Subject: [AVT] On the TS Preamble issue

From: Ingemar Johansson S <[email-masked]>
Date: Wed, 24 Mar 2010 01:48:39 +0100

Hi

I have tried to follow (with limited knowledge about MPEG TS) the debate around the two alternatives to send the preamble to the STBs. 
As I understand t one simple alterantive is to just collect all the PAT, CAT, PMT and other elements in one packet and send it to the STB. I got it explained that it may work for certain STBs while others might choke. 

One solution is then to pack the preamble elements with care and send them to the STBs where they are unpacked (draft-begen-avt-rtp-mpeg2ts-preamble-04). My question is then, if the STBs need to be upgraded to handle the nw format, why not upgrade them to handle the simple format ?. I believe I miss some important piece of information here (complexity, memory ?)

As regards to draft-xia-avt-mpeg2ts-preamble alternative, I am unclear of how much extra overhead in terms of unecessary data that is sent with the retransmission packets just to update the STB with the necessary preamble, from an engineers point of view it seems to me a bit awkward to e.g send 1000bytes of data for 10bytes of useful information (numbers are just wild guesswork from my side). 

Regards
/Ingemar
=================================
INGEMAR JOHANSSON  M.Sc. 
Senior Research Engineer 

Ericsson AB
Multimedia Technologies
Labratoriegränd 11
971 28, Luleå, Sweden
Phone +46-1071 43042
SMS/MMS +46-73 078 3289
[email-masked]
www.ericsson.com 
Visit http://labs.ericsson.com !
=================================

---

From: Frank Xia <[email-masked]>
Date: Wed, 24 Mar 2010 11:56:16 -0500

Hi Ingemar, 

Thank you very much for analyzing two drafts. Please see inline.

Peilin & Frank

----- 原邮件 -----
发件人: Ingemar Johansson S <[email-masked]>
日期: 星期三, 三月 24日, 2010 上午8:49
主题: On the TS Preamble issue
收件人: "[email-masked]" <[email-masked]>
抄送: "Ali C. Begen (abegen)" <[email-masked]>, "[email-masked]"
<[email-masked]>

Hi

I have tried to follow (with limited knowledge about MPEG TS) the debate
around the two alternatives to send the preamble to the STBs. 
As I understand t one simple alterantive is to just collect all the PAT,
CAT, PMT and other elements in one packet and send it to the STB. I got it
explained that it may work for certain STBs while others might choke. 

One solution is then to pack the preamble elements with care and send them
to the STBs where they are unpacked
(draft-begen-avt-rtp-mpeg2ts-preamble-04). My question is then, if the STBs
need to be upgraded to handle the nw format, why not upgrade them to handle
the simple format ?. I believe I miss some important piece of information
here (complexity, memory ?)

As regards to draft-xia-avt-mpeg2ts-preamble alternative, I am unclear of
how much extra overhead in terms of unecessary data that is sent with the
retransmission packets just to update the STB with the necessary preamble,
from an engineers point of view it seems to me a bit awkward to e.g send
1000bytes of data for 10bytes of useful information (numbers are just wild
guesswork from my side).

Peilin: I am sure that there is no such exaggerated extra overhead(sending
1000bytes of data for 10bytes of useful information). Commonly the preamble
information can be sent in one RTP packet. The extra information focus on
PAT, PMT and PCR TS packets(totally including 3*188 = 564bytes), and its
useful information is approximate 200bytes. If there are two TS packets for
ECM/EMM. Total information is about 940(5*188)bytes. The useful information
is about 576(200+2*188)bytes.  

Regards
/Ingemar