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Bluetooth accessories

F

Fitz

macrumors newbie
Original poster
Jan 10, 2003
7
0
Curious what bluetooth devices people out there are using with their powerbooks. I know that there is a sony cell phone, but curious what other devices people have found or are using. I have looked for a bluetooth adapter that would allow me to feed my audio out into my stereo, so in a sense i can amoung other things have a wireless mp3 player.

any thought?

late

fitz
 
I am using the sony-ericsson t68i as a basic PDA using my Tibook for the entries. I carry my contacts, tasks & calendar on it - isync and bluetooth are a great duo. I can also type long SMS on the Tibook and send it out, aswell as using the phone as a GPRS modem on the road - but I rarely use it because I don't bother without alot of bandiwth which I usually find at a hotel. I also use the phone as a bluetooth remote for DVD Player and itunes from time to time. Its a great technology as far as I am concerned and recommend it.

BTW - I don't think bluetooth has enough beandwith to effectively stream audio.
 
Bluetooth has a maximum bandwidth of 1Mbps. Assume that your mp3 is encoded at 128kbps. Clearly this could be transmitted in realtime. It could also transmit faster and buffer on the receiving end in case another blue tooth device momentarily used some bandwidth. Bluetooth would be good for streaming as suggested, but bad for mass file transfer. Good day.
 
Originally posted by thekaiser
Bluetooth has a maximum bandwidth of 1Mbps. Assume that your mp3 is encoded at 128kbps. Clearly this could be transmitted in realtime. It could also transmit faster and buffer on the receiving end in case another blue tooth device momentarily used some bandwidth. Bluetooth would be good for streaming as suggested, but bad for mass file transfer. Good day.
Click to expand...

I would rather think that the audio prog that plays mp3s would have to decode the music before it sends it to the stereo. That would make the data rate of 128 x 10 (or something like that) which means that you cannot stream that sound over BT since the required bandwidth would be over 1mbps.

/ filipp
 
Originally posted by filipp
I would rather think that the audio prog that plays mp3s would have to decode the music before it sends it to the stereo. That would make the data rate of 128 x 10 (or something like that) which means that you cannot stream that sound over BT since the required bandwidth would be over 1mbps.
Click to expand...

Where do you get that x10 multiplier? Just a guess regarding the compression?

I don't think that is how it works. The music isn't stored in a Stuffit archive or anything. The compression to MP3 was a lossy compression...you don't get the exact original during playback. Rather, the MP3 codec leaves out stuff is isn't "necessary".

So yeah something needs to translate the ones and zeros in an MP3 file into sound, but the "file" doesn't get any bigger in the process.
 
Bluetooth audio

Bluetooth audio protocols and profiles can handle MPEG 1 or 2 layer 3 (a.k.a. mp3) directly. An mp3 stream can therefore be sent directly to wireless speakers or a headset and be decoded there instead of before being transmitted via radio. Similar possibilities exist for video (MPEG 2 and 4) and Sony's audio coding ATRAC, typically used for MiniDisc.
 
You may be right, but I still think mp3s have to be decoded from the compressed to raw format. It's like raw wav and mp3. If you have a 10Mb wav-file and want to make mp3 of it, the mp3 gets like 1/10 of the size (if you take 128kbps), but you cannot just playback a mp3 file without decompressing if (winamp or iTunes do that on the fly). In other words, to hear music stored in the mp3s they have to be decompressed on some stage. To be able to use this 1Mb-mp3 you will have to decode it back to raw format which will give you initial 10Mb.

But you're right, mp3 does not store everything, so you get quality loss when you compress to it.

/ filipp
 
I'm still a newbie here, but I think I can give a cent or two regarding BT. I see alot of my friends using BT accessories. For Mac, there's a app called ROMEO, which lets you control your MAC via BT. It even has proximity functions, which lets you 'secure' your Mac automatically when you're away ;)

I have a friend that has a BT adapter/headset combo (USB) that supports voice functions (I think it's Billion, if I'm not mistaken). Heard that it can play MP3 thru the headset

As for me, I just own a Ericsson T39. So I don't have the privilage to try out BT.

Oh yeah, some of them can control Wintel PC with their Palm/BT mobile phone.
 
And a reminder

Incase you are planning to use a M$ bluetooth mouse, read the review at Titan City

"THE DAMN THING DOESNT WORK! Did I get a defective unit at the store? Oh no. My Mac recognises it well enough, but it just haven't got BlueTooth input support. Damn. Let's try on my Windows XP PC. Connect dongle to USB port on PC. Dingdong, you have installed new hardware, but no drivers were found... etc... I slip in CD that came with mouse, and then the fun starts:"
 
ok

Here is the deal. You never decompress the file. The file is stored as a digital data, 1's and 0's. The file is decoded this way when it is originally ripped or sampled. When decoding it does not exapnd the file. Merely, it passes the digital data through a D/A (digital-to-analog) converter. This is the whole premise of a CD player or any other sampled digital audio signal. The D/A converter would be located on the receiving end of the system. These devices are small and low power. They are in all portable devices. How else do you turn digital data back to a usable signal. This is how it is done. Being an electrical engineering, I do this **** a lot. I just did not want to get into the details in my earier post. In short...1Mbps is more than enough to stream mp3.
 
Ok, I just realized that I used the term "compressed" a bit wrong, you dont compress sound just as zip or rar, that's not what I meant, and I do know what binary is, and I know what d/a-conversion is. My point was that you MUST have a decoder somewhere, and if you have it on your stereo, fine, then you can send you encoded data over BT w/o problems, but since there are no amplifiers with mp3-decoder built-in as I know of, you have to decode the mp3 on you computer BEFORE you send if to the stereo over BT, which would mean that you eigher send the analog signal (bad idea, impossible over BT) or you send the RAW signal (just as audio-CDs) which infact does take alot of bandwidth. In this case, you would still need a d/a-converter in your stereo.

Now, I'm not an amateur myself and work with computers on professional basis.

/ filipp
 
Originally posted by filipp
Ok, I just realized that I used the term "compressed" a bit wrong, you dont compress sound just as zip or rar, that's not what I meant, and I do know what binary is, and I know what d/a-conversion is. My point was that you MUST have a decoder somewhere, and if you have it on your stereo, fine, then you can send you encoded data over BT w/o problems, but since there are no amplifiers with mp3-decoder built-in as I know of, you have to decode the mp3 on you computer BEFORE you send if to the stereo over BT, which would mean that you eigher send the analog signal (bad idea, impossible over BT) or you send the RAW signal (just as audio-CDs) which infact does take alot of bandwidth. In this case, you would still need a d/a-converter in your stereo.
Click to expand...

Filipp, you're still not grasping the concept that there is no way to to get the RAW signal back from an MP3. We agree MP3 is not a compressed format, rather an encoded format. Decoding something doesn't necessarily mean it gets bigger, because we are not specifying what it is getting decoded to.

How "big" is an analog signal? You can't quantify it in digital metrics. So let's revisit the two options once again:

1) Send digital data (128kbps) to the receiver. We agree this would fit over Bluetooth. Of course, as we all agree, we need some kind of d/a converter plugged into the RCA inputs on the receiver, but it could be a very very small dongle of sorts. It think this is what the original poster was looking for. But let's finally agree that THE MOST digital information that would be sent is 128kbps...there is no way to recover the 1's and 0's that were on the original CD.

2) Decode on the computer and send an analog signal over Bluetooth. I don't see why you believe this is impossible. I don't have numbers to prove otherwise either, but I have reasoning which I will explain, and I would appreciate it if someone could prove me wrong. Here goes...

Infrared headphones have existing for a long time. I believe the transmitter takes an analog signal, converts it to digital pulses/information that gets transmitted over line-of-sight infrared to the receiving headphones, which then converts it back to a analog signal to the headphone speakers.

Bluetooth I believe is comparable or faster than infrared (certainly as a new technology it couldn't be significantly slower). So if it's possible to send a digitally encoded audio signal over infrared, the same should be possible with Bluetooth.

BUT AGAIN, you'd need a dongle plugged into the RCA ports of your receiver, so you might as well use the dongle in option #1 above that can decode MP3 (as opposed to whatever a/d d/a encoding method the infrared transmitters use).

Anyone?
 
Hi Jackal

I agree with you on some points.
But, how do you explane that you cannot work with mp3 in editing, or editing a divx-movie just as you would do with RAW DV? Or why cant you watch a xvid movie without installing the xvid codec? Or why couldnt I then put my mp3s on a audio-CD without cenvering it to RAW format and play it on my arcam cd-player?
I'll tell you, because the data has to be decoded before you can use it. When you burn your mp3s to a CD, the what-ever burning app decodes the mp3 files to simple 16-bit wavbefore it puts them on the CD. You do not get exactly same data after decoding since the encoder drops some information while encoding, so you somply loose that data. Any encoded information, wether it's a mp3-file or a divx-movie, or any other data is worthless unless you have a decoder to decode the encoded data from those files. Do you get my point?

So, to be able to listen to your MP3s on your stereo, you have two options:

1. You send mp3-encoded stream over BT to your stereo with no problems (mp3s usually take 128, 160 or 192kbps). Then you have a mp3-decoder built in on you d/a-converter before it goes into your amp via RCA.

2. You decode your mp3 using iTunes or whatever app on your computer. Then you send the 16-bit raw singal over BT to your d/a-converter on the stereo and hear about every second second of your songs since the raw signal in 16 bits requires something like 1400kbps (705,600 bits per second per channel).

As you can see, you either listen to mono-sound which in fact would work on BT or find yourself a Bluetooth-mp3-decoder-d/a-converter thing to pop into your stereo.

As about infrared headphones, I've never seen any, but it actually could work since irDA 1.0 speed is 2mbps and irDA1.1 (fast irDA) is 4. But I would guess there are more of those analog hi-frequency-radio-signal-headphone out there rather than infrared.

I said that you cannot send analog signal via BT because BT is digital protocol, you would need to a/d - d/a the signal to use it.

But then again, you could actually send your music to your stereo over radio-waves the old-fassion-analog way, but that would be off-topic since this is a BT-discussion.

/ filipp
 
Originally posted by LosJackal
How "big" is an analog signal? You can't quantify it in digital metrics. So let's revisit the two options once again:
Click to expand...

And LosJackal, dont make fun of me, I never said that you can send analog signal over digital connection. Everyone understands it does not work that way.
 
seriously

People, I do this for a living...this is not that hard. You cannot recover that mp3 once it is compressed. It is never converted back. Frankly, it is not possible. All portable electronics have D/A's in them. What is the deal with transmitting the mp3 and decoding it. What do you think happens when you stream a 128kbps stream in iTunes. Do you think they decompress that and send you this massive file. Hell no. They stream 128kbps and your machine just processes that signal. It does not decompress it or anything. It just processes the raw bit stream. I hate to be forward about this, but this is how it works. If you don't believe go to your local university and enroll yourself in a EE class.
 
Re: seriously

Originally posted by thekaiser
People, I do this for a living...this is not that hard. You cannot recover that mp3 once it is compressed. It is never converted back. Frankly, it is not possible. All portable electronics have D/A's in them. What is the deal with transmitting the mp3 and decoding it. What do you think happens when you stream a 128kbps stream in iTunes. Do you think they decompress that and send you this massive file. Hell no. They stream 128kbps and your machine just processes that signal. It does not decompress it or anything. It just processes the raw bit stream. I hate to be forward about this, but this is how it works. If you don't believe go to your local university and enroll yourself in a EE class.
Click to expand...

Noone says that iTunes makes a huge file out of mp3 just to play it, but what it does is that it uses a LAME or some other mp3-codec to decode the file on the fly while it plays it.

If you do this for living, answer the questions in my previous post!
Otherwise, go surf the web, see if you find some answers.

And, you easily get RAW data out of mp3-encoded file, but you dont benifit from it since the lost data (under encoding) is already lost. But as CD-players do not accept any other formats than RAW, you have to have it raw to be able to play your music on your CD (just as audio-cd is).

And dont tell me that it's not true since DVD-players do play MP3s. They do play mp3s because they have a mp3-decoder among many other decoders like Dolby Digital, DTS and not least the DVD-video itselft (the format is called something else, dont remember)

/ filipp


edit:
"It just processes the raw bit stream"
Exactly, but tell me, how do you get your raw bit stream out of an mp3-stream if not decoding?
 
You are getting mean now and I do not feel the need to respond to ignorance. You can believe what you want, and I will believe what I want. I am sorry I even tried to help in this post. The purpose of these forums is for people that have knowledge to share it. However, if you are not going to believe anyone, why do you ask opinions. Oh well...ignorance can not be argued with.
 
Originally posted by thekaiser
You are getting mean now and I do not feel the need to respond to ignorance. You can believe what you want, and I will believe what I want. I am sorry I even tried to help in this post. The purpose of these forums is for people that have knowledge to share it. However, if you are not going to believe anyone, why do you ask opinions. Oh well...ignorance can not be argued with.
Click to expand...

Yes, it actually starts getting a bit ugly...
Partially because I refuse to agree to your arguments. So convince me and everybody else how do you think it works.

Sorry if I got too offensive, not intended.

/ f
 
ok

Sorry for ranting...anyway. You are correct that there is a mp3 decoder. However, this is just a specialized D/A converter. When the mp3 is made there is a software algorithm that runs and takes the raw digital data and puts it into a smaller form. This smaller form can never go back to the original. However, it contains enough information to do a pretty accurate representation of the original. This new smaller sampled signal is passed through the mp3 decoder...(D/A). I think this was part of the confusion. The mp3 decoder and D/A are one in the same. As I stated above the decoder is just a specialized D/A. This is a small chip that can be added to portable CD players and the like to allow them to suppor mp3 formats. Similarily in your DVD player there are different decoder (D/A) to convert the different audio formats. Or they are in the audio receiver if you use a digital link between the devices. If you were to build this bluetooth device you would send the encoded mp3 throuh the air. Then there would be a smaller decoder on the other end that could easily be incorporated without adding any sized to the receiver. I hope this makes things a little more clear. I think we just had some miscommunication in our terminology. I did not mean to yell at you, I was just getting frusturated. I forget that this is what I do, so it should be clear to me, but it may not be clear to everyone. I will be more than happy to answer any other questions about this. Please feel free to correct me if you think any of this statement was incorrect. I will try to respond today if I am around.
 
Cool, thekaiser!
This is exactly what I was trying to express. We agree that the mp3 has to be decoded, wether throu a hardware or a software decoder, that does not matter. I guess you work with hardware. Well, I work with software, so I know there are software decoders just as hardware ones. Do you remember, the mpeg-cards for decoding mpeg1 and mpeg2 files? They work just the way you described. In a computer, a hardware decoder helps the main CPU since it does not have to worry about decoding in that case. The software decoder does same job, but using the main CPU for precessing the algorythm. Stuff like dvd players and car-stereos have to use hardware-decoders since it's the simpliest way.

So here we have these two options: You send mp3 stream to the stereo, which uses a hardware decoder_slash_d/a converter. Or you decode the mp3 using software decoder and send it over BT so that the stereo does not need a decoder. Ofcourse, the first option is the way to go since hardware decoders are quite cheap I guess.

All in all, we talked about the same thing but from differant angles. So lets just shake hands and hope that the readers of our fight understood at least something :p


peace
/ f
 
Originally posted by filipp
So here we have these two options: You send mp3 stream to the stereo, which uses a hardware decoder_slash_d/a converter. Or you decode the mp3 using software decoder and send it over BT so that the stereo does not need a decoder. Ofcourse, the first option is the way to go since hardware decoders are quite cheap I guess.
Click to expand...

Yes, we arrive at the same two options. But I believe option #2 still requires a Bluetooth receiver that converts digital information into an analog signal inputting into RCA. So it's the same amount of equipment either way, now the debate is simply what to transfer digitally.

To answer your question about mpeg or divx editing, it is because the information is not in an easily malleable form. To illustrate, let me use a simple compression codec called frame differencing. If two frames of a DV movie are largely similar, you can throw out the pixels that are the identical in the second frame. Do that for 15 frames in a row, and you've maybe achieved a 10-to-1 compression.

If you wanted to edit these 15 frames, a program like iMovie would import these frames and copy the identical pixels from the first across the others to restore it to 15 full frames. That way it's easy to chop out the frames you don't want, no additional calculating necessary.

But during playback, the computer decoding the movie doesn't have to do the same amount of work. It just displays each of the 15 frames on top of each other, letting the identical pixels show through from previous frames. This example clearly shows how you are truly only dealing with the one-tenth size file during playback.
 
Sure, that's the whole thing with encoding/compressing stuff, to save space and energy.

But you see the problem with placing mp3-decoder in the bluetooth-receiver means that it would not work with, say, wma because you would need a separate decoder for that too. So the best way would be to let the computer decode whatever format it plays, and then send it raw to the stereo, but that would not work because of bandwidth limitations. So I guess we have to go with a bluetooth-box with all known (or most popular) hardware-decoders onboard. ( = not cheap).

do you see my point?
/ filipp
 
Originally posted by filipp
But you see the problem with placing mp3-decoder in the bluetooth-receiver means that it would not work with, say, wma because you would need a separate decoder for that too. So the best way would be to let the computer decode whatever format it plays, and then send it raw to the stereo, but that would not work because of bandwidth limitations. So I guess we have to go with a bluetooth-box with all known (or most popular) hardware-decoders onboard. ( = not cheap).
Click to expand...

You have a good point with regards to being open for several formats.

So I'll believe what you are saying if you can tell me this: after letting the computer decode whatever format it plays, say a 128kbps MP3, how big is the music that you are saying is too big for bandwidth limitations?
 
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