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Old 03-12-2008, 07:37 PM
woof woof is offline
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Default Questions of Bluetooth profile, over-modulation, etc.

Hi everyone,
I'm I NuBee to this forum but a long-time self-described "audiophile" (of sorts). I've been playing around with the 8gb Pilot and have some in-depth, mostly Bluetooth related questions. I apoligize in advance for such a wordy 1st posting.

I've found the Pilot's headphone output, when used as a line-output (with a 10-15kohm load), to be fairly clean and balanced (at least for a DAP). Using a variety of wired headsets it sounds OK, just not particulary strong, and like all DAPs it's power output stage seems sensitive to the whims of the electrical signature of the headset (resistance, inductance and to a lesser degree capacitance). But hey, all DAP's work off a single-ended, very low-voltage power supply and an amplifier with a slew-rate and damping factor of...well...not much, but I digress.

Using BT stereophones however has been a far less than satisfactory experience. I knew using BT for audio would result in a significant loss of dynamic range and frequency response but I was quite unaware of the amount of good ol' distortion and artifacts it would produce (having a situation where portable cordless is needed).

In trying to locate the source(s) of the distortions, I found that the Pilot equalizer has some effect on a distortion that sounds much like over-saturation (clipping). I believe Digialdel mentioned that the input to the BT encoder was fed a maximum volume signal all the time to provide the best S/N ratio for the BT link. It seems to make sense that reducing the BT input signal by using eq would help some. There also seems to be other BT distortions that I cannot pin down or correct. These sound like "grittyness" or "raspyness" on the edge of vocals, horrid smearing/distorting of cymbols, etc. I've tried all flavors and types of file encoding rates from MM and none seem alter this phenominom.

It was mentioned somewhere that the Pilots have BT version 1.2. Looking the Pilot up at the following site: https://www.bluetooth.org/tpg/QLI_viewQDL.cfm?qid=13059 indicates the Pilot's BT license was for 2.0/2.0+EDR (extended dynamic range) Edit Corrected to: Expanded Data Range. My limited knowledge of BT has led me to believe that it is possible for 2.0+EDR to enhance audio transmission but that it is an spec option, and not manditory for 2.0 devices. And both transmitter and receiver must have the profile for the link to function at the higher bitrate. Also from what I understand there seems to be no difference in the audio quality (bitrate) between 1.2 and 2.0 but there is between 1.2/2.0 verses 2.0+EDR. So my first question is: Is the Pilot BT 1.2, 2.0 or a fully-enabled 2.0+EDR? Edit: I figured out the answer...it's BT Core 2.0

This leads to my second question. Since these DMP manufacturers jealously guard information, like simple block diagrams of signal flow, I was wondering if it would be possible in a firmware revision to relocate the Pilot's master volume control so it is in-line before the BT encoder; sortof the way it is with the Samsung P2? That way the user could set the level for best encoder matching verses maxium BT volume (unfortunately the P2's eq doesn't work over BT). Alternatively, I think this volume control relocation would not be needed if ReplayGain or some other method of controlling codec playback volume was added.

As to the other sources of distortion, could it be simply the sampling rate of the BT encoder, especially if it's BT 1.2 or 2.0 or an encoding error with what may be an internal PCM or equivant bitstream? I've ruled out obvious external possiblities like interfearence, signal strength, etc.

BTW, the only BT headsets I've tested to date are the Sony DR-BT22, Sony DR-BT50 and the Insignia.

Also has anyone listened to a true, fully enabled profile 2.0+EDR audio source (i.e. a DAP with a SonyWLA-NWB1 or TMR-BT81P transmitter, a 2.0+EDR USB computer dongle, etc.) with matching profile headset?

Thanks to all in advance. Great forum here.

Woof
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  #2  
Old 03-14-2008, 10:22 AM
woof woof is offline
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Ok, it seems I may be talking to myself here.

I've done some additional research that I wanted to share/discuss with anyone who's interested. In reference to BlueTooth discussions, what the forums have been concentrating on are basic connection terms like A2DP and AVRCP. IMHO, the audio quality arguement should be realigned to BT core 2.0 verses 2.0/2.1+EDR discussions.

It turns out that for a full 3mps (EDR - Extended Dynamic Range) BT link to work it requires both radios (i.e. player and headset) to both have the full spec and both be fully enabled by the end product manufacturer. Simply having the 2.0+EDR chipset does not automaticly give the device high audio bandwidth capacity. Also as BT devices to date are backwards compatible, if either radio has a lower rating, i.e. core 2.0 or 1.2, then the entire link handshakes and adjusts downward to the lesser device.

To me this helps explain some of the audio quality issues I've been experiencing. Let me explain by providing the following list of BT registrations:

some Player examples:
Insignia Pilot = BT core 2.0
Samsung P2 = BT core 2.0
Sony NWZ-A829 = BT core 2.0+EDR

some headsets:
Sony DR-BT22 = BT core 2.0
Sony DR-BT50 = BT core 2.0+EDR (edit: not confirmed with EDR)
Insignia = BT core 2.0
Logitech FreePulse = BT core 2.0+EDR

and some transmitters of note:
Sony WLA-NWB1 = BT core 2.0+EDR
Sony TMR-BT81P = BT core 2.0+EDR

Now to try and put this information together: The effective BT 1.2 and 2.0 thruput (under ideal conditions) is about 700kps (listed as 1.0mps). The effective 2.0+EDR thruput rate is about 2.1mps (listed as 3.0mps). I know its been argued that 700kps is plenty of bandwidth, after all mp3 maxes out at 320kps. But that is a compressed data file rate. I'm not clear on this but I think the decompressed and decoded PCM stream would have much higher bit rate. Maybe those with info on this could chime in here. Anyway, then it gets down to the decoded audio stream bitrate (whatever form it is) verses the BT encoder bitrate. I think this is where things can really start to fall apart. It also brings up the point of what works best: applying PCM or analog audio to the BT transmitter? Case & point would be a iPod equipped with the Sony 2.0+EDR dongle (uses the iPod's analog line-output) verses say the Sony NWZ-829 (using what would be thought to be internal PCM?).

So anyone listening to a 2.0+EDR headset with, as an example, a Pilot or Samsung P2 will get no immediate BT audio improvement of such a headset. Conversely anyone with one of the Sony transmitters listed above would have no benefit with, as an example, the Sony DT-BR22 or Insignia headset. And anyone listening to the Sony DT-BR50 or Logitech FreePulse headphones have not listened to them in their best mode unless you have one of the few audio EDR enabled 2.0+EDR transmitters available.

For the purposes of audio quality, it appears there is no difference between BT 1.2 and 2.0. Core 2.0 adds to connectivity options, error correction and some other things but nothing that really aids audio quality.

I think the BT consortium would have not added the audio profile to the EDR spec if they felt there was no room for improvement. My personal listening experience says there is lots of room.

Woof
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  #3  
Old 03-14-2008, 06:03 PM
Skinjob Skinjob is offline
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I've researched this a bit myself because I was hoping to use a bluetooth player in conjunction with a Bluetooth car stereo. I'm by no means a bluetooth expert, but I think my responses below are accurate.

Quote:
In reference to Bluetooth discussions, what the forums have been concentrating on are basic connection terms like A2DP and AVRCP. IMHO, the audio quality arguement should be realigned to BT core 2.0 verses 2.0/2.1+EDR discussions
EDR actually stands for Enhanced Data Rate, not Extended Dynamic Range, and refers to the basic signaling rate. It doesn't really have any direct correlation with audio quality because devices can't just use the bluetooth bandwidth however they see fit. It depends on the profile used by the device (A2DP in this case).

Discussions of the A2DP profile are relevant because A2DP specifies how high quality audio is streamed between bluetooth devices. This incudes how the audio is compressed. A2DP requires support of the SBC codec (sub-band coding). This is a simple and fast lossy codec that delivers a stream somewhere in the 350kbs range (I forget the exact bitrate). Because emphasis in SBC is on computational simplicity, not accuracy, I don't think SBC comparable quality-wise to other more modern lossy codecs like high bitrate MP3 VBR or OGG.

So assuming your source files are already lossy compressed, using bluetooth will put them through another lossy compression. Even though it's a pretty high bitrate, it could definitely introduce undesireable artifacts like the smearing/distorting of cymbals you mentioned. This would obviously be worse if the original files are already heavilly compressed. If your source files are lossless or high bitrate lossy, the results will probably be decent.

Unfortunately for now, A2DP and the SBC Codec are the only game in town for buletooth audio. However, there is hope for lossless bluetooth audio:

http://www.engadget.com/2007/08/01/o...tooth-devices/

I wouldn't hold my breath, though. If it happens at all it will probably be a few years before it's widely supported.

As for your experience with bluetooth headphones, as far as I can tell, the consensus from people who are interested in high quality audio seems to be that bluetooth headphones just aren't there yet. However, I think in most cases this is not necessary due to them being Bluetooth, but more due to the general quality of the components. For example, the D/A converters and amps in bluetooth headphones are likely to be inferior compared to a those in a good PMP. So even if A2DP/SBC is delivering acceptable quality, the headphones can't reproduce it because of an inferior analog singal path.

Experience seems to be a lot better with streaming bluetooth to car/home stereos. But even then I haven't heard of anyone really reporting an "audiophile" grade experience.
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  #4  
Old 03-15-2008, 11:22 AM
woof woof is offline
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Good to see someone else also thinking about these things. Sorry about a mix up with the terminology {EDR actually stands for Enhanced Data Rate, not Extended Dynamic Range}. Thanks for the correction, My Bad.

As to SBC, I was under the impression it was one of several codecs approved for use with BT (but the only one mandatory). MPEG1/2 audio, MPEG2/4 AAC, ATRAC (all flavors) and maybe a couple of others which are optional can also be used with BT. Also using such alternative formats can eliminate the need for double conversion; i.e. direct steaming of MP3 to the headset for decoding.

I knew that under A2DP that SBC operates at a number of bitrates (at least these: 150, 250, 275, 320 and 345kbps) but had I assumed that the highest rate would be used (within a good link) since 700+kps thuput is available from BT 1.2 up. But I think most (if not all) the portable devices out there have limited themselves to a maximum of 320 kps (44.1khz). And only SBC @ 345kps supports a 48khz sampling rate.

One of 1.2/2.0 verses 2.0+EDR points that I wanted to make was that 2.0+EDR could at least improve current SBC performance from the perspective of less jitter, better Sink buffering, much better error correction (maybe help make up SBCs lack of robustness in this area), less dropouts, etc. Not to mention outside-the-box things like much lower power consumption in EDR (8DPSK) mode (read longer battery life).

Some of the things I'm hearing can be easily explained by the bandwidth/sampling constrants: limited frequency response, limited dynamic range and a low S/N ratio. However, some of the most offending sounds seem more like codec or sampling errors: gritty/odd sounds appearing out of "nowhere" (and perfectly repeatable, over and over), tearing of edges, etc. This leads me to a belief that even lowly MP3 @ 192kps over BT has to sound better than SBC at *any* bitrate due to the implementation/double-conversion process. To demonstrate the dehabiliting effect of this, I have been unable to decern with my ears any significant difference over a portable/headset BT link, using MP3 encodes of 128+kps, up to and including lossless.

I guess time will tell if the 2.0+EDR (with the current SBC codec) helps audio quality at all or if we will just have to wait for the industry to adopt yet another codec/protocol to hear the improvement that the hardware data thruput can already provide.

Woof
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  #5  
Old 03-15-2008, 03:45 PM
telliott telliott is offline
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I have the Pilot and find the BT distortion annoying. I have the Insignia BT speaker that was free with the Pilot 4GB player during a weekly sale. I would never consider BT headphones. The distortion would drive me nuts!

Where the speaker works is for lower bitrate audio with video. The slight lag isn't enough to create bad sync issues. It's nice to be able to hold the player without cords while watching video. It's also good for podcasts and audio books.

For "wireless" headphones, I've been thinking about using a smaller player like the Sansa Clip (great sound quality) and fitting it on a headband or hat and hiding the cord so nothing hangs down.

Thanks for the technical details guys. We are all learning something.
Tim
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  #6  
Old 03-17-2008, 12:37 AM
DanielNTX DanielNTX is offline
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I have the Pilot, Sport, Samsung P2 and S5. And as I said in my [url=http://www.anythingbutipod.com/forum/showthread.php?t=20850]original quick review[url]:
Quote:
So the Bluetooth Headsets I used to connect to these devices are the Logitech FreePulse Wireless (Bluetooth 2.0) and the Kyocera GSH300 (Bluetooth 1.2). I tested the headsets on the Insignia's and both sound roughly the same, but there was better bass response on the FreePulse. On the Samsung YP-P2, the FreePulse really shined and sounded like they were connected to the device because both are using the 2.0 standard. The Kyocera headset was acceptable but it didn't have the depth of sound that the FreePulse did. It's probably similar to comparing a MP3 with 128kpbs bitrate (Bluetooth 1.2) to one that's 160kpbs bit rate (Bluetooth 2.0).

So which player am I keeping and returning? I don't know yet. I'm leaning towards the Insignia line for expandability, but rebuilding the library DB every time you turn the unit on sucks. The Samsung YP-P2 is just plain cool, especially the quality of the display and the touch controls and the Bluetooth 2.0 gives it a boost in the audio.
But after listening to the Insignias and the Samsungs there's a world of difference in sound over Bluetooth. The Insignia does sound over powered and it is clipping. I'm hoping it gets fixed in a firmware update.
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  #7  
Old 03-17-2008, 07:00 PM
woof woof is offline
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Quote:
Originally Posted by DanielNTX View Post
But after listening to the Insignias and the Samsungs there's a world of difference in sound over Bluetooth. The Insignia does sound over powered and it is clipping. I'm hoping it gets fixed in a firmware update.
DanielNTX, can you expand on your differences between the Pilot's BT and the Samsung's BT sound using the same pair of headphones? Both DAPs are 2.0 but the Pilot has the BT "clipping" problem and running all it's EQ controls down to -8 or so is the only I can find to reduce the distortion to [near] acceptable levels. I've read that unlike the Pilot, the manual EQ is defeated on the Samsung. Are the preset curves on the Samsung also defeated over BT?

Thanks,
Woof
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  #8  
Old 03-17-2008, 10:19 PM
telliott telliott is offline
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I'm worried that developers are working on the next product instead of updating the firmware for the current products. I hope they realize that if there are no significant firmware updates for the Pilot, they have lost many of us as future customers.

Tim
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  #9  
Old 03-18-2008, 11:15 PM
Student Driver Student Driver is offline
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The Samsung does have the EQ dropped over BT, and a friend had the P2 before the Pilot. He returned the P2 to get the Pilot, and he did comment that both his Motorola HT820 and S9 sounded better with the P2.
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  #10  
Old 07-04-2008, 02:33 PM
james08 james08 is offline
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Default Question about logitech freepulse

Hi I'm new to this forum and definitely a newb when it comes to bluetooth, but I recently got the Logitech Freepulse 2.0 EDR headphones and an Insignia Pilot 4GB and I can't get them to sync up, people tell me that because the freepulse headphones came with a bluetooth adapter to plug into the 3.5mm port that you can't sync anything without the adapter, Does anybody know if it's possible to sync the freepulse headphones to a bluetooth enabled device without the adapter? And if so, how did you do it?
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  #11  
Old 07-04-2008, 08:58 PM
vferrari vferrari is offline
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I've paired the freepulse bluetooth adapter with the headphone jack with a pair of bluetooth headphones other than the freepulse but I haven't paired the freepulse with my Pilot. IMO the problem with the freepulse is that they lack any transport controls on the headphones. That's half the reason to get bluetooth headphones in the first place to have both wireless audio and the ability to control the player remotely. The freepulse headphones are designed primarily for players that don't have built-in bluetooth (hence the the headphone jack bluetooth adaptor). If I were you, and you have the ability to return the freepulse headphones, I would instead look into a set of stereo headphones that are designed to work with native bluetooth devices such as the Pilot. There are several mentioned on this forum including the Motorola S9's, the Insignia stereo bluetooth headsets, and stereo headsets from Jabra, Plantronics, Sony, and others.
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  #12  
Old 07-27-2008, 02:26 PM
hourglass hourglass is offline
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Quote:
Originally Posted by woof View Post
Hi ...In trying to locate the source(s) of the distortions, I found that the Pilot equalizer has some effect on a distortion that sounds much like over-saturation (clipping). I believe Digialdel mentioned that the input to the BT encoder was fed a maximum volume signal all the time to provide the best S/N ratio for the BT link. It seems to make sense that reducing the BT input signal by using eq would help some. There also seems to be other BT distortions that I cannot pin down or correct. These sound like "grittyness" or "raspyness" on the edge of vocals, horrid smearing/distorting of cymbols, etc. I've tried all flavors and types of file encoding rates from MM and none seem alter this... Woof
New member and new Pilot owner here, adding some additional info for the benefit of others who, like me, had bluetooth near the top of their "must have list" when comparing units.

Instead of bluetooth headphones, I connect the Pilot to a home stereo using bluetooth and the Motorola DC800 adapter. I too head the distorsions that Woof heard, EXCEPT when I switched the Pilot's Equalizer to "Normal", it seemed to vanish.

I'm not an audiophile, and the stereo I was using was far from first-rate, but I did an "A-B" comparison using the CD that the MP3 was created from, and the MP3 on the Pilot via bluetooth, pumped through the same amp & speakers. I was quite impressed how close the two sounded, WHEN the EQ was set to "Normal."

Another BT issue that I've seen is lag. Not a problem for audio only sources, but an issue for music videos, and TV/Movies. Here's what I found- The degree of lag is highly dependent on the audio bit rate used when coverting the source material. At 128 Kb/s, it's very very slight, and definately watchable. At 256 kb/s it's obvious and intolerable. I tried rates in-between and got "in-between" results. My sample was a avi file created using "SUPER" from a source VOB file. All other parameters were kept the same.

For those just starting out in BT, I want to make clear that the lag was only on the BT audio. The sound coming though the wired earphones stayed perfectly in sync with the video. (I had both on simultaneously: left ear wired, right ear BT.)

I want to thank all the other posters here for helping me make up my mind to purchase the Pilot. I've only had it for a week now, but so far I'm very saisfied with it. --hourglass

PS- For those worried about how long the battery charge lasts using bluetooth, I've avoided that issue by using the Motorola "USB style" charger that came with my cell phone BT earpeice (also Motorola). It plugged right into the Pilot, and DOES NOT put the pilot into "sync mode" like using the USB cable connected to a PC does.
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