IEEE P1722 technical issues and talking points Version 0.01, 2007-08-21 Alan K. Bartky [email protected] SNAP Networks Send comments to [email protected]@listserv.ieee.org.

IEEE P1722 technical issues and talking points

Version 0.01, 2007-08-21

Alan K. Bartky [email protected]

SNAP NetworksSend comments to [email protected]

April 20, 2023 IEEE P1722 AVBTP Working Group Contribution

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Bartky Networks www.bartky.net

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gm_discontinuity / holdover• gm_discontinuity

– Bump count on every discontinuity?• Picked for simplicity and to not have listeners need to have a timeout.• A step in time (no GM changes) does not need to have the talker set the hold

– Bump only once until holdover cleared?• NO

– Either?• NO

• holdover– Maximum holdover time?

• There is no maximum time for 802.1AS to stabilize.• This is dependency for us• There is a discussion going on in AS

– Minimum holdover time?• We don’t believe there is a need to define in 1722• If you step the time, the minimum could be zero.

– Holdover time/timeout reset?– Timestamp field use during holdover– 802.1BA does not exist and won’t in our timeframe needs. We need to define the minimum

accuracy for 802.1AS• 100 ppm• Talkers must be GM capable


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Permanent holder over (h bit always 1)

– A maximum time for AVBTP in addition to AS maximum time is required

– Notes from meeting• AS time

• Detection of loss of GM 200-300 ms

• Election of new grandmaster

• Wish from 1722 team: Keep max to 600-700 ms

• Must be less than 1 second


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Media clock Reset/discontinuity

• Bit to indicate?– Proposal Toggle on change– Consensus this is a useful thing to add – Consensus if there is a toggle, there also must be a

minimum time before you can toggle it again.

• Tie into holdover bit?– No


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Presentation time

• Late presentation time– As normal case, with LP bit

• Consensus to drop this bit from the spec

– Occasional & permanently late time• Application specific


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Data smoothing

• Multiple packets per 8 kHz tick single stream

• Multiple streams (smoothing across streams)

• What does and what should 802.1Qav handle?– Qav will handle this and we don’t have to talk

about this in 1722


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Mandatory padding of 1722 frame

• Should it be required?– No, Alan to change spec to remove this

requirement


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Deprecated 61883 types:

• Summary of 61883-6 support in AVB

• Below is a preliminary list of supported and unsupported parts of the TA Document 2001024 Audio and Music Data Transmission Protocol 2.1 for P1722 audio end-stations. P1722 Gateways may need to support any format available for maximum compatibility.


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Deprecated 61883 types

• These are recommendations for the minimal required support and are based on real world uses of the protocol on IEEE1394 devices. Removal of support for formats like DVD Audio may seem short sighted but DRM restrictions have made use of the format impractical and DVD players use the non-DRM version audio formats instead. The 32bit floating point format is included even though there are no existing implementations using the format because new audio CODECS will support 32bit floating point formatted audio directly and P1722 should be prepared to stream the new format.


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Supported 61883-6 Event Types

• 8.1 AM824 Data– 8.1.2 IEC 60958 Conformant Data – 8.1.3 Multi-bit Linear Audio (MBLA)– 8.1.5 MIDI Conformant Data– Allow mix of the above per 61883-6 rules

• 8.2 32-bit Floating Point Data

• All the above agree to keep


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Deprecated 61883-6 Event Types

• AM824 options to be deprecated– 8.1.1 Generic Format– 8.1.4 One Bit Audio– 8.1.6 SMPTE Time Code Data– 8.1.7 Sample Count Data– 8.1.8 High Precision Multi-bit Linear Audio– 8.1.9 Ancillary Data– 8.1.10 Application Specific Ancillary Data

• 8.3 24-bit * 4 Audio Pack• All the above agree to deprecate• Matt to inform 1394TA of our plans to support and

deprecate


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61883 timing

• Is current method of “editing instructions” adequate?– Agreed this is an issue, especially for 61883-6 over

AVBTP.– Matt to start working on a contribution


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“Gateway” / “IWU”

• Which term to use

• Details

• Work on Annex B– Agreed single term is needed– Alan to ping Norm on thoughts on a name

• Will copy AVBTP team

– If no suggestion in 2 weeks, Editor’s discretion on picking new name, then we can re-visit


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IIDC

• Channel mapping– 31 on AVBTP– Current IIDC spec specifies only 0 to 15 for valid

IDs– Same kind of “edit instructions” as done for 61883

series is needed– Additional work for Gateway/IWU for channel

mapping

• Alan to make fixes based on John’s comments


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Q tagging and TPID field

• MAAP protocol– Question: Should this be best effort instead of priority

6?• This standard will not specify nor recommend.

– Will only specify– Protocol MAC address– Protocol Ethertype

• Don and Michael to discuss this with Norm at the next 802 AVB meeting

• Stream data– Can the bridge strip the TPID and VLAN field on

sending to end stations for AVB streams?


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IEEE P1722 technical issues and talking points Version 0.01, 2007-08-21 Alan K. Bartky [email protected] SNAP Networks Send comments to [email protected]@listserv.ieee.org.

Documents

ieee p1722 avbtp

ieee p1722 technical

working groups

maximum time

minimum time

asminimum holdover time

holdover timetimeout

gm capable