g711

• dijital ses görüşmelerinde kullanılan, herhangi bir sıkıştırma algoritması kullanmayan ses codecidir.
  kendileri tek bir ses görüşmesi için 64kbps'lik bantgenişliği isterler. dolayısıyla ses kalitesi pürüzsüzdür.
• sikistirma kullanip daha az bandwidth isteyen codec'ler icin (bkz: g729) hatta (bkz: g723)
• g blok 7. katta yer alan sınıf/oda.^*
• formel adı pulse code modulation of voice frequencies'tir, pcm'i logaritmik yöntemle 8000 örnek/saniye ile gerçekleştirir...yüksek ses kalitesi sağlaması, kolay manipule edilmesi, asr için en uygun codec olması gibi avantajlara, düşük ağ verimi gibi dezavantajlara sahiptir...
• hd voice kodekleri çıkana kadar en kaliteli ses'in elde edildiği kodek tipi idi. 64kbps bantgenişiği gerektirir. g.729 ve g.723 gibi daha az bantgenişliği gerektiren kodeklere göre ses kalitesi oldukça iyidir.
• iki türü vardır. ulaw ve alaw. özet geçersek tek farkı ulaw amerikada, alaw avrupada kullanılır.
  
  "u-law (pronounce mu-law, the u is a greek mu) and a-law operate in the same way; that is they both sample audio at 8khz and taking into account low frequency and anti-alias filters give the standard telephony frequency response of 300hz to 3400hz.
  
  in a-law the audio is sampled with a 13 bit resolution and u-law with 14 bit resolution. what they then do is logarithmically compress the amplitudes so in both cases you compress the amplitude down to 8 bits. 8 bits at 8khz gives 64kbit bandwidth.
  
  the reason the amplitudes are compressed to 8 bits is because the human ear is sensitive to sound in a logarithmic fashion. most people simply won't notice the quantisation used for amplitude compression for a voice conversation. when u/a-law is received it's expanded back to it's original 13 or 14 bits. this way you get up to 14 bits of dynamic range using only 8 bit values. the difference between u-law and a-law are the parameters used to define the logarithmic function (the chords and from memory, exponent).
  
  europe, australia and most of the rest of the world use the a-law parameters and the usa and a few others use u-law. the itu g.711 standard spells out the parameters for both u-law and a-law and at the back of the document it provides a translation table for about 40 values that need to be mapped to ensure a good translation between both laws.
  
  the reason any voip provider is using u-law here in .au is because they are using usian software and equipment. if the u-law/a-law translation is done properly between the voip provider and pstn gateway as per the standard then you won't notice a thing."