srt_protocol/options/
bandwidth.rs

1// rate in bytes per second
2use super::*;
3
4/// https://datatracker.ietf.org/doc/html/draft-sharabayko-srt-00#section-5.1.1
5///
6/// Note that Maximum Bandwidth, Input Rate, and Input Rate Estimate are bytes per second
7/// and Overhead is a percentage.
8#[derive(Debug, Clone, Eq, PartialEq, Default)]
9pub enum LiveBandwidthMode {
10    /// Set the maximum bandwidth explicitly.
11    ///
12    /// The recommended default value is 1 Gbps. The default value is set only for live streaming.
13    ///
14    /// Note that this static setting is not well-suited to a variable input, like when you change
15    /// the bitrate on an encoder. Each time the input bitrate is configured on the encoder, this
16    /// value should also be reconfigured.
17    Max(DataRate), // m_llMaxBW != 0
18
19    /// Set the SRT send input rate and overhead.
20    /// In this mode, SRT calculates the maximum bandwidth as follows:
21    ///
22    ///   Maximum Bandwidth = Input Rate * (1 + Overhead / 100)
23    ///
24    /// Note that Input mode reduces to the Set mode and the same restrictions apply.
25    Input {
26        // m_llInputBW != 0
27        rate: DataRate,    // m_llInputBW
28        overhead: Percent, // m_iOverheadBW
29    },
30
31    /// Measure the SRT send input rate internally and set the Overhead.
32    ///
33    /// In this mode, SRT adjusts the value of maximum bandwidth each time it gets the updated
34    /// Input Rate Estimate of the Input Rate:
35    ///
36    ///   Maximum Bandwidth = Input Rate Estimate * (1 + Overhead / 100)
37    ///
38    /// Estimated mode is recommended for setting the Maximum Bandwidth as it follows the
39    /// fluctuations in SRT send Input Rate. However, there are certain considerations that
40    /// should be taken into account.
41    ///
42    ///
43    /// In Estimated mode, SRT takes as an initial Expected Input Rate. This should match the
44    /// configured output bitrate rate of an encoder (in terms of bitrate for the packets including
45    /// audio and overhead). But it is normal for an encoder to occasionally overshoot. At a low
46    /// bitrate, sometimes an encoder can be too optimistic and will output more bits than expected.
47    /// Under these conditions, SRT packets would not go out fast enough because the configured
48    /// bandwidth limitation would be too low. This is mitigated by calculating the bitrate
49    /// internally.
50    ///
51    /// SRT examines the packets being submitted and calculates an Input Rate Estimate as a moving
52    /// average. However, this introduces a bit of a delay based on the content. It also means that
53    /// if an encoder encounters black screens or still frames, this would dramatically lower the
54    /// bitrate being measured, which would in turn reduce the SRT output rate. And then, when the
55    /// video picks up again, the input rate rises sharply. SRT would not start up again fast
56    /// enough on output because of the time it takes to measure the speed. Packets might be
57    /// accumulated in the SRT send buffer, and delayed as a result, causing them to arrive too late
58    /// at the decoder, and possible drops by the receiver.
59    Estimated {
60        // m_llMaxBW == 0 && m_llInputBW == 0
61        overhead: Percent,  // m_iOverheadBW
62        expected: DataRate, // SRTO_MININPUTBW
63    },
64    #[default]
65    Unlimited,
66}
srt_protocol/options/bandwidth.rs

srt_protocol/options/
bandwidth.rs
