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Multiple-zone audio management - System Level Audio
Next Meeting - Thursday
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03 December 2020 - 11:30am CET (AUDIO_HAL
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CW49)
Click to Join Webex meeting
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- Access code: 297 637 101
- Meeting password: 92839687
Agenda
- Continuation of the Network Audio Synchronaztion session
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Participants
Gunnar Andersson Philippe Robin Piotr Krawczyk Unknown User (wassim.filali) Johan Suhasini Raghuram Stephen Lawrence Mohan Karthik Chris Simmonds Unknown User (niskandar)
Minutes
Wassim giving a session about Network Audio Synchronization (many additional information came from Mohan Karthik)
The Problem
- The problem is that different ECU in the audio network have different clocks.
- The most accurate clock is one that looses 1 second every 15 billion years.
- if we had such a clock then there would be no problem in just synchronizing the clocks in the network.
- In current ECUs, the clocks are loosing or gaining 10us every second. So in a 44.1 KHz sample, it's around 1 sample loss every 2 seconds.
- These clocks have an accuracy counted in parts per millions
- Q&A that for humans to notice the difference, we would be talking about a different in parts per 100 not parts per millions
- Link to the Oscillator design can be found here
- These clocks have an accuracy counted in parts per millions
- This will create asynchronous time inside the system and could lead to noticeable sound problems
- One solution to synchronize the clocks is using software.
The possible solution: Software
- By implementing the PTP protocol (Precision Time Protocol) we could synchronize the clocks inside the audio system.
- for example Tutorial on Time-Synchronization for AAA2C based onIEEE Std 802.1AS™-2011 is more explained.
- The main idea is
- the sender and receiver should know what is the delta time between them
- This will allow them to synchronize the packages sent
- The PTP would allow the calculation of the delta time by sending specific values within the packages for the sender and receiver to use
- PTP however does not:
- prevent problems with Latency
- prevent problems caused by Jitter
- provide a unified clock for the whole network.
- So another solution on top of PTP needs to be added to solve the other issues.
Some examples of the solutions mentioned
- Clock Recovery
- If I just sync my clock, I would lose the samples that were supposed to be playing now (already passed) → leads to cut in the sound
- Solution: Clock recovery not clock sync
- This means that we slow down or make the receiver's clock faster in progressively in order not to loose the samples, until the clocks are synchronized.
- Here we talk about a Skew in the clocks
- Resampling
- What if the clocks cannot be synchronized?
- Then we can do a resampling which will take the sample from the sender and resample it to the resceiver's clock
- This is however a very hard subject and there is currently a quest for the perfectest resampler
- This is caused by the new harmonies created by the resampling or in general the distortion of the original signal
- It also needs a lot of CPU power to be done
- Q&A: Why do I need to resample for example in the case of an amplifier, why can't I just make the playrate slower or faster?
- There is no market solution (cheap and easy) to change the frequency of the amplifier because of the complixty of the problem
- Usually all amplifiers are set at a certain frequency and there is no dynamic or adaptable playing rate
- Jitter as explained in Wikipedia
- So PTP does not solve the jitter problem, how can we solve it then?
- When we say jitter in this context we mean clock differences below 5ns.
- So PTP synchonizes the clocks up to 5ns, any difference below that is jitter.
- Actually the receiver would recover the clock by using the "presentation timestamp or PTS"
- In automotive domain, we mostly use a second layer on top of PTP → IEEE 1722-2016 - IEEE Standard for a Transport Protocol for Time-Sensitive Applications in Bridged Local Area Networks
- And we also use Qab to restrict the emission (Mohan Karthik , Unknown User (wassim.filali): Can you please expand this point, I didn't record it correctly. And please add a link about the Qab )
- Dilemma
- a real dilemma is the accuracy vs latency problem (Unknown User (wassim.filali) : could you please expand this point?)
Side discussion: AVB (Audio Video Bridging)
- AVB is about routing only (no control/ start/ skip/ pause)
- SRP (Stream Reservation Protocol) protocol was supposed to support the control but there is no dynamic protocol to control the media specially in automotive
- Usually some OEM do this with SOME/IP (Scalable service-Oriented MiddlewarE over IP) protocol but there is no standardization
- But it's also because there are some more controls like volume, surround, etc. that are not in SRP
- It's hard to catch up with technology
- Either you have an AVB hardware or not (you buy it) and then the vendor would give you the support needed and the explanation
- Presentation of AVB overview was shown.
- Check the progress and discuss the prioritized topics
- Check the priority of the prioritized topics and resolve conflicts if needed
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Participants
Gunnar Andersson Philippe Robin Piotr Krawczyk Unknown User (wassim.filali) Unknown User (niskandar)
Minutes
Going through the list of prioritized topics:
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Thursday - 5 November - 11:30am CET
Participants
Gunnar Andersson Philippe Robin Stephen Lawrence Suhasini Raghuram, Unknown User (wassim.filali), Chris Simmonds
Minutes
Review of the list of prioritarized topics
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Thursday - 1 October - 11:30am CEST
Participants
Gunnar Andersson Philippe Robin Stephen Lawrence Suhasini Raghuram Henric Carlsson
apologies: Unknown User (wassim.filali) Unknown User (niskandar)
Minutes
Review the work breakdown structure and update it to get a shared knowledge of the project status before preparing the agenda of the AHAL working session at the tech summit
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Participants
Gunnar Andersson Philippe Robin Stephen Lawrence Unknown User (wassim.filali) Suhasini Raghuram Henric Carlsson Unknown User (niskandar)
Minutes
Updates from last meeting:
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Thursday 17 September - 11:30am CEST
Participants
Gunnar Andersson Stephen Lawrence Henric Carlsson Piotr Krawczyk Unknown User (wassim.filali)
Minutes
Discussion on demo implementation status
Thursday 10 September - 11:30am CEST
Participants
Gunnar Andersson Stephen Lawrence Henric Carlsson Piotr Krawczyk Unknown User (wassim.filali) Philippe Robin
Minutes
Discussion on configuration & demo building & integration of the emulator project, followed by Jira review
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Participants
Gunnar Andersson Stephen Lawrence Henric Carlsson Piotr Krawczyk
Minutes
Discussion on feature content for MS3 demo (MS3 = virtual tech summit scheduled on October 26-30) Gunnar Andersson can you add the notes you took during the call ? thanks
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Participants
Gunnar Andersson Stephen Lawrence Henric Carlsson Piotr Krawczyk Unknown User (niskandar)
Minutes
Going through the previous minutes of the meeting.
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Participants
Suhasini Raghuram Gunnar Andersson Stephen Lawrence Unknown User (niskandar)
Minutes
Going through the previous minutes of the meeting.
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Participants
Philippe Robin Suhasini Raghuram Unknown User (wassim.filali) Unknown User (niskandar) Stephen Lawrence Piotr Krawczyk
Minutes
Going through the previous todo list:
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Participants
Philippe Robin Gunnar Andersson Unknown User (bartoszbialek) Suhasini Raghuram Unknown User (wassim.filali) Unknown User (niskandar) Stephen Lawrence
Minutes
Alternative board for Suhasini, any upadte on that matter?
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Participants
Philippe Robin Gunnar Andersson Piotr Krawczyk Unknown User (bartoszbialek) Henric Carlsson Suhasini Raghuram Unknown User (wassim.filali) Unknown User (niskandar)
Minutes
Should the minutes be more like a transcript?
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Participants
Unknown User (niskandar) Gunnar Andersson Unknown User (zafirulhassan) Piotr Krawczyk Unknown User (bartoszbialek) Unknown User (zafirulhassan)
Minutes
Looking at the history, the best course of action here is to go through the Jira tickets and assign them to start working on them.
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Participants
Unknown User (wassim.filali) Philippe Robin Gunnar Andersson Piotr Krawczyk Unknown User (bartoszbialek) Henric Carlsson Stephen Lawrence Suhasini Raghuram Unknown User (niskandar)
Minutes
Let's start by going through the points that we have gathered last time in PoC Milestones and Work Breakdown.
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Participants
Unknown User (wassim.filali) Unknown User (niskandar) Philippe Robin Gunnar Andersson Piotr Krawczyk Unknown User (bartoszbialek) @Henric Unknown User (zafirulhassan)
Minutes
Introduction to members and new member Zafirul
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Participants
Suhasini Raghuram Unknown User (wassim.filali) Unknown User (niskandar) Philippe Robin Gunnar Andersson Piotr Krawczyk Unknown User (bartoszbialek) @Henric
Minutes
Debriefing of the virtual summit
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Participants
Suhasini Raghuram Unknown User (wassim.filali) Unknown User (niskandar) Philippe Robin Andrii Chepurnyi Harald Bartholomae Ruslan Shymkevych Gunnar Andersson Piotr Krawczyk @Henric
Minutes
Going through the presentation of Wassim
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Anchor AUDIO_HAL_CW18 AUDIO_HAL_CW18
Thursday 30 April - 11:30am CET (AUDIO_HAL_CW18)
| AUDIO_HAL_CW18 | |
| AUDIO_HAL_CW18 |
Participants
Philippe RobinSuhasini Raghuram Unknown User (wassim.filali) @Henric Ruslan Shymkevych
apologies: Piotr Krawczyk Unknown User (bartoszbialek)
Minutes
Review of Ruslan's email of 23 April - archive
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Anchor AUDIO_HAL_CW17 AUDIO_HAL_CW17
Thursday 23 April - 11:30am CET (AUDIO_HAL_CW17)
| AUDIO_HAL_CW17 | |
| AUDIO_HAL_CW17 |
Participants
Philippe Robin Piotr Krawczyk Unknown User (bartoszbialek) Suhasini Raghuram Unknown User (niskandar) Unknown User (wassim.filali) @Henric
Minutes
Updates of the tasks done from last week: Wassim, Piotr, Nadim
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Anchor AUDIO_HAL_CW16 AUDIO_HAL_CW16
Thursday 16 April - 11:30am CET (AUDIO_HAL_CW16)
| AUDIO_HAL_CW16 | |
| AUDIO_HAL_CW16 |
Participants
Philippe Robin Gunnar Andersson Piotr Krawczyk Unknown User (bartoszbialek) Suhasini Raghuram Ruslan Murtazin Unknown User (niskandar) Unknown User (wassim.filali) Andrii Chepurnyi @Henric
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- Discuss the gathered topics, who can work on which topics and which strategy
- Status update on the "access raw streams"
Minutes
Changes done in this page Android and System Level Audio:
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Anchor AUDIO_HAL_CW15 AUDIO_HAL_CW15
Thursday 09 April - 11:30am CET (AUDIO_HAL_CW15)
| AUDIO_HAL_CW15 | |
| AUDIO_HAL_CW15 |
Participants
Philippe Robin Gunnar Andersson Piotr Krawczyk Unknown User (bartoszbialek)Andrii Chepurnyi@Henric Suhasini Raghuram Stephen Lawrence
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- from last week's minutes
- Discuss the gathered topics, who can work on which topics and which strategy
- Status update on the "access raw streams"
- AOB
- abstract of the GENIVI virtual tech summit AASIG Audio HAL workshop
Minutes
list of gathered topics on multi-zone audio management
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Thursday 02 April - 11:30am CET (AUDIO_HAL_CW14)
Participants
Philippe Robin Gunnar Andersson Piotr Krawczyk Unknown User (bartoszbialek) Unknown User (wassim.filali) Andrii Chepurnyi Unknown User (niskandar) @Henric Suhasini Raghuram
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- Slides from Wassim about the two models inside and outside of AA
- discussion of the cases/features that we are trying to solve
- checking the Audio Manager to decide whether or not it needs an update
Minutes
- 2 strategies or options:
- android provides sources and sinks
- Android controls the complete systems
- We will not discuss the need to have such options
- Basically some functions cannot be integrated to AA
- Audio sources coming from android or from external (android not aware of them)
- Each strategy has limitations and can be criticized
- Idea is to get each model and apply to it questions/cases
- Questions like safety sources, raw streams, etc.
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