Detection of average luminance levels in different areas of a video image, and automatic discrimination of the image display format based thereon

Abstract: A high precision aspect ratio auto-discrimination apparatus used for display apparatuses and television receivers comprising: an apparatus for detecting the upper edge and lower edge of a letter box picture through detecting the average luminance of every horizontal scan period; an apparatus for detecting respective average luminance levels in a plurality of specific regions in one field picture controlled by a horizontal synchronous signal and a vertical synchronous signal; and, an aspect ratio discrimination section to which the outputs of said both apparatuses are input.

Description: BACKGROUND OF THE INVENTION The present invention relates to an average luminance level detection apparatus for detecting an average luminance level in a specific region in the picture of one field of an video signal obtained from television receivers or VCR, and to an aspect ratio auto-discrimination apparatus using said average luminance level detection apparatus. Recently, wide screen displays such as ones of aspect ratio 16:9 used in wide screen television receivers and Hi-Vision television receivers (high definition television receivers in Japan) have been spread. To utilize the display such as of aspect ratio 16:9 effectively, aspect ratio auto-discrimination apparatuses for discriminating the aspect ratio of a video signal automatically to change picture display regions has become important. Hereafter an aspect ratio auto-discrimination apparatus in the prior art will be illustrated referring to Fig. 6 and Fig. 7. Fig. 6 is a block diagram of an aspect ratio auto-discrimination apparatus in the prior art, and Fig. 7 shows the relation between input video signal and luminance distribution. In Fig. 6, 12 is an integration circuit for integrating a digitized luminance signal Y for one horizontal scan period, 13 is a division circuit for dividing the output of integration circuit 12 by a sample number of the integration, 14 is a comparator circuit for comparing the output of division circuit 13 and a predetermined reference value, 15 is an edge detection circuit for detecting picture upper edge position 23 and picture lower edge position 24 in a picture such as of a letter box signal of an aspect ratio 16:9 as shown in Fig. 7 (a), through inputting the output of comparator circuit 14 for one field picture period, 31 is an aspect ratio discrimination section for discriminating the aspect ratio and to which section is input the output of edge detection circuit 15. The performance of an aspect ratio auto-discrimination apparatus in the prior art constituted as described above will be illustrated referring to Fig. 6 and Fig. 7 (a). First, a digital luminance signal Y is integrated by integration circuit 12 every horizontal scanning period. The value after the integration is divided by division circuit 13 to calculate an average luminance level in every horizontal scanning period. The calculated average luminance level and a predetermined reference value are compared in comparator circuit 14 and it is judged whether the average luminance level is higher or lower than the reference value. This result is input to edge detecting circuit 15 for one field period to obtain a picture upper edge position 23 and picture lower edge position 24 as shown in Fig. 7 (a), and the vertical size of the picture is calculated from the upper edge position information and the lower edge position information, and that said luminance signal Y is a letter box signal can be detected. However, with the above constitution, when the picture is special as shown in Fig. 7 (b), even if the aspect ratio of an input signal is 4:3, false picture upper edge position 23' and false picture lower edge position 24' are detected and the signal which should be properly judged as a video signal of aspect ratio 4:3 is mis judged as a letter box signal. Further prior art aspect ratio auto-detecting apparatuses are disclosed in EP-A-0624031, JP-A 05300448 and JP-A-07058973, all of which monitor the luminance signal of a video signal to detect upper and lower edges of a picture in similar manners to that already described above. However, in all of the above constitutions, the problem of misjudging the picture of aspect ratio 4:3, as shown in Fig. 7(b) herein, remains. SUMMARY OF THE INVENTION Considering the above problem, the invention provides an average luminance level detecting apparatus as defined in claim 1, for improving the discrimination rate of an aspect ratio auto-detecting apparatus by detecting average luminance levels in a plurality of vertical specific regions of a video signal, and an aspect ratio auto-detecting apparatus as defined in claim 2, including the average luminance level detecting apparatus as a constitutional element. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram of an average luminance level detection apparatus of a first embodiment of the invention. Fig. 2 is a block diagram of a control pulse generation circuit of the first embodiment of the invention. Fig. 3 is a timing chart of the control pulse generation circuit of the first embodiment of the invention. Fig. 4 is a drawing showing the sampling regions of a luminance signal by the average luminance level detection apparatus of the first embodiment of the invention. Fig. 5 is a block diagram of an aspect ratio auto-discrimination apparatus as a second embodiment of the invention. Fig. 6 is a block diagram of an aspect ratio auto-discrimination apparatus in the prior art. Fig. 7 (a) a drawing showing the luminance distribution and the picture upper edge and lower edge of a letter box signal. (b) a drawing showing the luminance distribution and the false picture upper edge and lower edge of a special signal of aspect ratio 4:3. [EXPLANATION OF THE REFERENCE NUMBERS] 1: counter 2: control pulse generation circuit 3, 4, 5, 12: integration circuit 6, 7, 8, 16: flip-flop 9, 10, 11, 13: division circuit 14: comparator circuit 15: edge detection circuit 17, 18, 19: coincidence detection circuit 20, 21, 22: average luminance level detection region 23: picture upper edge position of a letter box signal 23' : false picture upper edge position 24: picture lower edge position of a letter box signal 24': false picture lower edge position 25: average luminance level detection apparatus of the invention 26: aspect ratio discrimination section 27: edge detection section constituting an aspect ratio auto-discrimination apparatus in the prior art 28, 29, 30: average luminance level signal 31: aspect ratio discrimination section in the prior art EXEMPLARY EMBODIMENT A 1ST EMBODIMENT An average luminance level detection apparatus which is a first embodiment of the invention comprises: three integration circuits; three flip-flops; three division circuits; a counter; and a control pulse generation circuit. In the above constitution, a digital luminance signal Y is input to three integration circuits, in which the luminance signals of respective different regions are integrated, and each of obtained integration results is latched in each of the flip-flops, and the results are divided by division circuits by the number of samples integrated. As a result, the average luminance levels of the field intervals can be detected in three regions. Said three regions are respectively set at the center portion of the picture, near the left end of the picture, and near the right end of the picture. The constitution of an average luminance level detection apparatus of the first embodiment of the invention will be illustrated referring to the drawings. Fig. 1 is a block diagram of an average luminance level detection apparatus of the first embodiment of the invention. Said average luminance level detection apparatus comprises: a counter 1 to which a pulse signal H synchronized with a horizontal synchronizing signal is input as a reset input; a control pulse generation circuit 2 to which the count output CN of said counter 1 is input; a first integration circuit 3 to which a luminance signal Yand a first output P1 of said control pulse generation circuit 2 are input; a second integration circuit 4 to which the luminance signal Y and a second output P2 of said control pulse generation circuit 2 are input; a third integration circuit 5 to which the luminance signal Y and a third output P3 of said control pulse generation circuit 2 are input; a first flip-flop 6 to which the output Q1 of said first integration circuit 3 and a vertical synchronizing signal V as a trigger input are input; a second flip-flop 7 to which the output Q2 of said second integration circuit 4 and the vertical synchronizing signal V as the trigger input are input; a third flip-flop 8 to which the output Q3 of said third integration circuit 5 and the vertical synchronizing signal V as the trigger input are input; a first division circuit 9 to which the output T1 of said first flip-flop is input; a second division circuit 10 to which the output T2 of said second flip-flop is input; a third division circuit 11 to which the output T3 of said third flip-flop is input. The performance of the average luminance level detection apparatus of the first embodiment constituted as above will be illustrated referring to Fig. 2, Fig.3, and Fig.4. First, counter 1 counts clock pulses one by one from 0 using the pulse signal 11 synchronizing with a horizontal synchronizing signal as a reset input. When the clock frequency is 14.3 MHz, the counter counts from 0 to 909. Control pulse generation circuit 2 receives as an input the count output CN of counter 1 and generates pulse signals P1, P2, and P3 which become high levels for certain periods respectively. In the case where the control pulse generation circuit 2 is constituted as shown in Fig. 2, the count output CN of counter 1 is first latched by flip-flop 16. The output of the flip-flop 16 is input to coincidence detection circuits 17, 18, and 19, and compared with reference count numbers A, B, and C respectively. When the output of flip-flop 16 coincides with reference count numbers A, B, and C, coincidence detection circuits 17, 18, and 19 output high level signals respectively. When coincidence detection circuits 17, and 18, and 19 are constituted so that the widths of said high level signals become that of eight clock pulses, a timing chart of control pulse generation circuit 2 is as shown in Fig. 3. Integration circuits 3, 4, and 5 perform integration only while the outputs P1, P2, and P3 of control pulse generation circuit 2 are in high level. By this performance, said integration circuits 3, 4, and 5 can integrate the luminance level only in a certain span of a horizontal scan period. Flip-flops 6, 7 and 8 are operated utilizing a vertical synchronizing signal V in which is used to reset the outputs Q1, Q2, and Q3 of the integration circuits 3, 4, and 5 at the top position of the picture and latch them at the bottom position of the picture. Division circuits 9, 10, and 11 divide the outputs T1, T2, and T3 of flip-flops 6, 7, and 8 by the sample numbers of integration effected by integration circuits 3, 4, and 5 and output average luminance level signals 28, 29, and 30 showing average luminance levels 1, 2, and 3. As described above, average luminance levels 1, 2, and 3 of respective regions 20, 21, and 22 for the luminance signal of one field period can be detected as shown in Fig. 4. Here, the average luminance level detection regions are illustrated as three, but the number of regions is not limited to three, and the number of constituting circuits may change according to the number of regions. 2ND EMBODIMENT An aspect ratio auto-discrimination apparatus which is a second embodiment of the invention will be illustrated referring to drawings. A block diagram of said aspect ratio auto-discrimination apparatus is shown in Fig. 5. Said aspect ratio auto-discrimination apparatus comprises: an edge detection section 27 to which is input a luminance signal Y and which section outputs picture upper edge 27a and lower edge 27b signals and has been used in conventional examples; an average luminance level detection apparatus 25 to which is input the luminance signal Y and which apparatus outputs average luminance level signals of a plurality of regions and was shown as the first embodiment; and an aspect ratio discrimination section 26 which is input the output of said edge detection section 27 and the output of said average luminance level detection apparatus 25 and outputs an aspect ratio discrimination signal. We set following condition 1 that using said edge detection section 27, picture upper edge position 23 and picture lower edge position 24 as shown in Fig. 7 (a) are detected and said condition 1 is defined from said upper to said lower edge. Further we set a following condition 2 where all of average luminance level 1 of region 20 shown in Fig. 4 detected by average luminance level detection apparatus 25, average luminance level 2 of region 21, and average luminance level 3 of region 22, are intermediate between respective predetermined minimum reference values and maximum reference values. When both of the conditions are satisfied,the picture is discriminated as a wide aspect ratio, for example 16:9. When both of the conditions or one of them are not satisfied, the aspect ratio is discriminated as not wide aspect ratio, that is, the aspect ratio is discriminated as 4:3. Next, as mentioned in the claim 4, when both of said condition 1 and condition 2, or one of them are not satisfied, the aspect ratio discrimination action is repeated. If the result shows both conditions are satisfied, that the aspect ratio is wider than 4:3, for example 16:9 can be discriminated. Above is illustrated about an apparatus constitution and its method in which, based on a picture of aspect ratio 4:3, a wide picture such as of an aspect ratio 16:9 is discriminated though, the reverse is possible. As illustrated above, in the present invention, by discriminating an aspect ratio using the upper edge position information and lower edge position information of the picture obtained from an aspect ratio auto detection apparatus in the prior art and the average luminance level information of the picture, the misjudge rate of the aspect ratio of a video signal which have no aspect discriminating signal can be lowered, and its practical effect is large.

Claims: An average luminance level detection apparatus comprising: a counter (1) to which a pulse signal (H) synchronized with a horizontal synchronizing signal is input as a reset input and by which a clock pulse is counted; a control pulse generation circuit (2) to which the count output (CN) of said counter is input and by which a plurality of pulses (P1,P2,P3) controlled by a plurality of reference count numbers (A,B,C) are generated in each period between resets of said counters; a first integration circuit (3) for integrating a luminance signal (Y) of a video signal in the periods controlled by a first output (P1) of said control pulse generation circuit; a second integration circuit (4) for integrating the luminance signal (Y) in the periods controlled by a second output (P2) of said control pulse generation circuit; a third integration circuit (5) for integrating the luminance signal (Y) in the periods controlled by a third output (P3) of said control pulse generation circuit; a first flip-flop (6) to which the output (Q1) of said first integration circuit and a vertical synchronizing signal (V) as a trigger signal are input; a second flip-flop (7) to which the output (Q2) of said second integration circuit and the vertical synchronizing signal (V) as the trigger signal are input; a third flip-flop (8) to which the output (Q3) of said third integration circuit and the vertical synchronizing signal (V) as the trigger signal are input, wherein said vertical synchronizing signal resets the outputs of said integration circuits at the top position of a picture and latches said outputs at the bottom position of the picture ; a first division circuit (9) for dividing the output (T1) of said first flip-flop by the number of samples integrated by said first integration circuit; a second division circuit (10) for dividing the output (T2) of said second flip-flop by the number of samples integraded by said second integration circuit; and a third division circuit (11) for dividing the output (T3) of said third flip-flop circuit by the number of samples integrated by said third integration circuit, the divided outputs from said division circuits being provided as average luminance level outputs (28,29,30) of said apparatus. An aspect ratio auto-discrimination apparatus for detecting an aspect ratio of an input video signal, comprising: an integration circuit (12) for integrating a luminance signal (Y) for one horizontal scan period; a division circuit (13) for dividing the value integrated by said integration circuit by the number of samples of the integration; a comparator circuit (14) for comparing the output of said division circuit with a predetermined reference value; an edge detection means including an edge detection circuit (15) for detecting the upper edge position and lower edge position of a picture from the compared information of said comparator circuit during one field period, and for outputting respective upper and lower edge position signals; the average luminance level detection apparatus (25) defined in claim 1; and an aspect ratio discrimination means (26) to which the output signals of said edge detection means and the output signals of said average luminance level detection apparatus are input and which is arranged to detect an aspect ratio of the input video signal, from said output signals. The aspect ratio auto-discrimination apparatus of claim 2, wherein a detected condition corresponding to a position from said picture upper edge position to said picture lower edge position except the top position and bottom position of the picture of a first aspect ratio detected using said edge detection means is defined as condition 1, wherein a condition when all of the outputs of the average luminance level detection apparatus of claim 1 are intermediate values between respectively predetermined minimum values and maximum values is defined as condition 2, and wherein when both of the conditions are satisfied, the aspect ratio of the picture is discriminated as wider than the first aspect ratio. The aspect ratio auto-discrimination apparatus of claim 3, wherein said first aspect ratio is a ratio of 4:3 The aspect ratio auto-discrimination apparatus of claim 3, wherein when both the condition 1 and condition 2 are not satisfied, the discriminating actions are repeated, and if both of the conditions are satisfied after the repeating, the aspect ratio is discriminated as wider one than the first aspect ratio.

Inventors: OKUMURA NAOJI, TANI MASAHIRO, OKUMURA, NAOJI, TANI, MASAHIRO
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1995
Main classification: H04N5
IPC codes: H04N5