Understanding Streaming

Discussion in 'Sound Science' started by cpurick, Jun 13, 2018.
  1. cpurick
    I have a Sony Xperia which is only so-so through the 3.5mm jack, but it sounds much better over Bluetooth 2.x.

    I guess this means my Bluetooth devices have better DACs than the Xperia.

    The Xperia plays some high definition formats like FLAC, but when I use it with DLNA, for example, not all formats will go. Presumably DLNA streams the raw file, so it must rely on the player's own CODECs. I understand the original Bluetooth spec may allow for this by design (where both sides support the same format), but that it is not usually implemented. Therefore with Bluetooth your player's CODEC typically decodes, then some intermediate format is sent to the audio device and output by its DAC. What is the intermediate format? Is that PCM, or something similar? (I don't know if this is changed in later Bluetooth versions).

    When I use Chromecast Audio, which side of the WiFi connection does the decoding? Does the WiFi carry the decoded intermediate, or does it stream the source file to a CODEC on the Chromecast?

    I probably have a lot more questions, but maybe if I understood more about these questions right here I could figure out the rest myself.
     
  2. bigshot
    What kind of headphones and player are you using? It may be the built in amp, not the DAC, that is making the difference. Obviously the amp built into the bluetooth is designed for the headphones. The line out from the sony may be underpowered.
     
  3. overgang
    Highly unlikely. Sound quality depends most on the extremities of the chain: the headphone and the recording. Things in-between – file format, codec, DAC, cable – matters little. Your Bluetooth devices must have better transducers than whatever you plug into the jack.
     
    TheSonicTruth likes this.
  4. castleofargh Contributor
    streaming methods wired or not will have their own requirements and protocols. BT has several, wifi can pretty much do anything a wire can do. now when you pair 2 devices, they need to understand each other. for wifi if DLNA works, that's the standard you'll be using which is not just an audio protocol. it basically let you send stuff from one place to the other, no matter what it is you're trying to send. if the receiver is the master in that relation, maybe it will only show you what it can read, if the source is used with an app as master, it's more likely that you will see anything the app can play without regard for the receiver. so you try something and it fails when the receiver has no clue what to do with it.

    with BT, the most basic stuff can also send data whatever it is, but audio gears usually offer specific audio protocols instead. with those protocols the signal is converted at the source into something the receiver will know to decode as music, no matter if the source was wav, flac, mp3 or any other audio codec. so long as the source knows how to extract the file to PCM and then convert into the BT codec your devices have agreed upon, that is what will be sent to the receiver. so despite very inferior maximum bit rate, and much more limited range of operations, BT can end up looking like the one with best audio compatibility on occasion depending on the gears and apps used.
     
  5. Steve999
    I think the Sony Xperia is a phone (I had to check--it wasn't obvious to me). If you are using the same headphones wired and for bluetooth, it may be that some helpful EQ is applied in the headphones when they are powered up on bluetooth, so you would get a more even frequency response when using bluetooth. Just an idea.

     
    Last edited: Jun 18, 2018
  6. bigshot
    It's an impedance mismatch when you plug in. A headphone amp would correct that. When you stream using bluetooth, the headphone circuitry of the player is bypassed and the amp built into the headphones is used. Presumably that built in amp would have proper impedance because it's built right into the cans.
     
    Last edited: Jun 18, 2018
  7. amirm
    There are multiple codecs in Bluetooth. The most common are SBC and Apt-x.
     

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