JP5984462B2 - Image encoding device - Google Patents

Description

  The present invention relates to an image coding apparatus, and more particularly to an image coding apparatus that controls a coding mode, a quantization step, a frame rate, or the like by using a timing for changing a resolution when a bit rate is changed. is there.

  As an encoding technique for compressing moving image data with high efficiency, for example, MPEG-2 and H.264 which are international standards. H.264 / AVC and the like. These are hybrid coding schemes combining motion compensation prediction coding, discrete cosine transform coding, variable length coding, and the like. Motion compensation prediction includes intra-frame prediction (intra prediction) and inter-frame prediction (inter prediction). The type of picture to be encoded is classified according to the method of motion compensation prediction, and only encoding by intra-frame prediction is performed. Forward prediction in which motion prediction is performed between an intra-coded picture (hereinafter referred to as an I picture) and a temporally forward frame, and the difference value and motion prediction information are transmitted. Bidirectional predictive coded picture (hereinafter referred to as B picture) which performs motion prediction between a coded picture (hereinafter referred to as P picture) and temporally forward, backward or bidirectional frames and compresses data. (Referred to as pictures). In general, encoding is performed by periodically repeating a group of pictures called GOP (Group Of Pictures) starting from an I picture using these motion-compensated predictive encoding.

  Image data compressed by the image encoding device is transmitted via a network or the like, and image data decoded by the image decoding device can be obtained. At this time, depending on the transmission system, there are cases where the bit rate for transmitting the encoded data is a fixed rate and a variable rate. In a variable rate system in real-time transmission, it may be necessary to reduce the amount of information of encoded data at the time of rate switching. As a result, the decoded image is significantly deteriorated, or the encoded data is not fully suppressed. There is a problem that the decoded image is disturbed due to loss on the transmission path.

  The conventional image encoding apparatus performs encoding by changing at least one of the resolution and the frame rate according to the degree of difficulty of encoding the input image, and the resolution of the encoding target image according to the bit rate. The upper limit value or the lower limit value is determined, and control is performed to select the resolution within the range. Furthermore, by controlling the resolution not to change until a predetermined time elapses after the resolution is changed or until a predetermined number of input images are processed, blurring due to frequent switching of resolution at a low bit rate occurs. Image coding can be performed, and subjective image quality degradation is prevented (see, for example, Patent Document 1).

International Publication No. 2010/150470

  The conventional image coding apparatus switches the resolution in response to the change in the bit rate, but does not change the resolution until a predetermined time elapses, so the bit rate frequently changes and the bit rate greatly increases. When it is lowered, there is a problem that the quantization step becomes large and the decoded image deteriorates or the transmission buffer overflows. Alternatively, there is a problem in that encoded data is lost in the transmission path without being able to suppress the amount of information, and the decoded image is interrupted in the image decoding apparatus.

  The present invention has been made to solve the above-described problems, and reduces image quality degradation when changing the bit rate, prevents a decoding error from occurring in the image decoding apparatus, and prevents the decoded image from being interrupted. For the purpose.

  An image encoding apparatus according to the present invention receives an image signal, encodes the image signal using intra-frame prediction, inter-frame prediction, and variable-length encoding, and encodes the image signal on a transmission path in which the bit rate varies. In an image encoding device for transmitting converted image signal data, a resolution conversion unit that converts the resolution of the input image signal, and an arrangement that rearranges the image signals that have undergone resolution conversion by the resolution conversion unit from the input order to the encoding order A transmission unit that encodes the image signal output from the rearrangement unit, a transmission unit that accumulates the data encoded by the encoding unit, and sends the data to the transmission path according to the bit rate; Time stamp information adding means for adding time stamp information to transmitted data and resolution determining means for determining the resolution of the resolution converting means according to the bit rate And timing determination means for determining the timing for changing the resolution based on the bit amount of the encoded data stored in the transmission means when the bit rate is changed, and the timing for changing the resolution when the bit rate is changed. An encoding control means for controlling the encoding mode and the quantization step, and the encoding means performs encoding based on the encoding mode and the quantization step controlled by the encoding control means. is there.

  The image encoding device according to the present invention determines the timing for changing the resolution based on the bit amount of the encoded data stored in the transmission means when the bit rate is changed, and uses this timing to determine the encoding means. Controls the encoding mode and the quantization step, so that it is possible to reduce image quality degradation when changing the bit rate, and to prevent a decoding error from occurring in the image decoding apparatus and to prevent the decoded image from being interrupted. .

It is a block diagram which shows the image coding apparatus by Embodiment 1 of this invention. It is explanatory drawing which shows the write-in and read-out picture to the frame memory part of the image coding apparatus by Embodiment 1 of this invention. It is explanatory drawing which shows an example of a movement of the transmission buffer remaining amount at the time of the bit rate change of the image coding apparatus by Embodiment 1 of this invention. It is explanatory drawing which shows an example of a movement of the transmission buffer remaining amount in the case of changing a time stamp at the time of the bit rate change of the image coding apparatus by Embodiment 1 of this invention. It is a block diagram which shows the image coding apparatus by Embodiment 2 of this invention. It is a block diagram which shows the image coding apparatus by Embodiment 4 of this invention.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing the overall configuration of an image coding apparatus according to Embodiment 1 of the present invention.
In FIG. 1, a resolution conversion unit 1 is a block for reducing the resolution of an image signal 101 input to an image encoding device, and constitutes a resolution conversion unit. The frame memory unit 2 is a block including a memory (not shown) that stores the image signal 102 after the resolution conversion in the resolution conversion unit 1 in units of pictures according to the write control signal 103, and constitutes a rearranging unit. The image encoding unit 3 generates a read control signal 105 so that the image signal 102 stored in the frame memory unit 2 is rearranged in the encoding order in accordance with the GOP structure 120, and the read image signal 104 is subjected to intra-frame prediction or frame It is a block to be encoded using inter prediction, variable length encoding, etc., and constitutes an encoding means. The transmission buffer unit 4 temporarily accumulates video ES (Elementary Stream) data 106 output from the image encoding unit 3 in accordance with a write control signal 107, and outputs video ES data 108 in accordance with a read control signal 109 corresponding to the bit rate. At the same time, it is a block for outputting an accumulation amount (transmission buffer remaining amount) 110 of the video ES data 108 in the transmission buffer unit 4 and constitutes a transmission means.

  The time stamp adding unit 5 is a block for adding time stamp information to the video ES data 108 based on the transmission buffer delay time 112 and outputting the video TS (Transport Stream) data 111 to the transmission path. It is composed. The stream transmission time calculation unit 6 calculates the frame time required for the video ES data 108 to be extracted from the variable bit rate 113 specified from the outside and the transmission buffer remaining amount 110 when the bit rate is changed, and changes the resolution. The GOP switching timing information 114 is determined, and a time stamp change instruction 115 and a time stamp correction time 116 are output based on the remaining transmission buffer capacity 110, the bit rate 113, and the transmission buffer delay time 112. Is configured.

  The encoding control unit 7 calculates the target information generation amount based on the bit rate 113, the transmission buffer delay time 112, the transmission buffer remaining amount 110, and the picture type 117 determined from the GOP structure 120, and the macroblock according to the resolution 121 Each quantization step 118 and encoding mode 119 are determined and output to the image encoding unit 3. Further, when the bit rate is changed, the GOP switching timing information 114 output from the stream transmission time calculation unit 6 and the bit rate before the change are changed. This block outputs a new GOP structure 120 and in-GOP position information 122 based on the GOP structure, and constitutes an encoding control means. The resolution determination unit 8 is a block that determines the resolution 121 based on the variable bit rate 113, the GOP structure 120, and the intra-GOP position information 122, and constitutes a resolution determination unit.

Next, the operation of the first embodiment will be described.
In FIG. 1, the resolution converter 1 converts an input image signal 101 to a resolution 121 corresponding to a bit rate 113. For example, the number of pixels in the horizontal direction or the vertical direction is reduced to 3/4 times, 2/3 times, 1/2 times, or the like by filter processing. The converted image signal 102 is written in the frame memory unit 2 in picture order in accordance with the write control signal 103 in the order of input.

  The frame memory unit 2 rearranges the image signals 102 written in the order of input according to the read control signal 105 in the order of encoding and outputs them as the image signal 104. For example, FIG. 2 shows pictures to be written to and read from the frame memory unit 2 when M value (interval of I or P picture) = 3 and N value (interval of I picture) = 15.

  The image encoding unit 3 generates a read control signal 105 based on the GOP structure 120 and the picture type 117 as shown in FIG. 2, and reads the image signal 104 from the frame memory unit 2 in the encoding order. The read image signal 104 is encoded using intra-frame prediction or inter-frame prediction, variable-length encoding, etc. according to the picture type 117, quantization step 118, and encoding mode 119, and the variable-length video together with the write control signal 107. ES data 106 is output.

  The transmission buffer unit 4 temporarily stores the video ES data 106 in the memory, and outputs the video ES data 108 according to the read control signal 109 corresponding to the bit rate. Further, the remaining amount 110 of the transmission buffer stored in the memory is calculated from the bit amount of the written video ES data 106 and the bit amount of the read video ES data 108.

  The time stamp adding unit 5 adds time stamp information to the video ES data 108 based on the transmission buffer delay time 112, and outputs the video TS data 111 to the transmission path. Here, the transmission buffer delay time 112 is, for example, the VBV_delay initial value in the case of MPEG-2. In the case of H.264 / AVC, this is the amount of delay variation in the transmission buffer unit 4 corresponding to the CPB_removal_delay initial value. If the bit amount of the video ES data is controlled within the range of this delay variation, the reception buffer in the image decoding device It is guaranteed that it is possible to continue displaying the decoded image without causing underflow. The time stamp information is a time obtained by adding the delay time in the image encoding unit 3 and the transmission buffer delay time 112, and the time when the time stamp information is added to the time when the image signal 104 is started to be encoded is DTS ( Video TS data 111 is generated as Decoding Time Stamps).

  The encoding control unit 7 controls the bit amount of the video ES data 106 so that the transmission buffer remaining amount 110 does not exceed the transmission buffer delay time 112. That is, the target information generation amount of the next picture is calculated from the bit rate 113, the transmission buffer delay time 112, the transmission buffer remaining amount 110, and the picture type 117, and the quantization step 118 per macroblock and the encoding mode 119 are determined from the resolution 121. Are output to the image encoding unit 3.

  When the bit rate is fixed, by controlling the bit amount of the video ES data 106 as described above, it is possible to avoid an underflow of the reception buffer in the image decoding device, and to obtain a stable decoded image. it can. Here, the operation when the bit rate is variable will be described. The resolution determination unit 8 determines the optimal resolution 121 for encoding according to the bit rate 113. At this time, if it is necessary to change the resolution before and after changing the bit rate, once the GOP with the resolution before the change is finished once and encoded as a new GOP with the changed resolution, the decoded image is decoded by the image decoding apparatus. It is possible to change the resolution seamlessly without interruption.

  Accordingly, when the stream transmission time calculation unit 6 is instructed to change the bit rate 113 from the outside, the stream transmission time calculation unit 6 immediately sets the extraction rate of the video ES data 108 output from the transmission buffer unit 4 to a new bit rate. The read control signal 109 is changed. Also, the time required for the video ES data 108 to be extracted from the transmission buffer remaining amount 110 at this time at the changed bit rate 113 is calculated, and after that time has elapsed, a new one corresponding to the changed bit rate 113 is obtained. GOP switching timing information 114 is determined so that encoding is performed at resolution 121.

  An example of the movement of the transmission buffer remaining amount when the bit rate is changed is shown in FIG. The horizontal axis represents time, and T represents one picture time. The vertical axis represents the remaining amount of transmission buffer, and when the bit rate before change is R, the extraction amount per picture is RT. At this time, buffer control is performed in a state where the remaining buffer capacity is always accumulated for RT so that the transmission buffer does not underflow. In this figure, the time required to pull out the remaining buffer capacity to RT at the bit rate R ′ after the change when the bit rate change is instructed is 6T. Therefore, the GOP switching timing is determined so that encoding is performed at a new resolution 6 hours after the bit rate change instruction.

  At this time, the encoding control unit 7 performs the quantization step 118 and the encoding mode 119 so that encoding is performed in the Not Coded MB so that the amount of information generation is minimized during the period from the bit rate change instruction to the GOP switching timing. To control. Further, the GOP structure 120, the in-GOP position information 122, and the picture type 117 are output so that a new GOP can be started at the GOP switching timing. The resolution determination unit 8 outputs a new resolution 121 in consideration of the rearrangement from the input order to the encoding order in the frame memory unit 2 so that encoding can be started at the new resolution from the GOP switching timing. For example, when M value = 3, a new resolution 121 is output three pictures before the GOP switching timing in encoding.

When instructed to change the bit rate, the stream transmission time calculation unit 6 calculates the remaining buffer capacity (CPB_removal_delay initial value) corresponding to the transmission buffer delay time 112 using the changed bit rate. If the remaining buffer capacity at the time when the bit rate change is instructed is below the CPB_removal_delay initial value calculated at the changed bit rate, image decoding is performed by performing buffer control so as not to exceed that value. A stable decoded image can be obtained without causing a buffer failure in the apparatus.
On the other hand, when the remaining buffer capacity at the time when the bit rate change is instructed exceeds the CPB_removal_delay initial value calculated at the bit rate after the change, the time stamp adding unit 5 is notified of the picture immediately before the bit rate change. A time stamp change instruction 115 and a time stamp correction time 116 are output so as to recalculate the time stamp. After the remaining amount of the buffer falls below the CPB_removal_delay initial value calculated at the changed bit rate, the buffer control is performed so as not to exceed the value.

  An example of the movement of the remaining transmission buffer when changing the time stamp when the bit rate is changed is shown in FIG. Similar to FIG. 3, the horizontal axis represents time, and the vertical axis represents the remaining amount of transmission buffer. If CPB_removal_delay initial value at the bit rate R before change is N × RT, CPB_removal_delay initial value at the bit rate R ′ after change Becomes N × R′T. Since the remaining buffer capacity at the time when the bit rate change is instructed exceeds N × R′T, the time required for the time stamp of the encoded picture in 6T time to fall below N × R′T (here, 3T Time) Recalculate the time stamp to extend.

  As described above, in the image coding apparatus according to the first embodiment, when the bit rate of the transmission path changes, the bit rate is changed instantaneously and the bit rate according to the remaining amount of the transmission buffer at the time of changing the bit rate. The timing for changing to the optimum resolution and the encoding mode in the period from the bit rate change to the resolution change are controlled, and a new GOP is started after the transmission buffer remaining amount becomes minimum. Image quality degradation at the time of change can be reduced, and stream data is not lost in the transmission buffer or transmission path, and a stable decoded image can be obtained by the image decoding apparatus. Furthermore, since the time stamp is recalculated according to the remaining amount of the transmission buffer at the time of changing the bit rate and the bit rate after the change, the decoded image is not interrupted without causing a decoding error in the image decoding device. It becomes possible to do so.

  As described above, according to the image encoding device of the first embodiment, an image signal is input, and the image signal is encoded using intra-frame prediction, inter-frame prediction, and variable length encoding, In an image encoding device that transmits data of an image signal encoded on a transmission path with a variable bit rate, a resolution conversion unit that converts the resolution of the input image signal, and an image signal that has undergone resolution conversion by the resolution conversion unit Rearranging means for rearranging from the input order to the encoding order, encoding means for encoding the image signal output from the rearranging means, and data encoded by the encoding means are stored, and the data is transmitted to the transmission line according to the bit rate. A transmitting means for sending, a time stamp information adding means for adding time stamp information to data sent from the sending means, and a resolution converting means according to the bit rate. Resolution determining means for determining the degree, timing determining means for determining the timing for changing the resolution based on the bit amount of the encoded data stored in the transmitting means at the time of changing the bit rate, and resolution at the time of changing the bit rate. Coding control means for controlling the coding mode and the quantization step using the timing to be changed, and the coding means performs coding based on the coding mode and the quantization step controlled by the coding control means. Therefore, it is possible to reduce deterioration in image quality when changing the bit rate, and to prevent the decoding image from being interrupted without causing a decoding error in the image decoding apparatus.

  In addition, according to the image coding apparatus of the first embodiment, the timing determination unit determines the resolution according to the bit amount of the encoded data stored in the transmission unit and the bit rate after the change when the bit rate is changed. In addition, since the timing for changing the GOP is determined, it is possible to reduce the deterioration of the image quality when the bit rate is changed and to prevent the decoded image from being interrupted.

  In addition, according to the image coding apparatus of the first embodiment, the coding control unit performs the coding mode and the quantization step so that the amount of information generation is minimized in the period from the bit rate change to the resolution change. Since the control is performed, it is possible to reduce the deterioration of the image quality when the bit rate is changed and to prevent the decoded image from being interrupted.

  In addition, according to the image coding apparatus of the first embodiment, the time stamp information adding unit depends on the bit amount of the encoded data stored in the transmission unit and the bit rate after the change when the bit rate is changed. Since the time stamp information of the encoded data before changing the bit rate is changed, it is possible to prevent a decoded image from being interrupted without causing a decoding error in the image decoding apparatus.

Embodiment 2. FIG.
In the first embodiment, the encoding mode is controlled so as to minimize the amount of information generated during the period from the bit rate change to the resolution change. However, the image signal 104 in the encoding order read from the frame memory unit 2 is used. An example of controlling this will be described below as a second embodiment.

  FIG. 5 is a block diagram showing the overall configuration of the image coding apparatus according to the second embodiment. The difference in configuration is that the encoding control unit 7a outputs a readout plane repetition signal 123 when the bit rate is changed, and the image encoding unit 3a is based on the readout plane repetition signal 123, for the picture immediately before the bit rate change. The read control signal 105 is generated so that the image signal 104 is read repeatedly. Since the other configuration is the same as that of the first embodiment shown in FIG. 1, the same reference numerals are given to the corresponding portions and the description thereof is omitted.

Next, the operation of the second embodiment will be described while referring to differences from the first embodiment.
When the GOP switching timing information 114 is input when the bit rate is changed as in the first embodiment, the encoding control unit 7a reads the period from the bit rate change instruction to the GOP switching timing from the frame memory unit 2 in the encoding order. The readout surface repeat signal 123 is output so that the image signal 104 to be read repeatedly reads out the same picture data as before the bit rate change. The image encoding unit 3a generates the read control signal 105 so as to repeatedly read the image signal 104 of the picture immediately before the bit rate change, and repeatedly encodes the same picture so that the amount of information generation is minimized. Is encoded.

  As described above, according to the image encoding device of the second embodiment, an image signal is input, and the image signal is encoded using intra-frame prediction, inter-frame prediction, and variable length encoding, In an image encoding device that transmits data of an image signal encoded on a transmission path with a variable bit rate, a resolution conversion unit that converts the resolution of the input image signal, and an image signal that has undergone resolution conversion by the resolution conversion unit Rearranging means for rearranging from the input order to the encoding order, encoding means for encoding the image signal output from the rearranging means, and data encoded by the encoding means are stored, and the data is transmitted to the transmission line according to the bit rate. A transmitting means for sending, a time stamp information adding means for adding time stamp information to data sent from the sending means, and a resolution converting means according to the bit rate. Resolution determining means for determining the degree, timing determining means for determining the timing for changing the resolution based on the bit amount of the encoded data stored in the transmitting means at the time of changing the bit rate, and resolution at the time of changing the bit rate. Coding control means for controlling the selection of the image signal to be encoded using the timing to change, and the coding means changes the bit rate based on the selection of the image signal controlled by the coding control means Since the image signal to be encoded is selected so as to minimize the amount of information generated during the period from the resolution change to the resolution change, it is possible to obtain the same effect as in the first embodiment.

Embodiment 3 FIG.
In the second embodiment, the encoding order image signal 104 read from the frame memory unit 2 is controlled so that the amount of information generated in the period from the bit rate change to the resolution change is minimized. The readout of the image signal from 2 may be stopped, the frame rate may be lowered, and only the video ES data 108 may be extracted. This will be described below as a third embodiment.

  Since the block configuration in the drawing is the same as that of the second embodiment shown in FIG. 5, description will be made with reference to FIG. In the third embodiment, the readout surface repetition signal 123 of the second embodiment output from the encoding control unit 7a to the image encoding unit 3a is changed to a readout stop signal. Then, during the period from the bit rate change to the resolution change, the image encoding unit 3a stops reading the image signal 104 from the frame memory unit 2 and the image encoding process, and lowers the frame rate. Other configurations and operations are the same as those in the second embodiment.

  As described above, according to the image encoding device of the third embodiment, an image signal is input, and the image signal is encoded using intra-frame prediction, inter-frame prediction, and variable length encoding, In an image encoding device that transmits data of an image signal encoded on a transmission path with a variable bit rate, a resolution conversion unit that converts the resolution of the input image signal, and an image signal that has undergone resolution conversion by the resolution conversion unit Rearranging means for rearranging from the input order to the encoding order, encoding means for encoding the image signal output from the rearranging means, and data encoded by the encoding means are stored, and the data is transmitted to the transmission line according to the bit rate. A transmitting means for sending, a time stamp information adding means for adding time stamp information to data sent from the sending means, and a resolution converting means according to the bit rate. Resolution determining means for determining the degree, timing determining means for determining the timing for changing the resolution based on the bit amount of the encoded data stored in the transmitting means at the time of changing the bit rate, and resolution at the time of changing the bit rate. Encoding control means for controlling the frame rate of the image signal to be encoded using the timing to be changed, and the encoding means is configured to use bits based on the frame rate of the image signal controlled by the encoding control means. Since the frame rate of the image signal to be encoded is controlled so that the amount of information generation is minimized during the period from the rate change to the resolution change, it is possible to obtain the same effect as in the first embodiment. is there.

Embodiment 4 FIG.
In the first to third embodiments, when the remaining buffer capacity at the time when the bit rate change is instructed exceeds the CPB_removal_delay initial value calculated at the changed bit rate, the time stamp is changed. Although the video ES data 108 read out from the transmission buffer unit 4 may be controlled, this is described below as a fourth embodiment.

  FIG. 6 is a block diagram showing the overall configuration of the fourth embodiment. The difference from the first embodiment is that the image encoding unit 3b outputs the picture information generation amount 124 to the stream transmission time calculation unit 6a and the stream transmission time calculation unit 6a When the remaining buffer capacity at the time when the bit rate change is instructed exceeds the initial value of CPB_removal_delay calculated at the changed bit rate, the video ES data for how many pictures is obtained from the history of the picture information generation amount 124 This is a point that it is calculated whether or not to discard, and the read control signal 109a is sent to the transmission buffer unit 4 so as not to read the corresponding video ES data 108. Further, the time stamp change instruction 115 and the time stamp correction time 116 to the time stamp adding unit 5 in the first embodiment are deleted from the stream transmission time calculating unit 6a.

Next, the difference of the operation of the fourth embodiment from the first to third embodiments will be described.
The image encoding unit 3b outputs the picture information generation amount 124 of the video ES data 106 generated by the image encoding to the stream transmission time calculation unit 6a. The stream transmission time calculation unit 6a stores the picture information generation amount 124 for a predetermined number of pictures. If the buffer remaining amount at the time when the bit rate change is instructed exceeds the CPB_removal_delay initial value calculated at the changed bit rate, the CPB_removal_delay initial value calculated at the changed bit rate The video ES data is discarded so as to be less than. That is, the stream transmission time calculation unit 6a calculates how many video ES data should be discarded from the history of the picture information generation amount 124, and reads the control signal 109a so that the video ES data 108 is not read out. To control.

  As described above, according to the image coding apparatus of the fourth embodiment, at the time of changing the bit rate, according to the bit amount of the encoded data accumulated in the transmission unit and the bit rate after the change, the transmission unit Since the encoded data before changing the bit rate is discarded, it is possible to obtain the same effect as in the first embodiment.

Embodiment 5 FIG.
In Embodiment 4 above, when the remaining buffer capacity at the time when the bit rate change is instructed exceeds the CPB_removal_delay initial value calculated at the changed bit rate, the transmission buffer unit decreases below that value. Although the video ES data of 4 is discarded, the video ES data discard may be controlled for each picture type at this time, and this example will be described below as a fifth embodiment. The block configuration in the fifth embodiment is the same as that in the fourth embodiment shown in FIG. 6, and will be described with reference to FIG.

  In the image coding apparatus according to the fifth embodiment, the picture type is output together with the picture information generation amount 124 output from the image encoding unit 3b to the stream transmission time calculation unit 6a. When discarding the video ES data in the transmission buffer unit 4, the stream transmission time calculation unit 6a calculates the bit amount necessary to fall below the CPB_removal_delay initial value, and based on the picture type from the image encoding unit 3b, B The read control signal 109a is controlled so that only the B picture is discarded when only the picture needs to be discarded, and only the B picture and the P picture are discarded when only the B picture and the P picture are discarded.

  As described above, according to the image coding apparatus of the fifth embodiment, at the time of changing the bit rate, according to the bit amount of the encoded data accumulated in the transmission unit and the bit rate after the change, the transmission unit Since the discard of the encoded data before changing the bit rate is controlled for each picture type, the same effect as in the first embodiment can be obtained. In addition, it is possible to obtain a decoded image that has a smoother motion when the bit rate is changed than in the fourth embodiment.

  In the present invention, within the scope of the invention, any combination of the embodiments, or any modification of any component in each embodiment, or omission of any component in each embodiment is possible. .

  DESCRIPTION OF SYMBOLS 1 Resolution conversion part, 2 Frame memory part, 3, 3a, 3b Image encoding part, 4 Transmission buffer part, 5 Time stamp addition part, 6, 6a Stream transmission time calculation part, 7, 7a Encoding control part, 101, 102, 104 Image signal, 103, 107 Write control signal, 105, 109, 109a Read control signal, 106, 108 Video ES data, 110 Transmission buffer remaining capacity, 111 Video TS data, 112 Transmission buffer delay time, 113 Bit rate, 114 GOP switching timing information, 115 Timestamp change instruction, 116 Timestamp correction time, 117 Picture type, 118 Quantization step, 119 Coding mode, 120 GOP structure, 121 Resolution, 122 In-GOP position information, 123 Reading surface repetition And signal 124 picture information generation amount.

Claims (8)

An image signal is input, the image signal is encoded using intra-frame prediction, inter-frame prediction, and variable-length encoding, and the encoded image signal data is transmitted to a transmission path where the bit rate varies. In the image encoding device to
Resolution conversion means for converting the resolution of the input image signal;
Rearrangement means for rearranging the image signals having undergone resolution conversion by the resolution conversion means from the input order to the encoding order;
Encoding means for encoding the image signal output from the rearranging means;
Transmitting means for storing the data encoded by the encoding means and sending it to the transmission line according to the bit rate;
Time stamp information adding means for adding time stamp information to data transmitted from the transmitting means;
Resolution determining means for determining the resolution of the resolution converting means according to the bit rate;
Timing determination means for determining the timing for changing the resolution based on the bit amount of the encoded data stored in the transmission means when changing the bit rate;
Coding control means for controlling the coding mode and the quantization step using the timing of changing the resolution when changing the bit rate,
The image encoding apparatus, wherein the encoding unit performs encoding based on an encoding mode and a quantization step controlled by the encoding control unit. Said timing determination means, and wherein when the bit rate change, in response to said bit amount and the bit rate after the change of the data coded are stored in the transmission means, to determine when to change the resolution and GOP The image encoding device according to claim 1. The encoding control means controls the encoding mode and the quantization step so as to minimize the amount of information generated in the period from the bit rate change to the resolution change. The image encoding device described. An image signal is input, the image signal is encoded using intra-frame prediction, inter-frame prediction, and variable-length encoding, and the encoded image signal data is transmitted to a transmission path where the bit rate varies. In the image encoding device to
Resolution conversion means for converting the resolution of the input image signal;
Rearrangement means for rearranging the image signals having undergone resolution conversion by the resolution conversion means from the input order to the encoding order;
Encoding means for encoding the image signal output from the rearranging means;
Transmitting means for storing the data encoded by the encoding means and sending it to the transmission line according to the bit rate;
Time stamp information adding means for adding time stamp information to data transmitted from the transmitting means;
Resolution determining means for determining the resolution of the resolution converting means according to the bit rate;
Timing determination means for determining the timing for changing the resolution based on the bit amount of the encoded data stored in the transmission means when changing the bit rate;
Encoding control means for controlling selection of an image signal to be encoded using timing for changing the resolution when the bit rate is changed,
The encoding means, based on the selection of the image signal controlled by the encoding control means, the image signal to be encoded so that the amount of information generation is minimized in the period from the bit rate change to the resolution change. An image encoding apparatus characterized by selecting. An image signal is input, the image signal is encoded using intra-frame prediction, inter-frame prediction, and variable-length encoding, and the encoded image signal data is transmitted to a transmission path where the bit rate varies. In the image encoding device to
Resolution conversion means for converting the resolution of the input image signal;
Rearrangement means for rearranging the image signals having undergone resolution conversion by the resolution conversion means from the input order to the encoding order;
Encoding means for encoding the image signal output from the rearranging means;
Transmitting means for storing the data encoded by the encoding means and sending it to the transmission line according to the bit rate;
Time stamp information adding means for adding time stamp information to data transmitted from the transmitting means;
Resolution determining means for determining the resolution of the resolution converting means according to the bit rate;
Timing determination means for determining the timing for changing the resolution based on the bit amount of the encoded data stored in the transmission means when changing the bit rate;
Encoding control means for controlling the frame rate of the image signal to be encoded using the timing of changing the resolution when the bit rate is changed,
The encoding means is an image signal that is encoded based on a frame rate of the image signal controlled by the encoding control means so that an information generation amount is minimized in a period from a bit rate change to a resolution change. An image encoding apparatus for controlling the frame rate of the image. The time stamp information adding unit, when the bit rate change, in response to said bit amount and the bit rate after the change of the data coded are stored in the transmission unit, the time stamp of the data encoded in the pre-change bit rate The image coding apparatus according to any one of claims 1 to 3, wherein the information is changed. When the bit rate change, and wherein according to the bit amount and the bit rate after change in the encoded data accumulated in the transmission unit, for discarding the data encoded before bit rate change of the transmission means The image encoding device according to any one of claims 1 to 5. When the bit rate changes in accordance with the bit amount and the bit rate after the change of the data coded are stored in the transmitting unit, the discard of the data encoded in the previous bit rate change of the transmission unit for each picture type 8. The image coding apparatus according to claim 7, wherein the image coding apparatus is controlled.

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