RTSP timecodes

[Martin Huber]

Hi,

I'm using the Janus WebRTC gateway with streaming plugin to play back streams from IP cameras and/or recorders in the browser. The original RTSP stream data includes time information from when the video taken which is especially interesting for recorded streams. Is there a way to retrieve these timecodes from the WebRTC stream, e.g. to display in the browser?

Many thanks

Martin

[Lorenzo Miniero]

That depends on how that information is passed to clients. Is it an overlay on the video? A text stream? Something conveyed in the RTSP headers? And most importantly, is it a standard? Whatever it is, we won't do anything if it's specific to a model or vendor.

Lorenzo

[Martin Huber]

Hi Lorenzo,

Thanks for the quick reply.

The time information is inside RTP header extensions. I don't know if this is standard or not. It could be specific to the backend module passing the stream on to Janus.

If it is not standard, what are our options?

[Lorenzo Miniero]

If it's not standard, as anticipated we won't touch it: it would up to you to modify the Streaming plugin for your requirement, if you care about it.

At any rate, whether the RTP extension is standard or not, my guess is that the plugin would have to intercept the extension, extract the info, and then push it via datachannels or something like that: browsers will probably not support the extension, and even if they do, they most definitely won't make the info available at the application level when extracted.

Lorenzo

[Martin Huber]

Do you think that WebVTT sent via WebRTC data channels could work?

WebVTT files provide captions or subtitles for video content [...], and more generally any form of metadata that is time-aligned with audio or video content. (https://w3c.github.io/webvtt/)

Martin

[Lorenzo Miniero]

I don't think it should be a specific format, considering there might be different uses for the same thing. It should probably be an agnostic format, that can then be translated to whatever is needed for the specific use case (e.g., WebVTT in your case) directly in the application.

Lorenzo