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Old 5th August 2015, 15:39   #1  |  Link
bmcelvan
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Join Date: Mar 2014
Posts: 39
Bluetooth audio encoding - specs codecs etc

Hi,
I've searched this forum for a general bluetooth audio thread but could not find one, just a bunch of questions (which I have as well) but thought maybe a place for all bluetooth tech questions could be assimilated. If there is a thread I missed, can someone please share that link with me.

My main question are about figuring out the bluetooth specs for various devices (specifically the codecs used for streaming) and is there an easy way to do that?
Another question I have is about the bluetooth streaming technology.

I (currently) have a samsung galaxy s4 mini and just purchased a Sony SRS-X77 portable audio speaker which has both bluetooth and a network connection via WiFi or a LAN cable. Obviously the WiFi (or LAN cable) connection yields the best audio quality but being a portable unit and using the battery you only get about 3 hours of playtime on LAN versus 9.5 hours via bluetooth not to mention there is no WiFi media server when I'm say camping.

I am having an incredibly difficult time find the "specs" for bluetooth profiles/codecs used by devices online which include my s4 mini. Sony thankfully made it clear in regards to the srs-x77 speaker:
Compatible BLUETOOTH Profiles: A2DP (Advanced Audio DistributionProfile) / AVRCP (Audio Video RemoteControl Profile)
Supported codec: (SBC / AAC / LDAC)

The Sony manual then goes on to say the "best supported" codec will be used for transfer. So my first main goal is to figure out what that is. I know from www.aptx.com (AND ONLY aptx.com, Samsungs website nor manual mentions aptx anywhere) that the s4 mini has APTX, but Sony got rid of APTX compatibility (the srs-x7 had it, previous version) for their new LDAC codec...which is supposed to be the best but still pisses me off. Why get rid of it, not just add LDAC becasue as far as I know only the new Sony ($1000) walkman has and/or uses it. NOTHING else has the LDAC codec that I can find anyway. (sorry for rant)

So, will the s4 mini stream in bluetooth AAC codec or the standard SBC codec? Customer and technical service is literally useless in this department as well...Samsung's rep told me yes the s4 mini has and can play the AAC codec (no sh*t Sherlocke) and yes the s4 mini has bluetooth v4.0, A2DP, EDR, LE but didn't understand what I meant when asked if bluetooth will stream in the AAC codec.

Which brings me to by bluetooth audio tech questions. I assume the AAC codec is better than than the standard SBC but is that true and what technically does it mean. Does it mean that the device will on the fly convert whatever audio it is playing to an AAC file and that gets sent to the renderer which then decodes it? Because if that is the case then isn't the 328kbps bluetooth limit or whatever it is plenty of bandwidth of to transfer "high quality" audio. (I know some people will argue they can tell the difference between a 320kbps MP3 and a FLAC file which is complete BS as we now know from some quality double blind tests done in Boston but for me an MP3 or AAC file over ~200kbps is plenty for high quality audio).

Or does bluetooth only transfer 2 channel WAV or LPCM data and therefore the 328kbps data limit really does hinder quality.

Also, if it does decode and then re-encode to AAC_SBC_LDAC wouldn't streaming starting with a (lossless) FLAC file be much better than an already lossy file, say an MP3.

Lastly, in regards to the SBC codec, is it in the same league as the MP3 codec, or even the AAC codec? Will a FLAC file bluetooth streamed via SBC even be close to an a well encoded MP3 file played via USB or analog cables (without re-encoding)?

Thanks to anyone who has the knowledge, time and willingness to answer any of these questions
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bluetooth audio, codec, sbc, streaming

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