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Topic: What's with the awful sound of Opus through (some) bluetooth speakers ? (Read 2392 times) previous topic - next topic
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What's with the awful sound of Opus through (some) bluetooth speakers ?

Hello everyone. This thing annoys me to no end and when I search about it on the internet I find nothing : the sound of opus files is awful when using some bluetooth speakers. Let me explain :

I use the opus format on all of my devices : android devices with foobar2000 for android, Rockbox driven DAP (such as Ipod and Sandisk Clipzip), and a linux PC. I settled for a bitrate of 76kbps, which is fine for my use, almost transparent. Listening my music on these devices with headphones give me nice results, no complaints.

However, I have 3 bluetooth receivers and problems with 2 of them :
- a LiNKFOR DAC 192kHz (the same as shown here https://www.youtube.com/watch?v=1RfTmxm3uXI&t=72s&pp=ugMICgJmchABGAE%3D compared with the logitech one) plugged on my stereo system.
- a JBL GO
- a Earfun Uboom L

Everything is fine with the LiNKFOR 192kHz but with the two others the sound can be awful in the high frequency range : very "washy washy" sound especially on the cymbals sound.
I made tests with 96kbps or 128kbps Opus file and even though I still have the impression that the quality is deteriorated it remains... fine. But with 76kbps or 64kbps sound files it's awful. Mind you, I am aware that 64kbps files can exhibit artifacts in the high range but I am talking about something even more degraded and really disturbing notably with long cymbal sounds.
Tests made with ~80kbps Ogg Vorbis files do not give the same issue, I notice no degradation.

Also, very important point : the awful sound is the same even when the speaker is connected via the AUX cord ! (for both speakers)

Does anyone have any explanation for that ? Could it be a sample rate issue between a 48kHz opus file and a maybe locked in 44,1kHz bluetooth device ? This is the only explanation that I have in mind.

Re: What's with the awful sound of Opus through (some) bluetooth speakers ?

Reply #1
Based on your description, I think those bluetooth speakers are downmixing the stereo audio to mono. Try encoding your files with "--no-phase-inv" and see if that fixes the problem.

Re: What's with the awful sound of Opus through (some) bluetooth speakers ?

Reply #2
Boom, problem solved, with "--no-phase-inv" the sound issue vanished.
Thank you so much !

Re: What's with the awful sound of Opus through (some) bluetooth speakers ?

Reply #3
I forgot to mention it, but some players have an option to apply a fix when decoding. If your player has the option, you can use it to save yourself the trouble of re-encoding everything.

Re: What's with the awful sound of Opus through (some) bluetooth speakers ?

Reply #4
Thanks for the info. When you write "player" do you mean PC software or some DAP firmwares ?

Re: What's with the awful sound of Opus through (some) bluetooth speakers ?

Reply #5
Both. The option exists in the Opus specification and the reference Opus decoder, so it's possible for any PC software player or DAP firmware to include it - though I don't know if any of the ones you use actually do include it.

Re: What's with the awful sound of Opus through (some) bluetooth speakers ?

Reply #6
I think mainly about foobar2000 mobile, that would be sweet. When looking up on the internet I mainly found some forum posts with requests for this option in various softwares (Firefox for example) but did not found any actual implementation.