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N97, Bluetooth audio won't keep time, keeps speedi...

Mobile Guru
Posts: 3,500

N97, Bluetooth audio won't keep time, keeps speeding up?!

I've just got my pair of BH-905 Nokia headphones.. they're really very nice and loosing the audio cable is fab (bluetooth audio FTW!) Looking forward to testing the noise cancelling on the train next week

 

When playing tracks back, occasioning something crazy happens. The playback speed increases.. only very slightly. It causes the track to speed up and the pitch increase (by about 1/4 tone) I think in actual fact the track starts slow. If I rewind the track to before the speed jump, it doesn't happen again and it seems to be playing at the new speed.

 

Now, I appreciate bluetooth audio is streaming technology, so I *urgh it just did it again* can appreciate network congestion might be solved with a speed bump, but this is freaky.. Has anyone else ever noticed this behaviour using bluetooth playback?! *URGH again.. in the same track, now it feels too fast*

 

Seriously crazy. To be fair, I've not used wired headphones with this phone, I'd been waiting for to get wireless headphones so maybe I should try that too.. 

 

 

 

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Mobile Guru
sockatume
Posts: 1,634

Re: N97, Bluetooth audio won't keep time, keeps speeding up?!

Are they VBR (variable bit rate) files? Might be that the bluetooth audio doesn't work so well with VBR for some reason.
Help I'm trapped in a sig factory.
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Advisor
Posts: 22

Re: N97, Bluetooth audio won't keep time, keeps speeding up?!

I have the same problem with BH-103 and I have not had it on my previous E71 phone. Apparently the bluetooth processing on N97 has been assigned too low priority.
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Sage
Posts: 225

Re: N97, Bluetooth audio won't keep time, keeps speeding up?!


sockatume wrote:
Are they VBR (variable bit rate) files? Might be that the bluetooth audio doesn't work so well with VBR for some reason.

You don't send the raw data over BT. The sound is first expanded on the N97, and a constant bitrate is sent to the phones. This is most likely a problem with the BT implementation on the N97. Yet another bug...

 

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Mobile Guru
Posts: 3,500

Re: N97, Bluetooth audio won't keep time, keeps speeding up?!


sillbit wrote:

sockatume wrote:
Are they VBR (variable bit rate) files? Might be that the bluetooth audio doesn't work so well with VBR for some reason.

You don't send the raw data over BT. The sound is first expanded on the N97, and a constant bitrate is sent to the phones. This is most likely a problem with the BT implementation on the N97. Yet another bug...

 


 

First thing to point out is VBR changes the bit rate rapidly and randomly so a gradual shift shouldn't be possible..

 

However, A2DP is actually a bit **bleep**. The audio is not sent raw, it is sent in one of many lossy codecs. The main codec is SBC (which is pretty poor) but it can be one of many standard codecs if both devices support it (MP3, AAC, ATRAC are optionally supported (Nice one BT SIG, pick codecs that are heavily patented)

 

So, the phone either sends MP3 raw to the headphones or it decodes it and recompresses it with lossy SBC.. So the speed up could be caused in the headphones as they catch up on a lossy stream (rather than jump forward it plays the extra buffer slightly faster) or it could be caused by terrible MP3 decode / SBC encode software on the phone..

 

The problem is, if you replay the bit of track where the speed up happens, it doesn't happen again.. which makes me think this is actually a stream to the headset problem.. Maybe caused by low priority of the sending software on the phone (ie it doesn't send the data quickly enough or in crazy packet clumps)

 

Either, this is WELL weird and I'm slightly miffed that A2DP isn't lossless.. how useless is that! Should've checked first.. 

44.1KHz * 2 chan * 16bit = 1.41Mbit

48KHz * 2 chan * 24bit = 2.03Mbit

 

So, bluetooth 2 couldn't carry 48KHz 24bit, but it should be possible to send 44.1KHz 16bit, just.. 

 

There are some lossless codecs on the horizon as I understand, but they're all closed and a bit **bleep** :smileysad: 

 

This may be a problem with the technology in addition to yet more bugs in the N97, may not get solved.. pitty

 

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Sage
Posts: 225

Re: N97, Bluetooth audio won't keep time, keeps speeding up?!

Hmm. Bluetooth 2 is suppsed to be 3 Mbit/s, so it should do just fine with 2*48Khz @ 24 bits as well.

Bluetooth 1.2 will only do 1.2 Mbit/s, so with that version it won't handle uncompressed data either way.

 

But I would assume that the N97 is Bluetooth 2 (but I haven't checked). But anyway, I think this is just another bug in the system. Iv'e seen strange timing issues pop up in a few other places as well, which I need to reboot to get rid of (also related to Bluetooth).

 

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Mobile Guru
Posts: 3,500

Re: N97, Bluetooth audio won't keep time, keeps speeding up?!

according to the 2.0 specification, EDR provides the following benefits:

  • Three times the transmission speed — up to 10 times (2.1 MBits/s) in some cases.

 

 

It's not that fast in actual data transfer.. its like ATM, the packet sizes are small to reduce latency.. Plus you wouldn't want to have a stream that relied on best case scenario to work..

 

 Gotta love the copy & paste from wikipedia :smileyhappy:

 

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Sage
Posts: 225

Re: N97, Bluetooth audio won't keep time, keeps speeding up?!

Yeah, but you should probably have read the whole wikipedia article then (or atleast the whole section you quoted a little bit from). :smileywink:

 

But I agree with the basic line that you can't trust the speed anyway, so you'd better try to have large margins.

 

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Sage
Posts: 96

Re: N97, Bluetooth audio won't keep time, keeps speeding up?!

[ Edited ]

I have the same problem: audio pitch decreases while streaming audio over Bluetooth. I have had the issue mainly on FP2 devices (XM 5630 and now with my E72) using Nokia headsets: BH-103, BH-214 and BH-903. I never had the issue on N95 nor N85.

 

I was hoping firmware update would solve it (V22.007 on E72) as the official changelog reports bluetooth connection issues solved but unfortunately that's not the case.

 

did the latest firmware update of the N97 solve it ? I find the issue less obvious on my XM 5800.

 

anyone else having the issue, what model of phone and what models of headsets ?

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Sage
Posts: 194

Re: N97, Bluetooth audio won't keep time, keeps speeding up?!

I have the same problem on my N97 with my BH-905 noise-cancelling headphones.

 

It is very annoying because the speed-up is very often preceeded by two short pauses in playback, like the phone is doing something else and doesn't have enough buffered to the headphones.  Even in OFFLINE mode (when all other radio circuits should be off) it does it.

 

Very poor performance for an over-priced handset and over-priced headphones.

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Professor
froschy
Posts: 622

Re: N97, Bluetooth audio won't keep time, keeps speeding up?!

I have experienced this as well with my N97 and BH-903 and actually returned the stereo bluetooth headset to try other options but so far all of the Nokia stereo bluetooth headsets that I have tried have this problem.

 

I have heard that this problem is caused by interference from other wireless devices like wifi. I'm not sure on the validity of this but given the recent explosion in the number of wireless devices (wifi, wireless printers, cordless phones, etc...) it does make sense and would also explain why people are having this problem now and not with previous handsets.

 

Anyway, just another thought.

Nokia N97 (RM-507) v 22
iPhone 4 (Coming Soon) - Lemon N97 - SE - Nokia 8210 - Nokia 7710 - Nokia 5100
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Professor
matt_t
Posts: 654

Re: N97, Bluetooth audio won't keep time, keeps speeding up?!

Wifi can definitely mess it up.  I've not experienced this yet while running the 2.1 firmware, but previous firmwares had an issue.  If I was listening to an mp3 while using my Nokia BT headset and the handset happened to access the wifi network (to check for email etc) the playback speed of the mp3 would momentarily speed up and would drop back to normal shortly after.

 

 

Nokia N8 on O2-UK
Firmware 022.014
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New Member
_jai
Posts: 2

Re: N97, Bluetooth audio won't keep time, keeps speeding up?!

I was really hoping that the latest firmware for the n97 would fix this obvious problem.

 

I dont understand how this can be allowed to go on for so long. The n97 and the BH-905 are together in all the press shots, but obviously nobody in finland actually tried using them together.

 

At this point i have very little choice but to give up on nokia and get an android phone :smileysad:

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