201105131 六、發明說明： 【發明所屬之技術領域】 [0001] 本發明係有關去交錯（de-i nter 1 ac i ng )轉換，特別是 關於一種字幕區偵測方法，據以進行去交錯。 [先前技術3 [0002Γ —般的電視廣播視訊信號係採用交錯（interlaced)格 式，例如NTSC、PAL、SECAM，其以奇圖場（Held)及 偶圖場依序交錯顯示於電視機螢幕，利用視覺暫留原理 來顯示出圖框（frame)的視訊内容。交錯視訊信號僅需 ^ 使用低頻寬即可傳送可接受的視訊品質；然而，其缺點 為造成垂直解析度的降低、線條或區域的閃爍（f 1 icker )現象。一般電腦顯示器的視訊信號則是採用非交錯（ non-interlaced)或循序（progressive)格式，其 係直接將圖框的視訊内容顯示於電腦顯示器上。 [0003] 為了讓交錯視訊信號能夠顯示於循序信號掺式之顯示器 (例如電腦的顯示器）上’必須先將交錯視訊信號轉換 q 為非交錯/循序視訊信號，:此稜格式轉k處理過程稱為去 交錯（de-interlacing)或倍頻循序。藉由去交錯轉換 ，將原本的奇圖場（f ield )及偶圖場結合產生一個圖框 〇 [0004] 視訊信號的去交錯轉換方法可以歸納為下列兩種：空間 (spatial )轉換及時間（temporal )轉換。在空間轉 換中，僅使用同一圖場的像素（p i xe 1 )以產生新的像素 ，因此，此種轉換一般又稱為圖場内（intra-field) 轉換。在時間轉換中，使用相鄰不同圖場的像素來產生 098124522 表單編號A0101 0982041877-0 201105131 新像素’因此’此種轉換一般又稱為圖場間（inter_ field)轉換。通常，靜止區係以時間上或圖場間（ inter-field)插補技術來進行去交錯，而移動區則以 空間上或圖場内（intra-field)插補技術來進行去交 錯。 [0005] [0006] [0007] [0008] 098124522 一般來說，移動偵測（motion detection)通常採用 同一奇偶圖場（same parity field)相對應像素之間 的差值來判斷；差值大者表示有移動，差值小者表示沒 有移動。然而，字幕區的背景如果有移動時，則可能將 字幕區視為移動區來進行去交錯，因而造成字幕區的閃 動現象。 鑑於傳統技術無法正確判斷字幕區.因而造成字幕區的閃 動，因此亟需提出一種新穎移動偵測及去交錯機制，用 以正確偵測出字幕區，以利去交錯之進行。 【發明内容】 鑑於上述，本發明實施例提出一種字幕區之偵測方法， 用以正確偵測得到字幕區’據以進行去交錯，而得以改 善字幕區的閃動現象。 很骒丰發明實施例，首先，對目前掃描線的每一目標 素進行字幕像素❹！，用關定目前掃描線之每一像 是否為字幕像素。計數前―圖㈣字幕像素之個數（ )，當其大於-預設值時，則將目前掃描線的字幕像 設為靜止像素。計數目㈣字幕像素. 個數（spl)，當其大於-預設值時，則根據前一圖相 後-圖框，將目前掃描線的部分非靜 表單編號麵 第4_17頁 像素㈣汉疋< 201105131 靜止像素。 [0009] 根據一實施例，上述之字幕像素偵測步驟包含下列步驟 。首先，進行目標像素的移動偵測。偵測目標像素之相 鄰像素之亮度值，判定是否存在有特別大或特別小的亮 度值。接著，檢查前一圖框中，相應於目標像素的相鄰 像素之狀態是否為靜止。最後，偵測目標像素是否位於 字幕邊界。 Ο 【實施方式】 第一圖例示三個連續圖框（亦即，前一圖框、目前圖框 及後一圖框）的部分掃描線。其中，前一圖框及後一圖 框為奇圖場，而目前圖框為偶圖場。前一圖框顯示有掃 描線PA、PC、ΡΕ，目前圖框顯示有掃描線Β、D，而後一 圖框則顯示有掃描線NA、NC、NE。 [0011] 第二圖顯示字幕（subt i 11 e )像素之偵測方法的流程圖 ，用以偵測待去交錯之目前像素t(又稱為目標像素）， 以決定其是否可能為字幕像素。本實施例雖以步驟21至 〇 24依序偵測目標像素t，然而，這些步驟的順序是可以變 更的。再者，有些步驟可予以省略，也可增加其他額外 步驟。 [0012] 首先，以步驟21進行目標像素t的移動偵測（motion detection)。鑑於字幕出現的時間一般都會維持數秒 之久，以便觀看者進行閱讀。所以，對字幕區域進行移 動偵測時，至少二張以上的同奇偶（same parity)圖 場之間的差異會特別小。在本實施例中，上述同奇偶圖 098124522 場之差異係藉由量測相應於目標像素t之前一圖框多個像 表單編號A0101 第5頁/共17頁 0982041877-0 201105131 素點（你丨 如，涵盍像素Pc之視窗中的多個像辛彳si )=像素點（例如，涵蓋像素nc之視窗的多個像素 ，絕對差之和（sum of abs〇lute ences 〇AnN Ier_ ，AD)。絕對差之和的值SAD可以由下式表示： nci代表後—圖框之掃描線NC上的像素，pci代表 別圖植之掃描線PC上的像素，以表視窗的像素個數。 [0013] [0014] 對差之和SAD如果小於—預設值τ，則註明該目標 絕對的狀態為靜止（static)，並繼續後續步驟；如果 、，蛀之和SAD大於預設值T，則註明為移動（m〇ti〇n) 二、。束第二圖流程及決定該目標像素‘為字幕像素。 ，著’以步驟22傾測目標像素t之相鄰像素（例如目前圖 框中位於目標像素t上方的像素b及下方的像素d，及位於 ,圖樞中相應於目標像素t的像素pc)之亮度值，用以 伯測是否存在有特別大或特別小的亮度值。為了讓字幕 醒目並與背景產生區別，字幕通常會使m(特別小 亮度值）外框配合亮色（特別大亮度值）内字以加強對 比。因此，當步驟22偵測到特別大或特別小亮度值時， 該目標像素t即可能位於字幕區，並繼續後續步驟；否則 ，結束第二圖流程及決定該目標像素七非為字幕像素。在 本實施例中，步驟22係藉由判定像素b、d、^是否具特 別大売度值（大於預設值T2)或者是否具特別小亮度值 (小於預設值T3)。亦即，b>T2或d>T2或PC>T2或b<T3 或d<T3或pc<T3 。 [0015] 098124522 然而，如果像素落於平滑區時（亦即—般的單調亮度值 表單編號A0101 第6頁/共17頁 0982041877-0 201105131 巻 )，則上述步驟21及22並不足以辨別出字幕。甚者’還 有可能因而錯誤偵測出很多的字幕像素。因此’本實施 例繼續以步驟23及24來做進一步的偵測。 [0016] 於步驟23，檢查前一圖框中，相應於目標像素七的相鄰像 素（例如像素pb及pd)之狀態是否為靜止。如果為是’ 則繼續後續步驟；否則，結束第二圖流程及決定該目標 像素t非為字幕像素。在本實施例中，係檢查像素Pb及Pd 之狀態是否皆為靜止。 0 [0017] 最後，於步驟24，偵測目標像素t是否位於字幕邊界。字 幕的邊界一般具有下列兩種情形之一 ：（a)目標像素t的 上下相鄰掃描線（例如掃描ί§Β耘掃描線間的（絕 • :.響 S-Ι 對）差值很大；（b)目標像素t的上下袓鄭#描線之間的 (絕對）差值很小，但是，該上下相鄰掃描線與前一圖 框中相應目標像素t之掃描線（例如掃描線PC)之間的（ 絕對）差值卻很大。如果有情形（a)或（b)者，則判定目 標像素為字幕像素；否則，，結束第，二圖流程及決定該目 Ο 標像素t非為字幕像素。在丰施例中，情形（a)係判定 掃描線B (涵蓋像素b)之視窗平均值和掃描線1)(涵蓋像 素d)之視窗平均值的絕對差值是否大於_預設值Τ4。亦 即，丨B-D | >Τ4。情形（b)係判定掃描線Β (涵蓋像素b )之視窗平均值和掃描線D (涵蓋像素d)之視窗平均值 的絕對差值是否小於—預設值T5 (亦即，丨b_d丨 ，且掃描線Β/掃描線D與掃描線PC (涵蓋像素pc)之絕對 差值是否大於預設值T4 (亦即，| B-PC | >T4* ! D_pc I >T4)。 — 098124522 表單編號A0101 第7頁/共17頁 0982041877-0 201105131 [0018] $二圖顯示本發明實_之字幕區⑽彳方法的流程圖， ^所獲得的移動_結果可據以進行後續（未顯示於流 ::)的：交錯。首先’於步㈣中以第二圖之流程 對目則掃描線的每-目標像素進行字幕像素偵 用以判㈣掃描線之每-像素是否騎幕像素。、 測 [0019] 接著，於步驟32’計數前1框的字幕像素之個數（ _tltle pixels in — s⑷。由 :相同的字幕會連續出現於多張關t，因此，可藉由 别-圖框的結果以得知目前圓樞是否辱有字幕。一般來 說，-圖框中字幕像素個教(spf m大時，即可能真正 具有字幕。 [0020] 當前-圖框的字幕像素之個數（spf)大於—預設值以時 (步驟33)，則將目前掃描線的字幕像素設為靜止（ static)像素（步驟34);否則，即俵一般的移動摘測 (步驟35)之結果來進行去交錯。例如，以時間上或圖 場間（inter-field)插補技術以進行靜止區的去交錯 ，而以空間上或圖場内（intra_field)插補技術以進 行移動區的去交錯。接著，於步驟36，計數（目前圖框 )前一掃描線的字幕像素之個數（subtitle pixels in previous scan line, spl)。 [0021] 如果前一掃描線的字幕像素之個數（spl)大於一預設值 T6 (步驟37)，則目前掃描線即為具字幕之掃描線；否 則，即依一般的移動偵測（步驟35)之結果來進行‘交 錯。根據本實施例，可以由前一圖框運算完的資料（例 098124522 如spf )得知目前圖框是否具有字幕。 表單編號A0101 第8頁/共17頁 為了節省額外記錄 0982041877-0 201105131 訊息之儲存空間’字幕區的位置則由目前圖框的資料（ 例如s p 1 )來得到。 [0022] 經判定為具字幕之掃描線當中，有些像素係為靜止的， 而有些像素則非為靜止。如果”非靜止”像素所對應之 前一圖框像素及後一圖框像素之間的絕對差值小於一預 設值T7，則以步驟38將其調整設定為靜止（static)像 素。第四圖例示具字幕掃描線及其相應之前一圖框、後 一圖框掃描線。於此例子中，具字幕掃描線的第三像素201105131 VI. Description of the Invention: [Technical Field] [0001] The present invention relates to de-interlacing (de-i nter 1 ac i ng ) conversion, and more particularly to a subtitle area detecting method for deinterleaving. [Prior Art 3 [0002] The general TV broadcast video signal is in an interlaced format, such as NTSC, PAL, SECAM, which is sequentially displayed on the TV screen in the order of the odd field (Held) and the even field. The principle of visual persistence is used to display the video content of the frame. Interlaced video signals only need to use low frequency bandwidth to deliver acceptable video quality; however, the disadvantages are reduced vertical resolution, flickering of lines or areas. The video signal of a general computer monitor is in a non-interlaced or progressive format, which directly displays the video content of the frame on a computer monitor. [0003] In order to enable interlaced video signals to be displayed on a sequential signal-mixed display (such as a computer display), the interlaced video signal must be converted to a non-interlaced/sequential video signal: For de-interlacing or multiplying. By deinterlacing, the original singular field and even field are combined to produce a frame. [0004] The deinterlacing method of video signals can be summarized into the following two types: spatial conversion and time. (temporal) conversion. In spatial conversion, only pixels of the same field (p i xe 1 ) are used to generate new pixels, so such conversion is also commonly referred to as intra-field conversion. In time conversion, pixels from adjacent different fields are used to generate 098124522. Form number A0101 0982041877-0 201105131 New pixel 'so' This conversion is also commonly referred to as inter_field conversion. Typically, the quiescent zone is deinterleaved by temporal or inter-field interpolation techniques, while the mobile zone is de-interleaved by spatial or intra-field interpolation techniques. [0006] [0008] [0008] 098124522 In general, motion detection usually uses the difference between the corresponding pixels of the same parity field to determine the difference; Indicates that there is movement, and the difference is small, indicating no movement. However, if the background of the subtitle area is moved, the subtitle area may be regarded as a moving area for deinterleaving, thereby causing a flashing of the subtitle area. In view of the fact that the conventional technology cannot correctly judge the subtitle area, thus causing the subtitle area to flash, it is necessary to propose a novel motion detection and deinterlacing mechanism for correctly detecting the subtitle area to facilitate interlacing. SUMMARY OF THE INVENTION In view of the above, an embodiment of the present invention provides a method for detecting a subtitle area, which is used to correctly detect a subtitle area to perform deinterleaving, thereby improving a flickering phenomenon of a subtitle area. It is very advantageous to invent the embodiment. First, subtitle pixels are applied to each target of the current scan line! Use to determine whether each image of the current scan line is a subtitle pixel. Before counting, the number of subtitle pixels ( ) in Figure (4), when it is greater than - the preset value, the subtitle image of the current scan line is set as a still pixel. Count (4) subtitle pixels. The number (spl), when it is greater than - the default value, according to the previous picture phase - frame, the current scan line part of the non-static form number face 4_17 page pixels (four) Han < 201105131 Still pixels. According to an embodiment, the subtitle pixel detecting step includes the following steps. First, the motion detection of the target pixel is performed. The brightness value of the adjacent pixel of the target pixel is detected to determine whether there is a particularly large or particularly small brightness value. Next, it is checked whether the state of the adjacent pixel corresponding to the target pixel is still in the previous frame. Finally, it is detected whether the target pixel is at the subtitle boundary. Ο Embodiments The first figure illustrates partial scan lines of three consecutive frames (ie, the previous frame, the current frame, and the next frame). Among them, the previous frame and the next frame are odd fields, and the current frame is an even field. The previous frame shows the scan lines PA, PC, and ΡΕ. The current frame shows the scan lines Β and D, while the next frame shows the scan lines NA, NC, and NE. [0011] The second figure shows a flowchart of a method for detecting a subtitle (subt i 11 e ) pixel, which is used to detect a current pixel t (also referred to as a target pixel) to be deinterlaced to determine whether it is a subtitle pixel. . In this embodiment, the target pixel t is sequentially detected by steps 21 to 24, however, the order of these steps may be changed. Furthermore, some steps can be omitted and other additional steps can be added. [0012] First, the motion detection of the target pixel t is performed in step 21. Since the time of subtitles is generally maintained for a few seconds, the viewer can read it. Therefore, when moving the subtitle area for motion detection, the difference between at least two of the same parity fields is particularly small. In this embodiment, the difference between the above-mentioned parity and the 081124522 field is determined by measuring a frame corresponding to the target pixel t. A plurality of image form numbers A0101, 5th page, a total of 17 pages, 10,821,841, 877, 201105131, a prime point (you 丨For example, a plurality of images in the window of the pixel Pc include a pixel point (for example, a plurality of pixels covering a window of the pixel nc, the sum of absolute differences (sum of abs〇lute ences 〇AnN Ier_ , AD) The value of the sum of absolute differences SAD can be expressed by the following equation: nci represents the pixel on the scan line NC of the post-frame, and pci represents the pixel on the scan line PC of the map, in terms of the number of pixels in the view window. 0013] [0014] If the sum of the differences SAD is less than the preset value τ, the state indicating that the target is absolute is static, and the subsequent steps are continued; if, the sum of the SAD is greater than the preset value T, then Indicated as moving (m〇ti〇n) II. The second process of the beam and determining the target pixel 'is a subtitle pixel. 'Through step 22 to tilt the adjacent pixel of the target pixel t (for example, the current frame is located The pixel b above the target pixel t and the pixel d below, and located at The brightness value corresponding to the pixel pc) of the target pixel t is used to check whether there is a particularly large or very small brightness value. In order to make the subtitles conspicuous and distinguish from the background, the subtitles usually make m (especially small brightness value). The outer frame is matched with the bright color (especially large brightness value) to enhance the contrast. Therefore, when step 22 detects a particularly large or particularly small brightness value, the target pixel t may be located in the subtitle area and continue the subsequent steps; otherwise, Ending the second graph process and determining that the target pixel seven is not a subtitle pixel. In this embodiment, step 22 determines whether the pixel b, d, ^ has a particularly large value (greater than the preset value T2) or whether It has a particularly small brightness value (less than the preset value T3). That is, b>T2 or d>T2 or PC>T2 or b<T3 or d<T3 or pc<T3. [0015] 098124522 However, if the pixel falls on When smoothing the area (that is, the general monotonic brightness value form number A0101, page 6 / page 17 0982041877-0 201105131 巻), the above steps 21 and 22 are not enough to distinguish the subtitles. Even the 'may be wrong A lot of subtitle pixels are detected. This embodiment continues with steps 23 and 24 for further detection. [0016] In step 23, the state of the adjacent pixels (eg, pixels pb and pd) corresponding to the target pixel seven is checked in the previous frame. If it is YES, the subsequent steps are continued; otherwise, the second graph process is ended and it is determined that the target pixel t is not a subtitle pixel. In this embodiment, it is checked whether the states of the pixels Pb and Pd are all still. [0017] Finally, in step 24, it is detected whether the target pixel t is located at the subtitle boundary. The boundary of the subtitle generally has one of the following two situations: (a) the upper and lower adjacent scan lines of the target pixel t (for example, the difference between the scan lines and the scan lines (absolute::. S-Ι pair) is large. (b) The (absolute) difference between the upper and lower 袓 Zheng of the target pixel t is small, but the scan line of the corresponding target pixel t in the upper and lower adjacent scan lines and the previous frame (for example, the scan line PC) The (absolute) difference between them is very large. If there is a case (a) or (b), the target pixel is determined to be a subtitle pixel; otherwise, the end of the second and second graph processes and the determination of the target pixel t Non-subtitle pixels. In the case of the case, (a) is to determine whether the absolute difference between the window average of scan line B (covering pixel b) and the scan line 1) (covering pixel d) is greater than _ The default value is Τ4. That is, 丨B-D | > Τ 4. Case (b) is to determine whether the absolute difference between the window average of the scanning line 涵盖 (covering the pixel b) and the window average of the scanning line D (covering the pixel d) is less than - the preset value T5 (ie, 丨b_d丨, And whether the absolute difference between the scan line/scan line D and the scan line PC (covering the pixel pc) is greater than a preset value T4 (ie, | B-PC | > T4* ! D_pc I > T4). — 098124522 Form No. A0101 Page 7 / Total 17 Page 0982041877-0 201105131 [0018] $2 shows a flow chart of the method of the subtitle area (10) of the present invention, and the obtained movement_ result can be followed (not shown) In the flow::): Interleaving. First, in step (4), the process of the second figure is used to perform subtitle pixel detection on each target pixel of the scan line (4) whether each pixel of the scan line is a pixel. [0019] Next, in step 32', the number of subtitle pixels in the first frame is counted (_tltlepixel in - s(4). By: the same subtitles will appear continuously in multiple sets of t, therefore, by other-map The result of the box is to know whether the current round is insulted with subtitles. In general, - the subtitle pixel teaching in the frame (spf m large That is, the subtitle pixel (spf) of the current frame is greater than the preset value (step 33), and the subtitle pixel of the current scan line is set to a static pixel. (Step 34); otherwise, the result of the general motion sweep (step 35) is deinterleaved. For example, temporal or inter-field interpolation techniques are used to deinterlace the still region. The spatial or intra-field interpolation technique is used to perform de-interlacing of the moving region. Then, in step 36, the number of subtitle pixels of the previous scan line is counted (current frame) (subtitle pixels in previous scan line) [0021] If the number of subtitle pixels (spl) of the previous scan line is greater than a predetermined value T6 (step 37), the current scan line is a scan line with subtitles; otherwise, it is normal. The result of the motion detection (step 35) is performed for 'interleaving. According to the present embodiment, the data calculated by the previous frame (eg, 098124522, such as spf) can be used to know whether the current frame has subtitles. Form No. A0101 Page 8 / Total 17 pages in order to save extra Recording 09820431877-0 201105131 The storage space of the message 'The location of the subtitle area is obtained from the data of the current frame (for example, sp 1 ). [0022] Among the scan lines judged to have subtitles, some pixels are stationary, and Some pixels are not static. If the absolute difference between the pixel of the previous frame and the pixel of the next frame corresponding to the "non-stationary" pixel is less than a preset value T7, then the adjustment is set to a static pixel in step 38. The fourth figure illustrates a subtitle scan line and its corresponding previous frame and subsequent frame scan lines. In this example, the third pixel with the subtitle scan line
t3為非靜止像素，其相應之前一圖框像素為pc3，相應之 I 後一圖框像素為nc3 ^如果像素nc3和像素pc3的絕對差 值小於預設值T7 (亦即，| nc-pc | <T7)，則將像素t3 調整設定為靜止像素。 [0023] 根據本實施例，可使得字幕區及其鄰近區域判定為靜止 區，使其移動偵測不受背景移動的影響，並以時間上或 圖場間（inter-field)插補技術來進行該靜止區的去 交錯。 ^ [0024] 以上所述僅為本發明之較佳實施例而已，並非用以限定 本發明之申請專利範圍；凡其它未脫離發明所揭示之精 神下所完成之等效改變或修飾，均應包含在下述之申請 專利範圍内。 【圖式簡單說明】 [0025] 第一圖例示三個連續圖框的部分掃描線。 第二圖顯示字幕像素之偵測方法的流程圖。 第三圖顯示本發明實施例之字幕區偵測方法的流程圖。 第四圖例示具字幕掃描線及其相應之前一圖框、後一圖 098124522 表單編號 A0101 第 9 頁/共 17 頁 0982041877-0 201105131 框掃描線。 【主要元件符號說明】 [0026] 21-24 字幕像素之偵測步驟 31-38 字幕區偵測步驟 PA、PC、PE前一圖框的掃描線 B > D 目前圖框的掃描線 NA、NC、NE後一圖框的掃描線 pa、pb、pc、pd、pe前一圖框的像素 b、d 目前圖框的像素 na ' nc ' ne 後一圖框的像素 098124522 表單編號A0101 第10頁/共17頁 0982041877-0T3 is a non-stationary pixel, and the pixel of the previous frame is pc3, and the pixel of the corresponding frame is nc3 ^ If the absolute difference between the pixel nc3 and the pixel pc3 is less than the preset value T7 (ie, | nc-pc | <T7), the pixel t3 is adjusted to be a still pixel. [0023] According to the embodiment, the caption area and its adjacent area can be determined as a still area, so that motion detection is not affected by the background motion, and the inter-field interpolation technique is used. Deinterlacing of the quiescent zone is performed. The above description is only the preferred embodiment of the present invention, and is not intended to limit the scope of the claims of the present invention; all other equivalent changes or modifications which are made without departing from the spirit of the invention should be It is included in the scope of the following patent application. BRIEF DESCRIPTION OF THE DRAWINGS [0025] The first figure illustrates a partial scan line of three consecutive frames. The second figure shows a flow chart of a method for detecting subtitle pixels. The third figure shows a flow chart of a method for detecting a subtitle area according to an embodiment of the present invention. The fourth figure illustrates the subtitle scan line and its corresponding previous frame, the latter picture 098124522 Form No. A0101 Page 9 of 17 0982041877-0 201105131 Frame scan line. [Main component symbol description] [0026] 21-24 Subtitle pixel detection step 31-38 Subtitle area detection step PA, PC, PE scan line of the previous frame B > D Current frame scan line NA, The scan lines pa, pb, pc, pd, pe of the NC and NE frames, the pixels b, d, the pixels of the current frame na ' nc ' ne, the pixels of the next frame 098124522, the form number A0101, the 10th Page / Total 17 pages 0904041877-0