aptX/Bluetooth audio, any experience?

2014-02-17 09:14:39

Hi guys,

for a long time a dedicated notebook with Foobar2000 and remote controlled by Girder has been my living room solution. But after all it was not wifey compatible. The solution is Audio streaming via Bluetooth, which already works in our cars. After some research in that relatively new terrain, which has no oldschool audio ppl like us at HA around, I realized aptX is the way to go. It's all pretty badly documented, marketing fuss, they losely use the term "lossless", the vast majority pf the target audience doesn't care anyway, in times of Google Play Music etc...

So what I understood is, if source is mp3 (what if VBR? CBR?) it will package it into a container and transfer it as it is. On the other hand I think the source device would already transcode the file... because it supports altering the volume, I believe it is on audio altering level.
Also I read it tries to encode to a lossless format, and if the material does not allow to be compressed to a specific bitrate (at 320 kbps something?), then it falls back to lossy. Well, this should always be the case except maybe in piano music.

Anyway, does anybody know what's the best source material? Maybe it's a good idea to have mp3 @cbr 320 as a source and it will transfer it deirectly, without re-encode?

The chain will be:
Sony Xperia Z1 -> Advance Acoustic AptX.

TIA

aptX/Bluetooth audio, any experience?

Reply #1 – 2014-02-17 16:33:36

This comment's a bit out of point,

but if you want no re-encoding, how about using Kleer wireless transmitter?

i wonder is there any Kleer receivers available....

aptX/Bluetooth audio, any experience?

Reply #2 – 2014-02-17 19:45:23

No really controlled testing here, but I got the impression that the AptX connection sounded similar to a direct wired connection save for periodic dropouts. I have:

2008 24" Apple iMac with AptX enabled
Samsung Galaxy Tab 3

Yamaha YBA11 BT receiver connected via SPDIF to Benchmark DAC 2 HGC
Soundmatters FoxL v2 w/AptX

Among other things, I listened to this:
http://www.youtube.com/watch?v=RncvCSS1lL4

aptX/Bluetooth audio, any experience?

Reply #3 – 2014-02-18 14:44:19

I read about Kleer, but I cannot see how my XPeria Z1 could send the necessary signal. I'm pretty confident sound will be completely alright for me. I.e., somewhat very close to as if I would use I wired connection. I'm not very picky, i.e. after something is alright for me I continue in doing what it's good for: enjoying the music.
But I want to do best practise. IF there may be a prefered source format, I'd like to use it. Unfortunately there's not much technical information on the topic.
My biggest fear is not the sound itself, but sound skips and dropouts. Well I will know more from tomorrow on, when the aptx receiver arrives. A big step forward in usability, I hope.

aptX/Bluetooth audio, any experience?

Reply #4 – 2014-02-18 21:07:19

There has been a discussion about aptX [a href='index.php?showtopic=78217']here[/a].

The aptX codec in Bluetooth A2DP is a proprietary extension by CSR and licensed by "a few" device manufacturers.

aptX Bluetooth is a lossy subband ADPCM codec working at a bitrate of 352 kbps and thus capable of preserving the full bandwidth of a 16 bits stereo 44 kHz audio stream ("CD-like quality audio"). Its main advantage over other audio codecs used by Bluetooth (like SBC, MP3, AAC) is: "Low audio coding delay that minimises latency and audio/video syncing issues"

Bluetooth A2DP encodes the audio stream with a codec that's supported by both transmitter and receiver, usually the mandatory SBC, maybe aptX if you're lucky and compatible software (drivers) / devices are used. The format of the audio source data (MP3, FLAC, whatever) doesn't matter - transcoding on-the-fly always happens before Bluetooth A2DP transmission. Since aptX is a lossy codec there will be some quality loss caused by this. (audible or not? conduct a listening test!)

aptX/Bluetooth audio, any experience?

Reply #5 – 2014-02-18 21:39:38

In 2010 when the [a href='index.php?showtopic=78217']other thread[/a] was started, the website http://www.aptx.com had several documents about the technical details of the aptX codec variants.  Those links are dead now, but thanks to the Wayback Machine these interesting documents are still available:

https://web.archive.org/web/20100808133404/.../Downloads.aspx
https://web.archive.org/web/20100831222634/...-Bluetooth.aspx

aptX/Bluetooth audio, any experience?

Reply #6 – 2014-02-19 13:22:29

Thanks smack for searching for the thread, I will read it carefully. Device arrived today. I'm confident I will not need to perform a listening test between, say, FLAC/lame@V0/lame@cbr320 [edit: after first lose listen I hear no differences and I don't feel like finding some :-)] - very very likely audible issues are somewhere else.

So far, very nice. Not as great as with a dedicated notebook (has more features with fb2k), but mobility strength.

- Bluetooth connection/disconnection with an intended audible phone ring. Sony Z1 confirms an aptx connection via hint.
- A bit of hiss, may be my amplifier. Because it needs to be set loud, I listen to music with huge dynamics (classical) and want to control volume via smartphone only.
- Some soft crackles here and there when manually changing tracks, I expected this.
- A short break between tracks, i.e. no seamless transition (not sure if that was because of the player, Google Music in that case), will test seamless in Poweramp. [EDIT: Poweramp plays seamless]

I'm pretty satisfied with the solution. Even listening via Google Play Music via streaming was fun already.