rtc_rtp/codecs/av1/
mod.rs

1use bytes::{BufMut, Bytes, BytesMut};
2
3use crate::codecs::av1::leb128::BytesMutExt;
4use crate::codecs::av1::obu::{obu_has_extension, parse_obus, OBU_HAS_SIZE_BIT};
5use crate::codecs::av1::packetizer::{
6    get_aggregation_header, packetize, AGGREGATION_HEADER_SIZE, MAX_NUM_OBUS_TO_OMIT_SIZE,
7};
8use crate::packetizer::Payloader;
9use shared::error::Result;
10
11#[cfg(test)]
12mod av1_test;
13mod leb128;
14mod obu;
15mod packetizer;
16
17#[derive(Default, Clone, Debug)]
18pub struct Av1Payloader {}
19
20impl Payloader for Av1Payloader {
21    /// Based on https://chromium.googlesource.com/external/webrtc/+/4e513346ec56c829b3a6010664998469fc237b35/modules/rtp_rtcp/source/rtp_packetizer_av1.cc
22    /// Reference: https://aomediacodec.github.io/av1-rtp-spec/#45-payload-structure
23    fn payload(&mut self, mtu: usize, payload: &Bytes) -> Result<Vec<Bytes>> {
24        // 0                   1                   2                   3
25        // 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
26        // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
27        // |Z|Y|1 0|N|-|-|-|  OBU element 1 size (leb128)  |               |
28        // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+               |
29        // |                                                               |
30        // :                                                               :
31        // :                      OBU element 1 data                       :
32        // :                                                               :
33        // |                                                               |
34        // |                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
35        // |                               |                               |
36        // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
37        // |                                                               |
38        // :                                                               :
39        // :                      OBU element 2 data                       :
40        // :                                                               :
41        // |                                                               |
42        // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
43
44        // Parse the payload into series of OBUs.
45        let obus = parse_obus(payload)?;
46
47        // Packetize the OBUs, possibly aggregating multiple OBUs into a single packet,
48        // or splitting a single OBU across multiple packets.
49        let packets_metadata = packetize(&obus, mtu);
50
51        let mut payloads = vec![];
52
53        // Split the payload into RTP packets according to the packetization scheme.
54        for packet_index in 0..packets_metadata.len() {
55            let packet = &packets_metadata[packet_index];
56            let mut obu_offset = packet.first_obu_offset;
57            let aggregation_header = get_aggregation_header(&obus, &packets_metadata, packet_index);
58
59            let mut out = BytesMut::with_capacity(AGGREGATION_HEADER_SIZE + packet.packet_size);
60            out.put_u8(aggregation_header);
61
62            // Store all OBU elements except the last one.
63            for i in 0..packet.num_obu_elements - 1 {
64                let obu = &obus[packet.first_obu_index + i];
65                let fragment_size = obu.size - obu_offset;
66                out.put_leb128(fragment_size as u32);
67                if obu_offset == 0 {
68                    out.put_u8(obu.header & !OBU_HAS_SIZE_BIT);
69                }
70                if obu_offset <= 1 && obu_has_extension(obu.header) {
71                    out.put_u8(obu.extension_header);
72                }
73                let payload_offset = if obu_offset > obu.header_size() {
74                    obu_offset - obu.header_size()
75                } else {
76                    0
77                };
78                let payload_size = obu.payload.len() - payload_offset;
79                out.put_slice(
80                    obu.payload
81                        .slice(payload_offset..payload_offset + payload_size)
82                        .as_ref(),
83                );
84                // All obus are stored from the beginning, except, may be, the first one.
85                obu_offset = 0;
86            }
87
88            // Store the last OBU element.
89            let last_obu = &obus[packet.first_obu_index + packet.num_obu_elements - 1];
90            let mut fragment_size = packet.last_obu_size;
91            if packet.num_obu_elements > MAX_NUM_OBUS_TO_OMIT_SIZE {
92                out.put_leb128(fragment_size as u32);
93            }
94            if obu_offset == 0 && fragment_size > 0 {
95                out.put_u8(last_obu.header & !OBU_HAS_SIZE_BIT);
96                fragment_size -= 1;
97            }
98            if obu_offset <= 1 && obu_has_extension(last_obu.header) && fragment_size > 0 {
99                out.put_u8(last_obu.extension_header);
100                fragment_size -= 1;
101            }
102            let payload_offset = if obu_offset > last_obu.header_size() {
103                obu_offset - last_obu.header_size()
104            } else {
105                0
106            };
107            out.put_slice(
108                last_obu
109                    .payload
110                    .slice(payload_offset..payload_offset + fragment_size)
111                    .as_ref(),
112            );
113
114            payloads.push(out.freeze());
115        }
116
117        Ok(payloads)
118    }
119
120    fn clone_to(&self) -> Box<dyn Payloader> {
121        Box::new(self.clone())
122    }
123}
rtc_rtp/codecs/av1/mod.rs

rtc_rtp/codecs/av1/
mod.rs
