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Topic: Is encoding in AAC better if headphones support AAC codec? (Read 426 times) previous topic - next topic
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Is encoding in AAC better if headphones support AAC codec?

I usually encode my music in opus format to carry my collection on my mobile device.

I recently bought Sony Wireless Headphones (Sony WH-CH510). The manual says the headphones support SBC, AAC codecs.

Will there be any benefit if I encode my music in AAC instead of OPUS to listen using these headphones?

I am using a Samsung Android phone if that matters.

Re: Is encoding in AAC better if headphones support AAC codec?

Reply #1
There are voices on the internet saying it is better to code to AAC as it saves you 2 conversions from e.g. OPUS to PCM and from PCM to AAC.
They think a AAC file is transmitted unaltered to the headphone.
This is probably a wrong assumption.
As it is possible to hear multiple streams e.q. music and a ring tone, obvious the mixing is done by the OS of the sender (the mobile) so decoding/encoding is done before the audio stream is send to the headphone.
You can't mix without converting AAC to PCM first.

A bit more about Bluetooth including AAC: https://habr.com/en/post/456182/
TheWellTemperedComputer.com

Re: Is encoding in AAC better if headphones support AAC codec?

Reply #2
There's the misconception that (I myself had for a period) as long as the end receiver part of a bluetooth device supports a certain codec and the host device that is playing back audio that it is encoded into that particular codec that the host is going to bypass transcoding/reencoding the actual audio and it's going to feed the raw stream as is to the receiver which is not at all what happens for many reasons.

The reasons that you need to focus most are:

1. What you get from the host device, be that a phone, a tablet or whatever, is actually a mixdown of lots of stuff, like notification sounds, app sounds etc, even when they remain silent or even turned off. You just cannot bypass the internal mixing of the host device because this is how their OS is working so this will already mean that it will include atleast an extra reencode down the line of the transmission of the audio data.

2. The bluetooth spec of these audio codecs while it carries the same name as their consumer (for lack of better words) counterpart does not mean that it's identical into how it's being handled. In the case of AAC for example, the AAC streams stored inside your average m4a extension music file is not exactly ideal for real-time audio streaming. It would require extra steps on converting that into something that can be transmitted over bluetooth in real time which is quite an involved and time consuming process which would introduce some really serious lag at best case scenario. Also as far as I know (feel free to correct me) while this is theoretically possible, there's not a single consumer available device that feeds the untouched AAC stream of a music file to a receiver.

So to answer your question in a short manner, no you cannot avoid whatever codec you use for your audio to be reencoded the same amount of times it would anyway. Just make sure you have the best quality source audio file you can as a first step.

Re: Is encoding in AAC better if headphones support AAC codec?

Reply #3
I'm going to guess that there's no audible difference (in a proper blind, level-matched, listening test).

AAC might have a "theoretical" advantage because even if it's decompressed and re-compressed the "damage" from AAC doesn't accumulate with multiple generations of compression. 

Re: Is encoding in AAC better if headphones support AAC codec?

Reply #4
Thank you all for your inputs.

Based on what everyone said, playing a lossless file over a Bluetooth connection will be more advantageous as the device will be transcoding from a lossless to lossy which is more or less similar to me encoding them to lossless format myself.

Is my understanding correct?

Re: Is encoding in AAC better if headphones support AAC codec?

Reply #5
Thank you all for your inputs.

Based on what everyone said, playing a lossless file over a Bluetooth connection will be more advantageous as the device will be transcoding from a lossless to lossy which is more or less similar to me encoding them to lossless format myself.

Is my understanding correct?
Well, that's definitely the best case scenario.

 
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