Video Multiple Description Coding (mdc)

SPECIAL TOPICS Video Multiple Description Coding (MDC)

Prof. Enrico Magli

Campione Salvatore Peraldo Lorenzo

145781 150327

Brief overview and general description The aim of this project is to point out the performances of a multiple description algorithm. The MDC algorithm used in this project is the temporal division: two descriptions of the same video (table.yuv, made of 30 frames, 352x288) are created by means of a MATLAB function (Multidescription.m); each description is characterized by 15 frames (one takes the even frame, table_sideR.yuv, and the other the odd frame, table_sideL.yuv). Then, H.264 encoder/decoder (last version available) is applied to each sequence and, by means of another MATLAB function (Reconstruction.m), the central description (i.e. the description obtained when both sequences are received) is reconstructed (table_recon.yuv). If only one of the two descriptions is received, an Interpolation algorithm has to be applied in order to obtain a 30-frame video; depending on which description (left or right) is received, a slightly different algorithm is implemented: InterpolationL.m and InterpolationR.m. A linear interpolation is used and where it couldn’t be applied, we just replicated one frame (i.e. last frame in odd description and first frame in even description). The goals are to carry out some graphs which relate: • Central PSNR vs Side PSNR • Side PSNR vs Bit-Rate • Side PSNR vs Quality factor • Bit-Rate comparison between a situation where MDC is used and where is not The PSNR data are computed using MSU Visual Quality Measurement Tools.

Simulation results Central PSNR vs Side PSNR The analysis is done with constant quality factor. The results are the following: QP 10 20 30 40 50

L Side PSNR 27,90 27,80 26,95 25,41 24,26

R Side PSNR 29,04 28,91 27,80 25,92 24,53

Central PSNR 51,89 42,04 32,84 27,86 25,37

Table 1: Central PSNR vs Side PSNR

Central VS Side PSNR 55

50

Central PSNR

45

40 Left Side Right Side

35

30

25

20 23

24

25

26

27

28

29

30

Side PSNR

Figure 1: Central PSNR vs Side PSNR Looking at the graph, you notice that the results are as those expected from the theoretical side. Side PSNR vs Bit-Rate This simulation compares the performances of both side descriptions in terms of PSNR vs Bit-Rate. Bitrate (kbit/s) 10051,74 3437,89 593,87 91,30 34,93

L Side PSNR 27,90 27,80 26,95 25,41 24,26

Bitrate (kbit/s) 10253,00 3699,00 612,37 94,06 35,14

R Side PSNR 29,04 28,91 27,80 25,92 24,53

Table 2: Side PSNR vs Bit-Rate PSNR vs Bit-rate 30

29

Side PSNR

28

27 Left Side Right Side

26

25

24

23 0,00

2000,00

4000,00

6000,00

8000,00

10000,00

Bit-rate (kbit/s)

Figure 2: Side PSNR vs Bit-Rate The results respect the theoretical ones.

12000,00

Side PSNR vs Quality factor This figure shows the previous one vs the quality factor instead of the bit-rate. QP 10 20 30 40 50

L Side PSNR 27,90 27,80 26,95 25,41 24,26

R Side PSNR 29,04 28,91 27,80 25,92 24,53

Table 3: Side PSNR vs Quality factor Side PSNRvs Quality Factor 30

29

28

Side PSNR

27

26 Left Side

25

Right Side

24

23

22

21 10

20

30

40

50

Quality Factor

Figure 3: Side PSNR vs Quality factor Bit-Rate comparison between a situation where MDC is used and where is not In this analysis, we compare MDC with a Single Description implementation. The simulation is carried out with the same quality factor; this means that the PSNR in presence of MDC is almost equal to the one in absence of MDC. For this reason, the comparison can be done looking at the Bit-Rate. The Bit-Rate of the reconstructed files is computed summing the two side bit-rate of the side descriptions. Central PSNR no MDC 51,79 41,66 32,64 27,78 25,28

Central PSNR MDC 51,89 42,04 32,84 27,86 25,37

Bit-Rate no MDC (kbit/s) 9193,82 2747,87 486,19 71,44 27,84

Bit-Rate MDC (kbit/s) 20304,74 7136,89 1206,24 185,36 70,07

Bitrate Left Side (kbit/s) 10051,74 3437,89 593,87 91,30 34,93

Bitrate Right Side (kbit/s) 10253,00 3699,00 612,37 94,06 35,14

Table 4: Bit-Rate comparison between a situation where MDC is used and where is not

Bitrate comparison 25000

BitRate [Kbit/s]

20000

15000 without MDC with MDC Right Side Left Side 10000

5000

0 0

10

20

30

40

50

60

QP

Figure 4: Bit-Rate comparison between a situation where MDC is used and where is not As you can see from the graph, the Bit-Rate in presence of MDC is higher than the one without MDC, as expected from theoretical results.

Appendix Multidescription.m clc; or_path='table.yuv'; % Original file dest_pathL = 'table_sideL.yuv'; dest_pathR = 'table_sideR.yuv'; height=288; width=352; N=30; frame_size=height*width*1.5; f_or = fopen(or_path,'rb'); original = fread(f_or); fclose(f_or); flag = 0; sideL = []; sideR = []; for i=0:N-1 if(flag == 0) sideL= [sideL ; original(i*frame_size+1:(i+1)*frame_size)]; flag = 1; else sideR= [sideR ; original(i*frame_size+1:(i+1)*frame_size)]; flag=0; end end f_dst=fopen(dest_pathL,'wb'); fwrite(f_dst,sideL,'uint8'); fclose(f_dst); f_dst=fopen(dest_pathR,'wb'); fwrite(f_dst,sideR,'uint8'); fclose(f_dst);

Reconstruction.m clc f_orL=fopen('table_sideL.yuv','rb'); f_orR=fopen('table_sideR.yuv','rb'); originalL=fread(f_orL); originalR=fread(f_orR); fclose(f_orL); fclose(f_orR); height=288; width=352; N=30; frame_size=height*width*1.5; f_rec=fopen('table_recon.yuv','a'); for i=0:N/2-1 fwrite(f_rec, originalL(i*frame_size+1:(i+1)*frame_size), 'uint8'); fwrite(f_rec, originalR(i*frame_size+1:(i+1)*frame_size), 'uint8'); end fclose(f_rec); InterpolationL.m clc or_path='table_sideL_50.yuv'; % Original file dest_pathL = 'table_sideL_50_30frames.yuv'; f_or = fopen(or_path,'rb'); original = fread(f_or); fclose(f_or); height=288; width=352; N=30; frame_size=height*width*1.5; new = []; for i=0:N/2-2 new = [new ; original(i*frame_size+1:(i+1)*frame_size)]; new = [new ; (original(i*frame_size+1:(i+1)*frame_size)+original((i +1)*frame_size+1:(i+2)*frame_size) )/2]; end new = [new ; original(i*frame_size+1:(i+1)*frame_size)]; new = [new ; original(i*frame_size+1:(i+1)*frame_size)]; f_dst=fopen(dest_pathL,'wb'); fwrite(f_dst,new,'uint8'); fclose(f_dst);

InterpolationR.m clc or_path='table_sideR_50.yuv'; % Original file dest_pathL = 'table_sideR_50_30frames.yuv'; f_or = fopen(or_path,'rb'); original = fread(f_or); fclose(f_or); height=288; width=352; N=30; frame_size=height*width*1.5; new = []; i=0; new = [new ; original(i*frame_size+1:(i+1)*frame_size)]; for i=0:N/2-2 new = [new ; original(i*frame_size+1:(i+1)*frame_size)]; new = [new ; (original(i*frame_size+1:(i+1)*frame_size)+original((i +1)*frame_size+1:(i+2)*frame_size) )/2]; end new = [new ; original(i*frame_size+1:(i+1)*frame_size)]; f_dst=fopen(dest_pathL,'wb'); fwrite(f_dst,new,'uint8'); fclose(f_dst);