High HLS Chunk Duration from SRS

[himanshu101]

Hi Folks,

We are using SRS Image to convert RTMP Stream from OBS to HLS chunks. We have specified chunk duration of 2 seconds and Keyframe is enabled. But, I have observed 25% of the chunks has duration around ~ 3.5-4.0 seconds which has 2 Keyframes.

I want to understand how is it happening since we have specified 2 seconds duration for chunk and KeyFrame is enabled.

Srs version: ssrs/srs:5

Following is Srs configuration:

listen 80;
max_connections 1000;
daemon off;
srs_log_tank console;

http_api {
enabled on;
listen 1985;
}

exporter {
enabled on;
listen 1945;
}

vhost defaultVhost {
http_hooks {
enabled on;
on_publish {{http_url}}
on_unpublish {{http_url}};
}

hls {
    enabled on;
    hls_fragment 2;
    hls_dispose 600;
    hls_window 600;
    hls_wait_keyframe on;

    hls_path /var/srs/recordings/;
    hls_m3u8_file [stream]/media.m3u8;
    hls_ts_file [stream]/[timestamp].ts;
}

}

OBS Configuration:

Stream Settings:

Video Encoder: H264
Rescale Output: Disabled, 1920* 1080

Encoder Settings:
Rate Control: CBR
Bitrate: CBR
Keyframe Interval : 2s
CPU Usage Preset: veryfast
Profile: None
Tune: None

Video:
Base Resolution: 1920 * 1080
Output Resolution: 1920 * 1080
Aspect Ratio: 16:9
FPS: 30

Loking forward for some input to understand why chunks of more than 2s duration are being generated after specifying duration of 2 seconds and Keyframe at both OBS and SRS side.

Thanks in advance