ABSTRACT

The project focuses on error control and concealment for mobile video transmission using feedback techniques. The transmission of high quality real time interactive video over lossy networks due to data loss in the network causes video quality to degrade. The issue of error control and concealment in video transmission has become a very important aspect in video delivery over unreliable networks such as internet and wireless networks. Three techniques which are effective in controlling error during video transmission based on the role of the encoder and decoder was employed. In Retransmission, repair packets were retransmitted only when some packets are lost. This conventional data transmission retransmits the error packets and add at least one round trip time to the display time of a frame after its initial transmission. The packets that arrive after their display time was used to reduce error propagation. With Intra Update, one of the frames in the previous frame was used as a reference frame and encode the current frame in intra mode when a message was received from the decoder rather than using older frames as a reference frame. Under Reference Picture selection (RPS) which operates in both positive acknowledgement (ACK) and negative acknowledgement (NACK), the encoder selects one of the several previous frames as a reference frame for predictive encoding of subsequent frames. The Batch Video Quality Metric (BVQM) tool was used to determine the impact of the three feedback techniques. High quality videos with a wide variety of scene complexity and motion vector magnitude were selected and encoded. The results obtained reveal that at a higher round trip time of 240ms, video quality decreases for videos using Retransmission for repair but increases if the round trip time decreases at 60ms. With Intra Update, when the packet loss increases at 0.363, 0.521, 1.483, video quality degrades but a perfect video quality was achieved when the round trip time decreases at 0.731, 0.659 0.647. Under high packet loss of 1.111, 1.310, 2.169 at 20% and under high round trip time of 1.412, 2.419, 2.510 at 240ms, the quality of video degrades for RPS NACK but increases at a lower round trip time of 4.501, 4.471, 4.086 at 60ms and lower packet loss of 4.628, 4.456, 3.867 at 1%. With RPS ACK, video quality increases when the round trip time of 1.883, 1.722, 1.624 and packet loss of 45.323, 43.147, 42.529 was high but degrades when packet loss of 2.031, 2.568, 3.035 and round trip time of 1.121, 1.205, 1.283 decreases. When the results were compared, the loss rate was less than 1.482, RPS NACK performed better than RPS ACK but when it was higher than 1.482, RPS ACK performed better than RPS NACK at high round trip time and packet loss.