January 2016 - Bluetooth-dev

Re: Maximizing Data Transfer over BLE on iOS9
by Bill Bonney 26 Jan '16

26 Jan '16

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RE: Maximizing Data Transfer over BLE on iOS9
by Meyer, Chas 26 Jan '16

26 Jan '16

Ben, On the BLE121LR side, have you tried negotiating for more favorable connection parameters? Using iOS 8, we built a BLE interface that used the "SPPLE" service demo by Stone Street One (Bluetopia BT stack), now maintained by TI. I may have the exact numbers wrong, but we saw a best-case connection interval of about 35 msec with iOS, and an MTU size of about 130 bytes. At the time, these were iOS defaults. Using the SPPLE service, we saw a peak throughput of about 5-6 KB/s. Disclaimer: I was not the iOS developer; I worked on the BLE firmware for the accessory. Chas Meyer ---------------------------------------------------------------------- Message: 1 Date: Tue, 26 Jan 2016 15:40:08 +0000 From: Ben Flannery <ben.flannery(a)bigasssolutions.com> To: "bluetooth-dev(a)lists.apple.com" <bluetooth-dev(a)lists.apple.com> Subject: Maximizing Data Transfer over BLE on iOS9 Message-ID: <5F3E18CA-246E-46DF-B5B0-46A7D1BABA28(a)baf.mail.onmicrosoft.com> Content-Type: text/plain; charset="utf-8" I’m attempting to transfer 100-200 kB over BLE. I understand the limits of BLE for this purpose, and am willing for this transfer to be slow, but I would still like to maximize it as much as possible. There is a lot of information online regarding transmission rates, but much of it seems to be outdated (pre-iOS 7). My setup is as follows: CBCentral: iPhone 6S+ CBPeripheral: BLE121LR This transfer is going from the Central to the Peripheral through the `CBPeripheral.writeValue(data, forCharacteristic: characteristic, type: CBCharacteristicWriteType)` method. I have tried a variety of schemes. 1. Write 100kB once withResponse 2. Write a single 20 byte chunk withResponse 3. Write 4 20 byte chunks every 20ms withoutResponse 4. Write a single 80 byte chunk every 20ms withResponse Obviously using ‘withResponse’ gives a huge overhead & latency. The best transmission rates I have achieved are by writing 4 20 byte chunks every 20ms without notifications. Obviously, without loss, this is a hard limit of 4kB/s. I can typically achieve rates of 1-3 kB/s depending on connection strength. Are there any adjustments I can make to increase this? Can I modify the BLE connection parameters (MTU size)? Would increasing the characteristic size in the GATT profile give me any real-world benefit?

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Re: Maximizing Data Transfer over BLE on iOS
by Nick Brook 26 Jan '16

26 Jan '16

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Re: Maximizing Data Transfer over BLE on iOS9
by Aleksandar Mihailovski 26 Jan '16

26 Jan '16

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Maximizing Data Transfer over BLE on iOS9
by Ben Flannery 26 Jan '16

26 Jan '16

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Re: AAC MTU performance?
by Craig Dooley 22 Jan '16

22 Jan '16

AAC requires 1024 frame packets, and at 44.1kHz, that gives ~43 packets per second. If you lose ~10 bytes for L2CAP and AVDTP headers, that leaves 43 * 662, or ~227kb/s. If your device only supports 2Mbit EDR, 671 is a good compromise since any packet sent will fit in a 2DH5 packet, instead of needing to be split into a 2DH5 + a 2DH3. - Craig > On Jan 22, 2016, at 12:53 PM, Gordon Rankin <gordon(a)wavelengthaudio.com> wrote: > > Craig, > > We are releasing an A2DP AAC solution this month. I looked at our code after reading your response on the MTU subject and found we are negotiating at 672 bytes. Is there some sort of calculation with the MTU number and the bandwith? I searched older posts which indicated a maximum of 885 bytes. Any information would be appreciated. > > Thanks, > Gordon >> Date: Thu, 21 Jan 2016 11:07:01 -0800 >> From: Craig Dooley<cdooley(a)apple.com> >> To: Feng Yu Hong<fengyuhong(a)vimicro.com> >> Cc:"bluetooth-dev(a)lists.apple.com" <bluetooth-dev(a)lists.apple.com> >> Subject: Re: A2DP AAC codec bandwidth >> Message-ID:<B6156406-1236-4065-B7AF-C5C054D7581C(a)apple.com> >> Content-Type: text/plain; charset="utf-8" >> >> The encoder takes into account the MTU negotiated when determining the maximum frame size available. For example, if the device has an MTU of 565 for the AVDTP channel, that only allows for ~192kb/s, even if the endpoint configuration says the device can handle 262 kb/s. >> >> - Craig > > -- > J. Gordon Rankin > Owner and Chief Scientist > ====== Wavelength Audio, ltd ====== > _______________________________________________ Do not post admin requests to the list. They will be ignored. Bluetooth-dev mailing list (Bluetooth-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/bluetooth-dev/site_archiver%40lists… This email sent to site_archiver(a)lists.apple.com

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AAC MTU performance?
by Gordon Rankin 22 Jan '16

22 Jan '16

Craig, Thanks, Gordon Date: Thu, 21 Jan 2016 11:07:01 -0800 From: Craig Dooley<cdooley(a)apple.com> To: Feng Yu Hong<fengyuhong(a)vimicro.com> Cc:"bluetooth-dev(a)lists.apple.com" <bluetooth-dev(a)lists.apple.com> Subject: Re: A2DP AAC codec bandwidth Message-ID:<B6156406-1236-4065-B7AF-C5C054D7581C(a)apple.com> Content-Type: text/plain; charset="utf-8" The encoder takes into account the MTU negotiated when determining the maximum frame size available. For example, if the device has an MTU of 565 for the AVDTP channel, that only allows for ~192kb/s, even if the endpoint configuration says the device can handle 262 kb/s. - Craig -- J. Gordon Rankin Owner and Chief Scientist ====== Wavelength Audio, ltd ====== _______________________________________________ Do not post admin requests to the list. They will be ignored. Bluetooth-dev mailing list (Bluetooth-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/bluetooth-dev/site_archiver%40lists… This email sent to site_archiver(a)lists.apple.com We are releasing an A2DP AAC solution this month. I looked at our code after reading your response on the MTU subject and found we are negotiating at 672 bytes. Is there some sort of calculation with the MTU number and the bandwith? I searched older posts which indicated a maximum of 885 bytes. Any information would be appreciated.

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Apple iAP versions for iPad2 and iPhone6
by Gabriele Filosofi 22 Jan '16

22 Jan '16

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Re: A2DP AAC codec bandwidth
by Feng Yu Hong 22 Jan '16

22 Jan '16

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Re: A2DP AAC codec bandwidth
by Craig Dooley 21 Jan '16

21 Jan '16

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