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#[cfg(test)]
mod receiver_estimated_maximum_bitrate_test;
use std::any::Any;
use std::fmt;
use bytes::{Buf, BufMut};
use util::marshal::{Marshal, MarshalSize, Unmarshal};
use crate::error::Error;
use crate::header::*;
use crate::packet::*;
use crate::util::*;
type Result<T> = std::result::Result<T, util::Error>;
/// ReceiverEstimatedMaximumBitrate contains the receiver's estimated maximum bitrate.
/// see: https://tools.ietf.org/html/draft-alvestrand-rmcat-remb-03
#[derive(Debug, PartialEq, Default, Clone)]
pub struct ReceiverEstimatedMaximumBitrate {
/// SSRC of sender
pub sender_ssrc: u32,
/// Estimated maximum bitrate
pub bitrate: f32,
/// SSRC entries which this packet applies to
pub ssrcs: Vec<u32>,
}
const REMB_OFFSET: usize = 16;
/// Keep a table of powers to units for fast conversion.
const BIT_UNITS: [&str; 7] = ["b", "Kb", "Mb", "Gb", "Tb", "Pb", "Eb"];
const UNIQUE_IDENTIFIER: [u8; 4] = [b'R', b'E', b'M', b'B'];
/// String prints the REMB packet in a human-readable format.
impl fmt::Display for ReceiverEstimatedMaximumBitrate {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
// Do some unit conversions because b/s is far too difficult to read.
let mut bitrate = self.bitrate;
let mut powers = 0;
// Keep dividing the bitrate until it's under 1000
while bitrate >= 1000.0 && powers < BIT_UNITS.len() {
bitrate /= 1000.0;
powers += 1;
}
let unit = BIT_UNITS[powers];
write!(
f,
"ReceiverEstimatedMaximumBitrate {:x} {:.2} {}/s",
self.sender_ssrc, bitrate, unit,
)
}
}
impl Packet for ReceiverEstimatedMaximumBitrate {
/// Header returns the Header associated with this packet.
fn header(&self) -> Header {
Header {
padding: get_padding_size(self.raw_size()) != 0,
count: FORMAT_REMB,
packet_type: PacketType::PayloadSpecificFeedback,
length: ((self.marshal_size() / 4) - 1) as u16,
}
}
/// destination_ssrc returns an array of SSRC values that this packet refers to.
fn destination_ssrc(&self) -> Vec<u32> {
self.ssrcs.clone()
}
fn raw_size(&self) -> usize {
HEADER_LENGTH + REMB_OFFSET + self.ssrcs.len() * 4
}
fn as_any(&self) -> &(dyn Any + Send + Sync) {
self
}
fn equal(&self, other: &(dyn Packet + Send + Sync)) -> bool {
other
.as_any()
.downcast_ref::<ReceiverEstimatedMaximumBitrate>()
.map_or(false, |a| self == a)
}
fn cloned(&self) -> Box<dyn Packet + Send + Sync> {
Box::new(self.clone())
}
}
impl MarshalSize for ReceiverEstimatedMaximumBitrate {
fn marshal_size(&self) -> usize {
let l = self.raw_size();
// align to 32-bit boundary
l + get_padding_size(l)
}
}
impl Marshal for ReceiverEstimatedMaximumBitrate {
/// Marshal serializes the packet and returns a byte slice.
fn marshal_to(&self, mut buf: &mut [u8]) -> Result<usize> {
const BITRATE_MAX: f32 = 2.417_842_4e24; //0x3FFFFp+63;
/*
0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|V=2|P| FMT=15 | PT=206 | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SSRC of packet sender |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SSRC of media source |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Unique identifier 'R' 'E' 'M' 'B' |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Num SSRC | BR Exp | BR Mantissa |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SSRC feedback |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
*/
if buf.remaining_mut() < self.marshal_size() {
return Err(Error::BufferTooShort.into());
}
let h = self.header();
let n = h.marshal_to(buf)?;
buf = &mut buf[n..];
buf.put_u32(self.sender_ssrc);
buf.put_u32(0); // always zero
buf.put_slice(&UNIQUE_IDENTIFIER);
// Write the length of the ssrcs to follow at the end
buf.put_u8(self.ssrcs.len() as u8);
let mut exp = 0;
let mut bitrate = self.bitrate;
if bitrate >= BITRATE_MAX {
bitrate = BITRATE_MAX
}
if bitrate < 0.0 {
return Err(Error::InvalidBitrate.into());
}
while bitrate >= (1 << 18) as f32 {
bitrate /= 2.0;
exp += 1;
}
if exp >= (1 << 6) {
return Err(Error::InvalidBitrate.into());
}
let mantissa = bitrate.floor() as u32;
// We can't quite use the binary package because
// a) it's a uint24 and b) the exponent is only 6-bits
// Just trust me; this is big-endian encoding.
buf.put_u8((exp << 2) as u8 | (mantissa >> 16) as u8);
buf.put_u8((mantissa >> 8) as u8);
buf.put_u8(mantissa as u8);
// Write the SSRCs at the very end.
for ssrc in &self.ssrcs {
buf.put_u32(*ssrc);
}
if h.padding {
put_padding(buf, self.raw_size());
}
Ok(self.marshal_size())
}
}
impl Unmarshal for ReceiverEstimatedMaximumBitrate {
/// Unmarshal reads a REMB packet from the given byte slice.
fn unmarshal<B>(raw_packet: &mut B) -> Result<Self>
where
Self: Sized,
B: Buf,
{
let raw_packet_len = raw_packet.remaining();
// 20 bytes is the size of the packet with no SSRCs
if raw_packet_len < 20 {
return Err(Error::PacketTooShort.into());
}
const MANTISSA_MAX: u32 = 0x7FFFFF;
/*
0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|V=2|P| FMT=15 | PT=206 | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SSRC of packet sender |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SSRC of media source |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Unique identifier 'R' 'E' 'M' 'B' |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Num SSRC | BR Exp | BR Mantissa |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SSRC feedback |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
*/
let header = Header::unmarshal(raw_packet)?;
if header.packet_type != PacketType::PayloadSpecificFeedback || header.count != FORMAT_REMB
{
return Err(Error::WrongType.into());
}
let sender_ssrc = raw_packet.get_u32();
let media_ssrc = raw_packet.get_u32();
if media_ssrc != 0 {
return Err(Error::SsrcMustBeZero.into());
}
// REMB rules all around me
let mut unique_identifier = [0; 4];
unique_identifier[0] = raw_packet.get_u8();
unique_identifier[1] = raw_packet.get_u8();
unique_identifier[2] = raw_packet.get_u8();
unique_identifier[3] = raw_packet.get_u8();
if unique_identifier[0] != UNIQUE_IDENTIFIER[0]
|| unique_identifier[1] != UNIQUE_IDENTIFIER[1]
|| unique_identifier[2] != UNIQUE_IDENTIFIER[2]
|| unique_identifier[3] != UNIQUE_IDENTIFIER[3]
{
return Err(Error::MissingRembIdentifier.into());
}
// The next byte is the number of SSRC entries at the end.
let ssrcs_len = raw_packet.get_u8() as usize;
// Get the 6-bit exponent value.
let b17 = raw_packet.get_u8();
let mut exp = (b17 as u64) >> 2;
exp += 127; // bias for IEEE754
exp += 23; // IEEE754 biases the decimal to the left, abs-send-time biases it to the right
// The remaining 2-bits plus the next 16-bits are the mantissa.
let b18 = raw_packet.get_u8();
let b19 = raw_packet.get_u8();
let mut mantissa = ((b17 & 3) as u32) << 16 | (b18 as u32) << 8 | b19 as u32;
if mantissa != 0 {
// ieee754 requires an implicit leading bit
while (mantissa & (MANTISSA_MAX + 1)) == 0 {
exp -= 1;
mantissa *= 2;
}
}
// bitrate = mantissa * 2^exp
let bitrate = f32::from_bits(((exp as u32) << 23) | (mantissa & MANTISSA_MAX));
let mut ssrcs = vec![];
for _i in 0..ssrcs_len {
ssrcs.push(raw_packet.get_u32());
}
if
/*header.padding &&*/
raw_packet.has_remaining() {
raw_packet.advance(raw_packet.remaining());
}
Ok(ReceiverEstimatedMaximumBitrate {
sender_ssrc,
//media_ssrc,
bitrate,
ssrcs,
})
}
}