HLS first user issue

manikandan · Aug 10, 2020

Hi,

I m publishing the streams to origin servers and playing using HLS by edge servers. When a first user tries to view the stream, the stream can't be played in player and buffer gets stalled out.

If it is played again, then streams gets played. Based on this link https://docs.flashphoner.com/display/WCS52EN/In+a+browser+via+HLS#InabrowserviaHLS-Issues,
I configured below thing in edge servers,

hls_min_list_size=2

but still the first user issue still happens.

Any fix for this?

Rafael Ribeiro · Aug 10, 2020

I have the same issue.
Our workarround was starting HLS by API one page before the first user access the player, like into a login screen.

manikandan · Aug 10, 2020

Hi Rafael,

Thank you for the response. Can you share the API you used to trigger the HLS play?

Rafael Ribeiro · Aug 10, 2020

Code:

    $data_array_a = array(
        
                        "name" => $player_id
                        
                         );


    $data_string = json_encode($data_array_a);//
    $ch = curl_init($api_url_server."/rest-api/hls/startup");
    curl_setopt($ch, CURLOPT_POST, 1);
    curl_setopt($ch, CURLOPT_POSTFIELDS, $data_string);
    curl_setopt($ch, CURLOPT_HEADER, false);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

    $result = curl_exec($ch);
    //print_r($result);
    curl_close($ch);

Rafael Ribeiro · Aug 10, 2020

Today we test few settings regarding CDN Profiles and notice if streamname requested by HLS is the same as profile on CDN transcoder, starting by API is not needed and first error not happen.

Max · Aug 11, 2020

Good day.

manikandan said:
When a first user tries to view the stream, the stream can't be played in player and buffer gets stalled out.

Please check if HLS preloader is enabled

Code:

hls_preloader_enabled=true

Also, a stream published should provide a stable FPS and even keyframes flow. FPS for WebRTC publishing is set on client side:

Code:

    session.createStream({
        name: streamName,
        display: localVideo,
        cacheLocalResources: true,
        constraints: {
              video: {
                    frameRate: 30
              }
        }
        ...
    }).publish();

Regular keyframe (FIR) requests are set up on server side

Code:

periodic_fir_request = true
periodic_fir_request_interval = 2000
rtcp_pli_request_interval = 2000

In this case, server will request browser to send keyframe every 2 seconds. More often keyframe sending is not recommended because publisher channel may be overloaded due to bog amount of data passed.

Rafael Ribeiro said:
Today we test few settings regarding CDN Profiles and notice if streamname requested by HLS is the same as profile on CDN transcoder, starting by API is not needed and first error not happen.

Yes, transcoding helps to equalize FPS and to receive keyframes regularly on players side. For example, this profile

YAML:

 -360p:
  video:
    height : 360
    bitrate : 400
    gop : 50
    codec : h264
    codecImpl : FF

provides keyframe every 2 seconds for 25 fps
and the following Transcoder server settings

Code:

video_filter_enable_fps=true
video_filter_fps=25
video_filter_fps_gop_synchronization=50

provide 25 FPS for streams transcoded
So HLS should play smoothly. HLS warming as Rafael do is not necessary if transcoding is used and preloader enabled on Edge servers.

Rafael Ribeiro · Aug 13, 2020

Hello!

provide 25 FPS for streams transcoded
So HLS should play smoothly. HLS warming as Rafael do is not necessary if transcoding is used and preloader enabled on Edge servers.

Confirmed and very happy.
CND profiles works like a charm and not necessary to start by API, just removed it from our code.

Thanks Max!

manikandan · Aug 17, 2020

@Max to use CDN profiles, do we need to use separate servers?
My streaming setup uses Origin and Edge servers where WebRTC is pusblished to Origin server and stream is viewed using HLS from Edge servers.
https://docs.flashphoner.com/display/WCS52EN/CDN+2.0

Is that fine to setup those CDN profiles in Edge servers?

Also @Rafael Ribeiro I have tried to start the HLS agent in my Edge servers after publishing the stream in origin servers but it not fixing the HLS first user issue.
I think since stream is published on origin, it is not possible to start the HLS agent in edge servers. right @Max

Rafael Ribeiro · Aug 17, 2020

@manikandan did you setup cdn_profiles file on edge?
How are u calling the stream? It should be something like streamname-720p.m3mu

Max · Aug 17, 2020

CDN profiles were introduced for Transcoder nodes.

CDN 2.1 - Web Call Server 5.2 - EN - Flashphoner Documentation

docs.flashphoner.com

So if you use profiles, generally you have the following nodes in the CDN
- origin
- edge
- transcoder

The profiles are configured on Edge servers.
However transcoding is being performed on separate node(s) with role = transcoder

manikandan · Aug 17, 2020

Rafael Ribeiro said:
@manikandan did you setup cdn_profiles file on edge?
How are u calling the stream? It should be something like streamname-720p.m3mu

No. I haven't setup cdn_profiles on edge. I just want to start the HLS agent by using the REST API (hls/start_up) in edge servers. But it is not working.
Just to confirm, is separate transcoder server is required to call that API?

manikandan · Aug 17, 2020

Max said:
However transcoding is being performed on separate node(s) with role = transcoder

So a separate server has to be used for trancoding process for this HLS first user issue. right?

Rafael Ribeiro · Aug 17, 2020

PHP:

$data_array_a = array(
    
    "name" => $webrtcstreamname
                
);


$data_string = json_encode($data_array_a);//
$ch = curl_init("https://yourwcsserver:8444/rest-api/hls/startup");
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, $data_string);
curl_setopt($ch, CURLOPT_HEADER, false);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

$result = curl_exec($ch);
//print_r($result);
curl_close($ch);

Then you can open your stream into HLS player

https://yourwcsserver:8445/streamname/streamname.m3u8

If you decides use CDN profiles, just open stream like this:

https://yourwcsserver:8445/streamname-720p/streamname-720p.m3u8

Rafael Ribeiro · Aug 17, 2020

manikandan said:
So a separate server has to be used for trancoding process for this HLS first user issue. right?

On our scenario, we save resources to origin and execute transcoding on edge servers.
Using load balance, we are able to start edges on the fly, as needed based on CPU usage.

Max · Aug 18, 2020

manikandan said:
So a separate server has to be used for trancoding process for this HLS first user issue. right?

A separate Transcoder server is necessary to use CDN transcoding profiles like this

Code:

https://edge:8445/test-480p/test-480p.m3u8

manikandan said:
I just want to start the HLS agent by using the REST API (hls/start_up) in edge servers. But it is not working.

Let's clarify again.
To play WebRTC stream as HLS smoothly, there must be regular keyframes flow in the stream, and regular FPS.
HLS segments are cut by keyframe, so if keyframe is not received in, for example, 20 seconds, HLS will not be started until keyframe is received, and preloader will roll (if used) during this 20 seconds. And, when HLS segment is started, it will be written until the next keyframe is received even if fixed segment size is set.
And this behavior will be the same whatever you use to start HLS playback REST API /hls/startup or curl invocation. So HLS warming (preliminary HLS requesting on edge server before subscribers connect) can help to reduce playback starting delay for subscribers, but does not help to play smoothly.
Also HLS segments are written frame by frame, so, if FPS drops, there will be freezes while playing HLS.
That's why transcoding may be useful to play WebRTC as HLS.
But, if you decide to use CDN transcoding profiles, you should deploy Transcoder servers to CDN or allow transcoding on Origin (so, Origin should be powerful enough to do this) by setting the following parameter on Edge server

Code:

cdn_origin_allowed_to_transcode=true

Rafael Ribeiro said:
Then you can open your stream into HLS player
https://yourwcsserver:8445/streamname/streamname.m3u8

This is HLS warming example. You can use simple curl request without REST API, the result will be the same: HLS cut will start if the stream is available

PHP:

$ch = curl_init("https://yourwcsserver:8445/".$webrtcstreamname."/".$webrtcstreamname."m3u8");

manikandan · Aug 18, 2020

Rafael Ribeiro said:
PHP:

$data_array_a = array( "name" => $webrtcstreamname ); $data_string = json_encode($data_array_a);// $ch = curl_init("https://yourwcsserver:8444/rest-api/hls/startup"); curl_setopt($ch, CURLOPT_POST, 1); curl_setopt($ch, CURLOPT_POSTFIELDS, $data_string); curl_setopt($ch, CURLOPT_HEADER, false); curl_setopt($ch, CURLOPT_RETURNTRANSFER, true); $result = curl_exec($ch); //print_r($result); curl_close($ch);

Then you can open your stream into HLS player

https://yourwcsserver:8445/streamname/streamname.m3u8

If you decides use CDN profiles, just open stream like this:

https://yourwcsserver:8445/streamname-720p/streamname-720p.m3u8

Thank you @Rafael Ribeiro

manikandan · Aug 18, 2020

Max said:
A separate Transcoder server is necessary to use CDN transcoding profiles like this

Code:

https://edge:8445/test-480p/test-480p.m3u8

Let's clarify again.
To play WebRTC stream as HLS smoothly, there must be regular keyframes flow in the stream, and regular FPS.
HLS segments are cut by keyframe, so if keyframe is not received in, for example, 20 seconds, HLS will not be started until keyframe is received, and preloader will roll (if used) during this 20 seconds. And, when HLS segment is started, it will be written until the next keyframe is received even if fixed segment size is set.
And this behavior will be the same whatever you use to start HLS playback REST API /hls/startup or curl invocation. So HLS warming (preliminary HLS requesting on edge server before subscribers connect) can help to reduce playback starting delay for subscribers, but does not help to play smoothly.
Also HLS segments are written frame by frame, so, if FPS drops, there will be freezes while playing HLS.
That's why transcoding may be useful to play WebRTC as HLS.
But, if you decide to use CDN transcoding profiles, you should deploy Transcoder servers to CDN or allow transcoding on Origin (so, Origin should be powerful enough to do this) by setting the following parameter on Edge server

Code:

cdn_origin_allowed_to_transcode=true

This is HLS warming example. You can use simple curl request without REST API, the result will be the same: HLS cut will start if the stream is available

PHP:

$ch = curl_init("https://yourwcsserver:8445/".$webrtcstreamname."/".$webrtcstreamname."m3u8");

Thank you Max for the explanation. Will check on that.

HLS first user issue

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