Digital Signal Processing Reference
In-Depth Information
value is reached in all other cases. The new interarrival period is then appended as
RTP extension to the next packet to be transmitted.
The entire FIRO algorithm can be summarized as follows:
21.5.3 Performance Evaluation
To test the performance of the FIR and FIRO algorithms, the transmission of a 65 s
video stream between two cars in a highway scenario has been simulated. The input
video stream [
11
] has been compressed with the H.264/AVC codec [
12
]at
30 frames/s, 9 packets/frame, 600 kbit/s. The channel has been modeled with a
2-state Gilbert-Elliott model, with average packet loss rate of 10% and average
burst error length of 3 packets. The maximum allowed transmission delay has been
set to 400 ms, according to [
7
], while the maximum allowed packet loss rate has
been set to 5%. For the FIR algorithm, the RTCP interarrival time has been set equal
to 1 s, while for the FIRO, it can vary from a minimum of 0.1 s to a maximum of 1 s
with granularity of 0.1 s for increments/decrements. The received quality of the
video stream has been evaluated by means of Peak Signal-to-Noise Ratio (PSNR).
The performance of the following transmission techniques has been evaluated:
plain transmission, adaptive FEC only (without interleaving), adaptive interleaving
only (without FEC), FIR, and FIRO. Overall results are presented in Table
21.1
.
The FIR algorithm outperforms a plain transmission and the adaptive techniques
in which FEC and interleaving are used in isolation both in PLR and PSNR results.
By resorting to interleaving, FIR outperforms the adaptive FEC technique in terms
of reduction of the application-level PLR (
0.62%). The error bursts are split
between multiple FEC blocks, allowing the FEC to be more effective. In terms of
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