Subject: [AVT] Applicability of conceraled seconds measurement to video

From: Tom Taylor <[email-masked]>
Date: Fri, 05 Dec 2008 13:22:02 -0500

Looking through draft-ietf-avt-rtcp-xr-concsec-00.txt, I noted the question: 
does the concept of loss concealment apply to video? It strikes me that in the 
event of packet loss video applications can either freeze the last-played frame 
or try to extrapolate from it. I expect normal behaviour is to freeze the frame, 
which would normally result in a noticeable defect.

So basically, I expect the authors of the draft are right, that loss concealment 
and associated statistics primarily relate to audio. Does anyone have a 
different view?

Tom Taylor
_______________________________________________
Audio/Video Transport Working Group
[email-masked]
https://www.ietf.org/mailman/listinfo/avt

---

From: "Roni Even" <[email-masked]>
Date: Fri, 5 Dec 2008 22:31:18 +0200

Hi,
I assume that the concealment in this draft is for receiver side and not for
FEC based. I think that some text is needed to define the meaning here.
As for video - there are concealment techniques being used that are trying
to guess the motion vectors and continue the display and not freeze the
display.
Roni Even

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of Tom
Taylor
Sent: Friday, December 05, 2008 8:22 PM
To: IETF AVT WG
Subject: [AVT] Applicability of conceraled seconds measurement to video

does the concept of loss concealment apply to video? It strikes me that in
the 
event of packet loss video applications can either freeze the last-played
frame 
or try to extrapolate from it. I expect normal behaviour is to freeze the
frame, 
which would normally result in a noticeable defect.

So basically, I expect the authors of the draft are right, that loss
concealment 
and associated statistics primarily relate to audio. Does anyone have a 
different view?

Tom Taylor

---

From: Randell Jesup <[email-masked]>
Date: Fri, 19 Dec 2008 13:04:28 -0500

>to guess the motion vectors and continue the display and not freeze the

Yes.

>From: [email-masked] [mailto:[email-masked]] On Behalf Of Tom Taylor
>Looking through draft-ietf-avt-rtcp-xr-concsec-00.txt, I noted the
>question: does the concept of loss concealment apply to video? It strikes
>me that in the event of packet loss video applications can either freeze
>the last-played frame or try to extrapolate from it. I expect normal
>behaviour is to freeze the frame, which would normally result in a
>noticeable defect.

I disagree with the characterization of "normal behavior".  I believe the
most common behavior (by far) is to ignore the missing frame and keep
decoding as if it wasn't missing.  This leads to visual artifacts (until
intra-coded blocks or frames replace them), but it's better than freezing.
It's helped by the fact that for lots of video sources (not all!) large
parts of the screen don't have a lot of frame-to-frame change, so the
errors at least start off small in most cases, except at moving edges.

There are more fancy ways to conceal the lost frame possible, as mentioned
above.

-- 
Randell Jesup, Worldgate (developers of the Ojo videophone), ex-Amiga OS team
[email-masked]
"The fetters imposed on liberty at home have ever been forged out of the weapons
provided for defence against real, pretended, or imaginary dangers from abroad."
		- James Madison, 4th US president (1751-1836)