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What are head-fi members views on apt-x lossless codec (over bluetooth)?

Discussion in 'Sound Science' started by anakchan, Mar 19, 2012.
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  1. Denon2010
    Aah nice yeah I feel the same way in order to get rid of the wires I would happily sacrifice some SQ especially when I am traveling I have a Nexus 4 phone. Having listened to a number of different headphones over the years high end headphones that is, and realizing there is no difference between FLAC and 320k mp3 to the human ear, or realizing most headphones above $100 hardly has any improvement in quality I think I will make do with these Sony.
    If the battery lasts me 4 years I am cool with that won't bother replacing it by that time we will have Bluetooth 5.0 or whatever and i am certain way better stuff so when that time reaches I am sure I would end up investing a lot more into a much better wireless setup
  2. lampuiho
    cheap usb bluetooth 4.0 dongle uses csr chip and has aptx support.
    But back to the main subject, aptx is not that great unless the source is from a lossless source. M4a may employ different MP4 part3 profiles to encode audio. To support m4a fully, you need to support all the profiles, not just AAC-low complexity. Decoding mp4 and encoding the decoded signal with aptX means that the original now passes through two lossy channels which means noises from two different sources are added to the original signal. The aptX codec can't tell whether the peak in the spectrum comes from the noise or not and still use the noise to mask the nearby spectrum, thereby destroying the details unintentionally.
    Samsung iconx and apple products do support m4a fully so they sound a great deal better when playing back those mp3/mp4 music. But for the rest of the headphones that use CSR8645, not so much.
    I hate it when people are trying to make their own proprietary stuff instead of using the standards. If you truly believe your stuff is better, just go to the standard discussion meeting and propose a change instead of making a product that is not standard.
  3. Francisk
    Proprietary means business for some companies [​IMG]
  4. Roseval
    What I can imagen is that sender and receiver do device enumeration.
    Of course they do find SBC (mandatory) but there might be other codecs as well.
    Let’s assume both support AAC and decided to use this.
    The audio is send to the Bluetooth sender.
    Here the audio is encoded to a lossy format (AAC in this case) that fits into the bandwidth and of course decoded to raw PCM at the receiver because the receiver contains a DAC and DACs do not understand anything at all about any audio formats. The only thing they do understand is LPCM most of the time over I2S.
    This is how codecs work and this applies to any codec be it SBC, APT-X, AAC, MP3, etc.
    Suppose we play an ACC file. Will it be send straight to the Bluetooth Radio?
    I do think this highly unlikely.
    Select a AAC file in the media player.
    The media player invokes a codec (AAC of course) and expand the audio to raw PCM.
    If we want to use any kind of DSP e.g. volume control, it has to.
    If we use DS, we send it to the Win mixer so it must be raw PCM.
    As far as I know, it  is pretty difficult to do any kind of DSP on compressed formats.
    Hence I expect a media player to decode any format to PCM.
    This makes the scenario of sending any compressed file e.g. AAC straight to a Bluetooth sender highly unlikely.
  5. castleofargh Contributor
    I wondered about that myself, just digital volume(and of course any DSP) would need to extract the file. it's not like compressing to AAC twice at an OK bit rate is going to ruin the song, but it's not optimal. I wonder how much the BT drivers really impose on the "media player".
  6. reg66
    i'd like to know from anyone who has Creative BT-W1 or BT-W2. i'm thinking of getting one but as my laptop already has bluetooth 4.0, i'm wondering if there is any noticable difference with audio quality between standard BT 4.0 and BT 4.0 + aptX. is it worth it?  
    my system is HP probook 450 G2 and Dali zensor 1 ax speakers (which support aptX) 
    (new member so can't open my own thread) thanks
  7. lampuiho
    Actually, you can apply gain directly to an AAC file / AAC transmission. I do not know how exactly BT music playback is implemented but it's entirely possible to send stream of AAC signal directly to the receiving end and let it decode..
  8. StanD
    The receiving end would require a proper codec / firmware to be able to decode AAC. None of my existing BT cans/IEMs has this.
  9. lampuiho
    The only ones I know are apple airpods and samsung iconx
  10. StanD
    Neither of these two are headphones or sound good.
  11. SparkOnShore

    How do you know about airpods? Have you heard them yourself? They are not out yet, isn't it? Or are you basing upon internet "reviews" by "experts"??
  12. StanD
    I've read many unfavorable reviews, I've never heard a pair of earpods that sound any good. The only type of such devices that I've ever listened to that sounded good were ones that insert into the ear canal and form a seal, not pod devices. Are you betting that Apple will produce a great sounding device? They have never done so for such a device.
  13. SparkOnShore

    Sealing the ear has some positive and some negative effects. Bass increasing for sure when sealed, but I don't know how accurate it is for the sound in general...Just suggesting to listen first for yourself and don't base upon other people's assumptions...Open earphones or headphones are closer to the sound of loudspeakers due to the openness of the soundstage and this is preferable for some people...I can't bet on anything, I just guess they will be good enough for many applications...You can try the Solo3 and BeatsX wireless which will both have the new W1 chip by Apple. The newest Beats headphones have nothing to do with the old ones and they are quite praised for their sound here in HeadFi...
  14. SparkOnShore
    And one more thing: Apple actually has been producing really high quality sounding earphones through the years: Apple in ears double armature have been praised all around for their sound and have presented one of the 10 most balanced FR in all earphones...
  15. StanD
    I've listened to all of Apple's earpods and they don't ring my bell. I have hybrid dynamic/BA IEMs that I feel sounds way better than anything that Apple has to offer.
    I have open Planar/Ortho headphones that have phenomenal bass with great sub bass, so open doesn't mean that bass will be lacking. Solo and Beats headphones tend to have poorly controlled bass and U or V FR shapes which means the mids are lacking and trebles are exaggerated which is not to my tastes. I keep trying them and although they've improved over the years, I can get far better SQ for the same money.
    If anyone enjoys earpods or airpods or anything else, they should continue to enjoy them.
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