Re: [xrblock] Fw: I-D Action: draft-ietf-xrblock-rtcp-xr-jb-02.txt

[Alan Clark <[e-mail]>]

A typical jitter buffer uses the first packet received as its timing
reference, and applies a nominal delay to that before playing out.  During
later operation, the jitter buffer may increase or reduce the nominal delay
or may pick a new reference packet. This nominal delay represents the ³late
window² - so if a packet arrives more than ³nominal delay ms² after its
expected time then it will be discarded.

³On time² - in this case - refers to the expected arrival time of the packet
when calculated with reference to the first or a later selected reference
packet.

Jitter buffer implementations don¹t necessary do this mathematically however
this is a generalized description that models the behavior of most jitter
buffers used for VoIP and Videoconferencing.

Playout buffers used in video streaming applications operate quite
differently. Basically a received chunk of encoded video is added to the
playout buffer - encoded video is read from the buffer. When the buffer
level drops below a threshold then another chunk of video is requested from
the server. There is an equivalent to ³nominal delay² as the buffer will
always try to make sure there is at least a minimal level of video in the
buffer before playing out - however there would not be the equivalent of an
³on time² packet.

Regards

Alan


On 1/16/13 5:36 AM, "Dan (Dan)" <[e-mail]> wrote:

> Kevin, Qin,
>  
> Do you want to discuss this one2one, or should we organize a short conference
> call? Do other think that they can contribute to clarify the issues, or want
> to participate? 
>  
> Dan
>  
>  
>  
> 
> From: [e-mail] [mailto:[e-mail]] On Behalf Of
> Kevin Gross
> Sent: Tuesday, January 15, 2013 11:08 PM
> To: Qin Wu
> Cc: xrblock
> Subject: Re: [xrblock] Fw: I-D Action: draft-ietf-xrblock-rtcp-xr-jb-02.txt
>  
> I think we need to have a phone call to discuss this whole thing.
> 
> 
> Kevin Gross
> 
> [phone]
> 
> Media Network Consultant
> 
> AVA Networks - www.AVAnw.com <http://www.avanw.com/> , www.X192.org
> <http://www.X192.org>
>  
> 
> On Mon, Jan 14, 2013 at 8:27 PM, Qin Wu <[e-mail]> wrote:
> 
> Hi,Kevin:
> 
> I like to make some additioal clarification to your question.
> 
> I think the packet arrives exactly on time, is also referred to the packet
> that has nominal delay.
> 
> So we have two ways to address this.
> 
> a. It is more like implementation specific issue,e.g., rely on timing
> information in the headers of previous
> 
> packet and current packet or rely on time window to determine this. So we can
> leave this to the specific
> 
>  implemenations. 
> 
>  
> 
> b. we can explain the packet that arrives exactly on time as the packet that
> has nominal delay.
> 
> The nominal delay can either be choosen as the jitter buffer delay for the
> packet with minimal delay(i.e.,
> 
> the reference packet is choosen as the packet with minmal delay) or average
> delay for all the packets that arrives
> 
> within the implementation specific time window during the measurement
> interval.
> 
> I am not sure we should details to talk about this, but If we take (b), we
> prefer to add the following sentence in the draft to say:
> 
> "Note that the reference packet is generally selected as the packet
>  with minimum delay based on the most common criterion (see Sections 1
> <http://tools.ietf.org/html/rfc6798#section-1>  and 5.1 of [RFC5481
> <http://tools.ietf.org/html/rfc5481> ]).
> 
> "
> 
> Let me know what you think about this.
> 
>  
> 
> Regards!
> 
> -Qin
>> 
>> ----- Original Message -----
>> 
>> From: Qin Wu <mailto:[e-mail]>
>> 
>> To: Kevin Gross <mailto:[e-mail]>
>> 
>> Cc: xrblock <mailto:[e-mail]>
>> 
>> Sent: Monday, January 14, 2013 8:46 AM
>> 
>> Subject: Re: [xrblock] Fw: I-D Action: draft-ietf-xrblock-rtcp-xr-jb-02.txt
>> 
>>  
>> 
>> Kevin:
>> 
>> As I clarified to you in the previous email, "implemention specific time
>> window" described in Burst Gap drafts will be used to identify a "packet that
>> arrives exactly on time".
>> 
>> That is to say, if the receiving packet falls within  implemention specific
>> time window and can be sucessfully playout, such packet will be regarded as
>> packet that arrives exactly on time.
>> 
>> Hope this clarifies.
>> 
>>  
>> 
>> Regards!
>> 
>> -Qin
>>> 
>>> ----- Original Message -----
>>> 
>>> From: Kevin Gross <mailto:[e-mail]>
>>> 
>>> To: Qin Wu <mailto:[e-mail]>
>>> 
>>> Cc: xrblock <mailto:[e-mail]>
>>> 
>>> Sent: Sunday, January 13, 2013 6:04 AM
>>> 
>>> Subject: Re: offlist//Re: [xrblock] Fw: I-D Action:
>>> draft-ietf-xrblock-rtcp-xr-jb-02.txt
>>> 
>>>  
>>> Qin, 
>>> 
>>>  
>>> 
>>> Of the jitter buffer delay metric, the draft currently says "It is
>>> calculated based on the difference between the receipt time and the playout
>>> time for the packet that arrives exactly on time."
>>> 
>>>  
>>> 
>>> My issue is that I don't know how to identify a "packet that arrives exactly
>>> on time".
>>> 
>>> 
>>> Kevin Gross
>>> 
>>> [phone] <tel:%2B1-303-447-0517>
>>> 
>>> Media Network Consultant
>>> 
>>> AVA Networks - www.AVAnw.com <http://www.AVAnw.com> , www.X192.org
>>> <http://www.X192.org>
>>>  
>> 
>> 
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>> 
>> 
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