I am assuming bluetooth headphones are lossy or any bluetooth stream but wifi media sharing is not.
I am only assuming though, can someone confirm?
Almost all Bluetooth headphones are lossy as the A2DP protocol support the following Codecs
MPEG-1,2 Audio
MPEG-2,4 AAC
ATRAC (Sony)
All of them are lossy compression.
Proprietary protocols like KLEER use lossless compression.
http://thewelltemperedcomputer.com/HW/Conn...oth_connect.htm (http://thewelltemperedcomputer.com/HW/Connect/Bluetooth_connect.htm)
WiFi has sufficient bandwidth to stream lossless.
Not to be mistaken for all audio streaming over Ethernet or WiFi being lossless!
I have been looking into wireless standards too, and have been using Kleer for a while. For the most part it's pretty great. It doesn't seem to be gaining traction though, and it's been a while already. There are dedicated iPod transmitters/receivers but IME they drain the battery much faster (though still last very long for a media player, especially compared with my Discman and Minidisc I used to use back in the day!).
It's not technically lossless though, cause from what I can tell the devices already out can only take analog, so A/D/A conversion is always done, and I haven't seen anywhere that the standard could even allow for pure digital transmission. Still sounds much better than regular wireless solutions like IR and much better than bluetooth (lag, noise). In fact, I can't tell the difference between wired and my Sennheiser RS160. At regular volume levels there's no noise whatsoever. I use it while cooking (kitchen extractor on) and watching TV, and the only problem is that the microwave oven kills it!
I bought an analogue wireless headphone about two years ago and was very disappointed with the noise. Funny this thread pops up now, because I recently considered ditching my "old" (shitty!) Sennheiser RS120 in favor of a Bluetooth enabled product. I did some "research" over the weekend on the A2DP protocol and what codecs it supports. The mandatory codec is called SBC which is a low-complexity subband coder (similar to MPEG1 Layer 1). Since this is not for archival purposes but for "live transmission", I suppose this codec is good enough given a reasonably high bitrate (SBC is advertised to be transparent at and above 128kbps per channel and supports much higher bitrates approaching lossless data rates). Other codecs are supported as well, but A2DP-devices only have to support SBC. Supposedly many devices only do support SBC since it doesn't require any extra licensing.
Apparently, Bluetooth 2.0+EDR supports data rates of about 3 megabits/s which ought to be enough for lossless transmission of at least stereo 16/44 data. But I actually wouldn't mind some loss as long as it's not audible. From what I can tell, there would be enough "headrom" if you use SBC at rates like 400kbps for a stereo signal...
Cheers!
SG
IME there's significant lag with bluetooth though, long enough that it's useless for video. I also had sound quality problems (noise, pops), but that could be the devices themselves.
I would not "upgrade" to bluetooth though. Kleer is much better, including the option to use one transmitter with up to four headphones/receivers. Unnoticeable lag (perfect for video) and auto pairing (after you manually paired first). I use several transmitters with the same headphones/receivers, and as long as the other transmitters are off, they just work together with the one that's on.
IME there's significant lag with bluetooth though, long enough that it's useless for video.
That's odd. A2DP has been designed with "low-delay" in mind and SBC supports encoder/decoder delays as low as 4 milliseconds. Maybe the delay you observed is a matter of QoI (quality of implementation).
Could be, but if you google it seems like a common enough problem. The hardware I've used includes bluetooth dongles, and this Sony transmitter/receiver (http://www.amazon.com/Sony-Two-Way-Bluetooth-Adapter-Players/dp/B000P9CEV4). Didn't bother to test with the iPod Touch yet, but I'll try at home. I have a pair of Sony Ericsson bluetooth earphones, which have A2DP. IIRC I also tested with the Sony device as a receiver, though I'm not completely sure.
so a v0 mp3 is technically transcoded to a file less than 3mb via a2dp?
so a v0 mp3 is technically transcoded
Not necessarily. It's theoretically possible to send mp3 data directly to an A2DP sink. This requires an A2DP source that has access to the original MP3 data and is able to send it directly and a sink that supports MP3.
to a file
I don't think that intermediate files are involved. More like "on-the-fly conversion".
less than 3mb via a2dp?
Bluetooth 1 is limited to 1 megabit/s = 1000 kilobits/s. Bluetooth 2.1 is limited to 3 megabits/s = 3000 kilobits/s. Keep in mind that "/s" means "per second". Your MP3 files have at most a bitrate of 320 kilobits per second.
so a v0 mp3 is technically transcoded
Not necessarily. It's theoretically possible to send mp3 data directly to an A2DP sink. This requires an A2DP source that has access to the original MP3 data and is able to send it directly and a sink that supports MP3.
That's all quite idealistic, but in the real world, probability = zero or very close to it.
It is hghly probable that music files in *any* format are transcoded for transmission over the Bluetooth link. To do otherwise (except use an uncompressed audio format) would require the addition of file format support to the reciever which would make it more complex and therefore larger and more power-intensive.
According to the official Bluetooth SIG site:
Official Bluetooh web site statement about audio transmission (http://www.bluetooth.com/English/Technology/Works/Pages/Architecture__Baseband.aspx)
Audio
"In the air-interface, either a 64 kb/s log PCM (Pulse Code Modulation) format (A-law or ?-law) may be used, or a 64 kb/s CVSD (Continuous Variable Slope Delta Modulation) may be used. The latter format applies an adaptive delta modulation algorithm with syllabic companding. The voice coding on the line interface is designed to have a quality equal to or better than the quality of 64 kb/s log PCM. The table below summarizes the voice coding schemes supported on the air interface."
In the air-interface, either a 64 kb/s log PCM (Pulse Code Modulation) format (A-law or ?-law) may be used, or a 64 kb/s CVSD (Continuous Variable Slope Delta Modulation) may be used.
This is probably Bluetooth Audio.
A2DP allows for a bit more than 64 kbs
http://www.bluetooth.com/English/Technolog...on_Profile.aspx (http://www.bluetooth.com/English/Technology/Works/Pages/Implementing_Advanced_Audio_Distribution_Profile.aspx)
http://en.wikipedia.org/wiki/SBC_%28codec%29 (http://en.wikipedia.org/wiki/SBC_%28codec%29)
In addition to what's there on the wiki page, I'd like to mention that SBC can go as high as 16 bits/sample (excluding scale factors) -- as far as I can tell. So, eventually transparency is reached.
In the air-interface, either a 64 kb/s log PCM (Pulse Code Modulation) format (A-law or ?-law) may be used, or a 64 kb/s CVSD (Continuous Variable Slope Delta Modulation) may be used.
This is probably Bluetooth Audio.
A2DP allows for a bit more than 64 kbs
http://www.bluetooth.com/English/Technolog...on_Profile.aspx (http://www.bluetooth.com/English/Technology/Works/Pages/Implementing_Advanced_Audio_Distribution_Profile.aspx)
I tried to find a real-world implementation of this.
A likely candidate would seem to be the Sennheiser PX 210 BT
Link to Sennheiser PX 210 BT spec sheet (http://www.sennheiser.com/sennheiser/home_en.nsf/root/private_headphones_wireless-headphones_502378)
BTW, this requires the use of a Sennheiser BTD300I Self Powered Bluetooth Adapter or equivalent (optimal, extra).
At any rate the Sennehser PX 210 BT spec sheet says that is uses an audio encoding technique called APT-X. The APT-X web site seems to describe it as a lossy transmission technique and says something about transmitting audio at 64 kbps.
If it was my money on the line I'd skip the Bluetooth and put my bucks on the Sennehsier RS 170, or some such.
Right that's my opinion too. There's everything to gain and not much to lose, if anyjthing. I got both the RS160 and RS170 and they're practically the same headphones though. If you don't need the extra features of the 170 like bass boost or the super useless virtual surround, or the charging dock, you'll get pretty much the same experience with the 160.
One thing I did notice is that the 160 can even be better cause the 170 has automatic clipping prevention and only has a switch between low/high gain. The 160 has a manual continuous gain and lets you know when the sound clips (LED turns red) but doesn't auto-attenuate.
Link to Sennheiser PX 210 BT spec sheet (http://www.sennheiser.com/sennheiser/home_en.nsf/root/private_headphones_wireless-headphones_502378)
Have a look at MX W1, lossless (16/44) using KLEER
http://www.sennheiser.com/sennheiser/home_...less-headphones (http://www.sennheiser.com/sennheiser/home_en.nsf/root/private_headphones_style-line-mx-w1?Open&path=private_headphones_hifi_wireless-headphones)
Things have changed this this thread was posted. Nowadays, is the aptX protocol lossless? Are there any other formats as well? What's the basic aptX supported bitrate (bit-depth and sample rate) if anyone knows? Thanks!
Things have changed this this thread was posted. Nowadays, is the aptX protocol lossless? Are there any other formats as well? What's the basic aptX supported bitrate (bit-depth and sample rate) if anyone knows? Thanks!
apt-X for bluetooth is lossy, running at (about?) 352 kilobits per second. The marketing blurb talks about "non-destructive transport" (that's probably marketing speak for "transparent").
It just so happens that I have recently acquired an apt-X smartphone that was on sale, and an apt-X receiver, and while I haven't done any ABXing, I can't hear any obvious lossy artifacts (as opposed to the obvious ones that sounded really bad with the default codec, SBC, when I tried bluetooth 4-5 years ago). I plan on getting a larger microsdxc card some time in the future, to play lossyFLAC and reduce the chances of lossy-to-lossy transcoding artifacts (if any), which is, IMO, the perfect use-case for that awesome codec.
In any case, from my casual listening experience, I think that apt-X is very decent.
http://www.aptx.com/products/browse/categories (http://www.aptx.com/products/browse/categories)
Things have changed this this thread was posted. Nowadays, is the aptX protocol lossless? Are there any other formats as well? What's the basic aptX supported bitrate (bit-depth and sample rate) if anyone knows? Thanks!
apt-X for bluetooth is lossy, running at (about?) 352 kilobits per second. The marketing blurb talks about "non-destructive transport" (that's probably marketing speak for "transparent").
It just so happens that I have recently acquired an apt-X smartphone that was on sale, and an apt-X receiver, and while I haven't done any ABXing, I can't hear any obvious lossy artifacts (as opposed to the obvious ones that sounded really bad with the default codec, SBC, when I tried bluetooth 4-5 years ago). I plan on getting a larger microsdxc card some time in the future, to play lossyFLAC and reduce the chances of lossy-to-lossy transcoding artifacts (if any), which is, IMO, the perfect use-case for that awesome codec.
In any case, from my casual listening experience, I think that apt-X is very decent.
http://www.aptx.com/products/browse/categories (http://www.aptx.com/products/browse/categories)
Thanks!