Strange Alexa Bluetooth problem.

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My wife's Echo dot is usually connected via Bluetooth to a little BT receiver that plugs into the aux input of our dining room "HiFi".

 

After it's been connected for some time, the audio starts to experience short periods(sub second) of droput.

 

If I get Alexa to disconnect from BT, and then reconnect, everything is fine for a while, after which the problem re-occurs.

 

I've searched the web a few times to see if anyone else has experienced this problem, and come up with a solution, but so far to no avail.

 

I've idly wondered if the droupouts correspond with the BT frequency hopping, and whether some frequencies are experiencing interference from WiFi or something, but that wouldn't really explain why the disconnect/reconnect fixes the problem.

Also, I've no idea as to what sort of length of data dropout BT will tolerate(although I guess it's quite a lot, as one can move connected devices until the audio starts to dropout, and then move closer together again).

 

So if my theory is correct, and one or more of the hopped frequencies is being compromised, why would the disconnect/reconnect process fix it?

Any bright ideas?

Four legs good, two legs bad, three legs stable.

Last Edited: Fri. Mar 8, 2019 - 11:14 AM
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John_A_Brown wrote:
why would the disconnect/reconnect process fix it?

Changes the hop sequence, so lowers the interference until the sequence once again bangs into the trouble spot.

 

https://en.wikipedia.org/wiki/Fr...

 

Jim

 

 

 

 

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Well, its an easy theory to test.

If yo put the Echo very near / adjacent the HiFi then it should have a very strong signal, and you should not experience the drop outs. 

That would be a simple test to help confirm the theory.

 

If the BT stack somewhere within the Tx / Rx system has a buffer that overflows, etc., then placing the two devices side by side shouldn't make any difference, and one would still see the software bug manifest itself.

 

JC

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John_A_Brown wrote:
... but that wouldn't really explain why the disconnect/reconnect fixes the problem.
Audio codecs can be degraded by excessive latency.

Bluetooth Low Energy (BLE) 4.0 reduced latency; BLE is common for hands-free headsets (one or two earphones, one microphone)

BLE mesh networking (IIRC, optional in Bluetooth 4.2) further reduced latency.

Codecs are frame dependent; the start-of-frame signal is within a time window.

John_A_Brown wrote:
... why would the disconnect/reconnect process fix it?
Re-sync; akin to the SYNC character for UART auto-baud.

John_A_Brown wrote:
Any bright ideas?
Wi-Fi is non-deterministic though usually fast enough; might try Wi-Fi instead of Bluetooth or evaluate qualified Bluetooth 5 products.

fyi, MPLAB Harmony (PIC32) has audio codecs if you want another project smiley

 


Amazon.com: Certified Refurbished Echo Dot (2nd Generation) - Black: Amazon Devices

audio codecs, live to archival versus telephone to high fidelity

via Comparison – Opus Codec

SIG INTRODUCES BLUETOOTH LOW ENERGY WIRELESS TECHNOLOGY THE NEXT GENERATION OF BLUETOOTH WIRELESS TECHNOLOGY | Bluetooth Technology Website

...

  • Latency – Bluetooth low energy technology can support connection setup and data transfer as low as 3ms, allowing an application to form a connection and then transfer authenticated data in few milliseconds for a short communication burst before quickly tearing down the connection. 

...

Qualified Bluetooth Mesh Products | Bluetooth Technology Website

Decoder Libraries - MPLAB Harmony Help (AAC, FLAC, MP3, Opus, Speex, WMA)

via MPLAB Harmony | Integrated Embedded Software Development Framework | Microchip Technology

https://github.com/atmelcorp/atmel-software-package/tree/master/examples/usb_audio_speaker

http://asf.atmel.com/docs/latest/search.html?search=audio

 

"Dare to be naïve." - Buckminster Fuller

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Dumb questions are about to be typed.....

 

John_A_Brown wrote:
My wife's Echo dot is usually connected via Bluetooth to a little BT receiver that plugs into the aux input of our dining room "HiFi".

 

John_A_Brown wrote:
If I get Alexa to disconnect from BT, and then reconnect, everything is fine for a while, after which the problem re-occurs.

 

WHich one is connected to the receiver?  Or are you referring to the same device(using two different names)?

 

If both Alexa, and Echo are connected to this same receiver, I would suggest that you disable Alexa from the connection and see if the problem goes away.  If it does I would say that one of the two things is happening

 

1) the Receiver does not have the horsepower to handle two connections simultaneously - Although I thought BT was a single point to point connection only

 

2) Alexa is trying to connect to the Receiver on occasion for some reason and it is disturbing the link between Echo and the Receiver.

 

Sounds to me like Alexa is a trouble maker and should be removed from the house immediately.wink

 

JIm

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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jgmdesign wrote:
Although I thought BT was a single point to point connection only
plus two more (broadcast, mesh)

Topology Options | Bluetooth Technology Website

 

"Dare to be naïve." - Buckminster Fuller

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Thanks!!

 

JIm

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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"Or are you referring to the same device(using two different names)? "

That. Sorry for any confusion.

 

Four legs good, two legs bad, three legs stable.

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"Bluetooth Low Energy (BLE) 4.0 reduced latency; BLE is common for hands-free headsets (one or two earphones, one microphone) "

I've done a few jobs with BLE, and I wasn't aware that it had the throughput for audio streaming.

Four legs good, two legs bad, three legs stable.

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Can't you just ask Alexa to explain this?

 

 

 

 

 

 

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More dumb question time....

 

You posted:

John_A_Brown wrote:
BT receiver that plugs into the aux input of our dining room "HiFi".

 

By any chance is there a microwave oven nearby and was it started up when the dropout occurred?  I have a Bluetooth headset for my phone that has an audio 'hiccup' if I am in the kitchen and fire up the m-wave to heat up lunch.

 

JIm

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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No to the microwave question.

Once the dropout starts, the only way to sort it is the disconnect/reconnect, and that's the part I find puzzling.

I wll try moving the Alexa/Echo dot closer to the HiFi, but it's a bit of a pain when you live in old British house, with approx one socket oulet per square mile.

 

 

 

Four legs good, two legs bad, three legs stable.

Last Edited: Fri. Mar 8, 2019 - 06:12 PM
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Apparently yes though not recommended for mesh (a guess is the additional latency due to hops)

Supported Bluetooth profiles - Windows Help

Applies to: Windows 10

...

  • Advanced Audio Distribution Profile (A2DP 1.2)

...

due to

https://launchstudio.bluetooth.com/ListingDetails/64311?_ga=2.256916110.487096323.1552053418-209963323.1551898951

...

TMALL GENIE Smart speaker

...

[Bluetooth 4.2]

...

Advanced Audio Distribution Profile

...

[Mesh Model]

[Mesh Profile]

...

via Qualified Bluetooth Mesh Products | Bluetooth Technology Website

 


Alibaba's Smart Home Assistant Is Similar to Amazon Echo | Fortune

 

"Dare to be naïve." - Buckminster Fuller

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Well as far as I know, there may be one or two proprietary offerings for audio over BLE, but there is no published standard.

In my opinion, all the audio gadgets you see advertised as BT4, are actually also BT legacy capable, and the BT4 tag is just to confuse the purchaser into thinking they're buying the latest tech.

I hope I'm wrong.

 

 

Four legs good, two legs bad, three legs stable.

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Even machines are now dropping out to wife's voices, not just husbands.  devil

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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Maybe Alexa is listening to the music and thinks she

hears her name, causing enough activity to interrupt

the music?

 

--Mike

 

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avr-mike wrote:

Maybe Alexa is listening to the music and thinks she

hears her name, causing enough activity to interrupt

the music?

 

--Mike

 

I only listen to instrumental music.

 

Four legs good, two legs bad, three legs stable.

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Perhaps the Echo plays your instrumental music at 44.1kHz exactly, but the DAC in your audio dongle plays at 44.101kHz because they used a crappy crystal. Thus it will gradually empty any buffer down to zero bytes and that's when the dropouts occur.

 

Breaking & remaking the connection refills buffers again.

 

Anyone know how the Bluetooth A2DP stack works ?

 

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N.Winterbottom wrote:

Perhaps the Echo plays your instrumental music at 44.1kHz exactly, but the DAC in your audio dongle plays at 44.101kHz because they used a crappy crystal. Thus it will gradually empty any buffer down to zero bytes and that's when the dropouts occur.

 

Breaking & remaking the connection refills buffers again.

 

Anyone know how the Bluetooth A2DP stack works ?

 

I should have been clearer. This problem shows up after several hours.

 

Four legs good, two legs bad, three legs stable.

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John_A_Brown wrote:
I should have been clearer. This problem shows up after several hours.

My "2 clocks drifting apart" theory still applies in that condition.

 

Does the fault begin only after several hours of gapless playback; or just "being connected" without necessarily playing audio ?

If the audio stream stops & starts that may allow the stack to reinitialise and that would disprove my theory.

 

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Just being connected. I'm still fairly convinced it has to do with frequency hopping.

I'll plug the Alexa/Echo Dot in via a long extension lead and do some experiments - such as wait for the dropout to start, and then move closer to the receiver.

When the dropout kicks in, I'm talking about a 10mS or so of dropout, every couple of secomds(approx - it's probably not that regular, but unless I played a constant tone I wouldn't be able to check).

 

"Alexa, play a 440Hz tone"

"Hmmm. I don't know that one"

 

"Alexa, play middle C" (Yes I know 440 is an A)

"Playing middle C by somebody I'venever heard of and somebody else I've never heard of".

 

My problem with the "2 clocks drifting apart" theory, is that it would almost always apply to any setup, unless the BT sender and receiver shared the same clock.

Four legs good, two legs bad, three legs stable.

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John_A_Brown wrote:

My problem with the "2 clocks drifting apart" theory, is that it would almost always apply to any setup, unless the BT sender and receiver shared the same clock.

The slave should resynchronise it's local clock relative to the master's clock each time it receives a packet from the master.

In general, the procedure to allow for clock drift is something along the lines of

1) specify an upper limit for the crystal error

2) specify that the master must send some kind of packet to the slave at least once every so often

3)  the combination of 1) and 2) sets an upper limit on how far out the 2 clocks can be

4) the receiving device will widen its receive window by the amount in 3)

5) slave resynchronises each time it receives a packet

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MrKendo wrote:
5) slave resynchronises each time it receives a packet

A Ha - So does this resynchronise mechanism involve either dropping a sample or playing an extra zero sample ?

 

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N.Winterbottom wrote:

MrKendo wrote:
5) slave resynchronises each time it receives a packet

A Ha - So does this resynchronise mechanism involve either dropping a sample or playing an extra zero sample ?

 

I think we're talking about different things here.

I was referring to 'resynchronise' as the slave updates its estimate of the offset betwen its clock and the master's clock, such that it knows (close enough) when to start listening for a packet from the master and so won't start missing packets due to clock drift. Not talking about 'resynchronise' in the sense of the audio stream.

BT is all time driven, based on timing slots, with the timing on the link based on the master's clock.

When slave recieves a packet, it can use the difference between when it thought the packet should arrive and when it actually arrived to update its estimate of this offset.

So I'm just saying, the fact that the link has been up for several hours should not be a reason in itself to start missing packets.

 

I don't know what the problem is.

Could be interference, but it's strange if it only ever happens several hours after connecting, but that could just be coincidence.

Could be a bug at one end.

Does the Alexa thing also use 2.4G wifi? Maybe it starts to do something over 2.4G wifi which takes priority over BT? Who knows.

 

Ideally, I guess it would be useful if  you could replace the device at each end in turn with a different device, and see if it makes any difference.

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OK, I moved the Echo dot to within 18" or so of the BT recever last night.

As of now(around noon), I'm getting very occasional dropout. So I don't think it's a proximity thing.

 

I read that BT frequency hops 1,600 times a second. These dropouts are closer to 100mS, so f hopping may be irelevant.

 

I did change the Echo WiFi settings from 2.4g to 5G(or possibly the other way round) several months ago, while looking for a solution. Didn't make any difference.

 

I will try a different BT receiver, and then try the current BT receiver with a different source, e.g. and old phone or tablet.

 

Four legs good, two legs bad, three legs stable.

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N.Winterbottom wrote:

MrKendo wrote:
5) slave resynchronises each time it receives a packet

A Ha - So does this resynchronise mechanism involve either dropping a sample or playing an extra zero sample ?

 

Surely repeating a sample(or even interpolating) would be less noticeable than a zero?

 

Four legs good, two legs bad, three legs stable.

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"Dare to be naïve." - Buckminster Fuller