1、Rec. ITU-R BR.1385 1RECOMMENDATION ITU-R BR.1385*EXCHANGE OF SOUND PROGRAMMES ON RECORDABLECOMPACT DISCS (CD-R)(Question ITU-R 215/10)(1998)Rec. ITU-R BR.1385The ITU Radiocommunication Assembly,consideringa) that the exchange of sound programmes on recordable compact discs (CD-R) is becoming common
2、practice;b) that CD-R equipment is widely available and at low cost;c) that the compatibility with existing CD players must be guaranteed;d) that the alignment levels should be compatible with that of commercial CDs;e) that alignment tones are a very useful means for equipment set up,recommends1 tha
3、t if CD-R discs are supplied for programme exchange, they should conform to the requirements given inAnnex 1.ANNEX 1Exchange of sound programmes on recordable compact discs (CD-R)1 Discs1.1 SpecificationThe CD-R must be recorded according to the “Red Book” standard IEC 60908 1987, Amendment 1, 1992
4、and Amendment 2,1998 “Compact disc digital audio system”.1.2 Quality of the supportBlank discs should be good quality and there must be no obvious surface defects on the blank or recorded disc. (See alsosection 2.1 below.)1.3 ProtectionThe disc must be supplied in an undamaged “Jewel Case”.1.4 Recor
5、ding levelRecordings should be made such that the Permitted Maximum Level, PML, is 3 dBFS (dB Full Scale). (See alsoAppendix, section 1)._*This Recommendation should be brought to the attention of the International Electrotechnical Commission (IEC).2 Rec. ITU-R BR.1385NOTE If the programme material
6、is transferred from a DAT tape, recorded according to EBU Recommendation R64 1992 “Exchange of sound programmes as digital audio tape recordings”, the change in level and other processingdescribed in Appendix, section 2 will be necessary.Other recording levels should be used by prior agreement only.
7、1.5 Line-up toneIt is preferable that the first track of the disc should contain an alignment tone. This should be 30 s of 1 kHz tonerecorded on both channels at Alignment Level, as shown in Table 1.The left and right channels may be differentiated by using an interrupted tone on the left channel, a
8、s specified in EBURecommendation R49 1993 “Tape alignment leader for the exchange of television programmes”.Alignment Level should be 9 dB below PML, that is 12 dBFS, (actually 12.04 dBFS, corresponding to a ratio of 1:4).TABLE 1Digital codes for maximum levels and alignment levels1.6 EmphasisNo pre
9、-emphasis shall be used.1.7 TracksA continuous programme should occupy a single track. If the programme is in sections, then individual sections shouldoccupy separate, consecutively numbered, tracks.2 Accompanying information2.1 LabelsAll CDs and cases should be clearly labelled, indicating programm
10、e details. To avoid possible damage to the disc, itmust only be labelled using methods in accordance with the manufacturers instructions.2.2 Track informationTrack numbers must be documented, along with accurate timings of the programme and sections where appropriate.2.3 Recording reportA completed
11、recording report should accompany all programmes.Maximum coding level (0 dBFS) Audio alignment levelNegative peaks Positive peaks Negative peaks Positive peaks8 000 7FFF E000 1FFFRec. ITU-R BR.1385 3APPENDIX1 Recording levelIn making a CD-R, the aim is to produce a disc that is level compatible with
12、 commercial CDs. Experience has shownthat if the output level of a CD player is set so that 0 dBFS reads “+12” on a IEC type IIb Peak ProgrammeMeter (PPM), then, on average, audio signals from commercial CDs will peak to “+9”. In practice, this works well, andreduces the need for manual level adjust
13、ment.If the replay section of a CD recorder is aligned for 0 dBFS = “+9”, then by setting the record level for unity gain, therecording “headroom” of 3 dB is achieved by default. When the record signals are monitored on a PPM under carefullycontrolled conditions, the 3 dB margin is probably sufficie
14、nt to avoid digital clipping. If true peak reading meters areused on the editor/recorder, the aim should be for occasional peaks to 0 dBFS.2 Copying from DAT recordingsIf a digital copy of a DAT recorded to EBU Recommendation R64 2 is made on CD-R, the following processing willbe necessary: sample r
15、ate conversion from 48 kHz to 44.1 kHz; 6 dB of audio gain to compensate for the 9 dB of headroom allowed on the DAT.During the transfer, the level of the recorded programme should be carefully controlled to prevent overloading.3 Permitted maximum and alignment levelsPermitted Maximum Level reads “+
16、9” on an IEC Type IIb Peak Programme Meter (PPM).Alignment Level is 9 dB below Peak Maximum Level and reads “Test” on an IEC Type IIb PPM. (See Table 2 below.)4 Content of audio tracksWhen preparing material for a CD-R using a digital editor, a lead-in of least ten CD frames should be allowed betwee
17、nthe start of a track and the start of the audio. When using other methods of preparation, there should be at least 1/3 of asecond (25 CD frames) between the start of a track and the start of the audio. Some commercial (classical) CDs have agap of several seconds of “atmosphere”. In practice, most d
18、iscs will be automatically or manually cued on replay, so agap is preferable to a clipped start.If Start IDs are transferred from DAT recordings to be used as track starts on a CD-R, the audio may need to be delayedin order to compensate for processing delays; most converter equipment now provides a
19、djustable delay.5 P-Channel codesSome commercial CDs use “P-Channel coding” to mark the end of each track. Normally, a “flag” in the P-Channel is set“high” during the countdown period at the start of a new track. It then goes “low” when time 00:00 is reached. At thispoint, the INDEX display on the p
20、layer goes from 0 to 1. Many commercial CD recordings do not use the P-Channel atall, nor the countdown period at the start of a track. It appears that only the very first generation of CD players rely on P-Channel information to locate the tracks. It is now given as an option in the Red Book, rathe
21、r than being mandatory. Nooperational problems have been encountered when using discs without P-Channel information, although for consistencywith commercial CDs it is recommended that the P-Channel information is inserted if the recording system allows it tobe.4 Rec. ITU-R BR.1385Some CD manufacture
22、rs now use CD-R as the source for preparing a CD glass master. In this case, they will require thatthe P-Channel information is present.6 Meter readingsThe following table has been compiled from information given in Recommendation ITU-R BS.645 “Test signals andmetering to be used on international so
23、und-programme connections and the specification of the Nordic PPM scaleTechnical Recommendation N10 1993 “Sound Control Systems and Units” (4th edition).TABLE 2Indications produced on various types of programme meter bysine-waves at programme and alignment levelsPPM VuIECType IIECType IIa*IECType II
24、bNordicTest signal Germany, etc. UK EBU NordiccountriesAustralia,N. America,etc.FrancePermitted Maximum Level,PML“0 dB” “6” “+9 dB” “+9 dB” Off scale Off scaleAlignment Level, AL “ 9 dB” “4” “Test” (0 dB) “TEST” “0” “2”Measurement Level, ML “ 21 dB” “1” “12 dB” “12 dB” “12” “10”* This scale is in arbitrary units, NOT in dB.
