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Fig. 6 Simulation results for the proposed intra refresh algorithm sorted by descending motion activity. Estimation results are based on current motion and scaled to the measures range.

Figure 6 Simulation results for the proposed intra refresh algorithm sorted by descending motion activity. Estimation results are based on current motion and scaled to the measures range.

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TEQCAriins Fig. 1 Frame data rate for test sequence “mobile & calendar” (H.264, q=35, 1 reference frame). At the beginning of the “intra refresh” video sequence a single I-frame with coarse quantization (q=51) is transmitted.
TEQCAriins Fig. 1 Frame data rate for test sequence “mobile & calendar” (H.264, q=35, 1 reference frame). At the beginning of the “intra refresh” video sequence a single I-frame with coarse quantization (q=51) is transmitted.
Intra refresh is a common technique to avoid large intra coded frames by embedding intra coded frame sections into a video stream comprising only P-frames. In previous work, several intra refresh techniques for applications in the field of video communications and low bit rate coding were proposed [1]. However, techniques requiring signaling from the receiver to the transmitter [2] are generally not suitable for low-delay video applications due to unacceptable round-trip times. Prediction confinement techniques [1] as well as the adaptive refresh [3] and random refresh [4] try to minimize possible error propagation by different means, but only the forced intra refresh method described in [5,6] can guarantee error-free recovery within a defined refresh time. Fig. 2 Principle of a region-based intra refresh (N = 4).
Intra refresh is a common technique to avoid large intra coded frames by embedding intra coded frame sections into a video stream comprising only P-frames. In previous work, several intra refresh techniques for applications in the field of video communications and low bit rate coding were proposed [1]. However, techniques requiring signaling from the receiver to the transmitter [2] are generally not suitable for low-delay video applications due to unacceptable round-trip times. Prediction confinement techniques [1] as well as the adaptive refresh [3] and random refresh [4] try to minimize possible error propagation by different means, but only the forced intra refresh method described in [5,6] can guarantee error-free recovery within a defined refresh time. Fig. 2 Principle of a region-based intra refresh (N = 4).
Fig. 3. Intra-Refresh border protection. The critical chequered border blocks are frequently intra-coded. Arrows represent motion vectors for temporal prediction. At the beginning of a cycle, all regions are marked as potentially corrupted “dirty” regions, which become “clean” regions when they are intra-coded in a frame. For ensuring perfect recovery within one refresh cycle, it is essential to avoid prediction from dirty regions of old reference frames into clean regions of the current frame. Otherwise, possible errors could propagate into the clean regions and damage the intra update. The forced intra refresh can guarantee a worst- case error-recovery within 2*N-1 frames. As a side-effect, the beginning of a refresh cycle can be used as a decoding start point like I-frames in IP streams.
Fig. 3. Intra-Refresh border protection. The critical chequered border blocks are frequently intra-coded. Arrows represent motion vectors for temporal prediction. At the beginning of a cycle, all regions are marked as potentially corrupted “dirty” regions, which become “clean” regions when they are intra-coded in a frame. For ensuring perfect recovery within one refresh cycle, it is essential to avoid prediction from dirty regions of old reference frames into clean regions of the current frame. Otherwise, possible errors could propagate into the clean regions and damage the intra update. The forced intra refresh can guarantee a worst- case error-recovery within 2*N-1 frames. As a side-effect, the beginning of a refresh cycle can be used as a decoding start point like I-frames in IP streams.
The refresh sequence for the example in Fig. 4 is (1,2,3,4). Unprotected ,.dirty“ regions are marked gray.
The refresh sequence for the example in Fig. 4 is (1,2,3,4). Unprotected ,.dirty“ regions are marked gray.
computational complexity of the proposed algorithm, we defined a set of 28 strategies shown in Fig. 5. The sequences are related to common camera movement scenarios like pan, tilt and zoom. The set may be redundant or incomplete, but it worked well with all video sequences we evaluated. Fig. 5 Set of 4 * 3 region refresh patterns used for the simulations. The refresh starts with the region marked with a square and proceeds in the order indicated by the line.
computational complexity of the proposed algorithm, we defined a set of 28 strategies shown in Fig. 5. The sequences are related to common camera movement scenarios like pan, tilt and zoom. The set may be redundant or incomplete, but it worked well with all video sequences we evaluated. Fig. 5 Set of 4 * 3 region refresh patterns used for the simulations. The refresh starts with the region marked with a square and proceeds in the order indicated by the line.
Fig. 7 Average region motion vectors calculated by the simulation. The length of motion vectors is adaptively scaled per sequence for better visibility.
Fig. 7 Average region motion vectors calculated by the simulation. The length of motion vectors is adaptively scaled per sequence for better visibility.
Related topics:
Computational ComplexityVideo CodingVideo CommunicationElectrical and Electronic Engineering
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