1、CCIR RECMN*iqb 72 4855232 0520033 490 I Rec. 796 1 RECOMMENDATION 796 PARAMETERS FOR ENHANCED COMPATIBLE CODING SYSTEMS BASED ON 625-LINE PAL AND SECAM TELEVISION SYSTEMS (Question 42/11) ( 1992) The CCIR, considering a) and sound, including wider aspect ratio; that there are proposals to introduce
2、new systems of television broadcasting with improved quality of picture b) c) d) e) systems; 0 compatibility; that many broadcasting organizations will wish to enhance the quality of their existing services; that the majority of television receiving installations can receive only terrestrial transmi
3、ssions; that most broadcasting organizations are committed to maintaining a service to these viewers; that enhancements of existing terrestrial standards must maintain RF compatibility with current broadcasting that enhancements of existing terrestrial standards must maintain a high degree of pictur
4、e and sound 8) of enhancement ideaily required are: that in order to deliver improved images and sound by enhanced television transmission, the principal areas picture - wider aspect ratio; - reduced cross-effects; - ghost cancellation; - enhanced resolution; sound - digitai multi-channel sound; tha
5、t a modular approach to enhancements will ailow flexibility for different broadcasters to implement those h) enhancements independently or collectively; j) and SECAM enhancements, that for economical processing in the receiver, there is an advantage to maximize the commonality for PAL recommends tha
6、t, when enhancements to existing PAL or SECAM television systems are made, some or ail of the modular enhancement methods should be used, according to the following specification: 1. Picture enhancement techniques 1.1 Coder requirements for accommodating wide aspect ratio signals a) Method of format
7、 conversion from 16:9 to 4:3 b) Method of encoding additional information: - - method of deriving additional information; method of processing the additional information; - method of including the additional information in the broadcast signai. COPYRIGHT International Telecommunications Union/ITU Ra
8、diocommunicationsLicensed by Information Handling Services2 1.2 1.3 1.4 1.5 2. CCIR RECMN*79b 92 U 4d55252 0520034 327 Rec. 796 Coder requirements for reducing cross-eflecb and making optimal use of the signal spectrum a) Method of luminance filtering b) Method of chrominance filtering c) Method of
9、modulation d) Method of combining lumincmce and chrominance. Ghost cancellation a) Insertion test waveform b) Position in the signal. Coder requirements for increased resolution a) Method to derive extra information b) Method of including the extra information in the channel. Data signalling a) Deta
10、ils of the data waveform b) Position in the signal c) Data to be transmitted. Sound enhancement methods a) b) andjirther recommends Details of the sound coding technique Method of including the sound signal, that enhanced terresuial television broadcasting should not cause interference subjectively
11、greater than that considered acceptable with current broadcasting services in the VHFNHF bands. The main features of such a system, emphasizing the modular approach, are shown in the block diagram of an enhanced coder given in Fig. 1. The considerations to be borne in mind for each of the above cate
12、gories are described in more dedl in Annex 1. Note I - Administrations are invited to conduct further studies with the aim of making more specific proposals. COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling ServicesCCIR RECMN*7b i! 4855232 0520
13、035 263 - R, G, B input wide Augmentation - signai processing Augmentation signai aspect ratio signai -I- d Rec. 796 FIGURE 1 Block diagram of enhanced coder 413 aspect ratio signai .I I Y.C multi-dimensionai pre-coding processing 3 Compatible baseband composite signai I / 7 / Signalling signai Sign
14、alling for decoder control t Test signai Ghost test signai I for ghost I cancelling I To video/sound mixing Sound processing Sound input COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling ServicesCCIR RECflN*79b 92 m ld5523r2 05OQ3b 3rTT 4 Rec. 7
15、96 ANNEX 1 Factors which wlll Influence the choice of parameters 1. Picture enhancement techniques 1.1 Wide aspect ratio coding There are three approaches to accommodating the wide aspect ratio frame in a conventional 4:3 signal: 1.1.1 The letter-box format Widescreen displays with a 169 aspect rati
16、o are being made in Europe for enhanced television services. The most straightforward way to convey the 16:9 signal in the 625-line PAL/SECAM channel, and at the same time preserve the correct geometry for the viewer with a standard 43 receiver, is to use a letter-box format, In this format 432 of t
17、he 575 active lines are used to carry the 16:9 active picture area. In the widescreen receiver, the 432 lines are arranged, by up-conversion or other means, to fill the full height of the display. In the standard 4:3 receiver the viewer sees bhck bands above and below the active picture. 1.1.2 The s
18、de=panel approach The side-panel approach involves conveying additional picture information that is invisible to the 4:3 aspect ratio receiver, which in principle, continues to display a normal picture with full vertical and horizontal resolution. The enhanced widescreen receiver recovers this extra
19、 information and “stitches” the edges onto the central portion of the picture, to recreate a widescreen picture for l6:9 aspect ratio display. The additional picture information required for the side panels could be carried in various ways, including: - - - - quadrature modulation of the vision RF c
20、arrier; signals carried in the Fukinuki hole in human vision; signais cmied in the vertical blanking interval; signals cGed at the extremities of each active picture line, that would not normally be visible on conventional televisions due to overscan. 1.1.3 Window options There are several posible c
21、hoices for a compromise “letter-box” window solution, and one of these could be the mean aspect ratio between 43 and 169, i.e., 149. In this case, the blank bands displayed on a conventional 43 aspect ratio receiver would be reduced from the 125% of a 169 letter-box to some 6% of full picture height
22、 at top and bottom. However, in practice, the viewer would be likely to see only about 2% black bands, due to the typical receiver overscan. 1.2 Reduction of cross-effects Two approaches have been considered for reducing cross-effects in the PAL system, known in broad terms as band segregation and p
23、hase segregation. Band segregation is the simplest method to understand because the luminance and chrominance components are separated in the frequency domain. In the phase segregation method, high frequency luminance and chrominance signals are effectively carried on orthogonally-phased subcarriers
24、. Both methods involve complex multi-dimensional comb filter processing. It remains to be seen whether similar techniques can be applied in the SECAM systcm. COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling ServicesCCIR RECMN*796 92 4B55212 052
25、0037 036 Rec. 796 5 1.3 Ghost cancellation Proposals for ghost cancellation depend on the use of a test line signai. The form of the signal would consist of a rectangular pulse with sin xlx edges. The proposais for the duration and position of the pulse in the test line vary. Alternatively, the use
26、of a pseudo-random data sequence or the use of existing insertion test line signais has been proposed. In most cases there is the difficult requirement to allocate a test line in the already crowded vertical blanking interval. 1.4 Increased resolution In the circumstance where the source signal stan
27、dard contains more resolution than conventionai composite signals, there are proposals to include this information in the compatible enhanced signai. Such information might be accommodated by spectmm folding techniques and conveyed in the signal by coding methods such as those listed for the side-pa
28、nel approach in 5 1.1.2. 1.5 Dab signalling The enhanced signal coder would need to include information on the status of the coder processing methods to the decoder. Such information might simply indicate which parameters are being used in the coder or could consist of signal-related information, su
29、ch as movement vectors, to assist the decoder in, for example, up-conversion processes in the display. 2. Sound coding It is expected that improved quality sound coding, by digital means, will form an important enhancement to the broadcast composite signal. The choice of technique needs to be made in association with other requirements in the signal. COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services
