GB2398215A - Method of and apparatus for converting an audio signal between data compression formats - Google Patents
Method of and apparatus for converting an audio signal between data compression formats Download PDFInfo
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- GB2398215A GB2398215A GB0410811A GB0410811A GB2398215A GB 2398215 A GB2398215 A GB 2398215A GB 0410811 A GB0410811 A GB 0410811A GB 0410811 A GB0410811 A GB 0410811A GB 2398215 A GB2398215 A GB 2398215A
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Classifications
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
- G10L19/00—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis
- G10L19/02—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis using spectral analysis, e.g. transform vocoders or subband vocoders
- G10L19/032—Quantisation or dequantisation of spectral components
-
- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
- G10L19/00—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis
- G10L19/04—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis using predictive techniques
- G10L19/16—Vocoder architecture
- G10L19/173—Transcoding, i.e. converting between two coded representations avoiding cascaded coding-decoding
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Computational Linguistics (AREA)
- Signal Processing (AREA)
- Health & Medical Sciences (AREA)
- Audiology, Speech & Language Pathology (AREA)
- Human Computer Interaction (AREA)
- Acoustics & Sound (AREA)
- Multimedia (AREA)
- Compression, Expansion, Code Conversion, And Decoders (AREA)
Abstract
Useful subband information which is present in a first audio signal (for example, MPEG 1 Layer II) is discarded in the conventional approach of format conversion, only to be regenerated when encoding to the target format (for example, MPEG 1 Layer III). Instead, in the present invention, this useful subband information is re-used directly or indirectly in order to eliminate the conventional requirement to fully decode to PCM and then encode again. In particular, the signal to mask ratio applied in the first audio signal, as inferred from the scale factors used in the first audio signal, is used to estimate the signal to mask ratio required for the second audio signal.
Description
14-M9Y-204 13:24 FRCIM:ORIGIH LONDON +44-20080843 239821 5 TrAscodcr in
Method of and Apparans Or Convening an. Audio Signal between Data Cornprcosion Posmats
Field of the Inrenelon
I Tl.is invndon rcLates to me.od of and apparan;s for coc:vexang acidic signal. Erom one data compression former to Rnocr dabs compression formic. It may for example he used co convert hIPEG 1 Layer AX euc Steele to M. P7;C} 1 layer IN audio swirls, Dcscsptioa of tlc P;dcs Me Converting an audio signal in one data compression format to target cotta con:prcssion founat has tin thc past beck do.c as bo-tac process. The;s9t she is to ecompfe39 the audio gr31 in a decodc:r in order to cacta.tc Al intcr.. ruccU.u;y Banal. C:[this in.tet:mediary signal is,in esse<:l,cc fully decoded row date:ypically in PCM format. In e second static, dais raw audio signal is then re-coMpressed in the rarger foma.t in an cncodu:. science, o<:e solution. w the prolJlcn of cooverring MPE(: I dyer II audio signals to PIPED 1 Lance III i audio signals would be to decode the source slam using an.PI3G I t.,ayex X] decoder systrn; this is repregcnted sc1lcmti.c1y in Figure 1. Die resultant: PCLI signal would then be eDccded. mug Me MPEG I Layer III: encodes teprcontcd schnancally in [Figure 2. The 1 Encoding m:d decocling ptOCCSRCS arc discussed more film in "ISO-MPB Ammo: A Gen=r i for thorny of Hb-ú>ati DigrafAudio" Branlrg lY-I]., Shy (; ., Auto.ng. Sot., 42,.780-792, Our I9.
Acre e.re madly dlsadvangc to the oonventiona1 approach of converting an audio signs] between Clara compression forms. Firsts it rcqsc cxcneire computer CPU resonzees (particularly for the runerlc;dlr i:rtene;,ve reparations Irl Me encoder making it; fmp:matica1 to use this approach in real-umc in software only system. Secondly, it seguires expensive com.polonts (such as:05P chip to perforce. F;6Ts, Me encoder) for hardware un1ementsuol. Finally, the tesultsht audio s:n in tl:,c tat format will be of a lower quality then the;rpZlt sigr:kal in ':he source fosmat because of the extra clots reduction |0104123 14-May-04 0:1:24 14-M8Y-2004 13:24 FROM:ORIIN LONDON +44-207289843 TO:01633814444 P.013825 techni.ós applied in the ericoder (e.,;. psychu-acoustic compressions and the noise shaping or filtering; normally applied to Me input: audio aig; pl.
Whilst this invention rela:es to converting audio signals berweel1 different audio compressics1 rmtl, cEcscDce may a.l.so be maple to Me problem of con.verdng vi.d.eo s4gnr1 batwacn different Dormers. EP 0637B93 disrloes die general principle of ronveran source Do si.gs al from one video format to different video format by re-using information in the some video sisal, his iminP, ebe steed to complemly decode Done e first funn.at and then rc encode into Me di:Eferlt Arenas. EP 0637893 is howovct of only bclr.gxvund xclcn.cc to this intention since (i) it Jocs clot.rcla: to thc,.dic donor.
and 0; is in park: wholly silent on to using subband data. in the source signal Rcf.ctcncc may also be medc to IJS 5530750. l:lis discloses tecbqu. es for bit rate conversion. of signals that confirm co Me same compression format And tin particla:r IS sue e he re-use of sub-bacl data us part of tl:c hit rate conrcrsion pr.oceas, Refe,rlcc tTIay also bc:rnde to WO 0079771:1, Die desches a fornar converter for concerti, M1?3 i:: to another audio format. As pare of the pocks, al:: 1P i, converted lock up to PCM.
|0104123 14-May-04 01:24 1 14-MRY-2084 1s:24 FROM:CIRIGIN LONDON +44-2072090643 TO:D1635814444 P. 0145 Sunny of the Present Invention In accordance =tb first aspect of Me present iMYOO6011, iS a method. of convening a :5rst audio 5i1 in first dam co.prcssion format in wilicI' frame includes subbed da=, to second n..dlio signal in a second dual co:nprcssion format, characnserl j.T; ,:hze: the sul:cl Cam in the fast aud.i sing is used directly or indiicc6.y to constmcr Me second audio signal wiouc the firs: audio signal having to be fully decoded prior to cn.coding in the second data co1'np'rcssich Nimbi by the process of':he si.gl to mask redo applied in the first.udio signer! as inferred from the scale factors usecl in. Tic f,.tst aucli.o algal, being used a: estin.a.tc tl.lc signal to mask Omaha reqmted for tl.e seco::d audio signal.
Con=nticlnt.ll:v, if Ohc were convert B signal in MPEG 1 Layer II f. ox::at by decoding t.1.l..t signal w PCM a.. the encoding it in MPEC; 1 Lays III, the: subband. co-eEficLents present in an h1:PllO I l:.ycr II ftamc would bc stripped out by Me su.bband synthesis in a MPEC; 1 Layer II decoder, only to be:e-guxtated again in the subband snaly;is in the hEG I=yer III crcodcr. The prcsont invention however conrempleres, in one example, rid wry (as opposed to rgncri the subb.d co-efEcen to Echoic the need fin sulband. synthesis in 1:he dewder and the subbal:ld analysis in the encoder, Tl:!is has belch;FoLtn.d. tD significantly In reduce CPU loading.
In one im.plepentatiC., the sn,1 to nook Solo (0 used i':' t6ó ?,13 1 Layer T} Vital (rot Ample) can. be i.ntctrcd frv.tn its scale.iactofS (or scale Victor selector infiolin.ation SCFSI>; from. that, rce.son.sbly r.cliblc csHmtc of the signal to mask ratio which needs to be used in a hIP33G Layer III encocled signal, GRIl bus clrivEd. Essentially, Shim has the sane mearurg in loots M:.PEC; 1:Larer l.I nod III. They exc howcrcc n.ppll&d slightly dif.fcrcutly due to difEctc:tc:cs in die].n,ycr orgas:usac10n.
Hence, a conventional reason for using a RALM in, an ercod,cr (i.c. cl, cterm',nng t,1e slg';1. to ED masts.rado for eacl, bow, is f.u11y s:tisfcd in. a p.re.f.crccl implcmcn.tion of the i::cndon O104123 14-May- 04 01:24 | 14-M0Y-2004 13:25 FROM: CIRIGIN LONDON +44-207290643 TO: 1633814444 P. 015025 wit.b.out using PAM at all. Instead, dam present tin Me orient audio signal of inferred,1derived from the Orion audio signal is used to yield the required wi.nd.ow svntcI,ing and final. to mask ratio iD.f.orm. on.
Conventionally, Mere is dieorelon conr.x41 loop v.'hi.ch As e 'm.pled data to else available space as1CT co:Eltrols the quanusaio,:: Poise i. ncroduced.. TXi.s is performed In Lee APES st;mdtd. Die.ncsted letups, altl:lough other methods are possible. A prefc=cd. 1mpl.en,cntation of Tic invem.on reduces Me number of loop iceradons needed by using a lookup tidbit to determine the quariisation step size. Tl:,c Jookup table is based on disc Run or SMR clcmrmined f.totn Tic Lyct II flame.
The present Con applies equally die conversion between many ogler audio forbears, including for exanplc, 1<P:EG 1 flayer I1 to EG 1 01 2 I^YCE III, bIPEG 2 Layer II to hIPEO 1 or Layer III, L1PEG Layc.T HI to MEG 1 or 2 I^ycr II and beewcn once DOD AIREC; DUC1JO COrOPúCSS.j.OD formed. liOwcver, rCR].-li:C Cff;C;.CO: BOfRrC b0.SeJ CO1.IVCtS;.OD of MPECT 1 (01 2) LaYC! II SignalS tU M::PEG 1 (01 LaY III sign. ts.O n;est commeTciR]ly irnportanr application.. ThiS is pariienlaTIy useul in, or exam.ple, a DA13 6)itA1 AUd;O BrO8ACRSt) rCCC;Y=, SinCC it.OWS usCt trnSP8rCnt1Y and jn re!;mC [.CCOrd 1)AB bZOadCaSt sna1:e.rial in b1P3 format. :AB iS a dital.radjO DIOadCaSt tCC]3n.O chat is jusc statiLng to heCOIDe COmRner&;9IIY VSI1aBIe W;thin HI]rOPC. I)A.:13 húOaJ.CRStS MPG 1 (Or M.PEG:2) Yer Il. fne.q. h*[P3;.R CUZrdY the rCOúCIinK FOrmt Of CHOiCC fOS PC d hó.d];cld dli..l. qudio plyb,ck. partculsly por:able r0pCl;li.r,LeS SUCh aS he D; amO Rio. The efEue:n.cy of.e preselc implementad.ons means rlmt CPU resou:rces sced s: ot bc full,' devoted to thc fon:r;t conversion process. hat is PrtiCU1.arI! ;mPOr1:an[ in most consu.mor electronics products, where c CPU must bc evailabl.c continuously for. mLnv o.cr ta31. Furthcr information or MP,1SC; /2 ú^yer II n,d, MP6C:; I J: :La,ye: ].IX ca2> i: e found in Sle pe.mnent stanisrs (i) ISO 1 tI2,\ If 2frrnciion kebntogy - Ccding of mo;n,gpic*?r ard asSoriate] F'dia for 4F' .te - dia flt i0 aho l.5 Mb,:.,f.t paff): FO' 99} a.nd 01) [50 {38-3' Irmaon teh'7040=er=0di J"op'-res adarso7aa,cSio InfoPma-;;on- 30. 0, !.
|oio4123 i4-May-04: 01:24::1 14-M6Y-2084 13:25 FRnM:oRIcIN LONDON +44-E07EO90643 TO:B1633B14444 P. 016JO25 Ib.c aborc mcOlods can be i.mplemen.ted in DSP' EPOA or over chip level dcmccs. I,, over aspects of the present i.nvenrioD, there i..; an app..eup programmed to Perform. the shore m.ctb.ods. s
Bnef Descripon of e Dr - nga 0 The isV;nti.on will be decril;d with refier.cce eo thc accompa,nyng dsawings, i.n rhich.
Figum 1 is; a sch.cm.nric of fl prio.r rt M:P:EC; I l:Ar II decoder, Figure is a sc,herriari.c of pnor art: hIP1;C; 1 Lves III e,coder.; and Figurc ls a seb.cmadc of z M1?; Laycr II co MPEG Lyer III converter; rhis its an impl.ementaiion of tlac present inveniion.. L,
Detailed Desctipion The present invention vnJI row le descriled. in relation P - e 3. Note tharlFiguse shors n 'ttsnscod.cr, for thc r.e?l-. mc, soft'are based convers;.on fro.m hIPEG I byer II to MPEG I L^ycr III: this is a cxh:pk ctnbcdi.Tc.r3.t nd shou.ld not bc;al.ct.n to.lim.it thc scope of bc invenuen. Now lso thee:1:5e exm 'r:scode is sornetlmes used in elo:o to device which cn cl.n, d.e b.i. rate of alg:n.1 1ell: ctin Its conp.cssio: f.on;nt. As explained earlier, th.e present invention does not relate to is at, but instead devices whicb. can change tho cox:.prcssion fo:unat of signal. lSit rate alteration is not en. cxcludecl capabili of a transcoder covered by is inrenrion however, as it may!oe an inevital'1e cO1:tscquenec of channg e comptession tortnat of a sial.
|0104123 14-May-04 Oi:24 1 ! 14-4Y-2804 13:25 FROM:ORIIN LONDON +44-2872890b43 TO:B133814444 P. 017025 0r e Ret few years MP? (MPEC; Tayer III) rechnology has become vcr} widclr adopted. The I:lternct has crony sites devoted to music in MP3 font (Rich as h{P3,cotn), ar t hI:P3 players here become widely evulable or1 the high sheet. Layes II rind I,sty III Xó based on the same core icleas, but Layer III adds greater sopl:lsticgtio in order to achier Breath audio compression. The principle diere.nces are: I. use of difEc:rcot or modified psycho-acoustic model 2. use of window 5Witg to Seduce Me effects of pte-eo 3. non-1nca;ti;ioo it. Hufnan coding.
The PAM models Me human auditory system. (E-IAS) and removes sound.. that the HAS cannot detect. It Coca this both in the time Inca frequency domain, vl.lich inrohres expensive nLneric cransforma.dons. Onc of Tie outputs of the PAM is disc psycho a.cousti.c entropy (pe), Ibis quantity is used. to indicate sullen challgcs is the mrsi.c fin called percussive attacks). Percussive attacks can lead to audible attcfacts known. as prc-cóhoes, Dyer llI ted.u.ccs prc-cchocs by using it window.wiching:echnique based on Ehc psycho acoustic entropy.
Tbc no:n-ii.nct qurnti.sation iS very expensive clcttl on process. Ike process suggester by the strand <:so J 1 3' ]#iRrmaton e}7oo, - Comb otrmop,Fmr and oó;o achy far cltaiore made of up on 7.5 dips-part.3: polio) 9} 5C='S From ibid due and there gradually works towards the appropriate qu.=tisatcn step tizc.
As explained above and boom Acts ale a number of umenclly i.nensic Peons that moot be prri;orned on the data during encoding, as shown in tlac prior aft l7c sch.rJm.acic.
lathe decoding process (shown in.c ptlor He lPrc 1 schc,uatic), taking data in MPE(; format and converting it lock to PCM, does nor involve a PAbI M3d is consid.erbly cheaper operation. As explained alcoves this earls decodi::g the M:PEG Iycx II flames.
|0104123: 14-May-04 01:24 j 14-M,PY-2004 i5:86 FROM:ORIIN LONDON +44-20729843 TO:BlS33811444 P.18025 Audio filer.ingJsha.pl; its not mn.ndwd i:' the h1:PEC} sLrlclards, but is applied. by most decoders in order to improve the perception Cat die deccdod ud.io. For da':a conversion ! pu.oscs, this extra proccssiog is ecu as it Visits the onions data The lllusnd 3mplemenb,don i, based on Bee applicauc.n of the followi.r My ideas: 1. Usirg bloc stand dam from iM:PE(; Layer II as the sun clan for MPEC} Layer III, Though Me alcnthm for encoding the subban.d data is identical ire l:ayc II | end III, the usage its different enough bctwccr Tic two in.yers to malce this refuse of lo the subbed clam non-obou.s. By tC-UBi.Og SAC subbed date si - finest s..gB ! the CPU loading Xc possible.
2. The Layer D: data has Steady been through a PAM. Although tl:uc is not d:: e sa,:ne as the PAM used for Leycr III, it 1e very similar. We can then use the flJtC in the sc factors in the Layer 1{ subbancl deco to cstirnatc psyebo;ouRhc entropy. This its then use to deternlse Me ndcv switching.
3. Prom the data n the Ieyex I]: frame (or derived from id it is possible to make good estate of Me Layer IlI sign.l to nasl; Trio {Shy). Inborn Bus quantity good 2c esurnace of arc qu.entiser step size may be calcu1.ted. This results tin si.fic=.e CPU swings., At this point we h eye removed. Me need. for die PAM and for the 13:rbanks.
llenl:rninp; now to Figure 3 the initial stems of the processing are well known, tl.,c MPEG ftamc is dcm,Jl.6plcxed Ed the suhband daea is recneved from e Dame Ed dequanuscd At this point we sop deóod$ the frame and we In not. produce any PCM dam. Tic outputs we take 'ire the scale factors and. e 32 subband coef6.co:s. From the cl:.an.ge In the scale Actors we can calculate a pe equi:va enc. Usi' Tic ch.nn.gc in. the sca1.c factcxs JR the supernal approach to c31cu1ag a pe equivalent; och.c' ices satsfctor ways ts'11icb. me also within |01704123 14-May-04 01:24 1 14-MSY-204 13:26 FROM:ORICIN LONDON +44-287Z09BS43 TO:1633814444 P.01925 the scope oFthe present icon) Elude (a) using cite change in We subband dabs directly or (19 rnulUplying the 5clc factors lay thee subband data co obtain a dc-normalised quant:ty and then USi the cl. in. Tic de- normMiaed quaff to genemm the pc cq,il.ent. The signal to mask ratio (SMR) is calculaced from Me s<:alc factc::s. In fib can. be calcuL re.1 from Sac scale Actors.
Thc sulband coc[ficlonts arc thcr' p.esed direcely into tll.e CT tModiBed I:)isetctc Cosine Trs:n.sform). which ptodu.ces data in 576 gpectral lluc blocIrs' The ipU2Md. iR muse bc read iM thc co:rrect formr.. The pe i.is use:l Do du ermine e appropri.atc willcl.ow (cg. lort, 1rng, ccc.) cas ol pre-echoes.
The Disroroon Conorol block u.sc5 thc MI)CT dah3 snd th.e SMR Th.e SMR is used to flnd an. accute irnal viae for the quntiser seep iizc, so substantial.ly sed.llang tb.e CPU requnements. Tl:,is bl.ocl qu.an.uses the data to fit int:o Ehe allowed nuinbct of bc;s nd con.ol rl:c; di.stor. on;nt:rod.u.ced by is pMCCS5 50 that it d.ocs D.ot exceed th.e 3110wed clistortion lc,rcis.
The data ls then fi:ther compressed by being passed through a. HufEtan cod.e.r, nd rl;'e resultant data is en Formatcd to c snd=d MP EiG lyer III format' The present nv orl is cu:mmemi.ellr i.mple.tneoted. in the Warefinder DAB receivct from Psion Infomeclia Limited of London! United Kingdom c a real-iime, puse suEt:e irr:p].cm.cn=tiO.
cros,.yrns | DA1) 1.Dita1 Auilio 13roadcasrung ! | [iSP | 1)igi.t tl Siú P=cesslg...... I |0104123: :14-May-04 01:24 1 14-MpY-2004 13:26 FROM:ORIGIN LONDON +44-Z07289043 TO:01633814444 P. 020'025 PPGA Floating Polot Ciatc Array HAS Xomó.n Audln,:y Sysmrn hCT Modificd.Discrete Cosine Transfrm MP3 A poorly deficd a.eronyn thac is uSua.11y e= CO mcm T,Layer IIL _ Mong lPiciru:rc Expcrt C1r4up of the ISO. This actonyn s uged her.e to refer eo de sendards issu.cd by thc ISO.
MPEG I An aLIdio coding techlology.
MPEG 2 An tudio codig teebco]ogy used for low bit rate chnels (e'g. speech).
The algorithms usod arc the same as MPE12; 1, but sotre oE the pxamctcrs axe differene.
Rvcho Acous hIod.
PCM Pulse Code Modulation. A very shnple systom of quasing an. audio signal.
Tlis is e method used on C:l:>s.
Psycho acoustic cnopy. One of th.c 0tpll's of de PAM rhst decides thc D== Ia SCFSI Scale Pactot Sc]ctor In.formation. {Jsed in MPEG elcodirg to give : erlhanced comptessicn.
__
! SMR Signl t4 Mank Rano. The amount by which thc slal. exceed' e noise _u __ ! |0104123 14-May-04:01:24: :1
Claims (11)
14-MpY-804 13:26 FROM:ORIC9IN LONDON +44-207209043 TO:BlS33814444 P.021)
025 Claims 1. Al method of conv':reing a first audio 5i.gna1 in. fixer dam compression format, in Rich frame includes subtend cats, to a second studio siA1 in accord data compr.ession format, characterised. in at: Tic subhand data in the first audio signal is used directly or ini$ecy to construct the second audio signal without Tic first audio signal h.avlnE; to be fully decoded prior to encoding in eke second data compression format by the process of the signal co mask ratio applied in the fissr audio sign as inferred. {loom arc scale facing used in the first Audio Signal.' being used to stima.tc tl;'c sin: al to mask ratio required for. e second audio si:ial,
2. The method of Claim I in whic1., the sull:>pnd dam is rlle 32 sul'band analysis co cfficicnts tbt.t me output from FLlcerbnk or crRnsform -:,ch generates 32 subband rCpresC'stseion5 of an input audio stream.
3. Ibe method of Claim. 1 car 2 ire wl.iicl the eseirn.re si3ne1to ma.s1c redo is used to find Me initial. Clue ú.ox Juniper seep size.
4. The method of Claim 3 irk whi.ch lool-up mble its used to deco mC the inidJ value for Me qusnuser step ALSO.
5. The mctbocl. of any preceding Claim IN Welch die first signal is in MPEG I Lays II forma' and the second signal i' in MPEG I or 2 Layer III.
6. The method of any prccedig Claim in which Me First signal is in MP13G Laborer II for:: and the second signal is in MPEC; I or 2 Layer III.
0104123 14-May-04 O1 24 1 14-M'Y-2804 13:27 FROM:ORIGIN LONDON +44-Z07289BS43 TEI:01633814444 P. 0228Z5 7, The method of any prceedi.ng (claim in Reich the firs: signal is in MPE& Boyce. II]: forms and due second 9igDRI iS in MPEG I or 2 Layer II.
8. The metll.od of any prcccUlng Claim in which the At si0, is in MPEG 2 Layct III format and Me second signal is in ull?RC; I of: Layer II.
9. The method of any preceding Aim when pcfox;ned by rel-ane, software program.
10. Apparatus for converting a first auctio si$1, A: a Hat clans compression formats in which a frame includes Hubbard data' to a second sill In a second dam compr.cssion format, in Welch tile apparatus is pi ogmnet co persona any of the methods claimed in any preceding Claims 1 Y.
11. Th.e appatah,s of Claim 10, being I::,S1? chip, FRC;.A chip, or othe:e cl:up level device (0104123 14-May-04 01:24
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GBGB0003954.5A GB0003954D0 (en) | 2000-02-18 | 2000-02-18 | Method of and apparatus for converting a signal between data compression formats |
| GB0104035A GB2359468B (en) | 2000-02-18 | 2001-02-19 | Method of and apparatus for converting an audio signal between data compression formats |
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| Publication Number | Publication Date |
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| GB0410811D0 GB0410811D0 (en) | 2004-06-16 |
| GB2398215A true GB2398215A (en) | 2004-08-11 |
| GB2398215B GB2398215B (en) | 2004-09-22 |
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| GB0410811A Expired - Fee Related GB2398215B (en) | 2000-02-18 | 2001-02-19 | Method of and apparatus for converting an audio signal between data compression formats |
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0637893A1 (en) * | 1993-08-04 | 1995-02-08 | Koninklijke KPN N.V. | Transcoding device |
| EP0661885A1 (en) * | 1993-12-28 | 1995-07-05 | Canon Kabushiki Kaisha | Image processing method and apparatus for converting between data coded in different formats |
| US5530750A (en) * | 1993-01-29 | 1996-06-25 | Sony Corporation | Apparatus, method, and system for compressing a digital input signal in more than one compression mode |
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2001
- 2001-02-19 GB GB0410811A patent/GB2398215B/en not_active Expired - Fee Related
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5530750A (en) * | 1993-01-29 | 1996-06-25 | Sony Corporation | Apparatus, method, and system for compressing a digital input signal in more than one compression mode |
| EP0637893A1 (en) * | 1993-08-04 | 1995-02-08 | Koninklijke KPN N.V. | Transcoding device |
| EP0661885A1 (en) * | 1993-12-28 | 1995-07-05 | Canon Kabushiki Kaisha | Image processing method and apparatus for converting between data coded in different formats |
Also Published As
| Publication number | Publication date |
|---|---|
| GB0410811D0 (en) | 2004-06-16 |
| GB2398215B (en) | 2004-09-22 |
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Effective date: 20090219 |