Q67101-H6773 Просмотр технического описания (PDF) - Infineon Technologies

Номер в каталоге

Компоненты Описание

Список матч

Q67101-H6773

Joint Audio Decoder-Encoder - Multimode

Infineon Technologies 

PSB 7238

Introduction

1.7

System Integration

Example of integration in ISDN/analog videophone:

The first example represents a low-cost solution for a desk-top standalone videophone

that connects to an ISDN S0 bus (ISDN basic access) or an analog telephone line.

The ISDN basic access consists of two 64 Kbit/s so-called B-channels to carry user

information (voice, data, …), and a separate 16 Kbit/s D-channel primarily used for

signaling. The video and audio are both compressed so that they are carried, along with

additional control information, in the two B-channels, or 128 Kbit/s.

The analog telephone line can carry up to 33.6 Kbit/s using a V.34+ modem.

The general aspects of videotelephony are covered by ITU-T H.320/H.324

recommendations. The video is compressed according to the H.261 (sometimes called

“p × 64”) or the H.263 recommendation.

For the ISDN videophone (H.320) the compressed video and audio signals are

multiplexed together with additional synchronization and control information into two

B-channels, which are separately switched via the network and thus have to be

resynchronized at the other end. The multiplexing and resynchronization of the

B-channels is specified by the H.221 recommendation (see Figure 4).

For the analog videophone (H.324) the compressed video and audio signals are

multiplexed together with additional control information into a single communication link.

The multiplexing is specified by the H.223 recommendation (see Figure 4).

Figure 4

Using non-parametric compression techniques, audio can be compressed to 64 Kbit/s

PCM (logarithmical A- or µ-law approximation for 3.1-kHz voice acc. to G.711) or

48/56/64 Kbit/s sub-band coded adaptive PCM (for 7-kHz audio acc. to G.722). This

leaves, however, only approximately 64 Kbit/s for video on the ISDN which, at this rate,

yields only a marginally good picture quality. For the analog videophone it’s not even

possible to transfer only audio at this data rate.

Semiconductor Group

18

Data Sheet 1998-07-01

Share Link: