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MPEG Encoding

MPEG Encoding. The MPEG standards do not concern about the encoding process Vendors need to figure out the implementation to generate the content Usually let the content creators do the trial-and-error process for the “right” parameters Do not guarantee the quality is always optimal.

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MPEG Encoding

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  1. MPEG Encoding • The MPEG standards do not concern about the encoding process • Vendors need to figure out the implementation to generate the content • Usually let the content creators do the trial-and-error process for the “right” parameters • Do not guarantee the quality is always optimal

  2. Modeling MPEG-4 Interactive MOCPN--- An extension of Object Composition Petri Net MOCPN={P, T,A,M,D,TS,PT} Run time MOCPN generation according to the requirement of live video: mostly caused by user interaction. Such as old video cease and new video inserted.

  3. Three Scheduling Algorithms Goal: Distribute the encoding task of multiple video object to the cluster workstations for high speed up. Need a dynamic scheduling scheme because the non static nature of task situation. Scheduling is NP in nature, need to find heuristic methods RRS( Round Robin Scheduling) GS (Group Scheduling) GAS (GOV adjusting scheduling)

  4. Notation and Equation used Voj ith video object Vopi,j jth frame of video object Voj j start time of the video object Voj I synchronization interval of the video object Voj Sj,j Size of Vopi,j dj,I Playout deadline of Vopi,j Tvs Total execution time for entire session Tvo(i) execution time cost for Voj Tvop (i,j) execute time for Vopi,j Ts Scheduling time for task assignment

  5. Additional Notation for Scheduling Algorithms V Scheduling sequence of the video session Pk kth workstation of the system. K=1..K Rk scheduler on Pk Lx scheduling intervals triggered by user interaction Vx partitioned data of the VOP to Pk

  6. Tenc Encode time. TcomInterprocessors Communication time. Tp data partitione time. Tvop (i,j)=maxk {Tenck(i,j)+Tcom +Tp } Tenck(i,j)=.(Si,j /K) Tvo(i) =Ts+Sumj(maxk {Tenck(i,j)+Tcom +Tp }) To preserve the intraobject synchronization the encoding time must satisfy the following constraint: Sumj(maxk {Tenck(i,j)+Tcom +Tp })< dj,I -j

  7. RRS: Initialize the scheduling interval Lx, where x=0; Sort all VOP in v using EDF(earliest deadline first) rule. Initialize Rk={} and g0=K, where PkG0, k=0 …K-1; Point to the first VOP in V; Schedule Rk to the current VOP: Rk=Rk{VOP} Partition the VOP andmap the data area vk to Pk, Go to next VOP if no user event, else trigger the scheduler Rk to update the state of the video objects and begin the next scheduling interval Lx, where x=x+1, go to step 2 repeat the last three step.

  8. GS Algorithms: to minimize the inter processors communication posed in RSS Workstations was divided into N groups corresponding N independent video objects. The number of workstations in each group is proportional to the size and play out duration the GS only determines the workstation assignment at the beginning of each scheduling interval Lx. i=K.(Sx,i/x,i)/i=0 to N-1 (Sx,i/x,i) gi=the workstation number for ith group, which is the floor of i

  9. GAS Algorithms To overcome the load balance and limitation of workstations number in GS GAS periodically detect the workload of the workstations and performs rescheduling Smallest Object merged into one group to overcome the load imbalance, Merge stop criteria: the following inequation which indicate the imbalance did not hold. .(Sx,0/x,0)/i=0 to N-1 (Sx,i/x,i)<1/.K

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