Subject: Re: [AVT] 27MHz time stamp for MP2T

From: [email-masked]
Date: Mon, 19 Aug 2002 11:19:49 +0200

Hi,

IMHO 90 kHz is already very fast !

this high value was chosen to prevent rounding errors with the weird american video clock  (30000/1001)
while 27 MHz in MPEG was chosen  to provide a phase locked clock for the receivers which is a drastically different requirement ...

could you state why exactly you need such an accuracy ? (for dejittering ? of TS ? why VBR makes a difference ?)

also it would make the  RTP time stamp roll over in less than 3 minutes i.e. ... more trouble ?

regards,

Philippe Gentric
Software Architect
Philips MP4Net
[email-masked]
http://www.mpeg-4.philips.com

                      szhu                                                                                                             
                      <[email-masked]>             To:  [email-masked]                                                                   
                      Sent by:                     cc:  (bcc: Philippe Gentric/MP4-SUR/CE/PHILIPS)                                     
                      [email-masked]             Subject:   [AVT] 27MHz time stamp for MP2T                                          
                      rg                                                                                                               
                                                   Classification:                                                                     
                                                                                                                                       
                      02/08/2002 22:56                                                                                                 

Hi,

The current RTP time stamp resolution is 90K Hz for MP2T format. Some
people here have raised an issue that to handle MPTS and VBR, to have a
more precise time stamp, a dynamic payload format can be defined, which
should carry a 27M Hz timestamp. The 27M Hz time stamp will have the
same precision as that of the PCR in MPEG2 Transport Stream (MP2T). This
is for the IP dejittering purpose. May I have some expert's opinion on
this idea?

Thank you,
Shan Zhu

_______________________________________________
Audio/Video Transport Working Group
[email-masked]
https://www1.ietf.org/mailman/listinfo/avt

_______________________________________________
Audio/Video Transport Working Group
[email-masked]
https://www1.ietf.org/mailman/listinfo/avt