1、 Rec. ITU-R BR.1684 1 RECOMMENDATION ITU-R BR.1684 Recording of 5.1-channel audio programmes on video tape recorders (Question ITU-R 58/6) (2004) The ITU Radiocommunication Assembly, considering a) that Recommendation ITU-R BS.775-1 Multichannel stereophonic sound system with and without accompanyin
2、g picture, specifies a five-channel audio system with an additional channel designated for low-frequency enhancement (5.1-channel audio); b) that Recommendation ITU-R BR.1384 Parameters for international exchange of multi-channel sound recordings, specifies track assignments for 5.1-channel audio; c
3、) that Recommendation ITU-R BS.1548-1 User requirements for audio coding systems for digital broadcasting, specifies user requirements for contribution and distribution and further contains information on systems that have been shown to meet the listed requirements; d) that many broadcasters worldwi
4、de are providing television services that include multichannel sound by means of terrestrial, and satellite emission and secondary distribution via cable; e) that the recording of multichannel sound programmes for production and distribution for both standard-definition television and high-definitio
5、n television is now well advanced and that their international exchange for broadcast purposes is increasing; f) that specifications for preferred methods of recording multichannel audio on video tape recorders are needed to avoid operational problems and to facilitate the interchange of recordings,
6、 recommends 1 that when recording 5.1-channel audio programmes on VTRs that can directly record at least six channels of PCM audio, the track assignment, recording characteristics and level alignment should be in accordance with Recommendation ITU-R BR.1384; 2 that when employing bit-rate reduction
7、to allow the recording of 5.1-channel audio programmes on video tape recorders (VTRs) that can directly record four channels of PCM audio for the purposes of contribution and distribution: a two-channel stereo compatible version of the programme should be recorded on tracks 1 and 2, with the left ch
8、annel on track 1 and the right channel on track 2; the 5.1-channel audio programme should be encoded by a low bit-rate audio coding system that reduces the data rate to a value that can be recorded in an AES3 channel pair on the VTR; 2 Rec. ITU-R BR.1684 the audio coding system employed should meet
9、the requirements for contribution and distribution listed in Annex 1 of Recommendation ITU-R BS.15481; the low bit-rate encoded audio to be fitted into an AES3 compatible data stream may be formatted per SMPTE 337M-2000; the track assignment, recording characteristics and level alignment at the inte
10、rfaces into and out of the audio coding system should be in accordance with Recommendation ITU-R BR.1384; the low bit-rate encoded audio data stream should be recorded on tracks 3 and 4 of the VTR. NOTE 1 SMPTE Standard 337M-2000 is given in Annex 1 and is also available in electronic form at the IT
11、U website: http:/www.itu.int/ITU-R/study-groups/sg/sg6/smpte/. SMPTE Standard 337M-2000 refers to version 2000 only, which is the version approved, by administrations of Member States of the ITU and Radiocommunication Sector Members participating in the work of Radiocommunication Study Group 6 in ap
12、plication of Resolution ITU-R 1-3. By agreement between ITU and SMPTE, this version was provided and authorized for use by SMPTE and accepted by ITU-R for inclusion in this Recommendation. Any subsequent version of SMPTE Standard 337M, which has not been accepted and approved by Radiocommunication S
13、tudy Group 6 is not part of this Recommendation. For subsequent versions of SMPTE documents, the reader should access the SMPTE website: http:/www.smpte.org. Annex 1 SMPTE Standard 337M-2000. 1Recommendation ITU-R BS.1548 specifies that, for an audio coding system employed for contribution and distr
14、ibution: “The quality of sound reproduced after a reference contribution/distribution cascade (five contribution codecs and three distribution codecs working consecutively) should be subjectively indistinguishable from the source for most types of audio programme material. Using the triple stimuli d
15、ouble blind with hidden reference test, described in Recommendation ITU-R BS.1116 Methods for the subjective assessment of small impairments in audio systems including multichannel sound systems requires mean scores generally higher than 4.5 in the impairment 5-grade scale, for listeners at the reference listening position. The worst rated item should not be graded lower than 4 (Recommendation ITU-R BS.775).”
