Vinod Kumar Malamal Vadakital

Geo-predictive real-time media delivery in mobile environment

Multimedia streaming is one of the most popular services today. When the user is in a mobile scenario, the delivery of multimedia streaming services becomes more challenging. Mobile streaming suffers from discontinuous playback that sometimes impairs user experience. Among other factors, this is also due to the high network bandwidth variation that a user can experience along a path. In some cases, the available bandwidth is close to zero when traversing tunnels or areas where the network capacity goes below what is required for a multimedia session to be pause-less. Typically, media adaptation and rate control are used to fight against variable bandwidth. However, these are usually reactive algorithms, where an event is first detected (e.g., a drop in available bandwidth), and then an action is taken, either by the streaming client or by the server. This action may result just in a mitigation of the problem and not in the complete removal. In this paper we introduce the novel concept of Geo-Predictive mobile streaming. This is a collaborative service that makes use of prediction rather than reaction. Network coverage maps are built with the aid of mobile users; with these maps, the available network bandwidth for each location is recorded in a server, and when a user travels from point A to point B, it is possible to predict well in advance what will be the experienced bandwidth along that route. In case of bandwidth drops, these can be known in advance and media adaptation algorithms can be triggered so that a pause-less media playback experience can be guaranteed to the end users anywhere and all the time.

Comparison of Error Protection Methods for Audio-Video Broadcast over DVB-H

The paper discusses methods for robust audio-video broadcast over the digital video broadcasting-handheld (DVB-H) system. DVB-H includes a link-layer forward error correction (FEC) scheme known as multiprotocol encapsulation (MPE) FEC, which provides equal error protection (EEP) to the transmitted media streams. Several approaches for unequal error protection (UEP) have been proposed in the literature, and the applicability of some of them to DVB-H is analyzed in the paper. A link-layer UEP method based on priority segmentation of the media streams is chosen for more detailed analysis. According to the method, audio and the most important coded video pictures are protected by MPE-FEC more robustly compared to the remaining coded pictures. In order to compare EEP and UEP in a DVB-H environment, an error-prone DVB-H channel was simulated, audio-visual clips were sent through it, and a comprehensive subjective quality evaluation was conducted in a controlled laboratory environment. The results of the subjective evaluation revealed that the use of UEP improves the subjective quality of some test clips noticeably when the channel conditions were severe, while in other tested channel conditions and clips, UEP and EEP performed equally well.

Optimal Channel Changing Delay for Mobile TV Over DVB-H

This paper provides an analysis on the optimal channel changing delay in DVB-H (Digital Video Broadcasting for Handhelds) channels for Mobile Television. DVB-H uses a time-sliced transmission scheme to reduce the power consumption used for radio reception in DVB-H receivers. Channel changing delay, i.e. changing from one audio-visual service to another, is increased due to the time slicing scheme in DVB-H. One of the significant factors in channel changing delay is the Decoder Refresh Delay. The Decoder Refresh Delay is the time from the start of video decoding to the start of correct output from decoder. This delay is minimized when a time-slice starts with a random access point picture such as an instantaneous decoding refresh (IDR) picture in H.264/AVC standard. In DVB-H, encapsulation into time-slices is performed independently from content encoding. At the time of encoding, the exact time-slice boundaries are typically unknown, and therefore it is impossible to align the location of IDR pictures to time-slice boundaries. The average decoder refresh delay can decrease by frequent IDR pictures in the bit stream. However, using very frequent IDR pictures drops the compression efficiency and the quality of compressed video dramatically. Another factor in channel changing delay is the delay required to compensate the variation in bit rate. In video streaming over DVB-H the improved quality and compression efficiency obtained by using variable bit rate should be exploited. Higher quality and compression performance can be provided by higher delay. Moreover, when changing channels, a delay is required until the start of the desired time-slice and a further delay is incurred to complete the reception of the entire time-slice. These delays depend on the time-slicing parameters that define the power saving percentage obtained as the result of the time-slice scheme. The lower the receiver power consumption, the higher delay is required. Therefore, there is a strong multilateral relationship between the quality of compressed video, the channel changing delay and the power consumption in the receiver. Simulations were conducted and based on the simulation results an optimal operating area is proposed.

Method for Unequal Error Protection in DVB-H for Mobile Television

This paper introduces a method for unequal error protection (UEP) of media data in a time-sliced DVB-H channel. Media datagrams are assigned priorities using some a-priori knowledge. Datagrams covering a certain period of playback time are first grouped based on the priority assignment. Each group is then protected using Reed-Solomon forward error correction (FEC) codes and packed into multi-protocol encapsulation (MPE) FEC frames as defined by the DVB-H standard. All MPE-FEC frames for a certain period of playback time are then sent back to back without any delay between these MPE-FEC frames. This method of UEP is generic and can be tuned according to the priority assignment algorithm. Simulations using H.264/AVC video were conducted to evaluate the performance of the proposed method. It used a simple priority assignment algorithm. The resulting rate distortion graphs show good performance and an average luma peak signal-to-noise ratio (PSNR) improvement of up to 0.8 dB was achieved

Cross-layer optimized transmission of H.264/SVC streams over DVB-T2 broadcast system

DVB-T2 has been recently standardized by the DVB organization. In this paper the deployment of H.264/SVC in DVB-T2 is discussed. We focus on the system configuration aspects which provide optimal use of DVB-T2 features from the H.264/SVC point of view. We also propose modifications to the error protection mechanisms that would consequently lead to an improvement of user experience. The data dependencies in H.264/SVC are exploited to protect the media data unevenly according to their priorities.

Spliced Video and Buffering Considerations for Tune-In Time Minimization in DVB-H for Mobile TV

A novel video splicing method is proposed which minimizes the tune-in time of mobile TV in digital video broadcasting for handheld terminals (DVB-H). DVB-H uses a time-sliced transmission scheme to reduce the power consumption used for radio reception. Tune-in time in DVB-H refers to the time between the start of the reception of a broadcast signal and the start of the media rendering. One of the significant factors in tune-in time is the time from the start of media decoding to the start of correct output from decoder, which can be minimized when a time-slice is started with a random access point picture such as an independent decoding refresh (IDR) picture in H.264/AVC. In IP datacasting (IPDC) over DVB-H, the encapsulation to time-slices is performed independently from encoding in a network element called IP encapsulator. At the time encoding, time-slice boundaries are not known exactly, and it is impossible to govern the location of IDR pictures relative to time-slice boundaries. It is proposed that an additional stream consisting of IDR pictures only is transmitted to the IP encapsulator, which replaces pictures in a normal bitstream with IDR pictures according to time-slice boundaries in order to achieve the minimum tune-in time. It has to be ensured that the spliced stream resulting from the operation of the IP encapsulator complies with the hypothetical reference decoder (HRD) specification of H.264/AVC. The buffering requirements of spliced stream are analyzed and then a video rate control system is proposed to satisfy the HRD requirements for the spliced stream. Simulation results show that in addition to fulfilling HRD compliancy, good average quality of decoded video is achieved with minimum tune-in time

Time-interleaved simulcast and redundant intra picture insertion for reducing tune-in delay in DVB-H

Tune-in delay is the time elapsed from the instant a program is chosen, until the rendering of the chosen program begins. This paper provides an analysis of various components that affect tune-in delay and discusses methods to reduce this delay, in the Digital Video Broadcasting - Handheld (DVB-H) systems. In DVB-H, time-slicing, and misalignment of random access units relative to the timesliced burst boundaries are the major contributors to tunein delay. Two methods, namely time-interleaved simulcast and redundant intra picture insertion, are proposed for reducing tune-in delay. Simulcasting is a transmission mechanism, where multiple programs of the same source material are coded in different qualities, and transmitted simultaneously. The receivers choose the most appropriate of the simulcasted programs, matching its capabilities, to be consumed. In the proposed time-interleaved simulcast method, the delay caused due to DVB-H time-slicing is reduced. It is done so, by transmitting time-sliced bursts of the simulcast programs maximally apart from each other. The proposed redundant intra picture insertion method reduces the delay related to alignment of random access pictures with time-slice boundaries. Theoretical results show that the proposed methods provide up to 60% reduction in tune-in delay.

Optimal IP Packet Size for Efficient Data Transmission in DVB-H

This paper provides an experimental analysis on optimal Internet protocol (IP) packet size in error prone DVB-H channel. Efficient transmission of data requires reliability of the data and bandwidth efficiency of the data itself. Overheads in the form of IP packet header data reduce bandwidth efficiency. However, larger packet sizes minimize header data but have a high probability of being corrupted during transmission thus reducing the reliability. Obtaining a balance between optimal packet sizes that can reduce overheads while still providing reliability is essential. Simulation conducted show that IP packet sizes between the range of 1024 to 2048 bytes show good efficiency in terms of bandwidth and reliability

Cross-Layer Optimization of DVB-T2 System for Mobile Services

Mobile broadcast services have experienced a strong boost in recent years through the standardization of several mobile broadcast systems such as DVB-H, ATSC-M/H, DMB-T/H, and CMMB. However, steady need for higher quality services is projected to surpass the capabilities of the existing mobile broadcast systems. Consequently, work on new generations of mobile broadcast technology is starting under the umbrella of different industry consortia, such as DVB.nIn this paper, we address the question of how DVB-T2 transmission can be optimized for improved mobile broadcast reception. We investigate cross-layer optimization techniques with a focus on the transport of scalable video (SVC) streams over DVB-T2 Physical Layer Pipes (PLP). Throughout the paper, we propose different optimization options and verify their utility.

Synchronized audio redundancy coding for improved error resilience in streaming over DVB-H

Digital Video Broadcasting - Handheld (DVB-H) specification suite enables reception of point-to-multipoint multimedia transmission with mobile devices. It provides good forward error correction (FEC) capabilities to combat transmission errors. However, transmission errors can be occasionally so severe that FEC decoding fails. The residual transmission errors can degrade the audio-visual quality dramatically. This paper presents an error control method, called synchronized audio redundancy coding. It aims to ensure audio continuity under severe channel error conditions. The presented method was compared to conventional FEC-based error protection of DVB-H in a large-scale subjective experiment. It was found that synchronized audio redundancy coding outperformed the conventional error protection in most test cases.