mp4/mp4box/
elst.rs

1use byteorder::{BigEndian, ReadBytesExt, WriteBytesExt};
2use serde::Serialize;
3use std::io::{Read, Seek, Write};
4use std::mem::size_of;
5
6use crate::mp4box::*;
7
8#[derive(Debug, Clone, PartialEq, Eq, Default, Serialize)]
9pub struct ElstBox {
10    pub version: u8,
11    pub flags: u32,
12
13    #[serde(skip_serializing)]
14    pub entries: Vec<ElstEntry>,
15}
16
17#[derive(Debug, Clone, PartialEq, Eq, Default, Serialize)]
18pub struct ElstEntry {
19    pub segment_duration: u64,
20    pub media_time: u64,
21    pub media_rate: u16,
22    pub media_rate_fraction: u16,
23}
24
25impl ElstBox {
26    pub fn get_type(&self) -> BoxType {
27        BoxType::ElstBox
28    }
29
30    pub fn get_size(&self) -> u64 {
31        let mut size = HEADER_SIZE + HEADER_EXT_SIZE + 4;
32        if self.version == 1 {
33            size += self.entries.len() as u64 * 20;
34        } else if self.version == 0 {
35            size += self.entries.len() as u64 * 12;
36        }
37        size
38    }
39}
40
41impl Mp4Box for ElstBox {
42    fn box_type(&self) -> BoxType {
43        self.get_type()
44    }
45
46    fn box_size(&self) -> u64 {
47        self.get_size()
48    }
49
50    fn to_json(&self) -> Result<String> {
51        Ok(serde_json::to_string(&self).unwrap())
52    }
53
54    fn summary(&self) -> Result<String> {
55        let s = format!("elst_entries={}", self.entries.len());
56        Ok(s)
57    }
58}
59
60impl<R: Read + Seek> ReadBox<&mut R> for ElstBox {
61    fn read_box(reader: &mut R, size: u64) -> Result<Self> {
62        let start = box_start(reader)?;
63
64        let (version, flags) = read_box_header_ext(reader)?;
65
66        let header_size = HEADER_SIZE + HEADER_EXT_SIZE;
67        let entry_count = reader.read_u32::<BigEndian>()?;
68        let other_size = size_of::<i32>(); // entry_count
69        let entry_size = {
70            let mut entry_size = 0;
71            entry_size += if version == 1 {
72                size_of::<u64>() + size_of::<i64>() // segment_duration + media_time
73            } else {
74                size_of::<u32>() + size_of::<i32>() // segment_duration + media_time
75            };
76            entry_size += size_of::<i16>() + size_of::<i16>(); // media_rate_integer + media_rate_fraction
77            entry_size
78        };
79        if u64::from(entry_count)
80            > size
81                .saturating_sub(header_size)
82                .saturating_sub(other_size as u64)
83                / entry_size as u64
84        {
85            return Err(Error::InvalidData(
86                "elst entry_count indicates more entries than could fit in the box",
87            ));
88        }
89        let mut entries = Vec::with_capacity(entry_count as usize);
90        for _ in 0..entry_count {
91            let (segment_duration, media_time) = if version == 1 {
92                (
93                    reader.read_u64::<BigEndian>()?,
94                    reader.read_u64::<BigEndian>()?,
95                )
96            } else {
97                (
98                    reader.read_u32::<BigEndian>()? as u64,
99                    reader.read_u32::<BigEndian>()? as u64,
100                )
101            };
102
103            let entry = ElstEntry {
104                segment_duration,
105                media_time,
106                media_rate: reader.read_u16::<BigEndian>()?,
107                media_rate_fraction: reader.read_u16::<BigEndian>()?,
108            };
109            entries.push(entry);
110        }
111
112        skip_bytes_to(reader, start + size)?;
113
114        Ok(ElstBox {
115            version,
116            flags,
117            entries,
118        })
119    }
120}
121
122impl<W: Write> WriteBox<&mut W> for ElstBox {
123    fn write_box(&self, writer: &mut W) -> Result<u64> {
124        let size = self.box_size();
125        BoxHeader::new(self.box_type(), size).write(writer)?;
126
127        write_box_header_ext(writer, self.version, self.flags)?;
128
129        writer.write_u32::<BigEndian>(self.entries.len() as u32)?;
130        for entry in self.entries.iter() {
131            if self.version == 1 {
132                writer.write_u64::<BigEndian>(entry.segment_duration)?;
133                writer.write_u64::<BigEndian>(entry.media_time)?;
134            } else {
135                writer.write_u32::<BigEndian>(entry.segment_duration as u32)?;
136                writer.write_u32::<BigEndian>(entry.media_time as u32)?;
137            }
138            writer.write_u16::<BigEndian>(entry.media_rate)?;
139            writer.write_u16::<BigEndian>(entry.media_rate_fraction)?;
140        }
141
142        Ok(size)
143    }
144}
145
146#[cfg(test)]
147mod tests {
148    use super::*;
149    use crate::mp4box::BoxHeader;
150    use std::io::Cursor;
151
152    #[test]
153    fn test_elst32() {
154        let src_box = ElstBox {
155            version: 0,
156            flags: 0,
157            entries: vec![ElstEntry {
158                segment_duration: 634634,
159                media_time: 0,
160                media_rate: 1,
161                media_rate_fraction: 0,
162            }],
163        };
164        let mut buf = Vec::new();
165        src_box.write_box(&mut buf).unwrap();
166        assert_eq!(buf.len(), src_box.box_size() as usize);
167
168        let mut reader = Cursor::new(&buf);
169        let header = BoxHeader::read(&mut reader).unwrap();
170        assert_eq!(header.name, BoxType::ElstBox);
171        assert_eq!(src_box.box_size(), header.size);
172
173        let dst_box = ElstBox::read_box(&mut reader, header.size).unwrap();
174        assert_eq!(src_box, dst_box);
175    }
176
177    #[test]
178    fn test_elst64() {
179        let src_box = ElstBox {
180            version: 1,
181            flags: 0,
182            entries: vec![ElstEntry {
183                segment_duration: 634634,
184                media_time: 0,
185                media_rate: 1,
186                media_rate_fraction: 0,
187            }],
188        };
189        let mut buf = Vec::new();
190        src_box.write_box(&mut buf).unwrap();
191        assert_eq!(buf.len(), src_box.box_size() as usize);
192
193        let mut reader = Cursor::new(&buf);
194        let header = BoxHeader::read(&mut reader).unwrap();
195        assert_eq!(header.name, BoxType::ElstBox);
196        assert_eq!(src_box.box_size(), header.size);
197
198        let dst_box = ElstBox::read_box(&mut reader, header.size).unwrap();
199        assert_eq!(src_box, dst_box);
200    }
201}
mp4/mp4box/elst.rs

mp4/mp4box/
elst.rs
