[Live-devel] SDP ntp range attribute for live streams

[Ross Finlayson]

> On May 17, 2021, at 3:10 PM, Dmitry Bely <d.bely at recognize.ru> wrote:
> 
> Currently RTSP server generates the following SDP line for live streams:
> 
> a=range:npt=0-
> 
> I'm afraid it's not very correct and
> 
> a=range:npt=now-
> 
> should be used instead. A quote from rfc2326:
> 
>> The "now" constant allows clients to request to receive the live feed rather than the stored or time-delayed version. This is needed since neither absolute time nor zero time are appropriate for this case.

That paragraph describes what a RTSP client can specify when making a request, rather than what a server must specify when describing the stream.  According to the syntax rules (in RFC 2326, section 3.6), “npt=0-“ is valid syntax.  “ffmpeg” should really be able to handle this.  However, because one could argue that “npt=now-“ is a more meaningful description for live streams like this, I’ve just released a new version (2021.05.17) of the code that changes this.


Ross Finlayson
Live Networks, Inc.
http://www.live555.com/