New TCP-Friendly constraints require multimedia flows to reduce their data rates under packet loss to that of a conformant TCP flow. To reduce data rates while preserving real-time playout, temporal scaling can be used to discard the encoded multimedia frames that have the least impact on perceived video quality. To limit the impact of lost packets, Forward Error Correction (FEC) can be used to repair frames damaged by packet loss. However, adding FEC requires further reduction of multimedia data, making the decision of how much FEC to use of critical importance. Current approaches use either inflexible FEC patterns or adapt to packet loss on the network without regard to TCP-Friendly data rate constraints. In this paper, we analytically model the playable frame rate of a TCP-Friendly MPEG stream with FEC and temporal scaling, capturing the impact of distributing FEC within MPEG frame types with interframe dependencies. For a given network condition and MPEG video encoding, we use our model to exhaustively search for the optimal combination of FEC and temporal scaling that yields the highest playable frame rate within TCP-Friendly constraints. Analytic experiments over a range of network and application conditions indicate that adjustable FEC with temporal scaling can provide a significant performance improvement over current approaches. Extensive simulation experiments based on Internet traces show that our model can be effective as part of a streaming protocol that chooses FEC and temporal scaling patterns that meet dynamically changing application and network conditions.
The growing requirement of TCP-Friendly bandwidth use by streaming video plus the proven advantages of Forward Error Correction (FEC) to combat packet loss presents the opportunity to optimize the amount of FEC in a TCPFriendly video stream. In this paper, we derive an analytical model for predicting the playable frame rate in a TCPFriendly MPEG stream with FEC. Our model characterizes the Group Of Pictures (GOP) and Forward Error Correction (FEC) that are part of the MPEG video transmission. Assuming a network estimate for the packet loss probability, our model incorporates TCP-Friendly throughput constraints to calculate a total playable frame rate. For a given packet loss probability, we use our model to search the variable space to find the MPEG configuration that yields the optimal playable frame rate. Analysis over a range of network conditions indicates that adjusting FEC can provide a significant performance improvement, while adjusting a well-chosen GOP will contribute little improvement. Further analysis shows that a poor choice for a GOP can result in a large degradation of the playable frame rate. Overall, by introducing moderate amounts of FEC overhead, frame rates can be improved 10 to 50 times under network conditions with moderate to high loss rates.
Packet loss can severely impact streaming video quality. Repair techniques protect streaming video from packet loss but at the price of a reduced effective transmission rate when streaming a flow in a capacity constrained situation. This paper proposes an algorithm that optimizes the choice of Forward Error Correction (FEC) to repair packet loss for streaming MPEG videos under a capacity constraint with quality scaling. An analytic model is developed to estimate the video quality of streaming MPEG given a quality scaling level and a specific FEC strength. Given network conditions in terms of packet loss rate, the model searches the total variable space to find the combination of FEC and scaling that yields the optimal quality under the capacity constraint. Analysis over a range of network conditions indicates that adjusting FEC with quality scaling provides significant performance improvement.
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