scuffle_mp4/boxes/types/
subs.rs

use std::io;

use byteorder::{BigEndian, ReadBytesExt, WriteBytesExt};
use bytes::Bytes;

use crate::boxes::header::{BoxHeader, FullBoxHeader};
use crate::boxes::traits::BoxType;

#[derive(Debug, Clone, PartialEq)]
/// Subsample Information Box
/// ISO/IEC 14496-12:2022(E) - 8.7.7
pub struct Subs {
    pub header: FullBoxHeader,

    pub entries: Vec<SubsEntry>,
}

#[derive(Debug, Clone, PartialEq)]
/// Subs box entry
pub struct SubsEntry {
    pub sample_delta: u32,
    pub subsamples: Vec<SubSampleEntry>,
}

#[derive(Debug, Clone, PartialEq)]
/// Sub Sample Entry
pub struct SubSampleEntry {
    pub subsample_size: u32,
    pub subsample_priority: u8,
    pub discardable: u8,
    pub codec_specific_parameters: u32,
}

impl BoxType for Subs {
    const NAME: [u8; 4] = *b"subs";

    fn demux(header: BoxHeader, data: Bytes) -> io::Result<Self> {
        let mut reader = io::Cursor::new(data);

        let header = FullBoxHeader::demux(header, &mut reader)?;

        let entry_count = reader.read_u32::<BigEndian>()?;
        let mut entries = Vec::with_capacity(entry_count as usize);

        for _ in 0..entry_count {
            let sample_delta = reader.read_u32::<BigEndian>()?;
            let subsample_count = reader.read_u16::<BigEndian>()?;
            let mut subsamples = Vec::with_capacity(subsample_count as usize);

            for _ in 0..subsample_count {
                let subsample_size = if header.version == 1 {
                    reader.read_u32::<BigEndian>()?
                } else {
                    reader.read_u16::<BigEndian>()? as u32
                };
                let subsample_priority = reader.read_u8()?;
                let discardable = reader.read_u8()?;
                let codec_specific_parameters = reader.read_u32::<BigEndian>()?;
                subsamples.push(SubSampleEntry {
                    subsample_size,
                    subsample_priority,
                    discardable,
                    codec_specific_parameters,
                });
            }

            entries.push(SubsEntry {
                sample_delta,
                subsamples,
            });
        }

        Ok(Self { header, entries })
    }

    fn primitive_size(&self) -> u64 {
        let size = self.header.size();
        let size = size + 4; // entry_count
        let size = size
            + self
                .entries
                .iter()
                .map(|e| {
                    let size = 4; // sample_delta
                    let size = size + 2; // subsample_count

                    size + e.subsamples.len() as u64
                        * if self.header.version == 1 {
                            4 + 1 + 1 + 4
                        } else {
                            2 + 1 + 1 + 4
                        }
                })
                .sum::<u64>(); // entries
        size
    }

    fn primitive_mux<T: io::Write>(&self, writer: &mut T) -> io::Result<()> {
        self.header.mux(writer)?;

        writer.write_u32::<BigEndian>(self.entries.len() as u32)?;
        for entry in &self.entries {
            writer.write_u32::<BigEndian>(entry.sample_delta)?;
            writer.write_u16::<BigEndian>(entry.subsamples.len() as u16)?;
            for subsample in &entry.subsamples {
                if self.header.version == 1 {
                    writer.write_u32::<BigEndian>(subsample.subsample_size)?;
                } else {
                    writer.write_u16::<BigEndian>(subsample.subsample_size as u16)?;
                }
                writer.write_u8(subsample.subsample_priority)?;
                writer.write_u8(subsample.discardable)?;
                writer.write_u32::<BigEndian>(subsample.codec_specific_parameters)?;
            }
        }

        Ok(())
    }

    fn validate(&self) -> io::Result<()> {
        if self.header.version > 1 {
            return Err(io::Error::new(io::ErrorKind::InvalidData, "subs version must be 0 or 1"));
        }

        if self.header.version == 0 {
            for entry in &self.entries {
                for subsample in &entry.subsamples {
                    if subsample.subsample_size > u16::MAX as u32 {
                        return Err(io::Error::new(
                            io::ErrorKind::InvalidData,
                            "subs subsample_size must be less than 2^16",
                        ));
                    }
                }
            }
        }

        Ok(())
    }
}
scuffle_mp4/boxes/types/subs.rs

scuffle_mp4/boxes/types/
subs.rs
