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MP3 Recorders? 37

Posted by Cliff from the look-ma!-no-tapes dept.
ilbrec asks: "A friend of mine is a field biologist who studies frog calls. Recently when I was talking with him, he was interested in a MP3 recorder for his research use so that he can record the frog calls and analyze the sound on his computer later on. No, he does not care for DAT at all. He has one himself that he has so much trouble with. He is looking for a small device that takes at least 64 MB or so of solid-state removable memory that is easy to use. Sound recording quality does not have to be great, as frog calls can easily be analyzed at 96 kbps, according to him. No, he does not care for DAT at all. Does anybody know a good one?" Well, we have embedded devices that can playback MP3s...why not ones that can record live audio and use CompactFlash (or Smartmedia) cards, instead of the old cassette?
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MP3 Recorders? More

MP3 Recorders?

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  • If he can't stand DAT (he must not treat his deck well...), Minidisc is the next best thing, as far as sound quality goes. I wouldn't trust the DAC/ADC on an MP3 recorder, and I doubt the sound would come close to MD (let alone DAT).

    - A.P.

    --
    * CmdrTaco is an idiot.

  • problem with voice activation in an application like this is that the sound samples may be shorter than the time it takes for the tape to spin up. When I have counted on voice activation, I almost always missed the first couple words of what the speaker said, esp. in an environment with lots of ambient noise (i.e. a lecture hall)
  • Minidisc is a newer technology than the CD too. While I'm sure that now it would be readily plausible for a portable CD player to implement compression, at the time that the CD standard was developed it was not DUE TO battery consuption.

    -Andy
  • Yeah but do you remember the battery life of portable CD players from yesteryear. I remember my brother had one that took 4 AA batteries and still only lasted a few hours. Now you can pop in 2 (probably less) and get tons of playtime....

    Even though the DSP may have been there it would have made the player too power-hungry.

    -Andy

  • Why MP3? (Score:3)

    by yabHuj ( 10782 ) on Wednesday January 31, 2001 @01:25AM (#468253) Homepage
    Why does he want to have an MP3 gadget to record the sounds? I'd recommend a plain old music cassette recorder ("Walkman"-type, e.g. http://www.prodcat.panasonic.com/shop/product.asp? sku=RQ-L30&CategoryID=223 [panasonic.com]). You have 45 or 60 minutes recording for each side, media is EXTREMELY cheap (compared to any digital portable). Plus the recorder itself is cheap enough (~ $40) to be replaced easily in case is is dropped accidentally into the swamp. Some of these things even have voice-activated recording, so you can set it near the frogs, go away and just wait. Transfer to PC is done with any cheap soundcard.
  • I don't know a lot about the project these sounds are being recorded for, but I would imagine that discarding huge chunks of audio information (how do you think mp3's get so small?) that human beings can't hear is probably not a good way to go. If he is doing computer analysis of the sounds, wouldn't it be better to analyze a non-lossy recording? That way, even audio cues that a person can't hear (and that would be discarded by a lossy psychoacoustic model tuned for human beings) could be analyzed. Who knows? Maybe frogs do weird things with phase or overlapping near-frequency tones that we simply don't hear.
  • That was going to be my 2c too, although the problem is the lossy compression, not compression per se. I'd figure some stuff he's looking for - human-inaudible patterns - would be just the things lossy compressors introduce to get their jobs done. Sounds a quick way to wreck a science career, to me.

  • It's the conspiracy (Score:3)

    by dubl-u ( 51156 ) <2523987012&pota,to> on Tuesday January 30, 2001 @10:42PM (#468256)
    A recent Slashdot article pointed to a long essay by John Gilmore [toad.com], originally found on cryptome.org [cryptome.org] where, among other things, he basically claims that MP3 players don't record because their manufacturers are afraid that they'll get the pants sued off them.

    It seems plausible, but does anybody have facts to back it up?
  • You can do wonders with an IC. Especially repetetive things like mp3 encoding can be sped up trivially in hardware by just pipelining the encoder (or even just replicating the encoding circuits and buffer).

    This is exactly the sort of task a DSP or IC kicks a general CPU's ass at.
  • Are you getting realtime compression though? Anybody with a computer can encode .mp3s, it's just a matter of being patient. I've done it on my old P120 machine back in the day, granted a 5 minute track took 6 hours to encode and once I'd done that it took 100% of my processor to play it back, but it was cool. Now I've got an Athlon 800 machine and even with that kind of power it's just a little bit faster than real time in doing the compression.

    I'd say that the biggest problem with doing direct to mp3 recording is going to be getting the power to do real time compressions and getting it small and low powered. For now I'd stick with minidisks, they're cheap, small and fast.
    _____________

  • What your friend is asking for is a processor using under 500mW which can perform realtime MP3 compression. That simply isn't going to happen -- MP3 is simply too complicated to perform in realtime without using a lot of transistors, ie. lots of power.

    That's why CDs use raw audio, incidentally: audio compression was well understood at the time, but needed more computational power than was available in audio systems at the time.
  • Minidisc compresses on the fly, and it lasts for a couple of hours on one or two AA's... (Minidisc compresses at about 5:1).
  • There's no easy way to upload the data from a minidisc in better than realtime...which is a bit of a pain in the ass. I don't know why Sony doen't put usb ports on the their recorders, you can even play back ATRAC on the new realplayer 8.
  • That's not a problem, you could atach a microphone to the line in jack, which records at 128 kbits/s; *but* there are a lot of drawbacks to the the unit. 1. Uses a "MultiMediaCard" instead of Compactflash or Smartmedia. 2.Uses a parallel port instead of usb. 3. This is the worst--the mp3 files will only play on their computer mp3 player, and is *not* exportable due to copy restrictions! That really sucks!
  • http://www.aiwa.co.jp/english/exhibi/new_p2000/mm- fx500.html
  • I don't think that speed would be that much of a problem. Texas Instruments has had DSPs that were capable of 2Giga-flops performance in 1995. (Incedently, those are still used in the DirecTV sets that people use today)

  • It seems on the face of it that the thing keeping an embedded device from recording straight to mp3 would be the cpu required to do so. I'm basing this on the amount of time it takes my p2-450 equivalent machine to encode from .wav (uncompressed sound, basically what you're friend would be getting) to .mp3. Of course, yes, I'm going to 128+kbps, but still, there is only so much cpu you can cram into a portable the size of a pack of cigs.

    Naturally take my suspicious as to the unfeasibility of this with a grain of salt as I'm just a sysadmin/desktop/server-type person, not an embedded hardware designer (maybe there is some uber-l33t way of using a custom chip to do this). I'd have to cast my vote for minidisc too, it sounds quite nice (a friend of mine uses his portable MD recorder/player to sample stuff for his electronica band).


    --
    Fuck Censorship.

  • No, I'd guestimate that it takes about 6-8 minutes to encode a 5 minute track on my machine. So I'm not quite to the real-time level yet. Partially I think this is because the FPU on my proc (a celeron 300a that's been running @ 464 for about 18 months now) isn't as good as a normal p2 and it's cache isn't as big. :-) But it was cheeeep, and that's real good if you're a po' college student.

    My point was that it would take a pretty powerful CPU to encode to mp3 in real time. Namely a cpu you aren't likely to find in an embedded device due to cost, power, thermal, and space constraints...

    yes, anyone can encode to mp3 given patience, but the problem is that data collection has to be in real-time (i.e. you can't tell the frog to shut up for a sec while your recorder chugs away...).


    --
    Fuck Censorship.
  • Micronas [micronas.com], a german semiconductor company have an MP3 encoder/decoder chip [micronas.com] available. Expect to see products using this chip within 6-9 months.... As for products available at present, Idon't believe there are any, though the Nomad II will record voice using a built in mic at 32kbps.
  • Hey! I read the link last week when the rant was first linked to from /. I just didnt allude to it in my reply. What I am saying (now) is that such a product is feasible straightaway if you're willing to read the datasheet for the chip and build it yourself... These products will be made, thats for sure, whether by German electronics companies, or Taiwanese or Korean manufacturers, but I do concede that they may not be mass-marketed in the USA in the near future. (one of the posts further down linked to a new AIWA model for the japanese market which does however have watermarking built into it). Time will tell....

    As for the 32kbps that is not ridiculous. That is what is built into the Nomad. What is ridiculous is your assumption that I am a "slashdog" and couldnt read the specifications required by the person after he stated that he needed 96kbps. Why you jumped to the conclusion that I would have suggested that the Nomad (with only a puny builtin mic and no analog or mic input) would be suitable for this persons purposes - I really don't know ?

    I hoped to bring something more to the discussion than this sort of flame exchange. I thought the information regarding this chip might be of interest. However, next time i dash off a post to /. before running off for an appointment I'll try make and sure I dont generate this ill-tempered response from my (seemingly) poorly and hastily chosen words.

    ---

    Incidentally a friend of mine several years ago recorded deer dialect across several regions of the British Isles and Europe and did computer based voice analysis of the regional differences. It's a small world isnt it...?

    :)

  • In a way, that post is ASCII art. Very cool. ... Oh, and I like the content too. :)

    Louis Wu

    "One of life's hardest lessons is that life's lessons are hard to learn."

  • You can do MP3 voice recording with the Creative Nomad [nomadworld.com]
  • The AIWA recorder doesn't have a high enough sampling rate when used to record voice/etc. through the built-in mic.

    According to the spec table on that same web page: Recording with a built-in microphone: MP3/bit rate: 16Kbps/sampling frequency: 16 KHz

    The biologist asked for 96Kbps minimum for recording the frog calls.
  • That CLIK! disk will be knocked out of the water by the new DataPlay disk/drive, even if it stays WORM.

    http://www.dataplay.com/
  • I have seen some of the newer MP3 portables with the ability to record voice/sound/frog calls. But I don't think they are recording in MP3 mode--I think they are recording with no compression b/c the tech specs usually indicate they can only record a few minutes of voice.

    How about Minidisc player/recorders? They have optical out...you could either get an optical->analog converter, or get a sound card which accepts optical link cables.

  • i would say any lossy compression scheme is probably a bad idea. (that includes mp3 and ATRAC).. These compression schemes discard frequences outside the range of human hearing, and quite a bit from inside that range (20Hz - 20kHz).

    Of course, I am assuming he has a microphone with a frequency response > 20kHz in the first place.

    I don't know why he hates DAT, but there are some CD-R decks out there now.. That's about it for him, though.

    wishus
    ---
  • http://www.nomadworld.com/products/jukebox/

    This thing is able to record to WAV files on internal HDD (6G, upgradeble to 20G), and has various quality settings (sapmle rate, bits per sample), so the file size can be much reduced if you care about space more than quality.
    The only major low point is battery life (it would eat 4 AAs in about 3 hours or less). But it takes in 12V DC, so if I were him, I'd supplement it with something like small lead-acid battery (like one used in motorcycles) - and sure it'd handle all-night field recording sessions with no problem.

    I own this thing and it really rocks.
  • If he's going to be analising the recordings later, would it not make sense to use a format that isnt compressed?

    just my $.02
  • At the risk of sounding redundant, MiniDisc is exactly what you want...
    It can store 74 minutes of high-quality stereo on a 2.5" disc, housed in a protective cover. the media is cheap and you can get it anywhere, no need to buy expensive flash cards.
    when recording in mono on a standard recodring walkman, the recodring time is doubled. the newer models from Sony [64.14.40.118] can recodr up to 320 minutes in MDLP mode on one disc, check out the MZ-R900 [minidisco.com] on Minidisco.

    i've had a MZ-R50 for many years now, and it's still going strong, they are built to last.

    it's a sony...


    Verbing Weirds Language.
  • I was thinking of a similar recording project recording birds sounds, then analyzing the results with a program such as Praat http://fonsg3.let.uva.nl/paul/praat.html or Gipos http://www.ipo.tue.nl/ipo/gipos/ . I bought a mini-disk, but took it back because it does not have digital output. After doing some research I determined that mini-disks do not have digital out, because there the manufactures are afraid to be implicated in music piracy. MP3 is a lossy compression method that will degrade the sound quality slightly. The question is will it effect the analysis of your data.

    Taking all this into consideration I believe that your best bet would to simply use a laptop (many of which can work when closed), to do your recording. I found an old IBM Thinkpad 486/75MHz (sales on E-bay for $200) that can to simple real-time hard drive recording. A 1G hard drive could hold 4 hours or more of mono sound depending on the sample rate. There also embedded device "mother boards" that run Linux which are about 3" X 3".

    I installed a striped down version of Linux/GNU to setup a no-frills text based computer that can handle the job. Using the lap-tops internal ADC (analog to digital converter) will pickup some electronic noise from inside the computer. But I was able to keep this to a minimum by using an external amplified microphone. The best thing would be to use an external ADC which connects to a USB port that sells for $300.

    As far a recording software that works on Linux, you are pretty limited. I was able to hack together a script that utilized "arecord" (a CLI program produced by the ALSA project). My real project is to create a GPL program which I call Manauton, which stands for manual and autonomous recording. This program would determine when to save a sound to disk using some sort of trigger. The trigger could be a manual button press or it could be a sound trigger, hence manual or autonomous. The program also uses caching so the sound just prior to the trigger can be captured.

    If you are interested in my Manauton project feel free to e-mail me.

  • How about Minidisc player/recorders? They have optical out©©©you could either get an optical->analog converter, or get a sound card which accepts optical link cables©

    Yeah© I've got to go with a recommendation for minidisc recorders too:

    1© The media's alot cheaper, ¥unless you have a laptop handy to download all the mp3's too©

    2© They're about the same size as mp3 players / recorders© which is alot smaller than the dat recorders I've seen© ¥is size his issue? DAT is really good on other counts©©© :

    3© I don't want to start a war here, but minidisc recordings ¥ATRAC-3 are higher quality than most ¥though, truely, not all mp3s©

    4© Minidisc recorders with good solid state buffers ¥most have 40 second buffers, are as close to solid state as you probably need to get, if rough terrain is an issue©

    5© And despite what 'vraptor' said, you don't need an optical link to get the sound out of the minidisc recorder© It's better, of course, if you can keep your D->A->D chaining minimal, but almost every minidisc player has an analog out line© ¥For headphones, if nothing else

    Hope that helps!

    -Andrew
  • This isn't a good way to do this, but I've looked into it and I think it's possible but have yet to find the time or the money to attempt it.
    What I am thinking of is using a wearable device. You wont get super high quality but as you say nothing to fancy is required. The hard part comes from the fact that wearables are still mostly a hobbiest project. The hardware is easily obtainable and getting linux installed and running on a wearable has also been achieved. After that point the challenge is no longer hardware but software. I've looked a bit for mp3 recorders and found none. With minimalistic (nothing on the scale required) I haven't attempted to make one either. But from people I have discussed with it is seemingly possible. Buffer the sound and encode it. Depending on the hardware you could have 100 to 933Mhz at your disposal. My old AMD K6-550 with a heavy load was encoding at a bit over twice the speed so I further believe it can be done.

    Along with extended mp3 recording ability (assuming it can be done) he could also set it up for in the field data entry. Of course you still come to the usual problems Wearable hobbyists run into, a display, and battery power.

    (Wearable of course is a "wearable computer" compact, light, low power, for those not in the know)

    It aint no hand held 64mb AA operated device, but it could be done I say.
  • "With minimalistic (nothing on the scale required) [coding ability] I haven't attempted to make one either"

    And the k6-2 550 was a desktop box.
  • Expect to see products using this chip within 6-9 months.... As for products available at present, Idon't believe there are any, though the Nomad II will record voice using a built in mic at 32kbps.
    Look, no one is saying that such a product is not feasible. However, the industry will keep such products from ever coming to market in the US or EU. Because of the SDMI failure, the music industry cannot control MP3, and thus will do everything to prevent it. Look at how they killed DAT if you need an example.

    As for your assertion that the Nomad will record voice at 32 kbps, that is just plain ridiculous. You can get better fidelity than a 32k mp3 with a knitting needle and a wax record on a hot day. The question specifically states that the biologist needs at least 96kbps, and I'm willing to bet that the "built-in mic" is going to be horribly inadequate as well.

    If there is a hi-fidelity MP3 recorder that allows ordinary consumers to produce non-watermarked mp3s and transfer them to computer within the next year, I will publically recant. However, there is no chance of this. Read the cryptome article if you don't believe me.

  • MP3 recorders will never exist (Score:3)

    by Socializing Agent ( 262655 ) on Tuesday January 30, 2001 @09:16PM (#468284)
    Look at this excellent rant [cryptome.org] for why mp3 recorders will never exist. Minidisc is your best bet. You can get up to 149 minutes of monaural on a single minidisc, and the results will be very high quality. I personally used a minidisc for ornithology research back at Uni, with great success.

  • Some that I've come across:

    - Sensory Science MP3 players/recorders with built-in microphones [sensoryscience.com]
    - Samsung YP-E32 and E64 [samsungusa.com]
    - Olympus and other manufacturers also have Digital Voice Recorders that can download to PCs (albeit with unspecified file formats)

    There are bound to be more offerings out there, but they all do seem a bit vague on the recording format.
    .o

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