Various embodiment modes of the present invention will now be described in detail based upon accompanying drawings.
As the moving picture decoding apparatus according to the embodiments, a detailed explanation is made of a moving picture decoding apparatus 1 which receives a decoding image signal “a” employed in a wave digital broadcasting system, and the like, and then, decodes the received coded image signal “a.”
The moving picture decoding apparatus 1 shown in
As shown in
Since this coded moving picture signal “a” has contained image information of a plurality of frames “b”, the image information can be recognized as a moving picture by a user when the frames “b” are displayed in a frame feeding mode.
As this coding method, the below-mentioned two sorts of coding methods are employed:
(1) An inter-frame coding method
(2) An intra-frame coding method.
The inter-frame coding method corresponds to a method for coding a moving picture by employing difference information between a preceding frame “b” and the present frame “b” to be coded.
Typically correlation of a moving picture along a time direction and correlation between frames “b” are high, therefore an information amount can be largely compressed by utilizing a difference between continuous frames “D.”
However, when a content of a moving picture is largely changed, a difference between the preceding frame and the frame to be coded, so that a compression effect of an information amount achieved by the inter-frame coding method can be hardly expected. Also, in the case that an error has been mixed in received coded information, the error is propagated among the frames “b” on the decoding side.
The intra-frame coding method corresponds to such a coding method which is completed within a frame “b.”
In a continuous sequence, although such a compression effect as explained in the inter-frame coding method cannot be expected in this intra-frame coding method, the intra-frame coding method may be employed in a scene change occurred when image contents of frames “b” are largely changed, or when a refresh is performed.
The above-explained refresh implies that a frame “b” encoded by using the intra-frame coding method is inserted in a periodic manner in order to avoid that an error is propagated between frames “b” (namely, drawback of inter-frame coding method), and this inserted frame “b” constitutes a starting point of the inter-frame coding method. The frame “b” inserted for this refresh purpose is temporarily stored for referring to a difference when the inter-frame coding method is performed, and the preceding frame “b” encoded by using the inter-frame coding method.
Also, in a broadcasting service, when a reception side starts to receive a stream at arbitrary timing, if the reception side starts to receive the frame “b” encoded by using the inter-frame coding method, then such a frame “b” which becomes a starting point of a difference is not present, so that the receiving side cannot decode the frame “b.” Under such a circumstance, while the frame “b” encoded by using the intra-frame coding method is defined as a starting point, frames “b” encoded by using the inter-frame coding method subsequent to the above frame “b” of the starting point are decoded.
When the moving picture decoding apparatus 1 decodes coded information of a moving picture, the moving picture decoding apparatus 1 recognizes identification data of the inter-frame coding method and identification data of the intra-frame coding method, and then, performs a decoding process corresponding to each of these identification data. In the H.264, a plurality of reference frames “c” are utilized when a decoding operation for the frames “b” coded by the inter-frame coding method is carried out, so that these reference frames “c” are stored in the decoded image buffer 24. Then, while the moving picture decoding apparatus 1 refers to these reference frames “c”, the moving picture decoding apparatus 1 decodes the frames “b” coded by the inter-frame coding method.
Also, as a recovering process when an error is mixed in a stream of the H.264, normally, in such a case that an error is mixed in frames “b” coded by the inter-frame coding method, a concealment process operation (recovering process operation) using correlation among the frames “b” is carried out with reference to the reference frame “c.”
In the embodiments, the frames “b” will be explained as follows: That is, frames “b” coded by the intra-frame coding method are explained as reference frames “c”, whereas frames “b” coded by the inter-frame coding method are explained as subordinate frames “d.”
The coded moving picture signal “a” is arranged by enumerating reference frames “c” and subordinate frames “d” in a time sequential manner, which are obtained by coding the frames “b.” A reference frame “c” contains at least frame number information “e”, PTS information “f” indicative of a reproduction time, and fixed time interval information “g” indicative of a reproduction time interval among frames. Also, a subordinate frame “d” contains at least a frame number “e.”
As indicated in
At this time, the coded moving picture signal “a” contains parameter information such as the reproduction time management information (PTS information) and the frame number information, and error information in addition to image information.
The coded moving picture signal acquiring unit 25 acquires the coded moving picture signal “a” separated by the multiplexing separating unit 11 (step S102) The decoding unit 21 decodes this coded moving picture signal “a” so as to produce a moving picture signal “i” (step S103), and stores this moving picture signal “i” into the decoded image buffer 24 (step S104). Also, the decoding unit 21 transmits the frame number information “e” of the subordinate frame “d”, the frame number information “e” of the reference frame “c”, the PTS information “f”, and the fixed time interval information “g”, and the like to the display time calculating unit 22 (step S105).
The reproduction time calculating unit 22 judges as to whether or not the transmitted frame “b” corresponds to the reference frame “c” (step S106). When the transmitted frame “b” is the reference frame “c” (“YES” in step S106), the reproduction time calculating unit 22 transmits both the PTS information “f” and the frame number information “e” received from the decoding unit 21 to the reference time storage unit 23 (step S107). Also, the reproduction time calculating unit 22 has continuously stored thereinto the fixed time interval information “g” of the latest reference frame “c.”
The reference time storage unit 23 stores thereinto the transmitted PTS information “f” and the transmitted frame number information “e” (step S108) The reference time storage unit 23 has continuously stored thereinto the PTS information “f” and the frame number information “e” as to the latest reference frame “c”, and transmits this PTS information “f” and also this frame number information “e” to the display time calculating unit 22 in response to a request issued from the reproduction time calculating unit 22.
Also, the reproduction time calculating unit 22 calculates a reproduction time of the transmitted frame “b” (step S109), and then, stores reproduction time information “j” of this calculated display time in the decoded image buffer 24 (step S110).
The decoded image buffer 24 transmits a moving picture signal “i” received from the decoding unit 21 to the LCD control unit 13 based upon the reproduction time information “j” received from the reproduction time calculating unit 22 (step S111).
Next, a description is made of such a sequence that the reproduction time calculating unit 22 of the moving picture processing unit 12 employed in the moving picture decoding apparatus 1 calculates a reproduction time of a frame “b” as a first embodiment based upon
One example will now be explained below: That is, in the coded moving picture signal “a” acquired by the coded moving picture signal acquiring unit 25, although data as to frames “b” having frame numbers “0” and “1” have been acquired under normal condition, data as to a frame “b” having a frame number 2 is dropped, and next, data as to a frame “b” having a frame number 2 is acquired.
The frame “b” having the frame number “0” corresponds to the reference frame “c”, and the frames “b” having the frame numbers 1, 2, 3, 4, . . . , which are continued to this reference frame “c”, correspond to the subordinate frames “d.”
Only the reference frame “c” contains the PTS information “f” and the fixed time interval information “g” indicative of the fixed time interval “ΔT” which corresponds to a fixed time interval for indicating the frame “b.”
In this case, as represented in
Reproduction time (frame number)=reference reproduction time+change amount of frame number×fixed time interval ΔT (1)
In the formula (1), “reference reproduction time” indicates a reproduction time which is mainly acquired from the PTS information “c” of the latest reference frame “c”, and is used as a reference when the reproduction time of the subordinate frame “b” is calculated.
The change amount of the frame number corresponds to a difference between the frame number (reference frame number)of the latest reference frame “c” and the relevant frame number.
In the beginning, the reproduction time calculating unit 22 defines the reproduction time contained in the PTS information “f” of the reference frame “c” having the frame number “0” as a reproduction time and a reference display time:
reproduction time (0)=PTS (2)
reference reproduction time=PTS (3)
Next, since the frame “b” having the frame number 2 cannot be received, the reproduction time calculating unit 22 calculates a reproduction time of the frame “b” having the frame number 3 by skipping over the frame number 2. The reproduction time of the frame “b” having the frame number 3 is calculated as follows:
As explained above, since the reproduction times are calculated by using the frame numbers, even when the frame “b” is dropped, the correct reroduction times of the frame “b” can be calculated.
On the other hand, as explained in the related art, in the method for reproducing the continuous frames “b” by merely making the fixed time interval ΔT in the received coded moving picture signal “a”, when one frame “b” is dropped, all of reproduction times of the subsequent frames “b” are shifted, so that qualities of images are largely lowered.
The qualities images of the embodiments may improve the qualities of moving picture is much better than those of the related art.
In accordance with the first embodiment, the reproduction time calculating unit 22 of the moving picture processing unit 12 can correctly calculate the respective frames “b” even in such a case that either one or plural frames “b” in the received coded moving pictured signal “a” are dropped, so that the quality of the moving picture image can be improved.
The moving picture decoding apparatus 1 according to a second embodiment will now be explained with reference to
Another example will now be explained below: That is, in the coding image signal “a” acquired by the coded moving picture signal acquiring unit 25, although data as to frames “b” having frame numbers “0” and “1” have been acquired under normal condition, data as to a frame “b” having a frame number 2 is dropped, and next, data as to a frame “b” having a frame number 3 is acquired, and further, an error is mixed in such a manner that a frame number 6 is attached to a frame “b” having a frame number 4.
In this case, as indicated in
As shown in
As a consequence, as the second embodiment, a description is made of a calculating process with reference to a flow chart of
Firstly, as shown in
Reproduction time (0)=PTS (7)
Then, the reproduction time calculating unit 22 sets a preceding reproduction time indicative of a reproduction time of such a frame “b” immediately before the above-described frame “b” to this reproduction time (step S204). It should be understood that this preceding reproduction time is continuously stored in the reproduction time calculating unit 22.
Also, when the image information of the frame “b” does not contain the PTS information (“NO” in step S201), the reproduction time calculating unit 22 judges as to whether or not the image information of the frame “b” contains the error information “h” (step S205).
If the image information of the frame “b” does not contain the error information “h” (“NO” in step S205), the reproduction time calculating unit 22 judges as to whether or not the frame number of this frame “b” is larger than the reference frame number (step S206).
In the case that the frame number of this frame “b” is larger than the reference frame number (“YES” of step S206), the reproduction time calculating unit 22 judges that this frame “b” corresponds to the subordinate frame “d”, and the frame number (“1” in
Also, when the image information of the frame “b” contains the error information “h” (“YES” in step S205), and also, when the frame number of the frame “b” is smaller than, or equal to the reference frame number (“NO” in step S106), the reproduction time calculating unit 22 judges that the frame number (“b” of
As a consequence, the reproduction time calculating unit 22 calculates a reproduction time of this frame “b” by employing the preceding reproduction time and the below-mentioned reproduction time, while the frame number of this frame “b” is not used (step S208):
Reproduction time (4)=preceding reproduction time+ΔT (9)
According to the second embodiment, the reproduction time calculating unit 22 of the moving picture processing unit 12 can correctly calculate the respective frames “b” even in such a case that either one or plural frames “b” in the received coded moving picture signal “a” are dropped, and furthermore, even in the case that the error is contained in the image information of the frame “b”, so that the image quality of the moving picture image can be improved.
Number | Date | Country | Kind |
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2006-244549 | Sep 2006 | JP | national |