1、CCIR RECMN*b46-3 92 H 4855232 0539280 396 W Rec. 646-1 51 RECOMMENDATION 646-1* SOURCE ENCODING FOR DIGITAL SOUND SIGNALS IN BROADCASTING STUDIOS (Question 86/10) (1986- 1992) The CCiR, considering 3 as well as operational facilities; that the introduction G digitai techniques in the studio for broa
2、dcasting applications shou nprove quality b) that there is a need to define a common sampling frequency for sound-programmes and for sound accompanying television programmes in studio applications; cl that this sampling frequency should be simply related to the 32 kHz sampling frequency recommended
3、for transmission links, and for satellite broadcasting by the CCIR in order to reduce the cost of transcoding equipment; d) that the dynamic range has to provide adequate headroom for processing and overload margin, taking into account that a dynamic range equivalent to at least 14 bits per sample r
4、esolution is recommended for some existing broadcasting applications, and a dynamic range equivalent to 16 bits per sample resolution is proposed for some future services, recommends 1. that the sampling frequency for the digitai encoding of sound signals in broadcasting studio applications includin
5、g recording should have a nominal value of 48 kHi; 2. that the sampling frequency for the digital encoding of sound signals in television applications should have the same value; 3. that when an item of digital audio equipment is operating in a free-running mode, the maximum tolerance for the intern
6、al sampling frequency should be t 1 x 10-5. When items of digital audio equipment are interconnected, in sound broadcasting or television applications, provision must exist for locking the internal sampling frequency clocks to an external sampling frequency (e.g., television synchronizing signals, b
7、roadcasting house master clock, high- accuracy clock from a telecommunication network); 4. 5. resolution of 18 bits per sample is advantageous; 6. that the coding used should have a minimum resolution equivalent to 16 bits per sample uniform coding; that where the dynamic range of the service exceeds the equivdent of 14 bits per sample resolution, a that no pre-emphasis should be used. * This Recommendation should be brought to the attention of Study Group 11 and the CMTT.
