Not hearing any audio from ONVIF audio backchannel - rtsp

Question

I'm trying to write a small program using node-JS and ffmpeg to test the audio backchannel functionality of my Hikvision DS-2CD2145FWD-IS IP camera. I'm using a lightgly modified version of the rtsp-client libraray (so I can add in the "Require:www.onvif.org/ver20/backchannel" header) to sent up the stream, and then ffmpeg to actually stream the audio.
The problem is after I have sent the play request (to which I get a 200/OK response) and then start playing the audio I want to stream, I'm not hearing anything coming out of the speaker connected to my camera, and a few seconds after trying to start playing the audio the rtsp connection resets. I'm pretty sure I've encoded the audio correctly (8000Hz, 16bit, PCM), and I can see from the response to the describe message that the camera definitely supports this feature.
Here is my code
const RTSPClient = require('rtsp-client');
const { exec } = require("child_process");
var client;
var session;
async function shutdown()
{
console.log("Doing shutdown now");
const tear = await client.teardown();
console.log("---- teardown ----");
console.log(tear);
}
function setup()
{
//Create client
client = new RTSPClient();
client.on("error", function(e, err){
console.log("***GOT ERROR:", err);
setup();
})
//Connect to url
client.connect("rtsp://192.168.0.41");
const headers = {"Require" : "www.onvif.org/ver20/backchannel"};
client.addExtraHeaders(headers);
client.authenticate("admin","changeme1");
if(session)
{
console.log("Re suing old session " + session);
client.setSession(session);
}
}
async function start()
{
setup();
//Get options
const options = await client.options();
//Describe
const describe = await client.describe();
console.log("---- DESC ----");
console.log(describe.body.plain);
//Dump SDP
const parts = describe.body.plain.split("\r\n");
var isSend = false;
var controlUrl = false;
for(i in parts)
{
const p = parts[i];
if(isSend && 0 == p.indexOf("a=control:"))
{
controlUrl = p.split(":").splice(1).join(":");
break;
}
else if(p == "a=sendonly")
{
isSend = true;
}
else if (p == "a=recvonly")
{
isSend = false;
}
}
if(controlUrl === false)
{
console.log("no backchannel url");
}
console.log("Backchannel control url = " + controlUrl);
const set = await client.setup(controlUrl, "RTP/AVP");
console.log("---- SETUP ----")
console.log(set);
port = 0
ssrc = "0000"
for(i in set.headers)
{
if("Session" == set.headers[i].name)
{
session = set.headers[i].values[0].value.split(";")[0];
console.log("Session:" + session);
client.setSession(session);
}
else if ("Transport" == set.headers[i].name)
{
console.log("Transport:", set.headers[i].values);
var transParts = set.headers[i].values[0].value.split(";");
for(i=0; i< transParts.length;i++)
{
if(transParts[i].indexOf("server_port=") ==0)
{
port = transParts[i].split("=")[1].split("-")[0];
}
else if(transParts[i].indexOf("ssrc=") ==0)
{
ssrc = transParts[i].split("=")[1].split("-")[0];
}
}
}
}
console.log("Got port:" + port);
console.log("Got ssrc:" + ssrc);
ssrcInt = parseInt(ssrc, 16);
console.log("Got ssrc(dec)" + ssrcInt);
const start = await client.play().catch(function(err){ console.log("Got error ", err)});
console.log("---- play ----");
console.log(start);
const ffmpegCmd = "ffmpeg -re -i ./stt.1073.8000.wav -c:a copy -f rtp -ssrc " + ssrcInt + " -sdp_file ./out.sdp rtp://192.168.0.41:" + port;
console.log("Running ffmpeg Command " + ffmpegCmd);
exec(ffmpegCmd, (error, stdout, stderr) => {
if (error) {
console.log(`error: ${error.message}`);
return;
}
if (stderr) {
console.log(`stderr: ${stderr}`);
}
console.log(`stdout: ${stdout}`);
shutdown();
});
}
start();
And here is the output.
---- DESC ----
v=0
o=- 3714769719012 3714769719012 IN IP4 192.168.0.41
s=Media Presentation
e=NONE
b=AS:5100
t=0 0
a=control:rtsp://192.168.0.41/
m=video 0 RTP/AVP 96
c=IN IP4 0.0.0.0
b=AS:5000
a=recvonly
a=x-dimensions:1280,720
a=control:rtsp://192.168.0.41/trackID=1
a=rtpmap:96 H264/90000
a=fmtp:96 profile-level-id=420029; packetization-mode=1; sprop-parameter-sets=Z01AH42NQCgC3/gLcBAQFAAAD6AAAw1DoYA9MAANWfrvLjQwB6YAAas/XeXCgA==,aO44gA==
m=audio 0 RTP/AVP 0 102
a=rtpmap:102 G726/8000
c=IN IP4 0.0.0.0
b=AS:50
a=sendonly
a=control:rtsp://192.168.0.41/trackID=4
a=rtpmap:0 PCMU/8000
a=Media_header:MEDIAINFO=494D4B48010300000400000100000000000000000000000000000000000000000000000000000000;
a=appversion:1.0
Backchannel control url = rtsp://192.168.0.41/trackID=4
---- SETUP ----
{
protocolVersion: 'RTSP/1.0',
statusCode: 200,
statusMessage: 'OK',
messageSize: 172,
headersSize: 145,
bodySize: 0,
headers: [
{ name: 'CSeq', values: [Array] },
{ name: 'Session', values: [Array] },
{ name: 'Transport', values: [Array] },
{ name: 'Date', values: [Array] }
]
}
Session:818031296
Transport: [
{ value: 'RTP/AVP;server_port=8342-8343;ssrc=40a54b6c;mode="play"' }
]
Got port:8342
Got ssrc:40a54b6c
Got ssrc(dec)1084574572
---- play ----
{
protocolVersion: 'RTSP/1.0',
statusCode: 200,
statusMessage: 'OK',
messageSize: 105,
headersSize: 78,
bodySize: 0,
headers: [
{ name: 'CSeq', values: [Array] },
{ name: 'Session', values: [Array] },
{ name: 'RTP-Info', values: [] },
{ name: 'Date', values: [Array] }
]
}
Running ffmpeg Command ffmpeg -re -i ./stt.1073.8000.wav -c:a copy -f rtp -ssrc 1084574572 -sdp_file ./out.sdp rtp://192.168.0.41:8342
***GOT ERROR: Error: read ECONNRESET
at TCP.onStreamRead (internal/stream_base_commons.js:209:20) {
errno: 'ECONNRESET',
code: 'ECONNRESET',
syscall: 'read'
}
Re suing old session 818031296
stderr: ffmpeg version 4.4.1-3ubuntu5 Copyright (c) 2000-2021 the FFmpeg developers
built with gcc 11 (Ubuntu 11.2.0-18ubuntu1)
configuration: --prefix=/usr --extra-version=3ubuntu5 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libdav1d --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librabbitmq --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzimg --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opencl --enable-opengl --enable-sdl2 --enable-pocketsphinx --enable-librsvg --enable-libmfx --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
libavutil 56. 70.100 / 56. 70.100
libavcodec 58.134.100 / 58.134.100
libavformat 58. 76.100 / 58. 76.100
libavdevice 58. 13.100 / 58. 13.100
libavfilter 7.110.100 / 7.110.100
libswscale 5. 9.100 / 5. 9.100
libswresample 3. 9.100 / 3. 9.100
libpostproc 55. 9.100 / 55. 9.100
Guessed Channel Layout for Input Stream #0.0 : mono
Input #0, wav, from './stt.1073.8000.wav':
Metadata:
encoder : Lavf58.76.100
Duration: 00:01:01.05, bitrate: 128 kb/s
Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 8000 Hz, mono, s16, 128 kb/s
Output #0, rtp, to 'rtp://192.168.0.41:8342':
Metadata:
encoder : Lavf58.76.100
Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 8000 Hz, mono, s16, 128 kb/s
Stream mapping:
Stream #0:0 -> #0:0 (copy)
Press [q] to stop, [?] for help
size= 963kB time=00:01:00.92 bitrate= 129.4kbits/s speed= 1x
video:0kB audio:954kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.913954%
stdout:
Doing shutdown now
Stopping 818031296 on rtsp://192.168.0.41
---- teardown ----
{
protocolVersion: 'RTSP/1.0',
statusCode: 454,
statusMessage: 'Session Not Found',
messageSize: 357,
headersSize: 68,
bodySize: 249,
headers: [
{ name: 'CSeq', values: [Array] },
{ name: 'Session', values: [Array] },
{ name: 'Date', values: [Array] }
],
body: {
plain: 'RTSP/1.0 401 Unauthorized\r\n' +
'CSeq: 1\r\n' +
'Session: 0\r\n' +
'Date: Thu, Feb 12 1970 23:53:50 GMT\r\n' +
'WWW-Authenticate: Digest realm="IP Camera(F2585)", nonce="98dd3d29b86a40ee2ed1cc9c74b54ed0", stale="FALSE"\r\n' +
'Date: Thu, Feb 12 1970 23:53:50 GMT\r\n' +
'\r\n'
}
}
An linux shows the file I'm trying to send as
$ file ./stt.1073.8000.wav
./stt.1073.8000.wav: RIFF (little-endian) data, WAVE audio, Microsoft PCM, 16 bit, mono 8000 Hz