Re: [payload] Adam Roach's Discuss on draft-ietf-payload-rtp-ancillary-10: (with DISCUSS and COMMENT)

[Thomas Edwards <[e-mail]>]

Is there an understanding that FID grouped objects are to be presented in time synchronized fashion?

(It might not matter - implementations are likely to synchronize presentation of the FID grouped streamed anyway based on RTP timestamps and RFC 7273, RTP Clock Source Signalling).

Thanks!

-Thomas

On 9/21/17, 8:22 AM, "Adam Roach" <[e-mail]> wrote:

    On 9/20/17 08:31, Thomas Edwards wrote:
    > Adam,
    >
    > Thanks for your DISCUSS on the Ancillary RTP I-D.  I understand your concern about the difference between RTP streams that are simply synchronized using “LS” versus RTP streams that also have an intimate relationship (such as being part of the same “m=” media section).
    >
    > The challenge is that the use case of the Ancillary I-D within the SMPTE ST 2110 architecture would generally require separate network destination addresses for the different elements (video, audio, ancillary data) so they can be flexibly composed within broadcast plants at the network level.  Your alternative SDP example appears to place both the video and the ancillary data onto the same destination address (https://urldefense.proofpoint.com/v2/url?u=http-3A__233.252.0.1&d=DwIDaQ&c=uw6TLu4hwhHdiGJOgwcWD4AjKQx6zvFcGEsbfiY9-EI&r=lekNOOM5noV61zrPH3rwPyhtNnLLWoLEHgd0quQxly8&m=HESr2t9GphJ1DG-VC5BBE5bqCuFq085olInzqKtqp4k&s=AmiuURi1XkubNbBE2DmLed7zdEsZV6utcHjhHSXP6ls&e= ).  Is there an appropriate SDP mechanism to communicate the intimate relationship between the RTP streams, but also have them transmitted on separate destination IP addresses (and synchronized)?
    
    With that requirement, I think Ali's suggestion is the right one: the 
    grouping you want to use to bind these together is FID. I believe that 
    simply replacing "LS" with "FID" in the document would be adequate 
    (i.e., I don't think this document needs a treatment of LS). It is 
    probably also worth mentioning in the document that the other approach 
    (i.e., including both the smpte291 format and the main video codec 
    format in the same session) is _valid_, but that using different IP 
    addresses is frequently necessary, and FID is the mechanism used to do so.
    
    Thanks!
    
    /a