MOVING IMAGE ENCODING APPARATUS, MOVING IMAGE ENCODING METHOD, AND MOVING IMAGE ENCODING COMPUTER PROGRAM

• US 20110292995A1
• Filed: 08/09/2011
• Published: 12/01/2011
• Est. Priority Date: 02/27/2009
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: KUBOTA, Tomonori
• Granted Patent: US 9,025,664 B2
• Time in Patent Office: Days
• US Class Current: 375/240.02
• CPC Class Codes: G06F 5/06 for changing the speed of data flow, i.e. speed regularising or timing, e.g. delay lines, FIFO buffers; over- or underrun control therefor G06F7/78 takes precedence
• CPC Class Codes: G06F 5/065 Partitioned buffers, e.g. allowing multiple independent queues, bidirectional FIFO's
• CPC Class Codes: H04N 19/115 Selection of the code volume for a coding unit prior to coding
• CPC Class Codes: H04N 19/152 by measuring the fullness of the transmission buffer
• CPC Class Codes: H04N 19/177 the unit being a group of pictures [GOP]
• CPC Class Codes: H04N 19/436 using parallelised computational arrangements
• CPC Class Codes: H04N 21/23406 involving management of server-side video buffer
• CPC Class Codes: H04N 21/23424 involving splicing one content stream with another content stream, e.g. for inserting or substituting an advertisement
• CPC Class Codes: H04N 21/2401 Monitoring of the client buffer
• CPC Class Codes: H04N 21/25833 involving client hardware characteristics, e.g. manufacturer, processing or storage capabilities allocation of resources considering hardware capabilities in multiprogramming arrangements G06F9/5044; allocation of resources considering software capabilities in multiprogramming arrangements G06F9/5055

Abstract

A moving image encoding apparatus, which divides moving image data into a plurality of sub-data, encodes the sub-data in parallel by using a plurality of encoders, and thereafter splices the resulting encoded sub-bitstream data into a single bitstream, includes a convergence target deriving function for determining a target value for a first amount of buffer occupancy so that the first amount of buffer occupancy at a point in time at which data corresponding to a last picture contained in first sub-bitstream data is removed from a first hypothetical buffer does not drop below a second amount of buffer occupancy which represents the amount of space that second sub-bitstream data occupies in a second hypothetical buffer at that point in time.

Claims

1. A moving image encoding apparatus comprising:

a storage unit which stores moving image data which includes at least first sub-data and second sub-data each containing a plurality of pictures;

a processing unit which, by encoding said moving image data, generates bitstream data whose amount of data is smaller than the amount of data of said moving image data; and

an output unit which outputs said bitstream data, wherein

said processing unit implements;

a convergence target deriving function which, on the assumption that said bitstream data is transferred to a hypothetical decoder at a prescribed transfer rate and stored into a buffer in said decoder and that data corresponding to said pictures contained in said bitstream data are sequentially removed from said buffer at predetermined intervals of time, determines a target value for a first amount of buffer occupancy so that said first amount of buffer occupancy, which represents the amount of space that said bitstream data occupies in said buffer at a first point in time at which data corresponding to a last picture contained in first sub-bitstream data generated by encoding said first sub-data is removed from said buffer, does not drop below a second amount of buffer occupancy which represents the amount of space that second sub-bitstream data generated by encoding said second sub-data occupies in said buffer at said first point in time;

a first encoding function which determines the number of encoding bits to be allocated to each picture contained in said first sub-data so that said first amount of buffer occupancy becomes identical with said target value, and which generates said first sub-bitstream data by encoding said first sub-data in accordance with said allocated number of encoding bits;

a second encoding function which generates said second sub-bitstream data by encoding said second sub-data; and

a splicing function which generates said bitstream data by splicing said first sub-bitstream data and said second sub-bitstream data.

2. The moving image encoding apparatus according to claim 1, wherein said splicing function inserts, between said first sub-bitstream data and said second sub-bitstream data, a bit string having a length corresponding to a difference obtained by subtracting said second amount of buffer occupancy from said first amount of buffer occupancy at said first point in time.

3. The moving image encoding apparatus according to claim 2, wherein said bit string is an invalid bit string that, when the last picture contained in said first sub-bitstream data is decoded by said hypothetical decoder, is extracted from said buffer along with the data corresponding to said last picture, and that does not affect the decoding of said last picture.

4. The moving image encoding apparatus according to claim 1, wherein said first encoding function includes:

an amount-of-occupancy limit value determining function which, when data corresponding to a first picture contained in said first sub-bitstream data is removed from said buffer, increases a lower limit value for the amount of space that said bitstream data occupies in said buffer so that said lower limit value comes closer to said target value as said first picture is located nearer to a back end of said first sub-bitstream data; and

an information rate control function which determines the number of encoding bits to be allocated to said first picture so that, when said first picture is removed from said buffer, the amount of space that said bitstream data occupies in said buffer does not drop below said lower limit value.

5. The moving image encoding apparatus according to claim 4, wherein said amount-of-occupancy limit value determining function determines an upper limit value for the amount of space that said bitstream data occupies in said hypothetical buffer when data corresponding to a second picture contained in said first sub-bitstream data is stored into said hypothetical buffer and, if said determined upper limit value is lower than said target value, said amount-of-occupancy limit value determining function corrects said upper limit value so that said upper limit value becomes higher than said target value.

6. The moving image encoding apparatus according to claim 4, wherein

said first encoding function further includes:

a quantizing function which generates a frequency signal by applying an orthogonal transform to a signal corresponding to each pixel in each of said plurality of pictures contained in said first sub-bitstream data, and which quantizes said frequency signal with a quantization step size that becomes smaller as said allocated number of encoding bits becomes larger; and

a variable-length encoding function which generates said first sub-bitstream data by applying variable-length coding to said quantized frequency signal, and wherein

when said lower limit value determined in connection with said first picture contained in said first sub-bitstream data is denoted as a first lower limit value, and the lower limit value determined in connection with a picture encoded one picture before said first picture is denoted as a second lower limit value, said information rate control function determines said number of encoding bits to be allocated to said first picture by subtracting an amount of correction, which corresponds to a difference between said first lower limit value and said second lower limit value, from a basic number of encoding bits supposed to be allocated to said first picture when said first lower limit value is equal to said second lower limit value.

7. A moving image encoding method for encoding moving image data, which includes at least first sub-data and second sub-data each containing a plurality of pictures, and thereby generating bitstream data whose amount of data is smaller than the amount of data of said moving image data, comprising:

on the assumption that said bitstream data is transferred to a hypothetical decoder at a prescribed transfer rate and stored into a buffer in said decoder and that data corresponding to said pictures contained in said bitstream data are sequentially removed from said buffer at predetermined intervals of time, determining a target value for a first amount of buffer occupancy so that said first amount of buffer occupancy, which represents the amount of space that said bitstream data occupies in said buffer at a first point in time at which data corresponding to a last picture contained in first sub-bitstream data generated by encoding said first sub-data is removed from said buffer, does not drop below a second amount of buffer occupancy which represents the amount of space that second sub-bitstream data generated by encoding said second sub-data occupies in said buffer at said first point in time;

determining the number of encoding bits to be allocated to each picture contained in said first sub-data so that said first amount of buffer occupancy becomes identical with said target value, and generating said first sub-bitstream data by encoding said first sub-data in accordance with said allocated number of encoding bits;

generating said second sub-bitstream data by encoding said second sub-data; and

generating said bitstream data by splicing said first sub-bitstream data and said second sub-bitstream data.

8. A computer readable recording medium having a moving image encoding computer program for causing a computer to encode moving image data, which includes at least first sub-data and second sub-data each containing a plurality of pictures, and to thereby generate bitstream data whose amount of data is smaller than the amount of data of said moving image data, said computer program comprising instructions for causing the computer to execute the steps of:

on the assumption that said bitstream data is transferred to a hypothetical decoder at a prescribed transfer rate and stored into a buffer in said decoder and that data corresponding to said pictures contained in said bitstream data are sequentially removed from said buffer at predetermined intervals of time, determining a target value for a first amount of buffer occupancy so that said first amount of buffer occupancy, which represents the amount of space that said bitstream data occupies in said buffer at a first point in time at which data corresponding to a last picture contained in first sub-bitstream data generated by encoding said first sub-data is removed from said buffer, does not drop below a second amount of buffer occupancy which represents the amount of space that second sub-bitstream data generated by encoding said second sub-data occupies in said buffer at said first point in time;

determining the number of encoding bits to be allocated to each picture contained in said first sub-data so that said first amount of buffer occupancy becomes identical with said target value, and generating said first sub-bitstream data by encoding said first sub-data in accordance with said allocated number of encoding bits;

generating said second sub-bitstream data by encoding said second sub-data; and

generating said bitstream data by splicing said first sub-bitstream data and said second sub-bitstream data.