Re: [mpeg2-dev] Error concealment of libmpeg2

[Michel L. <wa...@zo...>]

On Fri, Oct 05, 2001 at 11:29:02PM -0700, Lu Xiaoxiang wrote:
> Hi Michel,
>    Thank you for your answer. Yes, I am interested in the error
> concealment stuff. Now I am working on mpeg2 video over IP network. I use
> libmpeg2 package as the decoder. I concern the video quality degradation
> after transmission across the network.So actually I will implement some
> error concealment algorithms.I think the first step is how libmpeg2
> detects errors. 

Are you thinking about LAN or WAN applications ?

I suppose for IP networks the first layer of error correction should
be on the coded stream itself - using some kind or redundancy in the
packet transmission. I had sent an email to the videolan mailing list
not long ago about that subject, I also recommended people to have a
look at http://www.csl.sony.co.jp/person/morelos/ecc/codes.html and
http://www.iet.unipi.it/~luigi/fec.html

You probably knew some of that already but I figure extra information
never hurts :)

As for the error detection in libmpeg2. The most common cause of
problems (segfaults) right now is when we get an incorrect motion
vector and we try to use pixels outside of the prediction frame and
boom! I've started some work to detect that but I need to finish
it. The second step would be to detect parsing errors like invalid
huffman codes. I suppose after that we'll have a quite reliable
detection of fscked up slices.

-- 
Michel "Walken" LESPINASSE
Of course I think I'm right. If I thought I was wrong, I'd change my mind.