[SR-Users] Video Key-Frame Request using RTCP FIR or SIP INFO message

[Muhammad Shahzad]

Thank you so much guys for this insight into the issue. Let me talk to the
SIP client developers and see what is their point-of-view on this.

Thank you



On Sun, Feb 1, 2015 at 10:36 PM, Richard Fuchs <rfuchs at sipwise.com> wrote:

> On 02/01/15 09:17, Muhammad Shahzad wrote:
> > Thanks for detailed reply and sharing the valuable information. You are
> > right i should also post this on discuss-webrtc forum, will do after i
> > get a fresh call trace, possibly tomorrow.
> >
> > Regarding your questions, yes the call establishes successfully at
> > signalling level and audio stream works perfectly fine. I see DTLS
> > certificates generated, sent, received, accepted etc. in RTPEngine logs.
> > Both SIP and WebRTC clients successfully negotiate ICE and choose
> > RTPEngine for media relay. However, the SIP client looses video after
> > 1-2 seconds of call establishment, the audio still works during the
> > entire call. So, i am convinced that problem is entirely related to
> > video as far as the call establishment is concerned.
> >
> > The WebRTC client is based on JSSIP but i am not aware of any config or
> > method that may give us such control over media in response to this SIP
> > INFO method. Any experienced JSSIP users / developers out there who may
> > help on this?
> >
> > The SIP client is based on a commercial SIP SDK. Both WebRTC and SIP
> > clients work perfectly fine as long as other end is same, i.e. SIP to
> > SIP and WebRTC to WebRTC video calls work as expected under same network
> > conditions. Each client has only one video codec enabled, which is VP8,
> > without any trans-coding etc. involved in between.
>
> To my (limited) knowledge, requests for key frames are sent as
> AVPF-profile RTCP packets. Meanwhile, most regular SIP clients don't
> speak AVPF but rather AVP only, and so don't support these requests for
> key frames. Which results in the AVPF client never sending any key
> frames because nobody requests any.
>
> To allow interoperability, the translating agent (rtpengine) would need
> to support and understand the video codec in use (VP8) at least to a
> minimal extent and simulate AVPF key frame requests. Which it currently
> doesn't.
>
> cheers
>
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