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From:   Guillaume Martres <smarter@ubuntu.com>
Date:   Mon, 23 Mar 2020 16:01:39 +0100
Message-ID: <CAMM3rS01a6UH=atXGUL6gqAvS9Mit4hqhzhBrEtVX7-nWP92Pg@mail.gmail.com>
Subject: Re: [PATCH v6 2/2] bluetooth:btusb: handle msbc audio over USB Endpoints
To:     sathish.narasimman@intel.com, marcel@holtmann.org
Cc:     linux-bluetooth@vger.kernel.org
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On Sat, 21 Mar 2020 at 17:55, Guillaume Martres <smarter@ubuntu.com> wrote:
> Since then, I was made aware of the existence of this patchset, after applying
> this patch (and [3] which apparently only exists as v5 and not v6), my
> headphones stopped sending zero-filled packets, but:
> - the recorded audio quality is again extremely bad and robotic.
> - when audio is being played, the headphones do not emit any sound.

I figured out what the problem was: pulseaudio assumes an MTU of 48
but with this
patch it now ends up being 60, I've left a comment on the pulseaudio MR [1].
After fixing this, audio input and output seem to be working correctly, however
from time to time pulseaudio fails to decode an mSBC packet, but I don't know
whose fault that is.

[1]: https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/merge_requests/254#note_444249

On Sat, 21 Mar 2020 at 17:55, Guillaume Martres <smarter@ubuntu.com> wrote:
>
> From: Guillaume Martres <smarter3@gmail.com>
>
> Hi Sathish, Marcel,
>
> > I would really prefer to have some Tested-by lines from people that can verify that this patch works.
>
> Here's my experience: a recent pulseaudio MR [1] added support for mSBC. When I
> tried it using my laptop (Intel AX200) and headphones (Bose Headphone 700), the
> voice quality was extremely bad. I eventually realized that this could be fixed
> by ignoring all zero-filled packets sent by the headphones when decoding
> mSBC [2], after that everything worked fine.
>
> Since then, I was made aware of the existence of this patchset, after applying
> this patch (and [3] which apparently only exists as v5 and not v6), my
> headphones stopped sending zero-filled packets, but:
> - the recorded audio quality is again extremely bad and robotic.
> - when audio is being played, the headphones do not emit any sound.
>
> Note that I applied this patchset on top of the current Ubuntu 20.04 kernel [4],
> let me know if it's worth retesting on top of the mainline kernel, or if there
> is something else I could try.
>
> Hope this helps,
> Guillaume
>
>
> [1]: https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/merge_requests/254
> [2]: https://gitlab.freedesktop.org/smarter/pulseaudio/-/commit/bb716b03002841e1092b4200935566d5c1a951fe
> [3]: https://www.spinics.net/lists/linux-bluetooth/msg82149.html
> [4]: https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/focal/commit/?h=Ubuntu-5.4.0-18.22&id=93dfa5b8e12fed29933f3451db44d88c0e4b5aed