On Tuesday 29 October 2019 11:24:06 Hyperion wrote: > > > 29.10.2019, 10:24, "Pali Rohár" <pali.rohar@xxxxxxxxx>: > > On Monday 28 October 2019 17:12:45 Hyperion wrote: > >> 28.10.2019, 16:11, "Tanu Kaskinen" <tanuk@xxxxxx>: > >> > On Sat, 2019-10-26 at 20:23 +0200, Hyperion wrote: > >> >> 26.10.2019, 14:39, "Tanu Kaskinen" <tanuk@xxxxxx>: > >> >> > On Sat, 2019-10-19 at 18:42 +0200, Pali Rohár wrote: > >> >> > > On Saturday 19 October 2019 19:27:19 Tanu Kaskinen wrote: > >> >> > > > On Sat, 2019-10-19 at 18:16 +0200, Pali Rohár wrote: > >> >> > > > > On Saturday 19 October 2019 19:07:44 Tanu Kaskinen wrote: > >> >> > > > > > On Sat, 2019-10-19 at 17:20 +0200, Pali Rohár wrote: > >> >> > > > > > > On Friday 18 October 2019 15:29:43 Tanu Kaskinen wrote: > >> >> > > > > > > > On Thu, 2019-10-17 at 15:34 +0200, Hyperion wrote: > >> >> > > > > > > > > Regression would mean that some devices can't connect anymore : this > >> >> > > > > > > > > won't happen if a workaround is provided, and this workaround won't > >> >> > > > > > > > > be used often. > >> >> > > > > > > > > > >> >> > > > > > > > > Most (99% ?) of the devices will work correctly with my patch (many > >> >> > > > > > > > > of them in XQ mode, and some in legacy mode because they will fall > >> >> > > > > > > > > back to legacy bitpool during negociation) > >> >> > > > > > > > > > >> >> > > > > > > > > The remaining (1% ?) : will need a simple boolean swicth in one of > >> >> > > > > > > > > the PA config files to restrict negociation to legacy bitpool (a > >> >> > > > > > > > > module option ? or daemon.conf ?). > >> >> > > > > > > > > > >> >> > > > > > > > > I think it's really "simple", efficient, and not dependent of any > >> >> > > > > > > > > upcoming Bluez feature. > >> >> > > > > > > > > > >> >> > > > > > > > > "The complex solution is always the best until one find a simpler one" > >> >> > > > > > > > > >> >> > > > > > > > I don't know the number of users who use bluetooth headsets with > >> >> > > > > > > > PulseAudio, but even just 1% regression rate can mean quite a few > >> >> > > > > > > > unhappy users. When your headset suddenly stops working, it's not > >> >> > > > > > > > trivial to figure out that you may need to pass a special argument to > >> >> > > > > > > > module-bluetooth-discover in order to make it work again. > >> >> > > > > > > > > >> >> > > > > > > > It would be better to have a module argument to enable the XQ settings. > >> >> > > > > > > > >> >> > > > > > > Main question, do we really need this special "settings"? Because my > >> >> > > > > > > patch series introduce also SBC XQ profile and basically replaces above > >> >> > > > > > > module parameter, by runtime configuration. > >> >> > > > > > > > >> >> > > > > > > For me above solution looks like a hack. It adds some module parameter > >> >> > > > > > > for tweaking configuration. And what would happen with that parameter > >> >> > > > > > > after we have "proper" support for multiple codecs? Do we need to > >> >> > > > > > > maintain backward compatibility? Or would we remove that configuration > >> >> > > > > > > and therefore revert to state prior existence of new module parameter > >> >> > > > > > > (which is current situation)? > >> >> > > > > > > >> >> > > > > > After your patches there's still the "automatic bitpool" mode > >> >> > > > > > available, right? > >> >> > > > > > >> >> > > > > Yes, I wanted to have it there for legacy/backward compatibility reasons > >> >> > > > > for those devices which could be broken with new settings. That is the > >> >> > > > > reason I do not wanted to touch Automatic mode, to have exact same > >> >> > > > > behavior as in current (and older) pulseaudio versions. > >> >> > > > > > >> >> > > > > But if automatic mode is going to be changed, I do not see reason for > >> >> > > > > keeping it (the argument for backward compatibility would not apply > >> >> > > > > anymore, if it is going to be changed). My patch series with new A2DP > >> >> > > > > API can fully replace that automatic mode. > >> >> > > > > >> >> > > > I don't see how the proposed option changes anything about > >> >> > > > compatibility. The option will be disabled by default, so the default > >> >> > > > behaviour will be the same as always. > >> >> > > > >> >> > > And what should happen after support for multiple A2DP codecs (from my > >> >> > > patch series) would be there? Basically it obsoletes that config option. > >> >> > > As all such settings can be set at runtime. > >> >> > > >> >> > If the "enable XQ in the automatic bitpool mode" option is made run- > >> >> > time configurable, then yes, the module argument will become obsolete. > >> >> > >> >> I don't think so : by default Pali's patch first connects using one of the 2 XQ modes : so > >> >> it will fail with devices not "XQ able". Since we are having this discussion only because > >> >> we don't want ANY regression (even as rare as the devices that can't do bitpool 38 dual > >> >> , and even for users who don't know how to switch SBC modes) : then the default mode > >> >> of operations shouldn't allow XQ at all. > >> > > >> > I think we're talking about different things here. > >> > > >> > A mode for automatic bitpool is needed and will have to be the default. > >> > XQ bitpool values need to be disabled by default. An option for > >> > enabling XQ bitpool values in the automatic mode would be useful, so I > >> > hope we will have that. > >> > > >> > When I said that "the module argument will become obsolete" didn't mean > >> > that the XQ option itself would become obsolete. If the option can be > >> > configured at run-time, for example with "pactl enable-sbc-xq true" or > >> > with pavucontrol, then that will not be implemented via a module > >> > argument. It will be implemented using the message API (which is still > >> > under review), and the option value will be stored in a database. > >> > Having a module argument doesn't add any value in this scheme, which is > >> > why I said the module argument will become obsolete. > >> > > >> > This depends on someone actually implementing the interface for setting > >> > the XQ option, however. I hope someone will promise to do that. It > >> > could be you, or it could be Pali. I'm not promising to do it myself. > >> > If nobody promises to implement that, then I'm going to accept a module > >> > argument, because having something is better than having nothing. > > > > I have already implemented it! It is in my patch series. Currently > > selection is done by choosing PA profile (because there is no other > > mechanism yet). > > > >> It's not obvious to get details of the A2DP protocol without reading the RFC, > >> so I'm going to give a few tracks : > >> > >> - Bluetooth packet size is not constant : BT traffic is splited in radio slots > >> that have fixed time lengh : so for a given bandwidth : slots size vary > > > > Plus there is retransmission at low bluetooth layer when they are lost. > > > > Also radio slots are shared across all bluetooth traffic between host > > and device. So not only A2DP packets are transmitted, but also other > > packets, like established HSP / HFP or anything else. > > > >> - Bitpool is dynamically reduced when the bandwidth decrease : for example > >> when the emitter go away from the receiver. > >> - Bitrate is related to bitpool but depends on other parameters (see the attached sheet) > >> - Bluetooth A2DP emiters (SRC) usually specify a maximum value for Bitpool. > > > > It specify both minimum and maximum (range) > > > >> This value is not the value that will be negociated but rather a > >> highest negociation value. > > > > Result of negotiation is bitpool range, which must be continuous subset > > of intersect of supported range of host and device. > > > > And then emitter choose any bitpool value from negotiated range, > > probably always the highest value from that range. > > > >> - SBC XQ is standard SBC codec operating at high bitrates and thus reaching > >> the transparent audio transport quality of AptX (HD) . It can be achieved either > >> in STEREO MODE, with bitpool ~ 76, or in DUAL CHANNEL MODE, with bitpool ~ 38 > >> per channel (simplified) > >> - "Legacy automatic" is the barbarous name I gave to the traditional negociated algorithm > >> with max bitpool=53 and STEREO MODE prefered to DUAL CHANNEL MODE : it is implemented > >> in current PA > >> - "XQ automatic" is the barbarous name I gave to the negociated algorithm > >> implemented in my patch with max bitpool=38 per channel, and DUAL CHANNEL > >> prefered to STEREO MODE (simplified) > >> - "Forced XQ" modes are several algorithms implemented by Pali with fixed > >> bitpool values : not negociated : if the receiver can do the fixed bitpool it works, else > >> it fails (simplified) > > > > It is negotiated too. If remote side does not announce that it (may) > > support "forced XQ" then it is not available for PA. > > > >> Now the "quaity switch" idea : > >> The "quaity switch" (aka module param or pactl API call, all good for me) is a way > >> to switch between "Legacy automatic" and something else giving better quality. > >> The "something else" could be : > >> - "XQ automatic" + several "Forced XQ" modes (my latest idea, relies on Pali's code + my code + "quaity switch") > >> - "XQ automatic" alone (my former idea, relies on my "simple" patch + "quaity switch") > >> - several "Forced XQ" modes alone (Pali's idea, relies on Pali's code +"quaity switch") > > > > My proposed API in PA server allows to define any settings or > > combination for SBC codec. So it would be easy to define any such > > "SBC profile" with my patches. > > So it's all fine for me. Plus the fact that you implemented the bitpool > automatic recovery grow up when bandwidth grow : it's perfect. No, grow up is not implemented. This is missing and I do not know how to implement it. Because I do not know how to detect that conditions allows computer to start sending more A2DP packets. > I would just suggest to add an automatic XQ profile (inspired from > my patch if you want to) and make it default when XQ is available > on SNK side. > This way we don't have to wait for Bluez to provide codec switching > and it allows for a 14.0 PA release at the date already scheduled by Tanu. > > JP > > > > >> Pali : please fix the above in case I did some mistakes > >> JP > >> > >> > > >> > -- > >> > Tanu > >> > > >> > https://www.patreon.com/tanuk > >> > https://liberapay.com/tanuk > > > > -- > > Pali Rohár > > pali.rohar@xxxxxxxxx -- Pali Rohár pali.rohar@xxxxxxxxx _______________________________________________ pulseaudio-discuss mailing list pulseaudio-discuss@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/pulseaudio-discuss
