dvb_si/descriptors/
mvc_extension.rs

1//! MVC Extension Descriptor — ISO/IEC 13818-1 §2.6.78, Table 2-100 (tag 0x31).
2//!
3//! Carries MVC (Multiview Video Coding, H.264 Annex H) extension parameters
4//! for a video elementary stream.
5
6use super::descriptor_body;
7use crate::error::{Error, Result};
8use dvb_common::{Parse, Serialize};
9
10/// Descriptor tag for MVC_extension_descriptor.
11pub const TAG: u8 = 0x31;
12const HEADER_LEN: usize = 2;
13const BODY_LEN: u8 = 8;
14
15/// MVC Extension Descriptor.
16#[derive(Debug, Clone, Copy, PartialEq, Eq)]
17#[cfg_attr(feature = "serde", derive(serde::Serialize))]
18pub struct MvcExtensionDescriptor {
19    /// Average bit rate in kbit/s (`0` means unspecified).
20    pub average_bit_rate: u16,
21    /// Maximum bitrate in kbit/s (`0` means unspecified).
22    pub maximum_bitrate: u16,
23    /// View association not present flag.
24    pub view_association_not_present: bool,
25    /// Base view is left eye view flag.
26    pub base_view_is_left_eyeview: bool,
27    /// Minimum view order index.
28    pub view_order_index_min: u16,
29    /// Maximum view order index.
30    pub view_order_index_max: u16,
31    /// Temporal ID start (inclusive).
32    pub temporal_id_start: u8,
33    /// Temporal ID end (inclusive).
34    pub temporal_id_end: u8,
35    /// No SEI NAL unit present flag.
36    pub no_sei_nal_unit_present: bool,
37    /// No prefix NAL unit present flag.
38    pub no_prefix_nal_unit_present: bool,
39}
40
41impl<'a> Parse<'a> for MvcExtensionDescriptor {
42    type Error = crate::error::Error;
43
44    fn parse(bytes: &'a [u8]) -> Result<Self> {
45        let body = descriptor_body(
46            bytes,
47            TAG,
48            "MvcExtensionDescriptor",
49            "unexpected tag for MVC_extension_descriptor",
50        )?;
51        if body.len() != BODY_LEN as usize {
52            return Err(Error::InvalidDescriptor {
53                tag: TAG,
54                reason: "MVC_extension_descriptor length must equal 8",
55            });
56        }
57        let average_bit_rate = u16::from_be_bytes([body[0], body[1]]);
58        let maximum_bitrate = u16::from_be_bytes([body[2], body[3]]);
59        let b4 = body[4];
60        let b5 = body[5];
61        let b6 = body[6];
62        let b7 = body[7];
63        let view_association_not_present = (b4 & 0x80) != 0;
64        let base_view_is_left_eyeview = (b4 & 0x40) != 0;
65        // b4 bits 5-4: reserved
66        let view_order_index_min = ((b4 as u16 & 0x0F) << 6) | ((b5 as u16 >> 2) & 0x3F);
67        let view_order_index_max = ((b5 as u16 & 0x03) << 8) | (b6 as u16);
68        let temporal_id_start = (b7 >> 5) & 0x07;
69        let temporal_id_end = (b7 >> 2) & 0x07;
70        let no_sei_nal_unit_present = (b7 & 0x02) != 0;
71        let no_prefix_nal_unit_present = (b7 & 0x01) != 0;
72        Ok(Self {
73            average_bit_rate,
74            maximum_bitrate,
75            view_association_not_present,
76            base_view_is_left_eyeview,
77            view_order_index_min,
78            view_order_index_max,
79            temporal_id_start,
80            temporal_id_end,
81            no_sei_nal_unit_present,
82            no_prefix_nal_unit_present,
83        })
84    }
85}
86
87impl Serialize for MvcExtensionDescriptor {
88    type Error = crate::error::Error;
89
90    fn serialized_len(&self) -> usize {
91        HEADER_LEN + BODY_LEN as usize
92    }
93
94    fn serialize_into(&self, buf: &mut [u8]) -> Result<usize> {
95        let len = self.serialized_len();
96        if buf.len() < len {
97            return Err(Error::OutputBufferTooSmall {
98                need: len,
99                have: buf.len(),
100            });
101        }
102        buf[0] = TAG;
103        buf[1] = BODY_LEN;
104        buf[HEADER_LEN..HEADER_LEN + 2].copy_from_slice(&self.average_bit_rate.to_be_bytes());
105        buf[HEADER_LEN + 2..HEADER_LEN + 4].copy_from_slice(&self.maximum_bitrate.to_be_bytes());
106        let vmin = self.view_order_index_min & 0x03FF;
107        let vmax = self.view_order_index_max & 0x03FF;
108        buf[HEADER_LEN + 4] = ((self.view_association_not_present as u8) << 7)
109            | ((self.base_view_is_left_eyeview as u8) << 6)
110            | ((vmin >> 6) as u8 & 0x0F);
111        buf[HEADER_LEN + 5] = (((vmin & 0x3F) << 2) as u8) | ((vmax >> 8) as u8 & 0x03);
112        buf[HEADER_LEN + 6] = (vmax & 0xFF) as u8;
113        buf[HEADER_LEN + 7] = ((self.temporal_id_start & 0x07) << 5)
114            | ((self.temporal_id_end & 0x07) << 2)
115            | ((self.no_sei_nal_unit_present as u8) << 1)
116            | (self.no_prefix_nal_unit_present as u8);
117        Ok(len)
118    }
119}
120impl<'a> crate::traits::DescriptorDef<'a> for MvcExtensionDescriptor {
121    const TAG: u8 = TAG;
122    const NAME: &'static str = "MVC_EXTENSION";
123}
124
125#[cfg(test)]
126mod tests {
127    use super::*;
128
129    #[test]
130    fn parse_extracts_fields() {
131        let bytes = [
132            TAG, 8, 0x00, 0x64, // average_bit_rate = 100
133            0x00, 0xC8, // maximum_bitrate = 200
134            0x0F, // VA_not_present=0, left_eye=0, reserved=0, vmin_high=15
135            0xFC, // vmin_low=63, vmax_high=0
136            0xE8, // vmax_low=232
137            0x4A, // temporal_id_start=2, temporal_id_end=2, no_sei=1, no_prefix=0
138        ];
139        let d = MvcExtensionDescriptor::parse(&bytes).unwrap();
140        assert_eq!(d.average_bit_rate, 100);
141        assert_eq!(d.maximum_bitrate, 200);
142        assert!(!d.view_association_not_present);
143        assert!(!d.base_view_is_left_eyeview);
144        assert_eq!(d.view_order_index_min, (15 << 6) | 63);
145        assert_eq!(d.view_order_index_max, 232);
146        assert_eq!(d.temporal_id_start, 2);
147        assert_eq!(d.temporal_id_end, 2);
148        assert!(d.no_sei_nal_unit_present);
149        assert!(!d.no_prefix_nal_unit_present);
150    }
151
152    #[test]
153    fn parse_flags() {
154        let bytes = [
155            TAG, 8, 0, 0, 0, 0, 0xC0, // VA_not_present=1, left_eye=1
156            0, 0, 0x03, // temporal_start=0, temporal_end=0, no_sei=1, no_prefix=1
157        ];
158        let d = MvcExtensionDescriptor::parse(&bytes).unwrap();
159        assert!(d.view_association_not_present);
160        assert!(d.base_view_is_left_eyeview);
161        assert!(d.no_sei_nal_unit_present);
162        assert!(d.no_prefix_nal_unit_present);
163    }
164
165    #[test]
166    fn parse_max_10bit_fields() {
167        let bytes = [
168            TAG, 8, 0, 0, 0, 0, 0x0F, 0xFF, // vmin = 1023
169            0xFF, 0x00, // vmax = 1023
170        ];
171        let d = MvcExtensionDescriptor::parse(&bytes).unwrap();
172        assert_eq!(d.view_order_index_min, 1023);
173        assert_eq!(d.view_order_index_max, 1023);
174    }
175
176    #[test]
177    fn parse_rejects_wrong_tag() {
178        let err = MvcExtensionDescriptor::parse(&[0x02, 8, 0, 0, 0, 0, 0, 0, 0, 0]).unwrap_err();
179        assert!(matches!(err, Error::InvalidDescriptor { tag: 0x02, .. }));
180    }
181
182    #[test]
183    fn parse_rejects_wrong_length() {
184        let err = MvcExtensionDescriptor::parse(&[TAG, 7, 0, 0, 0, 0, 0, 0, 0]).unwrap_err();
185        assert!(matches!(err, Error::InvalidDescriptor { .. }));
186    }
187
188    #[test]
189    fn serialize_round_trip() {
190        let d = MvcExtensionDescriptor {
191            average_bit_rate: 5000,
192            maximum_bitrate: 10000,
193            view_association_not_present: false,
194            base_view_is_left_eyeview: true,
195            view_order_index_min: 512,
196            view_order_index_max: 256,
197            temporal_id_start: 3,
198            temporal_id_end: 5,
199            no_sei_nal_unit_present: true,
200            no_prefix_nal_unit_present: false,
201        };
202        let mut buf = vec![0u8; d.serialized_len()];
203        d.serialize_into(&mut buf).unwrap();
204        let reparsed = MvcExtensionDescriptor::parse(&buf).unwrap();
205        assert_eq!(d, reparsed);
206    }
207
208    #[test]
209    fn serialize_round_trip_reserved_preserved() {
210        // Reserved bits in byte 4 are not part of any field that the struct
211        // can round-trip; the serializer writes zero for those bits.
212        // This test confirms we parse and re-serialize deterministically
213        // with the reserved bits wiped.
214        let bytes_with_reserved = [
215            TAG, 8, 0, 0, 0, 0, 0, 0, 0, 0, 0x30, // reserved bits non-zero (bits 5-4 = 11)
216        ];
217        let d = MvcExtensionDescriptor::parse(&bytes_with_reserved).unwrap();
218        let mut buf = vec![0u8; d.serialized_len()];
219        d.serialize_into(&mut buf).unwrap();
220        // Re-parse the serialized output and verify it's stable
221        let reparsed = MvcExtensionDescriptor::parse(&buf).unwrap();
222        let mut buf2 = vec![0u8; reparsed.serialized_len()];
223        reparsed.serialize_into(&mut buf2).unwrap();
224        assert_eq!(buf, buf2);
225    }
226
227    #[test]
228    fn serialize_rejects_small_buffer() {
229        let d = MvcExtensionDescriptor {
230            average_bit_rate: 0,
231            maximum_bitrate: 0,
232            view_association_not_present: false,
233            base_view_is_left_eyeview: false,
234            view_order_index_min: 0,
235            view_order_index_max: 0,
236            temporal_id_start: 0,
237            temporal_id_end: 0,
238            no_sei_nal_unit_present: false,
239            no_prefix_nal_unit_present: false,
240        };
241        let mut tiny = vec![0u8; 5];
242        let err = d.serialize_into(&mut tiny).unwrap_err();
243        assert!(matches!(err, Error::OutputBufferTooSmall { .. }));
244    }
245}
dvb_si/descriptors/mvc_extension.rs

dvb_si/descriptors/
mvc_extension.rs
