IP Camera RTSP Restreaming Startup Delay

[Walter_Dearing]

Hi,

We’re using Wowza to restream an Axis h.264 video encoder. All communication (between Camera/Wowza/Player) is Interleaved RTSP. The application is a RTP-live type. We are using stream aliasing (not StreamManager) to identify the cameras on demand (to conserve bandwidth).

We see roughly a 13 second delay when the camera is accessed by Wowza the first time. Is this expected?

If not are there any settings to tweak (besides Key Interval of the stream)? Or should we look elsewhere for the problem.

We see roughly 4 seconds of delay when subsequent viewers of the video access the video.

Thanks!

[Richard_Lanham]

The best thing to do you have ruled out already: start the stream in StreamManager. Increasing FPS can help with startup latency in Flash, shave something off the 4 seconds. But the initial extra start up time, which sounds like 9 seconds in your case, is the penalty you pay for saving bandwidth by not using StreamManager

Richard

[Charlie_Good]

Richard’s recommendation to start the stream using the stream manager is a good one. Also, try increasing the frequency of key frame (less time between key frames). The first time someone tries to play the stream we need to connect to the camera and can’t start playback until there is a key frame. Also, if you can try a higher frame rate. It can have an affect as well.

Charlie

[Charlie_Good]

Can you send me the RTSP URL to the camera and zip up conf and logs (support@wowza.com). Be sure to reference this forum thread.

Charlie

[Charlie_Good]

It sounds like you are not starting the stream using the stream manager properly.

Charlie

[Richard_Lanham]

But you point out this is about the first viewer, that subsequent views are 4 seconds not 15 or 13, and that using StreamManager solves the problem for the first view.

Richard

[Walter_Dearing]

It looks like it’s taking 11 seconds to reply to the initial rtsp description request - which results in 15 seconds overall delay (from initial ‘play’ command to video display with VLC, QuickTime, and a custom player). Our customer is asking why there is so much extra delay when restreaming through Wowza - is there any details you could explain as to what results in the extra delay?

When accessing the camera directly (with VLC) it takes about 4 seconds to play.

When accessing the camera through Wowza and playing with a flash player there is an 8 second delay.

The Camera is using FPS=15, GOV=16, and a bitrate of 200 kbit/s.

The customer is looking for 10 seconds or less startup delay - we are using pretty beefy servers, so if there’s some less CPU-efficient options to use that would decrease this delay, we’d be open to it.

Any help would be great.

[Walter_Dearing]

Thanks Charlie.

The Network is extremely bandwidth limited and there are multiple cameras, so using stream manager is not an option.

With the GOV set to 16 and the FPS set to 15 we should be getting a key frame every 1 second.

I’m just surprised it’s taking Wowza almost twice as long to start streaming when accessing Wowza with RTSP (roughly 15 seconds) as compared to when we access Wowza with RTMP (roughly 8 seconds).

I can even email a link to two demo camera’s we have online so you can see this effect (with quicktime or VLC). Are there any config files I can post that would be related to this - maybe I have something configured incorrectly?

[Walter_Dearing]

Thanks Richard.

I have - and it makes them more confused as to why it takes so long the first time (since the player/Wowza can open it in as little as 4 second for subsequent views). I thought it was the GOV/FPS combination, but it looks like that’s only a second, so now I’m struggling to give any answers.