Media Clock Distribution in a 1722 Network Dave Olsen (dolsen@harman.com) 22 October 28 22 October 28 IEEE 1722
Capabilities Synchronize Media clock on multiple 1772 endpoints Allow multiple talkers to produce multiple 1722 streams that are all synchronized Listener can receive 1722 streams from multiple sources without making use of sample rate conversion 22 October 28 IEEE 1722
Media clock sources Any active stream can be designated as the media clock source stream This stream could be a standard stream or a null stream that contains only clock information Since any stream can supply media clock, there is no need for a special stream type 22 October 28 IEEE 1722
Talkers Talkers receive the designated stream and synchronize their media clock to the incoming stream Streams produced by the talker are then automatically syntonized with the designated stream 22 October 28 IEEE 1722
Listeners Listeners receive the designated stream and synchronize their media clock Listeners utilize the presentation time of individual stream to time align the streams 22 October 28 IEEE 1722
Outgoing Stream 1722 Stream 82.1AS Wall Time Timestamps 7166667 7333333... 8666667 8833333 9 Data Media clock (local oscillator) Incoming Analog Data AVBTP Timestamp Generator A/D 1722 Data 22 October 28 IEEE 1722
Incoming Stream 1722 Stream 82.1AS Wall Time Timestamps 7166667 7333333... 8666667 8833333 9 AVBTP Timestamp Comparator Data Clock Generator AVBTP timestamps Generated media clock Outgoing Analog Data D/A 22 October 28 IEEE 1722
Outgoing Stream Media clock stream Timestamps Data 1722 Stream Timestamps Data 65 6333333... 4833333 4666667 4333333 82.1AS Wall Time 7166667 7333333... 8666667 8833333 9 AVBTP timestamps Generated media clock Incoming Analog Data AVBTP Timestamp Generator A/D 1722 Data 22 October 28 IEEE 1722
Incoming Stream Media Clock Stream Timestamps Data 1722 Stream Timestamps Data 65 6333333... 4833333 4666667 4333333 82.1AS Wall Time 7166667 7333333... 8666667 8833333 9 AVBTP timestamps Generated media clock AVBTP Timestamp Comparator Outgoing Analog Data D/A 22 October 28 IEEE 1722
Sync Streams Locally administered Sync Streams Allow completely user defined environment No wasted bandwidth on unused sync streams All equipment must be manageable Interoperability between brands could be problematic 22 October 28 IEEE 1722
Sync Streams Globally defined Sync Streams Reduce system setup Interoperability between brands improved No need to assign sync streams for each piece of equipment Possible wasted bandwidth on unused streams Who supplies the sync streams must be managed 22 October 28 IEEE 1722
Sync Streams Global sync streams must be easily identifiable Defined multicast address Defined Stream ID 22 October 28 IEEE 1722
Sync Streams Sync streams need to be stable A recurring election process may introduce too much instability Can we use MAAP to allocate designated multicast addresses? First one to acquire the address supplies the designated sync stream forever Management interface need to reliably set the provider of sync streams 22 October 28 IEEE 1722
Sync Streams Number of sync streams to be defined Default Audio sync Set at the default rate for the network Standard set of audio syncs 44.1, 48, 88.2, 96,. Default Video sync Set at the default rate for the network Standard set of video syncs???? 22 October 28 IEEE 1722
Sync Streams 48khz Sync Stream 22 October 28 IEEE 1722
Sync Streams 48khz Sync Stream 48khz AVB Stream 22 October 28 IEEE 1722
Sync Streams 48khz Sync Stream 44.1khz Sync Stream 48khz AVB Stream 22 October 28 IEEE 1722
Sync Streams 48khz Sync Stream 44.1khz Sync Stream 48khz AVB Stream 44.1khz AVB Stream 22 October 28 IEEE 1722
Sync Streams 48khz Sync Stream 44.1khz Sync Stream 48khz AVB Stream 44.1khz AVB Stream Video Sync Stream 22 October 28 IEEE 1722
Sync Streams 48khz Sync Stream 44.1khz Sync Stream 48khz AVB Stream 44.1khz AVB Stream Video Sync Stream Video AVB Stream 22 October 28 IEEE 1722
Proposal Reserved addresses/stream IDs for a set of Sync Streams Network default audio/video sync streams Allows a device to learn the defaults for the network and sync to it if possible A set of designated rate audio/video sync streams Allows for interoperability of multiple clock domains A device that cannot sync to the default can still find a compatible sync domain 22 October 28 IEEE 1722
Proposal 64 reserved Multicast addresses from the MAAP range xx:..:1 Default Audio Sync xx:..:2 Default Video Sync xx:..:3 48khz Audio Sync xx:..:4 44.1khz Audio Sync xx:..:5??? Video Sync etc. 22 October 28 IEEE 1722
22 October 28 IEEE 1722