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Moode 4.2. thoughts and feelings
#21
(07-16-2018, 10:31 PM)gothard Wrote: ...
The Bad:

-The Bluetooth sound quality is abysmal. I wasn't expecting miracles because its Bluetooth which is more designed for convenience than getting the best possible sound quality, but the Bluetooth output from Moode sounded significantly worse than the audio output from my phone on Tracks Air headphones. Maybe the built it Bluetooth on the Pi is just junk or maybe the feature is not fully optimized. 
...
Although not superb, I find the bluetooth in Moode acceptable. Moreover I have the feeling that this does not depends on Moode rather on the bluetooth itself.
In my opinion Bluetooth sourcing capability is a big plus and, as far as I know, a unique feature of Moode.

I do not understand why streaming from a Iphone on standard bluetooth headphones   should give better results compared to Moode, except in case the headphones has some specific feature for Apple devices like direct AAC encoded stream management (is this the case of Tracks-Air headphones?).
Apple world use AAC encoding and Bluetooth protocol is specified to make possible the direct use MP3 or AAC codec instead of the SBC one, but I do not think that many headphones out there are able to do that.
If the reciving unit (i.e. the headphones) does not accept MP3 or AAC codec, the bluetooth standard forces an automatic switch to SBC protocol for A2DP profile.
In this case the AAC stream should be decoded and then a second encoding step with SBC protocol should be necessary.
This will produce a loss of quality, idependently of the sourcing device (Iphone or Moode).
I am not an expert but I imagine that this double encoding process, together with the fact that SBC protocol is probably not optimal for preserving audio quality, is the reason why often Bluetooth is not considered the best solution for listen HQ music.
From the point of view of the band, the high-quality A2DP profile mode offers 320k+ bandwidth that is absolutely decent in my opinion to make quality losses negligible.
Also aptx standard (not aptx-HD) does not offer much more bandwidth so again, the most probable reason to claim a better performance of the aptx compared to non-aptx should is the fact that SBC codec is not optimal for preserving audio quality compared to aptx one.

There is a point that may be consider for future releases.
Most of the internet streams are MP3 or AAC so why not to implement in Moode the possibility to manage natively MP3 or AAC protocols for both source and sink mode in with bluetooth A2DP profile?
This option would give the possibility to transfer directly the MP3 or AAC stream when the other end of the bluetooth channel can also manage this option.
In this case the SBC protocol would be skip, avoiding the dual encoding process mentioned above, and surely improving the audio quality throught the bluetooth channel.
Honestly I have never understood why headphones manufacturers do not massively use this feature offered by the bluetooth standard.
I do not remember a manufacturer that clearly mentioned the possibility to manage MP3 and/or AAC protocols directly in their products with bluetooth A2DP profile.
Regards

Roberto
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