JP2017216625A5

JP2017216625A5 -

Info

Publication number: JP2017216625A5
Application number: JP2016110213A
Authority: JP
Filing date: 2016-06-01
Publication date: 2019-06-27
Anticipated expiration: 2036-06-01

Claims

An image encoding apparatus for encoding moving image data captured by an imaging unit, comprising:
Frequency conversion means for frequency converting a frame of interest in the moving image data to generate a plurality of sub bands;
Quantizing means for quantizing coefficient data of each sub-band in accordance with a quantizing parameter determined according to the set target code amount;
Encoding means for encoding coefficient data after quantization to generate encoded data;
Code amount control means for setting a target code amount according to the code amount of the immediately preceding frame generated by the encoding means;
An image coding apparatus characterized by further comprising: determining means for determining whether there is a scene change between the focused frame and the immediately preceding frame for each of the plurality of sub-bands.

The image coding apparatus according to claim 1, wherein the determination means determines whether there is a scene change in the sub-band according to a coding result of the coefficient data of the sub-band by the coding means. .

The code amount control unit is not a target code amount determined based on the code amount of the previous frame generated by the encoding unit for the sub-bands determined by the determination unit to have a scene change. The image coding apparatus according to claim 1, wherein a target code amount for a scene change set in advance is set.

The code amount control means sets a target code amount determined in accordance with the code amount of the previous frame generated by the encoding means for the sub-bands determined by the determination means that there is no scene change. The image coding apparatus according to claim 3, characterized in that:

The quantizing means quantizes coefficient data of each subband in a predetermined area unit,
The encoding means performs encoding for each of the predetermined areas,
The image coding apparatus according to claim 1, wherein the judgment means judges whether there is a scene change at the timing when coding of a preset area is completed in each subband.

The predetermined area is one line, and
6. The image encoding apparatus according to claim 5, wherein the determination unit performs the determination each time encoding of a predetermined line position is completed in each subband.

The determination means compares the code amount generated up to the line position where encoding is completed with a value obtained by multiplying the code amount generated up to the line position in the immediately preceding frame by a predetermined value. The image coding apparatus according to claim 6, wherein it is determined whether or not there is.

The determination means calculates, for each of the plurality of sub-bands, an evaluation value indicating a degree of change between the frame of interest and the immediately preceding frame, and adds a total value of evaluation values of all sub-bands and a predetermined threshold value. Determine whether there is a scene change by comparing
When the determination unit determines that there is a scene change, the code amount control unit determines a target code amount determined according to the code amount of the previous frame generated by the encoding unit for all subbands. 2. The image coding apparatus according to claim 1, wherein a target code amount for a scene change set in advance is not set.

2. The apparatus according to claim 1, wherein said determination means determines whether or not there is a scene change for a plurality of predetermined sub-bands, not all sub-bands generated by the frequency conversion means. Image coding device.

The determination means
The image coding apparatus according to claim 1, wherein for each of the plurality of sub-bands, it is determined whether there is a scene change based on an index value indicating the degree of difficulty of the image of the sub-band.

The code amount control means
In the sub-band determined to have no scene change by the determination means, target code amount of the predetermined area to be quantized next is information about code amount generated in the sub-band in the frame of interest and the immediately preceding Calculation based on the information on the code amount of the corresponding subband of the frame, and setting the quantization parameter from the difference between the target code amount and the actual coded data amount;
In a sub-band determined to have a scene change by the determination means, the target code amount of the predetermined area to be quantized next is set to a preset fixed value, and the sub-band in the frame of interest And setting means for setting the quantization parameter from the difference between the code amount generated in
The image coding apparatus according to claim 5, characterized in that:

The setting means is
The quantization parameter used in the i-1th line immediately before the i-th line in the target subband is Qp [i-1], and the code amount of the encoded data in the i-1th line is S [i- 1], the complexity X [i-1] of the (i-1) th line is obtained by the following equation (1),
X [i-1] = Qp [i-1] x S [i-1] (1)
Assuming that the target code amount of the subband of interest is Tsb, and the total value of the complexity of the corresponding subband of the immediately preceding frame is Xsb_N-1, quantize next in the subband determined to have no scene change. Line target code quantity T [i] of the line to be obtained is T [i] = Tsb × X [i−1] / Xsb_N−1
Calculated as
To claim 11, characterized in that a scene change there with the determined next value Tsc which previously statistically determined line target code amount T of the line that will quantized [i] in the sub-band Image coding apparatus as described.

The setting means is
The initial quantization parameter when there is no scene change, Qpini,
The control sensitivity of the case have a scene change is no r,
The initial quantization parameter when there is a scene change is Qpinisc,
Rsc the control sensitivity of the case of there is a scene change,
Integration of the difference between the encoded data amount up to the (i-1) th line and the target code amount is ΣE [i-1]
When we define
The quantization parameter Qp [i] of the line to be quantized next in the focused subband when there is no scene change is obtained by the following equation (2): Qp [i] = Qpini + r × rE [i−1] ((2) 2)
The quantization parameter Qp [i] of the line to be quantized next in the focused subband in the presence of a scene change is obtained by the following equation (3): Qp [i] = Qpinisc + rsc × ΣE [i-1]. (3)
The image coding apparatus according to claim 12 , characterized in that:

A control method of an image encoding apparatus for encoding moving image data captured by an imaging unit, comprising:
A frequency conversion step of frequency converting a frame of interest in the moving image data to generate a plurality of sub-bands;
A quantization step of quantizing coefficient data of each subband according to a quantization parameter determined according to the set target code amount;
An encoding process in which encoding means encodes the coefficient data after quantization to generate encoded data;
A code amount control step of setting a target code amount according to the code amount of the immediately preceding frame generated in the encoding step;
A control method of an image coding apparatus, comprising: a determination step of determining whether there is a scene change between the focused frame and the immediately preceding frame for each of the plurality of sub-bands.

By executing read into a computer program to function as the image coding apparatus according to the computer, in any one of claims 1 to 13.