A 160 KBPS, HAR KUNNUWA MAFI KAIFI BA SA IYA DOKE CODEC ƊIN

Matsawa mai asara (lossy compression) ita ce babbar hanyar rarrabawa da yaɗa kiɗa. Codec yana jefar da wani ɓangare na sautin, yana caca cewa kunnen ɗan adam ba zai rasa shi ba. Opus, codec na buɗaɗɗen tushe da Internet Engineering Task Force ta daidaita, ana amfani da shi sosai wajen yaɗawa; yana haɗa injin ɗaya da aka tsara don magana da wani da aka tsara don kiɗa, kuma littattafan da marubutan suka ambata sun gano ya fi MP3, Vorbis ko HE-AAC a daidai bitrate ɗaya.

Duk da haka, galibin gwaje-gwajen saurare masu kulawa na Opus sun mai da hankali kan magana da ƙananan bitrate. Benjamin Martin da Romain Hennequin, na Deezer Research, sun yi wata tambaya mai sauƙi: daga wane bitrate ne kiɗan da aka matse ba zai yiwu a bambance shi da asali mara matsawa mai ingancin CD ba? Sun lura cewa gwaje-gwajen al’umma sun nuna alamar amsa, amma ba tare da sakamako na hukuma da za a iya maimaitawa ba.

Gwajin da aka gina don kama ƙananan kurakurai

Sun yi amfani da daidaitaccen ma’auni na duniya don gano ƙananan lahani, ITU-R BS.1116-3. A kowane gwaji, mai sauraro yana fara jin asali mara matsawa, wanda aka yi wa lakabi da haka. Sannan gutsuttsura biyu na makafi suna zuwa, A da B: ɗaya shi ne wanda aka matse, ɗayan kuma kwafin asalin ne da aka ɓoye. Mai sauraro yana ba duka biyun maki daga 1 (“mai ɓata rai sosai”) zuwa 5 (“ba a iya ji”), kuma dole ne koyaushe ya ba ɗaya daga cikinsu daidai 5.0, ko da yana nufin yin hasashe. Makin da ke da muhimmanci shi ne giɓin da ke tsakanin makin wanda aka matse da na asalin da aka ɓoye.

An sarrafa komai: ɗakuna keɓaɓɓu da hayaniyar muhalli ƙasa da decibel 32, belun kunne masu rufe baya da aka daidaita a kwance, zama na mintuna 30 a mafi yawa tare da hutun sa’a guda a tsakaninsu, da wani nau’i mara kyau da gangan na 32 kbps da aka saka cikin kowane zama don tabbatar da cewa masu sauraro suna iya jin wani abu ko kaɗan.

An zaɓi kiɗan don ya zama mai wahala: gutsuttsura 23, ciki har da samfura bakwai mafi muni daga wani ma’aunin al’umma da guntaye masu wadatar harmonics masu yawa, kamar igiyoyin da ake tsinkawa, waɗanda aka san suna damun codec ɗin. Ma’aikata 26 na Deezer masu sa kai sun shiga, ban da marubutan; biyar sun kasa wuce tantancewa — biyu saboda karya dokoki, uku saboda ba su iya gano nau’in 32 kbps da tabbaci ba — suka bar 21.

128 ya wuce, sannan aka kama shi

A mataki na farko, an gano kilobit 32 da 64 a daƙiƙa a fili. Ba a gano 128 kbps ba: matsakaicin giɓinsa na maki −0.08 bai bambanta da sifili a ƙididdiga ba (p = 0.456). Amma ya ɗan kasa wani gwaji mafi tsauri da ke neman tabbataccen hujja ta daidaito a cikin ±0.25 maki.

Don haka ƙungiyar ta gina mafi munin yanayi. Ta amfani da samfurin ƙididdiga da ke raba yadda kowane mai sauraro yake da tsananin bincike da yadda kowane gutsure yake bayyanawa, sun riƙe masu sauraro 10 mafi tsananin bincike da gutsuttsura 8 waɗanda lahaninsu ya fi sauƙin ji kawai, suka sake gwadawa a 32, 96, 128 da 160 kbps. A ƙarƙashin wannan bincike, an gano 128 kbps (giɓi −0.24, p = 0.030).

160, ba a iya bambancewa

A 160 kbps, giɓin ya faɗi zuwa −0.04 (p = 0.747): waɗannan kunnuwan ƙwararru ba su sake bambance shi da asalin ba. Kuma a wannan karon gwaji mafi tsauri ma ya wuce (p = 0.024), yana ba da tabbataccen hujjar ƙididdiga ta daidaito.

Ƙarshen maganar marubutan yana da matakai biyu. Ga jama’a gaba ɗaya, 128 kbps tuni ba ya nuna wani muhimmin lalacewa. Don saurare mai tsananin bincike kan abubuwa mafi wahala, ana buƙatar 160 kbps don kaiwa ga rashin bambanci a ji (perceptual transparency). Suna mai da hankali kan iyakarsa: samfurin belun kunne ɗaya, kwamitin da aka zaɓo daga kamfani ɗaya, da masu sauraro goma kawai a mataki mai yanke hukunci. Gwaji da wasu kayan aikin masu son sauti (audiophile) da ƙarin rukunin ƙwararru, in ji su, za a buƙace shi kafin a kira wannan iyaka ta duniya baki ɗaya. An fitar da sakamakonsu, bayanan masu sauraro da aka ɓoye sunayensu da halayen gutsuttsuran ga jama’a, ga duk wanda yake son gwadawa.