Method and device for calculating distortion of a video being affected by compression artifacts and channel artifacts
View Patent ↗In video quality control and estimation, the joint evaluation of compression artifacts and channel artifacts is a problem. The invention considers the joint perception of both a compression artifact level D m (V) and a channel artifact level D h (V) in a method for calculating overall distortion in a video being affected by compression artifacts and channel artifacts. The method comprises a step of adding a compression artifact level D m (V) and a summand S that is derived from log (D h (V)) multiplied with a factor that decreases with increasing compression artifact level D m , such as D(V)=D m (V)+c·(K−D m (V))·log(D h (V)). The result obtained is a measure for the overall distortion.
1. A method comprising calculating the overall distortion D(V) of a video stream V being affected by compression artifacts represented by a compression artifact level D m (V) and channel artifacts represented by a channel artifact level D h (V), comprising:
calculating, by at least one processor, a summand S from log (D h (V)) multiplied with a compression artifact factor (K−D m (V)) that decreases with increasing compression artifact level D m (V), where K is a positive constant summand;
adding, by the at least one processor, the compression artifact level D m (V) and summand S to obtain a measure for said overall distortion D(V); and
minimizing the measured overall distortion D(V) by assigning available bandwidth to the video stream based on an output of the measured overall distortion D(V) to correct the video stream affected by compression artifacts and channel artifacts.
2. The method according to claim 1 , wherein the summand S is calculated according to S=c 0 (K−D m (V))log(D h (V)), with c 0 and K being positive constants, the channel artifacts level D h (V) being positive and log(D h (V)) being a logarithm of the channel artifacts level D h (V).
3. The method according to claim 2 , wherein the compression artifact level D m (V) and the channel artifact level D h (V) are measured in a range between a minimum value and a maximum value, and K is equal to the maximum value.
4. The method according to claim 3 , wherein c 0 is equal to 0.9/log(K).
5. The method according to claim 3 , further comprising:
receiving control data from a user interface; and
setting or adjusting the parameter c 0 according to the control data.
6. The method according to claim 2 , wherein the minimum value is 1 and the maximum value is 5, and c 0 is equal to 1.2876.
7. The method according to claim 1 , further comprising a mapping, wherein the compression artifact level D m (V) and the channel artifact level D h (V) are measured in a range between a minimum value and a maximum value, and wherein the minimum value is mapped to 1 and the maximum value is mapped to 5 by a linear operation in said mapping step, and wherein K is substantially equal to 5 and c 0 is equal to 0.9/log(5) which is equivalent to 1.28.
8. The method according to claim 1 , wherein the assigning further comprises assigning, in a bandwidth limited transmission system, available bandwidth b to a video stream and to a packet loss recovery stream, wherein a bandwidth x assigned to the video stream leads to a compression artifact level D m (x) and the bandwidth b−x assigned to the packet loss recovery stream leads to a channel artifacts level of D h (b−x), wherein an overall distortion D tot of the video is calculated according to claim 1 , the method further comprising selecting the bandwidth x to minimize the overall distortion according to D tot (D m (x), D h (b−x)).
9. An apparatus comprising calculating overall distortion in a video stream-V being affected by both compression artifacts represented by a compression artifact D m (V) and channel artifacts represented by a channel artifact level D h (V), comprising:
a calculator for calculating, by at least one processor, a summand S from log (D h (V)) multiplied with a compression artifact factor (K−D m (V)) that decreases with increasing compression artifact level D m (V), where K is a positive constant summand;
an adder for adding the compression artifact level D m (V) and the summand S to obtain a measure for said overall distortion D(V); and
a controller for minimizing the overall distortion by assigning available bandwidth to the video stream based on an output of the overall distortion to correct the video stream affected by compression artifacts and channel artifacts.
10. The apparatus according to claim 9 , wherein the compression artifact level D m (V) and the channel artifact level D h (V) are measured in a range between a minimum value and a maximum value and K is substantially equal to the maximum value.
11. The apparatus according to claim 10 , wherein the minimum value is 1 and the maximum value is 5, and c 0 is equal to 1.2876.
12. The apparatus according to claim 9 , further comprising input unit for receiving control data from a user interface, and a controller-for setting or adjusting at least one of the parameters K, c 0 according to the control data.
13. The apparatus according to claim 9 , wherein the summand S is calculated according to S=c 0 (K−D m (V))log(D h (V)), with c 0 and K being positive constants, the channel artifacts level being positive and log(D h (V)) being a logarithm of the channel artifacts level.
14. The apparatus according to claim 9 , wherein the assigning further comprises assigning, in a bandwidth limited transmission system, available bandwidth b to a video stream and to a packet loss recovery stream, wherein a bandwidth x assigned to the video stream leads to a compression artifact level D m (x) and a bandwidth b−x assigned to the packet loss recovery stream leads to a channel artifacts level of D h (b−x), the overall distortion D tot of the video being calculated in an apparatus according to claim 10 , the apparatus for assigning available bandwidth comprising a selector for selecting the bandwidth x to minimize the overall distortion according to D tot (D m (X), D h (b−x)).
15. A method for controlling a video quality by calculating the overall distortion D(V) of a video stream V being affected by compression artifacts represented by a compression artifact level D m (V) and channel artifacts represented by a channel artifact level D h (V), comprising:
calculating, by at least one processor, a summand S from log (D h (V)) multiplied with a compression artifact factor (K−D m (V)) that decreases with increasing compression artifact level D m , where K is a positive constant summand;
adding, by the at least one processor, the compression artifact level D m (V) and summand S to obtain a measure for said overall distortion D(V); and
controlling the video quality of the video stream V based on an output of the measured overall distortion D(V) to correct the video stream affected by compression artifacts and channel artifacts.
16. An apparatus for controlling a video quality by calculating overall distortion in a video stream-V being affected by both compression artifacts represented by a compression artifact D m (V) and channel artifacts represented by a channel artifact level D n (V), comprising:
a calculator for calculating, by at least one processor, a summand S from log (D h (V)) multiplied with a compression artifact factor (K−D m (V)) that decreases with increasing compression artifact level D m (V), where K is a positive constant summand;
an adder for adding the compression artifact level D m (V) and the summand S to obtain a measure for said overall distortion D(V); and
a controller for controlling the video quality of the video stream V based on an output of the overall distortion to correct the video stream affected by compression artifacts and channel artifacts.
17. A non-transitory computer-readable storage medium comprising a computer-readable program for controlling a video quality by calculating the overall distortion D(V) of a video stream V being affected by compression artifacts represented by a compression artifact level D m (V) and channel artifacts represented by a channel artifact level D h (V), wherein the computer-readable program when executed on a computer causes the computer to perform the steps of:
calculating, by at least one processor, a summand S from log (D h (V)) multiplied with a compression artifact factor (K−D m (V)) that decreases with increasing compression artifact level D m , where K is a positive constant summand;
adding, by the at least one processor, the compression artifact level D m (V) and summand S to obtain a measure for said overall distortion D(V); and
controlling the video quality of the video stream V based on an output of the measured overall distortion D(V) to correct the video stream affected by compression artifacts and channel artifacts.