Trying to experiment with running vorbis with 0.15.x (0.15.5+ fedora 21 server and client) generates a non-stop stream of "found large packet" warnings in server output.
2016-01-08 15:10:50,230 found large packet (21133 bytes): sound-data, argument types:[<type 'str'>, <type 'str'>, <type 'dict'>], sizes: [6, 0, 21143], packet head=['sound-data', 'vorbis', '', {'duration': 23219954, 'timestamp': 492757913832, 'caps': 'application/x-gdp, streamheader=(buffer)< 0100000000a6000000acffffffffffffffff00000000000000000000000000000000000000000000000000000000000000000000000000000000000000004773744576656e744e65777365676d656e742c207570646174653d28626f6f6c65616e2966616c73652c20726174653d28646f75626c6529312c206170706c6965642d726174653d28646f75626c6529312c20666f726d61743d28477374466f726d6174294753545f464f524d41545f54494d452c2073746172743d2867696e74363429302c2073746f703d2867696e743634292d312c20706f736974696f6e3d2867696e74363429303b00, 0100000000b60000003bffffffffffffffff00000000000000000000000000000000000000000000000000000000000000000000000000000000000000007461676c6973742c20636f6465633d28737472696e6729566f726269732c20617564696f2d636f6465633d28737472696e6729566f726269733b00, 010000000002000019d200000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000617564696f2f782d766f726269732c2073747265616d6865616465723d28627566666572293c203031373636663732363236393733303030303030303030313434616330303030303030303030303038303338303130303030303030303030623830312c203033373636663732363236393733326630303030303035383639373036383265346637323637323036633639363235363666373236323639373332303439323033323330333133343330333133323332323032383534373537323730363136626333613437326333613436613639363936653239303030303030303030312c20303537363666373236323639373332323432343335363031303034303030303032343733313832613436613537333136383431303161343235303139653331633432636536626563313934323463313138323163333234633562636232353733393032316134613034323838356232383831643039303535303030303430303030303837343137383134383438613431303832313834323533643538393238333237336430383231383438383339373831343834363934313038323138343130343230383231383431303432303832313834343533393638393238333237343130383164383465333330333830633833653533386638316338343435333935383130383332373431653832303834306634326238396138336163333930383231383432343335343835303833303633396538316338346332326332383861383263343330623831363834303433353238386338326534333063386434383330623432383839613833343933356638316138343637343137383136383436393431303832313834323434313438393038333036343163383138383434363431353839323833303633396238313438346362343161383161383432613339303831663834323033343634313530303930303030306130613232383861613232383061313031616232306130306338303030303130343035313134633737313163633939313163633962313163306230383064353930353030303030313030303830303030613034383861613434383865653434383932323435393932323535393932323535393932653638396161326363626232326363626232326363623332313031616232306130303438303030303530353130633435373131343037303830643539303530303634303030303038613033383861613535383861613536383861653738383865303838343836616330323030383030303030303430303030313033343433353333633437393434346366353435356437623636646462623636646462623636646462623636646462623636643562393636353139303830643539303530303430303030303130643236393636613930363838333030333139303634323433353630313030303830303030383031313861333063343830643039303535303030303430303030303830313834613065613230396164333964663963653361303539306539613461623133393164396334386235373939323962386162393339653739633733636563396536396333316365333965373963613239633539306339613039616433396537396363346130353930613961303961643339653739633237623137396430396132616164333965373963373163656539363039633131633633396537396332366164373939303961386462353339653739633035616436393865396134626231333965373963343862393739353239623462623533396537396337336365333965373963373363653339653739636561633565393163396331336365333965373963613862646239393639626430633533396537396334666336653964653963313063653339653739633733636533396537396337336365333965373963323033343634313530303030303430303430313038363864363164633239303864326537363832303436313136323161333265393431663765383330303931613833396334326561643165383638613439343361303832353935373135323461323730383064353930353030303030323030343030383231383531343532343832313835313435323438323138353134363238383231383631383732636132396137613038323461326161396138613238633332636232636233636333326362326362336363336165636163623330653362306333316334313034333262616463343532353336643335643635383662656533396537396138336234353635613662616462353532346132396135393435323061343234333536303130303230303030303034343230363139363439303531343832313835313436323838323961373963373230613261613838306430393035353030303032303030383030303030303030303466663231636431313131646431313131646431313131646431313131646431663131636366313132353531313232353531313232646433333233356433353334353535373536356437393637353539623737643562643838353564663737646464663737646464663837353631353839363635353939363635353939363635353939363635353939363635353939363230333436343135303030303032303030303230383431303432343832313835313435323438323963363138373363633339653832343934313030383064353930353030303030323030303830303030303037303134343737313163633939313163343962323234346264323234636464323263346666333334346631333364353131343435643333343535643131353564353133373664353133363635643333353564353333363564353535363664353739363664356262363735646239373635646266373764646666373764646666373764646666373764646666373764356430373432343335363031303031323030303033613932323332393932323232393932653333383865323434393430363863383261303034303036303034303030303038616532323838656533333839323234343939323235363939323637373939366138393939616539393939653261616134303638633832613030303031303030343030303030303030303030303038616136373838616139373838616138373838656538383839323638393939366138613939613262636161366563626161656562626161656562626161656562626161656562626161656562626161656562626161656562626161656562626161656562626161656562626161656562626161653062383438366163303230303234303030303734323434373732323434373532323434353532323434373732383064303930353530303830306330303830303030303163633333313234343537323263636264323334346666333334346631333364643131333364643335333435353737343831643039303535303030303230303038303030303030303030303030303063633962303134636264313163346431323235643535323264353535333264643535323435643535333535353535353535353535353535353535353535353535353535353535353535353535353535353535353535353535353535353535353535353535353535353535353464643333343464313330383064353930393030303030313030643035613733636361643937386534316538616339376338323861346130643734653339653661346437636332383832396365373130333136333938633735323331343330636336393634313834393430353432343335363034303035313030303038303331633833316334316337326365343965613234343563653339326131646135633633393437613961336434353134616231613635613362346161356236353436626533396361336434353163613238613535613462616231646135353436626161623130303030383030303037303038303030306261316430393031353031343031343030303038313063353230613239383539343632636532396537393035326361333965363163363238613339613739633633636533393238396439346361333932373964393331323239613539633633636532396537396339346365343965363963393364323439323830303030323063303031303032306330343232383334363434353030313032373030653037303163346439333334346431343235346431333435346631343564643731333435643539353334636433343335353135343535346431343464643535343535353931363464353539363235346433333464346431343535353331333435353531353535353339363464353562353635636633343664643935343535646431363535643562363635356266363764353739363735646433333464643931363535643562363464353562353735353739363735356462363664646439373334636433343335353135343535346431343535643735343535646233363535643562363335353137343564353135353635353935343535353937363564353964373535353764363764346431343535643535333464643931353535353539363535643964353635353539363735356637343535646435363564643964373535353964363764646264363835356664363764633261386161626136656361616561656162623261636662623232656662626165646562393434396433346335333133343535356435343435313535346435376235366435333735366435623133343564373135353564353936343535333735363535353936376435663735363564396437343464313735343535353935363535313535363535393935363535643737363535376237343535356435366435353736376464663734356435643937373535643538363635626637383564333735373535643935363564663537363535396637363535646337643637356466663734636433623634646437643537356433353537356466643637356535393936646462663834353535643537353535393638353566393536356466643738356531373936656464313739653531353537356464393435643566353736353539313736653566333764616265366533636166366436336462336562326166323330633437626562303263356464623336626162653464393837356464653831623433653133373836333464336234366464333535373564643734356435663937373564643638656262613530353435353564353736356439663735353537663637643562663738356531663637646466313835356437663735353539313638366435393639643631663737646135656530623935353562363835646664363735653739383664356435383765653365386663626533323734373535623638656262616231636362656165336362623731373438363365303230303030303631633030303030323463323830333835383661633038303065323034303031383834396334333463343138383134383331303432343832393834393035326334313838346363333932393139373335323432323961393835353235323862313838333930333932363235373334653461323861316135353034613462613138346436343232396231383535323561366361646435396135613862333538346432356132386135623535303461386261396135316135623662333534363863343163383963393339323339323761353934643235613238613562356363333932613964383339343361303832396135393435613263323963353538333932373235383338653461303732316135393234613463323561353138343332616231393539343632326332396335643835613663623963353938373332386135633539323461366332356135353835623463333962363138373338653138383339303339323732353733346534613238613562353532353236623935373335323361303832393635306534613261323963353538346134613331373334653461303732316135306534323461323561353138353334616231383535323632326232396435353834613661623163353938373334623331643635303532386232356135313834623461333162363138373336656231653564363431363832646134313236333238323563363136363361656164623531613433323962313935393436323263323964353136363361646264633539383733323832356336393234613864323561353538356238646239633631383733346562316535396135616163623963356438366236646239663539613733643061396235356135333463623962363138373338656239303535393733656562643833643035613238613563353530346138636164623535613562386333393837353236323262323964353538346138616235633539383733366262316636353034613863323561353538346234613335623631383662386533356636396135616162623563353938366236616231653639613733656633316536643835333662333562373138366234656231653535613733656562646536643636333031303030303033306530303030303132363934383134323433353630323030353130303030303432313461333130366131343138383331653761343334303833316536396339343861333165373230613435323331653631633834353233326537323039343932353265363163383435323532306161356134393235323662613139343532353236616164303030303830303230373030383030303162333432353136303732383334363432353030393030613030363037303163636266323363353133343535643937363263633966333434643133343535643562363164636266323363353133343464353562353664636266333434643133343535643537353735646466323363353133343535353537353564356466373434353133353535643537353635353966373364353133343535353537353564353966363764643335343535643537353635353962363835356633343535353737353564353939363635646635383564643537353635353962363735356231383536643537353564353939363664356233373836356264373735646466373835363133393361623736656562626165666662633266313362633730303030663030343037303061303032316235363437333832393161306232633334363432353030393030313030343031383833393034313438323138333130353234383231613531303532346130393030303031383730303030303038333061313063313431616232313230303838303230303030303839313532346132393864393435323461323961353931353234613239613539343132343230383231383431303432303832313834313034323038323138343130343230383231383431303432303832313834313034323038323138343130343230383035303066383466333830306638336664386130323962313338343061313231326230313830373030303030633031386135393837323063336130393239333538633339303661313934393435323661616436313863333130386135613464343561346239353733313034613439613962356438363261633963383335303532346161646335316136333037323161356436356161636231643639613362303832396135313636626163333964383163346136393264633635383733636562646637393035323662333164363561373365666264393764363632616333356537646338333130633262343134363361656239663665303762656632396236356136626364336466383230383435306231643535613733663034313038323138343862333166376463383366303364303832313563386333396537316538346630633130373631303030303737383330333030343438323864333361633234396431353865303631373161623231323030303830393030323031303632386133316537396338333130343230383931353238633339653731633834313034323238323535323861333165373963383330653432303832353634386333396537316338343130343232386135393438633331653739633833313034323039613539343932333965373163383431303432323861353934353233326537613038333130343230396135393435323461653731633834313034323038613539343532346165396130383331303432303961353934353234613239323138343130343230396135393435323461323932353834313034323039613539343532346132396135383431303461323861353934353234613239613539343130343232396135393435323461323961353934313234323238613539343532346132396135393439323432323961353934353234613239613539343532353232386135393435323461323961353934353234613039613539343532346132396135393439343532343930353030303031633338303030303034313834313237313935353136363161333039313731653830343234333536303230303430303030303134633435363533383939643431636333313637613932313038333161386139343234613239383633313433636132306136323935333061323138353231373338613231303261316335353634626335303030303030313030343030303830383039303033303430353033303033303030633065313033653037343132373430373062343031303030383432363438363438333432633034383730373935303031313331313530303234323632386534303234303835633534356461633530353734313965303832326565653361313034323130383231306334653230303061343863306331303933373363663138363237646365303034396461323532303730313030303030303030373030303030306630303030633730353130313164313163343638366336303634373837633730373438343830303030303030303030633830306330303730306330323130323434343433343837393161316231633164316531663130313132313230303030303030303030303030303030303030343034303430303030303030303030303230303030303030343034203e00, 0100000000010000001effffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff004000000000000000000000000000000000000001766f72626973000000000144ac0000000000008038010000000000b801, 0100000000010000003fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff004000000000000000000000000000000000000003766f726269732f000000586970682e4f7267206c6962566f726269732049203230313430313232202854757270616bc3a472c3a46a69696e290000000001, 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 >', 'sequence': 0, 'time': 1452294650227}]
--speaker-codec=vorbis server or client side isn't respected.
--speaker-codec= flag as being Microphone Codecs.
--microphone-codec= displays in Session Info as being the codecs available for Speakers.
The confusion between speaker and microphone is unfortunate but expected: one side is sending sound (and maybe "microphone" was not the best term to use for that - though this is what is usually used in applications) and the other end is receiving and outputting ("speaker"). And this can go both ways: the client can also forward its sound back to the server. (client then uses microphone and server uses speaker)
At the time, I remember hesitating between the terms "input" / "output", "source" / "???" and "microphone" / "speaker".
I am open to changing this (in a backwards compatible way obviously) to make it clearer: we just need two terms that make it clearer that one is for the sender and the other is for the receiver. (then it should be clearer that the codecs from the sender must be matched by the receiver?)
Now that this is out of the way. Specifying speaker-codec=vorbis on the client should select it, as long as the server supports it (in its microphone-codec..)
As you found out, "vorbis" was missing from the list of codecs (which means this is the first attempt to run vorbis in 0.15? ouch), I have added it in r11620. r11621 fixes a harmless warning, r11622 fixes the "stream of warnings" and should reduce the packet size in all cases, which is a worthy fix to have - I have verified that we never actually use the caps for anything, so this should not break other codecs, but is definitely worth double checking.
One last thing: you should not be using anything as outdated as 0.15.5.. there are important bug fixes you're missing out on.
In the spirit of that last detail... I will just close this, trust that the fix works, and stop using anything as old as 0.15.5.
this ticket has been moved to: https://github.com/Xpra-org/xpra/issues/1083