rtc_rtp/codec/av1/
mod.rs

1use bytes::{BufMut, Bytes, BytesMut};
2
3use crate::codec::av1::leb128::BytesMutExt;
4use crate::codec::av1::obu::{OBU_HAS_SIZE_BIT, obu_has_extension, parse_obus};
5use crate::codec::av1::packetizer::{
6    AGGREGATION_HEADER_SIZE, MAX_NUM_OBUS_TO_OMIT_SIZE, get_aggregation_header, packetize,
7};
8use crate::packetizer::Payloader;
9use shared::error::Result;
10
11#[cfg(test)]
12mod av1_test;
13mod depacketizer;
14mod leb128;
15mod obu;
16mod packetizer;
17
18pub use depacketizer::Av1Depacketizer;
19
20#[derive(Default, Clone, Debug)]
21pub struct Av1Payloader {}
22
23impl Payloader for Av1Payloader {
24    /// Based on <https://chromium.googlesource.com/external/webrtc/+/4e513346ec56c829b3a6010664998469fc237b35/modules/rtp_rtcp/source/rtp_packetizer_av1.cc>
25    /// Reference: <https://aomediacodec.github.io/av1-rtp-spec/#45-payload-structure>
26    fn payload(&mut self, mtu: usize, payload: &Bytes) -> Result<Vec<Bytes>> {
27        // 0                   1                   2                   3
28        // 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
29        // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
30        // |Z|Y|1 0|N|-|-|-|  OBU element 1 size (leb128)  |               |
31        // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+               |
32        // |                                                               |
33        // :                                                               :
34        // :                      OBU element 1 data                       :
35        // :                                                               :
36        // |                                                               |
37        // |                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
38        // |                               |                               |
39        // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
40        // |                                                               |
41        // :                                                               :
42        // :                      OBU element 2 data                       :
43        // :                                                               :
44        // |                                                               |
45        // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
46
47        // Parse the payload into series of OBUs.
48        let obus = parse_obus(payload)?;
49
50        // Packetize the OBUs, possibly aggregating multiple OBUs into a single packet,
51        // or splitting a single OBU across multiple packets.
52        let packets_metadata = packetize(&obus, mtu);
53
54        let mut payloads = vec![];
55
56        // Split the payload into RTP packets according to the packetization scheme.
57        for packet_index in 0..packets_metadata.len() {
58            let packet = &packets_metadata[packet_index];
59            let mut obu_offset = packet.first_obu_offset;
60            let aggregation_header = get_aggregation_header(&obus, &packets_metadata, packet_index);
61
62            let mut out = BytesMut::with_capacity(AGGREGATION_HEADER_SIZE + packet.packet_size);
63            out.put_u8(aggregation_header);
64
65            // Store all OBU elements except the last one.
66            for i in 0..packet.num_obu_elements - 1 {
67                let obu = &obus[packet.first_obu_index + i];
68                let fragment_size = obu.size - obu_offset;
69                out.put_leb128(fragment_size as u32);
70                if obu_offset == 0 {
71                    out.put_u8(obu.header & !OBU_HAS_SIZE_BIT);
72                }
73                if obu_offset <= 1 && obu_has_extension(obu.header) {
74                    out.put_u8(obu.extension_header);
75                }
76                let payload_offset = if obu_offset > obu.header_size() {
77                    obu_offset - obu.header_size()
78                } else {
79                    0
80                };
81                let payload_size = obu.payload.len() - payload_offset;
82                out.put_slice(
83                    obu.payload
84                        .slice(payload_offset..payload_offset + payload_size)
85                        .as_ref(),
86                );
87                // All obus are stored from the beginning, except, may be, the first one.
88                obu_offset = 0;
89            }
90
91            // Store the last OBU element.
92            let last_obu = &obus[packet.first_obu_index + packet.num_obu_elements - 1];
93            let mut fragment_size = packet.last_obu_size;
94            if packet.num_obu_elements > MAX_NUM_OBUS_TO_OMIT_SIZE {
95                out.put_leb128(fragment_size as u32);
96            }
97            if obu_offset == 0 && fragment_size > 0 {
98                out.put_u8(last_obu.header & !OBU_HAS_SIZE_BIT);
99                fragment_size -= 1;
100            }
101            if obu_offset <= 1 && obu_has_extension(last_obu.header) && fragment_size > 0 {
102                out.put_u8(last_obu.extension_header);
103                fragment_size -= 1;
104            }
105            let payload_offset = if obu_offset > last_obu.header_size() {
106                obu_offset - last_obu.header_size()
107            } else {
108                0
109            };
110            out.put_slice(
111                last_obu
112                    .payload
113                    .slice(payload_offset..payload_offset + fragment_size)
114                    .as_ref(),
115            );
116
117            payloads.push(out.freeze());
118        }
119
120        Ok(payloads)
121    }
122
123    fn clone_to(&self) -> Box<dyn Payloader> {
124        Box::new(self.clone())
125    }
126}
rtc_rtp/codec/av1/mod.rs

rtc_rtp/codec/av1/
mod.rs
