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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. Giogio

    You had already given the link to that conversation (where, as said, I took part).
    The fact is, I might be in dumb mode but I still do not understand why.
    He just says what happens, "computer does that". He does not explain why that happens. He eventually just say "because it is needed" or "because you need to unzip a file to read the content".
    Which is clear, I got it.
    But somehow, it must be something related to language (no native for me) or to way of thinking, because the way he talks of it makes me still feel like "it should be possible" and I just miss a real "WHY" that is not possible.
    It's difficult to explain :)
    I will probably ask to somebody else, maybe it is just, you know, one of those cases where you need to find somebody with a similar way of thinking who would explain things the way you will understand.
    Thanks :)
     
  2. james444 Contributor
     
    Maybe if you try to think of mp3, aac, flac, etc... just as storage formats. These are different ways to store audio data and save space in doing so. But they are not directly playable without prior decoding. The only directly playable audio formats with current computer technology are PCM and DSD. What you want isn't impossible per se, but simply not implemented in current technology.
     
  3. Giogio
    I understood that already.
    But my brain gets in short when he talks of unzipping.
    I see PCM like bits. The bricks of informations. So, for me it is not unzipping or converting.
    It is just, reading.
    Anyway, if PCM is the basic brick, why is so important if the file is AAC when using AAC codec? At the end it is, apparently (or according to you two) impossible that an AAC file is streamed directly in AAC, no matter if transmitter and receiver both uses the AAC codec.
    So, it should really make no difference at all if we use aac or aptx as codec, as long as the codec allows enough data transfer to preserve the original quality.
     
    I should suppose that the size of the PCM file obtained after "unzipping" of the aac/mp3/flac/wave file will be bigger of smaller depending on the original format? Or would lot of empty bits added like when converting from mp3 to wave?
     
  4. james444 Contributor
     
    That's a misconception. All digital information is composed of bits, and digital audio is no exception. Different audio formats use different algorithms (follow different rules) to store audio information, but the result is always a collection of bits. PCM is such a format and is usually stored as WAV files on Windows PCs or AIFF files on MACs. Other formats like FLAC, AAC and MP3 store the same (= lossless) or almost the same (= lossy) audio information, but according to different rules. Converting a WAV / PCM file to FLAC is an exact analogy to zipping, a lossless conversion from a format that occupies more space to a format that occupies less space, while retaining the same information.
     
     
    As yet, the popular codecs for BT-transmission are all lossy (SBC, AAC, aptX). A lossy codec will never fully preserve the original information. Even though the degradation of sound quality may be inaudible or almost inaudible, it still makes sense to use the best codec available.
     
     
    A constant bitrate (CBR) audio format like PCM will always use the same number of bits / second, regardless of its content. Doesn't matter if you convert something from mp3, AAC or FLAC, the resulting 16-bit/44.1kHz PCM file will always use 1411kbps to store its digital audio information.
     
    Traveller likes this.
  5. watchnerd
     
    This is not correct:
     
    FLAC is not "another format" from PCM.  It's just a container to hold compressed, lossless audio.  The same for ALAC.  The audio data is PCM.
     
    FLAC is just as much PCM as AIFF or WAV.
     
    Also, WAV exists on the Mac, too, as well as Linux.  It's not PC-specific.
     
  6. james444 Contributor
     
    Wikipedia on audio file formats:
     
     
    Would you agree to "losslessly compressed PCM" for FLAC vs. "uncompressed PCM" for WAV or AIFF then? Just head over to xiph.org/flac/, they themselves call FLAC an audio format and use the Zip analogy.
     
    Traveller likes this.
  7. watchnerd
     
    It gets confusing because the term 'format' is used both for "file format", in which case they're all different vs "audio format", in which case they're not -- all the lossless ones are PCM.
     
    Contrast this to DSD/DSF which is a completely different audio format and file format.
     
  8. castleofargh Contributor
    it's the difference between compression and conversion. FLAC will only compress PCM, but the practical result is the same, some precessing has to be applied to FLAC before it's PCM again and can go to the DAC, or can be processed to be sent through BT. so it's a different format IMO. just like .zip is a different format.
     
  9. davidmthekidd
    After spending two weeks with a NON APT-X Headphoes (ParrotZik 2.0) I would say that APT-X makes a HUGE difference, to the point that the compression level on my Zik got a bit too obvious and heavy. I had to return the Zik's 2.0 and instead got the Sennheiser's Momentum Wireless, oh boy, what a difference. I can't really tell the difference between WIRED or APT-X Wireless, its that GOOD. A+++ to the guys at CSR, loving this codec.
     
  10. amature101
    hi, im looking for a usb bluetooth with aptx. Anyone know of a good one to recommend?
     
  11. amature101
    hi, is it truly plug and play for windows? worth to get it?
     
  12. ClieOS Contributor
     
    Yes it is true PnP. Well worth the money if you need aptX transmitter for Windows. However, you should consider the newer BT-W2 first, as it supports the newer apyX Low Latency and also voice input (for BT headset with mic). It is true PnP as well.
     
    lennyr likes this.
  13. Giogio
    Anybody here with experience with AAC+ who could compare Aptx, AAC and AAC+?
    I also wonder if both devices must support AAC+. I suppose it should be so, like with Aptx Low Latency, if one device is LL and on not, the connection is not LL.
    So I suppose that if an AAC device is paired with an AAC+ device, the connection is AAC.
     
    I cannot find much info though, not even a list of devices which support AAC+.
     
  14. Giogio
    Searching this thread for 320kbps I have only found your post. But I remembered that somebody here told me that Aptx can stream 320kbps uncompressed.
    Any info about that?
     
    About that comparison, it is for audio codecs, not for bt codecs.
    I cannot find any comparison of bt codecs, do you know of any?
     
  15. james444 Contributor
     
    That's an oxymoron.
     
     
    BT codecs are audio codecs.
     
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