retina/examples/client/mp4.rs
2021-09-09 17:34:49 -07:00

738 lines
28 KiB
Rust

// Copyright (C) 2021 Scott Lamb <slamb@slamb.org>
// SPDX-License-Identifier: MIT OR Apache-2.0
//! Proof-of-concept `.mp4` writer.
//!
//! This writes media data (`mdat`) to a stream, buffering parameters for a
//! `moov` atom at the end. This avoids the need to buffer the media data
//! (`mdat`) first or reserved a fixed size for the `moov`, but it will slow
//! playback, particularly when serving `.mp4` files remotely.
//!
//! For a more high-quality implementation, see [Moonfire NVR](https://github.com/scottlamb/moonfire-nvr).
//! It's better tested, places the `moov` atom at the start, can do HTTP range
//! serving for arbitrary time ranges, and supports standard and fragmented
//! `.mp4` files.
//!
//! See the BMFF spec, ISO/IEC 14496-12:2015:
//! https://github.com/scottlamb/moonfire-nvr/wiki/Standards-and-specifications
//! https://standards.iso.org/ittf/PubliclyAvailableStandards/c068960_ISO_IEC_14496-12_2015.zip
use anyhow::{anyhow, bail, Context, Error};
use bytes::{Buf, BufMut, BytesMut};
use futures::{Future, StreamExt};
use log::{info, warn};
use retina::{
client::Transport,
codec::{AudioParameters, CodecItem, VideoParameters},
};
use std::num::NonZeroU32;
use std::path::PathBuf;
use std::{convert::TryFrom, pin::Pin};
use std::{io::SeekFrom, sync::Arc};
use tokio::{
fs::File,
io::{AsyncSeek, AsyncSeekExt, AsyncWrite, AsyncWriteExt},
};
#[derive(structopt::StructOpt)]
pub struct Opts {
#[structopt(flatten)]
src: super::Source,
/// Policy for handling the `rtptime` parameter normally seem in the `RTP-Info` header.
/// One of `default`, `require`, `ignore`, `permissive`.
#[structopt(default_value, long)]
initial_timestamp: retina::client::InitialTimestampPolicy,
/// Don't attempt to include video streams.
#[structopt(long)]
no_video: bool,
/// Don't attempt to include audio streams.
#[structopt(long)]
no_audio: bool,
/// Allow lost packets mid-stream without aborting.
#[structopt(long)]
allow_loss: bool,
/// Duration after which to exit automatically, in seconds.
#[structopt(long, name = "secs")]
duration: Option<u64>,
/// The transport to use: `tcp` or `udp` (experimental).
///
/// Note: `--allow-loss` is strongly recommended with `udp`.
#[structopt(default_value, long)]
transport: retina::client::Transport,
/// Path to `.mp4` file to write.
#[structopt(parse(try_from_str))]
out: PathBuf,
}
/// Writes a box length for everything appended in the supplied scope.
macro_rules! write_box {
($buf:expr, $fourcc:expr, $b:block) => {{
let _: &mut BytesMut = $buf; // type-check.
let pos_start = $buf.len();
let fourcc: &[u8; 4] = $fourcc;
$buf.extend_from_slice(&[0, 0, 0, 0, fourcc[0], fourcc[1], fourcc[2], fourcc[3]]);
let r = {
$b;
};
let pos_end = $buf.len();
let len = pos_end.checked_sub(pos_start).unwrap();
$buf[pos_start..pos_start + 4].copy_from_slice(&u32::try_from(len)?.to_be_bytes()[..]);
r
}};
}
async fn write_all_buf<W: AsyncWrite + Unpin, B: Buf>(
writer: &mut W,
buf: &mut B,
) -> Result<(), Error> {
// TODO: this doesn't use vectored I/O. Annoying.
while buf.has_remaining() {
writer.write_buf(buf).await?;
}
Ok(())
}
/// Writes `.mp4` data to a sink.
/// See module-level documentation for details.
pub struct Mp4Writer<W: AsyncWrite + AsyncSeek + Send + Unpin> {
mdat_start: u32,
mdat_pos: u32,
video_params: Option<Box<VideoParameters>>,
audio_params: Option<Box<AudioParameters>>,
allow_loss: bool,
/// The (1-indexed) video sample (frame) number of each sync sample (random access point).
video_sync_sample_nums: Vec<u32>,
video_trak: TrakTracker,
audio_trak: TrakTracker,
inner: W,
}
/// Tracks the parts of a `trak` atom which are common between video and audio samples.
#[derive(Default)]
struct TrakTracker {
samples: u32,
next_pos: Option<u32>,
chunks: Vec<(u32, u32)>, // (1-based sample_number, byte_pos)
sizes: Vec<u32>,
/// The durations of samples in a run-length encoding form: (number of samples, duration).
/// This lags one sample behind calls to `add_sample` because each sample's duration
/// is calculated using the PTS of the following sample.
durations: Vec<(u32, u32)>,
last_pts: Option<i64>,
tot_duration: u64,
}
impl TrakTracker {
fn add_sample(
&mut self,
pos: u32,
size: u32,
timestamp: retina::Timestamp,
loss: u16,
allow_loss: bool,
) -> Result<(), Error> {
if self.samples > 0 && loss > 0 && !allow_loss {
bail!("Lost {} RTP packets mid-stream", loss);
}
self.samples += 1;
if self.next_pos != Some(pos) {
self.chunks.push((self.samples, pos));
}
self.sizes.push(size);
self.next_pos = Some(pos + size);
if let Some(last_pts) = self.last_pts.replace(timestamp.timestamp()) {
let duration = timestamp.timestamp().checked_sub(last_pts).unwrap();
self.tot_duration += u64::try_from(duration).unwrap();
let duration = u32::try_from(duration)?;
match self.durations.last_mut() {
Some((s, d)) if *d == duration => *s += 1,
_ => self.durations.push((1, duration)),
}
}
Ok(())
}
fn finish(&mut self) {
if self.last_pts.is_some() {
self.durations.push((1, 0));
}
}
/// Estimates the sum of the variable-sized portions of the data.
fn size_estimate(&self) -> usize {
(self.durations.len() * 8) + // stts
(self.chunks.len() * 12) + // stsc
(self.sizes.len() * 4) + // stsz
(self.chunks.len() * 4) // stco
}
fn write_common_stbl_parts(&self, buf: &mut BytesMut) -> Result<(), Error> {
// TODO: add an edit list so the video and audio tracks are in sync.
write_box!(buf, b"stts", {
buf.put_u32(0);
buf.put_u32(u32::try_from(self.durations.len())?);
for (samples, duration) in &self.durations {
buf.put_u32(*samples);
buf.put_u32(*duration);
}
});
write_box!(buf, b"stsc", {
buf.put_u32(0); // version
buf.put_u32(u32::try_from(self.chunks.len())?);
let mut prev_sample_number = 1;
let mut chunk_number = 1;
if !self.chunks.is_empty() {
for &(sample_number, _pos) in &self.chunks[1..] {
buf.put_u32(chunk_number);
buf.put_u32(sample_number - prev_sample_number);
buf.put_u32(1); // sample_description_index
prev_sample_number = sample_number;
chunk_number += 1;
}
buf.put_u32(chunk_number);
buf.put_u32(self.samples + 1 - prev_sample_number);
buf.put_u32(1); // sample_description_index
}
});
write_box!(buf, b"stsz", {
buf.put_u32(0); // version
buf.put_u32(0); // sample_size
buf.put_u32(u32::try_from(self.sizes.len())?);
for s in &self.sizes {
buf.put_u32(*s);
}
});
write_box!(buf, b"stco", {
buf.put_u32(0); // version
buf.put_u32(u32::try_from(self.chunks.len())?); // entry_count
for &(_sample_number, pos) in &self.chunks {
buf.put_u32(pos);
}
});
Ok(())
}
}
impl<W: AsyncWrite + AsyncSeek + Send + Unpin> Mp4Writer<W> {
pub async fn new(
video_params: Option<Box<VideoParameters>>,
audio_params: Option<Box<AudioParameters>>,
allow_loss: bool,
mut inner: W,
) -> Result<Self, Error> {
let mut buf = BytesMut::new();
write_box!(&mut buf, b"ftyp", {
buf.extend_from_slice(&[
b'i', b's', b'o', b'm', // major_brand
0, 0, 0, 0, // minor_version
b'i', b's', b'o', b'm', // compatible_brands[0]
]);
});
buf.extend_from_slice(&b"\0\0\0\0mdat"[..]);
let mdat_start = u32::try_from(buf.len())?;
write_all_buf(&mut inner, &mut buf).await?;
Ok(Mp4Writer {
inner,
video_params,
audio_params,
allow_loss,
video_trak: TrakTracker::default(),
audio_trak: TrakTracker::default(),
video_sync_sample_nums: Vec::new(),
mdat_start,
mdat_pos: mdat_start,
})
}
pub async fn finish(mut self) -> Result<(), Error> {
self.video_trak.finish();
self.audio_trak.finish();
let mut buf = BytesMut::with_capacity(
1024 + self.video_trak.size_estimate()
+ self.audio_trak.size_estimate()
+ 4 * self.video_sync_sample_nums.len(),
);
write_box!(&mut buf, b"moov", {
write_box!(&mut buf, b"mvhd", {
buf.put_u32(1 << 24); // version
buf.put_u64(0); // creation_time
buf.put_u64(0); // modification_time
buf.put_u32(90000); // timescale
buf.put_u64(self.video_trak.tot_duration);
buf.put_u32(0x00010000); // rate
buf.put_u16(0x0100); // volume
buf.put_u16(0); // reserved
buf.put_u64(0); // reserved
for v in &[0x00010000, 0, 0, 0, 0x00010000, 0, 0, 0, 0x40000000] {
buf.put_u32(*v); // matrix
}
for _ in 0..6 {
buf.put_u32(0); // pre_defined
}
buf.put_u32(2); // next_track_id
});
if let Some(p) = self.video_params.as_ref() {
self.write_video_trak(&mut buf, p)?;
}
if let Some(p) = self.audio_params.as_ref() {
self.write_audio_trak(&mut buf, p)?;
}
});
write_all_buf(&mut self.inner, &mut buf.freeze()).await?;
self.inner
.seek(SeekFrom::Start(u64::from(self.mdat_start - 8)))
.await?;
self.inner
.write_all(&u32::try_from(self.mdat_pos + 8 - self.mdat_start)?.to_be_bytes()[..])
.await?;
Ok(())
}
fn write_video_trak(
&self,
buf: &mut BytesMut,
parameters: &VideoParameters,
) -> Result<(), Error> {
write_box!(buf, b"trak", {
write_box!(buf, b"tkhd", {
buf.put_u32((1 << 24) | 7); // version, flags
buf.put_u64(0); // creation_time
buf.put_u64(0); // modification_time
buf.put_u32(1); // track_id
buf.put_u32(0); // reserved
buf.put_u64(self.video_trak.tot_duration);
buf.put_u64(0); // reserved
buf.put_u16(0); // layer
buf.put_u16(0); // alternate_group
buf.put_u16(0); // volume
buf.put_u16(0); // reserved
for v in &[0x00010000, 0, 0, 0, 0x00010000, 0, 0, 0, 0x40000000] {
buf.put_u32(*v); // matrix
}
let dims = self
.video_params
.as_ref()
.map(|p| p.pixel_dimensions())
.unwrap_or((0, 0));
let width = u32::from(u16::try_from(dims.0)?) << 16;
let height = u32::from(u16::try_from(dims.1)?) << 16;
buf.put_u32(width);
buf.put_u32(height);
});
write_box!(buf, b"mdia", {
write_box!(buf, b"mdhd", {
buf.put_u32(1 << 24); // version
buf.put_u64(0); // creation_time
buf.put_u64(0); // modification_time
buf.put_u32(90000); // timebase
buf.put_u64(self.video_trak.tot_duration);
buf.put_u32(0x55c40000); // language=und + pre-defined
});
write_box!(buf, b"hdlr", {
buf.extend_from_slice(&[
0x00, 0x00, 0x00, 0x00, // version + flags
0x00, 0x00, 0x00, 0x00, // pre_defined
b'v', b'i', b'd', b'e', // handler = vide
0x00, 0x00, 0x00, 0x00, // reserved[0]
0x00, 0x00, 0x00, 0x00, // reserved[1]
0x00, 0x00, 0x00, 0x00, // reserved[2]
0x00, // name, zero-terminated (empty)
]);
});
write_box!(buf, b"minf", {
write_box!(buf, b"vmhd", {
buf.put_u32(1);
buf.put_u64(0);
});
write_box!(buf, b"dinf", {
write_box!(buf, b"dref", {
buf.put_u32(0);
buf.put_u32(1); // entry_count
write_box!(buf, b"url ", {
buf.put_u32(1); // version, flags=self-contained
});
});
});
write_box!(buf, b"stbl", {
write_box!(buf, b"stsd", {
buf.put_u32(0); // version
buf.put_u32(1); // entry_count
self.write_video_sample_entry(buf, parameters)?;
});
self.video_trak.write_common_stbl_parts(buf)?;
write_box!(buf, b"stss", {
buf.put_u32(0); // version
buf.put_u32(u32::try_from(self.video_sync_sample_nums.len())?);
for n in &self.video_sync_sample_nums {
buf.put_u32(*n);
}
});
});
});
});
});
Ok(())
}
fn write_audio_trak(
&self,
buf: &mut BytesMut,
parameters: &AudioParameters,
) -> Result<(), Error> {
write_box!(buf, b"trak", {
write_box!(buf, b"tkhd", {
buf.put_u32((1 << 24) | 7); // version, flags
buf.put_u64(0); // creation_time
buf.put_u64(0); // modification_time
buf.put_u32(2); // track_id
buf.put_u32(0); // reserved
buf.put_u64(self.audio_trak.tot_duration);
buf.put_u64(0); // reserved
buf.put_u16(0); // layer
buf.put_u16(0); // alternate_group
buf.put_u16(0); // volume
buf.put_u16(0); // reserved
for v in &[0x00010000, 0, 0, 0, 0x00010000, 0, 0, 0, 0x40000000] {
buf.put_u32(*v); // matrix
}
buf.put_u32(0); // width
buf.put_u32(0); // height
});
write_box!(buf, b"mdia", {
write_box!(buf, b"mdhd", {
buf.put_u32(1 << 24); // version
buf.put_u64(0); // creation_time
buf.put_u64(0); // modification_time
buf.put_u32(parameters.clock_rate());
buf.put_u64(self.audio_trak.tot_duration);
buf.put_u32(0x55c40000); // language=und + pre-defined
});
write_box!(buf, b"hdlr", {
buf.extend_from_slice(&[
0x00, 0x00, 0x00, 0x00, // version + flags
0x00, 0x00, 0x00, 0x00, // pre_defined
b's', b'o', b'u', b'n', // handler = soun
0x00, 0x00, 0x00, 0x00, // reserved[0]
0x00, 0x00, 0x00, 0x00, // reserved[1]
0x00, 0x00, 0x00, 0x00, // reserved[2]
0x00, // name, zero-terminated (empty)
]);
});
write_box!(buf, b"minf", {
write_box!(buf, b"smhd", {
buf.extend_from_slice(&[
0x00, 0x00, 0x00, 0x00, // version + flags
0x00, 0x00, // balance
0x00, 0x00, // reserved
]);
});
write_box!(buf, b"dinf", {
write_box!(buf, b"dref", {
buf.put_u32(0);
buf.put_u32(1); // entry_count
write_box!(buf, b"url ", {
buf.put_u32(1); // version, flags=self-contained
});
});
});
write_box!(buf, b"stbl", {
write_box!(buf, b"stsd", {
buf.put_u32(0); // version
buf.put_u32(1); // entry_count
buf.extend_from_slice(&parameters.sample_entry().unwrap()[..]);
});
self.audio_trak.write_common_stbl_parts(buf)?;
// AAC requires two samples (really, each is a set of 960 or 1024 samples)
// to decode accurately. See
// https://developer.apple.com/library/archive/documentation/QuickTime/QTFF/QTFFAppenG/QTFFAppenG.html .
write_box!(buf, b"sgpd", {
// BMFF section 8.9.3: SampleGroupDescriptionBox
buf.put_u32(0); // version
buf.extend_from_slice(b"roll"); // grouping type
buf.put_u32(1); // entry_count
// BMFF section 10.1: AudioRollRecoveryEntry
buf.put_i16(-1); // roll_distance
});
write_box!(buf, b"sbgp", {
// BMFF section 8.9.2: SampleToGroupBox
buf.put_u32(0); // version
buf.extend_from_slice(b"roll"); // grouping type
buf.put_u32(1); // entry_count
buf.put_u32(self.audio_trak.samples);
buf.put_u32(1); // group_description_index
});
});
});
});
});
Ok(())
}
fn write_video_sample_entry(
&self,
buf: &mut BytesMut,
parameters: &VideoParameters,
) -> Result<(), Error> {
// TODO: this should move to client::VideoParameters::sample_entry() or some such.
write_box!(buf, b"avc1", {
buf.put_u32(0);
buf.put_u32(1); // data_reference_index = 1
buf.extend_from_slice(&[0; 16]);
buf.put_u16(u16::try_from(parameters.pixel_dimensions().0)?);
buf.put_u16(u16::try_from(parameters.pixel_dimensions().1)?);
buf.extend_from_slice(&[
0x00, 0x48, 0x00, 0x00, // horizresolution
0x00, 0x48, 0x00, 0x00, // vertresolution
0x00, 0x00, 0x00, 0x00, // reserved
0x00, 0x01, // frame count
0x00, 0x00, 0x00, 0x00, // compressorname
0x00, 0x00, 0x00, 0x00, //
0x00, 0x00, 0x00, 0x00, //
0x00, 0x00, 0x00, 0x00, //
0x00, 0x00, 0x00, 0x00, //
0x00, 0x00, 0x00, 0x00, //
0x00, 0x00, 0x00, 0x00, //
0x00, 0x00, 0x00, 0x00, //
0x00, 0x18, 0xff, 0xff, // depth + pre_defined
]);
write_box!(buf, b"avcC", {
buf.extend_from_slice(parameters.extra_data());
});
});
Ok(())
}
async fn video(&mut self, mut frame: retina::codec::VideoFrame) -> Result<(), Error> {
println!(
"{}: {}-byte video frame",
&frame.timestamp,
frame.data().remaining(),
);
if let Some(p) = frame.new_parameters.take() {
if self.video_trak.samples > 0 {
bail!("parameters change unimplemented. new parameters: {:#?}", p);
}
self.video_params = Some(p);
}
let size = u32::try_from(frame.data().remaining())?;
self.video_trak.add_sample(
self.mdat_pos,
size,
frame.timestamp,
frame.loss,
self.allow_loss,
)?;
self.mdat_pos = self
.mdat_pos
.checked_add(size)
.ok_or_else(|| anyhow!("mdat_pos overflow"))?;
if frame.is_random_access_point {
self.video_sync_sample_nums
.push(u32::try_from(self.video_trak.samples)?);
}
let mut data = frame.into_data();
write_all_buf(&mut self.inner, &mut data).await?;
Ok(())
}
async fn audio(&mut self, mut frame: retina::codec::AudioFrame) -> Result<(), Error> {
println!(
"{}: {}-byte audio frame",
&frame.timestamp,
frame.data.remaining()
);
let size = u32::try_from(frame.data.remaining())?;
self.audio_trak.add_sample(
self.mdat_pos,
size,
frame.timestamp,
frame.loss,
self.allow_loss,
)?;
self.mdat_pos = self
.mdat_pos
.checked_add(size)
.ok_or_else(|| anyhow!("mdat_pos overflow"))?;
write_all_buf(&mut self.inner, &mut frame.data).await?;
Ok(())
}
}
/// Copies packets from `session` to `mp4` without handling any cleanup on error.
async fn copy<'a>(
opts: &'a Opts,
session: &'a mut retina::client::Demuxed,
stop_signal: Pin<Box<dyn Future<Output = Result<(), std::io::Error>>>>,
mp4: &'a mut Mp4Writer<File>,
) -> Result<(), Error> {
let sleep = match opts.duration {
Some(secs) => {
futures::future::Either::Left(tokio::time::sleep(std::time::Duration::from_secs(secs)))
}
None => futures::future::Either::Right(futures::future::pending()),
};
tokio::pin!(stop_signal);
tokio::pin!(sleep);
loop {
tokio::select! {
pkt = session.next() => {
match pkt.ok_or_else(|| anyhow!("EOF"))?? {
CodecItem::VideoFrame(f) => {
let start_ctx = f.start_ctx();
mp4.video(f).await.with_context(
|| format!("Error processing video frame starting with {}", start_ctx))?;
},
CodecItem::AudioFrame(f) => {
let ctx = f.ctx;
mp4.audio(f).await.with_context(
|| format!("Error processing audio frame, {}", ctx))?;
},
CodecItem::SenderReport(sr) => {
println!("{}: SR ts={}", sr.timestamp, sr.ntp_timestamp);
},
_ => continue,
};
},
_ = &mut stop_signal => {
info!("Stopping due to signal");
break;
},
_ = &mut sleep => {
info!("Stopping after {} seconds", opts.duration.unwrap());
break;
},
}
}
Ok(())
}
/// Writes the `.mp4`, including trying to finish or clean up the file.
async fn write_mp4<'a>(
opts: &'a Opts,
session: retina::client::Session<retina::client::Described>,
video_stream: Option<(usize, VideoParameters)>,
audio_stream: Option<(usize, AudioParameters)>,
stop_signal: Pin<Box<dyn Future<Output = Result<(), std::io::Error>>>>,
) -> Result<(), Error> {
let mut session = session
.play(
retina::client::PlayOptions::default()
.initial_timestamp(opts.initial_timestamp)
.enforce_timestamps_with_max_jump_secs(NonZeroU32::new(10).unwrap()),
)
.await?
.demuxed()?;
// Append into a filename suffixed with ".partial", then try to either rename it into
// place if it's complete or delete it otherwise.
const PARTIAL_SUFFIX: &str = ".partial";
let mut tmp_filename = opts.out.as_os_str().to_owned();
tmp_filename.push(PARTIAL_SUFFIX); // OsString::push doesn't put in a '/', unlike PathBuf::.
let tmp_filename: PathBuf = tmp_filename.into();
let out = tokio::fs::File::create(&tmp_filename).await?;
let mut mp4 = Mp4Writer::new(
video_stream.map(|(_, p)| Box::new(p)),
audio_stream.map(|(_, p)| Box::new(p)),
opts.allow_loss,
out,
)
.await?;
let result = copy(opts, &mut session, stop_signal, &mut mp4).await;
if let Err(e) = result {
// Log errors about finishing, returning the original error.
if let Err(e) = mp4.finish().await {
log::error!(".mp4 finish failed: {}", e);
if let Err(e) = tokio::fs::remove_file(&tmp_filename).await {
log::error!("and removing .mp4 failed too: {}", e);
}
} else {
if let Err(e) = tokio::fs::rename(&tmp_filename, &opts.out).await {
log::error!("unable to move completed .mp4 into place: {}", e);
}
}
Err(e)
} else {
// Directly return errors about finishing.
if let Err(e) = mp4.finish().await {
log::error!(".mp4 finish failed: {}", e);
if let Err(e) = tokio::fs::remove_file(&tmp_filename).await {
log::error!("and removing .mp4 failed too: {}", e);
}
Err(e)
} else {
tokio::fs::rename(&tmp_filename, &opts.out).await?;
Ok(())
}
}
}
pub async fn run(opts: Opts) -> Result<(), Error> {
if matches!(opts.transport, Transport::Udp) && !opts.allow_loss {
warn!("Using --transport=udp without strongly recommended --allow-loss!");
}
let creds = super::creds(opts.src.username.clone(), opts.src.password.clone());
let stop_signal = Box::pin(tokio::signal::ctrl_c());
let session_group = Arc::new(retina::client::SessionGroup::default());
let mut session = retina::client::Session::describe(
opts.src.url.clone(),
retina::client::SessionOptions::default()
.creds(creds)
.session_group(session_group.clone())
.user_agent("Retina mp4 example".to_owned())
.transport(opts.transport),
)
.await?;
let video_stream = if !opts.no_video {
session
.streams()
.iter()
.enumerate()
.find_map(|(i, s)| match s.parameters() {
Some(retina::codec::Parameters::Video(v)) => Some((i, v.clone())),
_ => None,
})
} else {
None
};
if let Some((i, _)) = video_stream {
session.setup(i).await?;
}
let audio_stream = if !opts.no_audio {
session
.streams()
.iter()
.enumerate()
.find_map(|(i, s)| match s.parameters() {
Some(retina::codec::Parameters::Audio(a)) => Some((i, a.clone())),
_ => None,
})
} else {
None
};
if let Some((i, _)) = audio_stream {
session.setup(i).await?;
}
let result = write_mp4(&opts, session, video_stream, audio_stream, stop_signal).await;
// Session has now been dropped, on success or failure. A TEARDOWN should
// be pending if necessary. session_group.teardown() will wait for it.
if let Err(e) = session_group.teardown().await {
log::error!("TEARDOWN failed: {}", e);
}
result
}