Patent Application
20090115894
This application claims priority of application No. 096141624 filed in Taiwan R.O.C on Nov. 5, 2007 under 35 U.S.C. §119; the entire contents of which are hereby incorporated by reference.
The invention relates to a video playback control method, particularly to a video playback control method capable of eliminating black bars and a black bar elimination module used in a video playback device.
Conventionally, a video playback device often has a preset aspect ratio. When the aspect ratio of a source video frame to be displayed and the aspect ratio of the video playback device are different, black bars are added to the top and bottom, or left and right sides of each frame displayed on the video playback device to maintain the original aspect ratio of the source video frame and completely show the video content as a result.
Currently, a film is often produced conforming to an aspect ratio of 16:9 or 2.35:1. The aspect ratio of 16:9 is a widescreen standard aspect ratio, and the aspect ration of 2.35:1 is an anamorphic standard aspect ratio. Taking a common home-theater projector as an example, its preset aspect ratio is 16:9. Hence, in case a movie having an aspect ratio of 16:9 shown in
Though the above-mentioned problems may be cured by first anamorphically scaling the picture frame to eliminate the black bars and then recovering it by an anamorphic lens installed on the video playback device, the installation of the anamorphic lens considerably increases the fabrication cost.
The invention provides a video playback control method capable of eliminating black bars and a black bar elimination module used in a video playback device.
According to an embodiment of the invention, a video playback control method adapted for a video playback device includes the following steps. First, at least one source frame is fetched, with the source frame being corresponding to the video content that is to be displayed on the video playback device. Next, a first aspect ratio of the source frame is compared with a second aspect ratio of the video playback device, and the source frame is directly displayed on the video playback device when the first aspect ratio is the same as the second aspect ratio. Also, when the first aspect ratio is different to the second aspect ratio, the periphery of the source frame is overscanned.
In one embodiment, the periphery of the source frame is overscanned at a region outside an action safe area and a title safe area, and the overscan step includes detecting whether the first aspect ratio is larger or smaller than the second aspect ratio. When the first aspect ratio is smaller than the second aspect ratio, the top side and the opposite bottom side of the source frame is overscanned. When the first aspect ratio is larger than the second aspect ratio, the source frame is enlarged according to a scale factor and the left side and the opposite right side of the enlarged source frame is overscanned.
In one embodiment, the first aspect ratio of the source frame is 16:9, the second aspect ratio of the video playback device is 2:1, and the top side and the bottom side of the source frame are respectively overscanned by about 7% and 3% of the vertical span of the source frame.
In one embodiment, the first aspect ratio of the source frame is 2.35:1, the second aspect ratio of the video playback device is 2:1, the scale factor has a value that is equal to the first aspect ratio divided by the second aspect ratio, and the left side and the right side of the enlarged source frame are each overscanned by about 7.45% of the horizontal span of the enlarged source frame.
In one embodiment, the first aspect ratio of the source frame is 2.35:1, the second aspect ratio of the video playback device is 16:9, the scale factor has a value that is smaller than the first aspect ratio divided by the second aspect ratio, and the left side and the right side of the enlarged source frame are each overscanned by about 7.45% of the horizontal span of the enlarged source frame.
According to another embodiment of the invention, a black bar elimination module used in a video playback device includes a reception unit, an operation processing unit, and a size-adjusting unit. The reception unit is used for acquiring at least one source frame corresponding to the video content that is to be displayed on the video playback device. The operation processing unit is used for comparing a first aspect ratio of the source frame with a second aspect ratio of the video playback device and calculating a scale factor for the source frame when the first aspect ratio is larger than the second aspect ratio. The size-adjusting unit is used for enlarging the source frame according to the scale factor and overscanning the periphery of the enlarged source frame.
In one embodiment, the size-adjusting unit is a scalar chip, and the operation processing unit is a micro controller.
According to the above-mentioned embodiments, the black bar may be completely removed or considerable reduced to improve the visual effect. Also, the scale factor value and the overscan proportion may be varied as long as the key portion of the video content is not affected.
Other objectives, features and advantages of the present invention will be further understood from the further technological features disclosed by the embodiments of the present invention wherein there are shown and described preferred embodiments of this invention, simply by way of illustration of modes best suited to carry out the invention.
In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings which form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology is used with reference to the orientation of the Figure(s) being described. The components of the present invention can be positioned in a number of different orientations. As such, the directional terminology is used for purposes of illustration and is in no way limiting. On the other hand, the drawings are only schematic and the sizes of components may be exaggerated for clarity. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. Also, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms “connected,” and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings. Similarly, “adjacent to” and variations thereof herein are used broadly and encompass directly and indirectly “adjacent to”. Therefore, the description of “A” component facing “B” component herein may contain the situations that “A” component directly faces “B” component or one or more additional components are between “A” component and “B” component. Also, the description of “A” component “adjacent to” “B” component herein may contain the situations that “A” component is directly “adjacent to” “B” component or one or more additional components are between “A” component and “B” component. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive.
Before each of the embodiments of the invention is set forth below, the overscan treatment and the reservation of safe areas in the process of making films are explained here. For early CRT televisions that fail to perfectly fetch TV signals, an overscan process should be performed to avoid noises appear in the periphery of each displayed frame. However, in order to prevent any key portion of video content from being removed, the overscan process is performed outside an action safe area and a title safe area to ensure key pictures, subtitles or graphics do not exceed the viewing zone of a monitor. Though the overscan process is no longer needed for nowadays video playback device, the film maker is still in the habit of keeping any key portion of video content within the action safe area and the title safe area. For example, as shown in
Further, the term “aspect ratio” used in the following description and appending claims refers to a common frame ratio known by skilled artisan in the art, and it does not mean a precise value that may limit the invention. More specifically, the skilled artisan may comprehend an aspect ratio of 16:9 (1.78:1) means a typical widescreen aspect ratio but not a rigidly precise value of a displayed width divided by the height. For example, in case the actual measured value of a displayed width divided by the height equals 1.77 or 1.79, it may also be considered as in the scope of the aspect ratio of 16:9.
According to this embodiment, first, as the video playback device fetches a source frame, it automatically detects the aspect ratio of the source frame, recognizing whether the aspect ratio is 16:9 or 2.35:1.
As shown in
F=(the aspect ratio of the source frame)/(the preset aspect ratio of the video playback device). As a result, a preferred scale factor F equals 1.175 (=2.35/2) in this embodiment. Referring to
Next,
In one embodiment, the top side and the bottom side are overscanned to different extents, because the subtitles often appear in the bottom side of each video frame. For example, the top side is cut by 7% while the bottom side is cut by 3% of the vertical span of the source frame 12. This may ensure safe display of the subtitles because the bottom side is cut to a lesser extent to provide more spare areas.
According to this embodiment, first, as the video playback device fetches a source frame, it automatically detects the aspect ratio of the source frame, recognizing whether the aspect ratio is 16:9 or 2.35:1. In case the aspect ratio of the source frame is recognized as 16:9, the video playback device directly displays the source frame. In comparison, in case the aspect ratio of the source frame is recognized as 2.35:1, the treatment is illustrated in
As shown in
Hence, according to this embodiment, a safe overscan proportion of 7.45% is adopted to avoid the miss of the key portion of video content, and as a result a safe scale factor F′ of 1.175 is obtained. When the source frame 12 is enlarged according to the safe scale factor F′ of 1.175, its vertical pixel number is changed to 640 (≈544×1.175). In that case, though the black bar fails to be completely removed, part of it, i.e. 96(640−54) pixels in the vertical span, is cut away to considerably improve the visual effect.
According to the above-mentioned embodiments, it is seen the scale factor F may be determined according to the tolerant extent of overscan. In order to completely remove the black bar, a preferred scale factor F is set to have a value that is equal to the aspect ratio of the source frame divided by the aspect ratio of the video playback device. However, the scale factor may also be set to have a value smaller than the preferred scale factor F to avoid the overscan proportion exceeding the tolerant extent, match with the selection of the video playback device, or take other factor into consideration. In that case, though the black bar fails to be completely removed, a considerable part of it is allowed to be cut away to also improve the visual effect.
Accompanying with the flow chart shown in
In one embodiment, the size-adjusting unit 24 is a scalar chip, and the operation processing unit 26 is a micro controller.
Note though the preset aspect ratio of the video playback device is exemplified as 16:9 or 2:1 in the above-mentioned embodiments, this not limited. The method described in the above-mentioned embodiments where the source frame is scaled and overscanned to completely eliminate or considerably reduce the black bar is suitable for different video playback devices having their respective aspect ratios.
Further, the aspect ratio of the source frame is not limited; for example, various widescreen standard aspect ratios (such as 16:9, 1.85:1 or 16:10) or anamorphic standard aspect ratios (such as 2.35:1 or 2:1) may be applied in the above-mentioned embodiments where the source frame is scaled and overscanned to completely eliminate or considerably reduce the black bar.
The foregoing description of the preferred embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form or to exemplary embodiments disclosed. Accordingly, the foregoing description should be regarded as illustrative rather than restrictive. Obviously, many modifications and variations will be apparent to practitioners skilled in this art. The embodiments are chosen and described in order to best explain the principles of the invention and its best mode practical application, thereby to enable persons skilled in the art to understand the invention for various embodiments and with various modifications as are suited to the particular use or implementation contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents in which all terms are meant in their broadest reasonable sense unless otherwise indicated. Therefore, the term “the invention”, “the present invention” or the like does not necessarily limit the claim scope to a specific embodiment, and the reference to particularly preferred exemplary embodiments of the invention does not imply a limitation on the invention, and no such limitation is to be inferred. The invention is limited only by the spirit and scope of the appended claims. The abstract of the disclosure is provided to comply with the rules requiring an abstract, which will allow a searcher to quickly ascertain the subject matter of the technical disclosure of any patent issued from this disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Any advantages and benefits described may not apply to all embodiments of the invention. It should be appreciated that variations may be made in the embodiments described by persons skilled in the art without departing from the scope of the present invention as defined by the following claims. Moreover, no element and component in the present disclosure is intended to be dedicated to the public regardless of whether the elements or component is explicitly recited in the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 096141624 | Nov 2007 | TW | national |
