived quantities cannot be computed at all.
41	///
42	/// Dimensions arrive as a pair of `u32`, so their product reaches ~1.8e19
43	/// before anything else looks at them. That overflows the two things every
44	/// encoder derives from a size: the default bitrate (pixels x framerate) and
45	/// a packed frame's byte count (up to 4 bytes per pixel for RGBA). Both would
46	/// panic, which for a binding is an aborted host process rather than an
47	/// error return, so refuse the config here instead.
48	///
49	/// This is arithmetic, not policy: it rejects only what cannot be represented,
50	/// leaving "no encoder handles a frame that large" to the backend.
51	pub(crate) fn validate_encodable(&self, what: &str, framerate: u32) -> Result<(), Error> {
52		let pixels = self.pixels();
53		let representable = pixels.checked_mul(framerate as u64).is_some()
54			&& usize::try_from(pixels).is_ok_and(|pixels| pixels.checked_mul(4).is_some());
55
56		if !representable {
57			return Err(Error::Codec(anyhow::anyhow!(
58				"{what} {self} at {framerate}fps: dimensions too large to represent"
59			)));
60		}
61		Ok(())
62	}
63
64	/// The half of [`Size::validate`] that is not about chroma, for the surfaces
65	/// that hold RGB and so tolerate odd dimensions (a render target sized to a
66	/// window).
67	pub(crate) fn validate_nonzero(&self, what: &str) -> Result<(), Error> {
68		if self.width == 0 || self.height == 0 {
69			return Err(Error::Codec(anyhow::anyhow!(
70				"{what} {self}: dimensions must be non-zero"
71			)));
72		}
73		Ok(())
74	}
75}
76
77impl std::fmt::Display for Size {
78	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
79		write!(f, "{}x{}", self.width, self.height)
80	}
81}
82
83impl From<(u32, u32)> for Size {
84	fn from((width, height): (u32, u32)) -> Self {
85		Self::new(width, height)
86	}
87}
88
89#[cfg(test)]
90mod tests {
91	use super::*;
92
93	#[test]
94	fn validate_rejects_odd_and_zero() {
95		assert!(Size::new(320, 240).validate("frame").is_ok());
96		assert!(Size::new(0, 240).validate("frame").is_err());
97		assert!(Size::new(320, 0).validate("frame").is_err());
98		assert!(Size::new(321, 240).validate("frame").is_err());
99		assert!(Size::new(320, 241).validate("frame").is_err());
100	}
101
102	/// Regression: `u32` dimensions can reach a pixel count whose derived
103	/// quantities overflow. A binding hands these straight through, and a panic
104	/// there aborts the host process, so the size has to be refused first.
105	#[test]
106	fn validate_encodable_rejects_unrepresentable_sizes() {
107		// A frame nobody can encode, but whose arithmetic still fits: the backend
108		// decides, not us.
109		assert!(Size::new(65534, 65534).validate_encodable("frame", 30).is_ok());
110
111		// pixels x framerate overflows u64.
112		assert!(
113			Size::new(u32::MAX - 1, u32::MAX - 1)
114				.validate_encodable("frame", 30)
115				.is_err()
116		);
117		// ...and it is the product that matters, not either side alone.
118		assert!(Size::new(u32::MAX - 1, 2).validate_encodable("frame", 30).is_ok());
119	}
120
121	#[test]
122	fn display_reads_as_a_resolution() {
123		assert_eq!(Size::new(1920, 1080).to_string(), "1920x1080");
124	}
125}
moq_video/size.rs

moq_video/
size.rs
