Video communication is gaining quite a bit of momentum, driven by the rapid deployment of high-bandwidth, low-latency LTE networks and the increasing popularity of products such as smart phones and tablets (and even smart TVs!) that support front-camera applications. With real-time voice and video over Internet Protocol (V.VoIP), video communication on all of these devices is now becoming mainstream.
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Video conferencing adoption has also increased tremendously in both consumer and enterprise environments. In the enterprise, video conferencing historically has been limited to PCs and desktop video phones. But with bring-your-own-device (BYOD), video conferencing on mobile platforms is gaining popularity. Video conferences with remote satellite offices in the enterprise have become common.
To support the proliferation of these applications, there has been a great deal of development in video technologies, providing multiple choices to the semiconductor industry and OEMs. The choice of the right video technology depends on various technical factors, enterprise/consumer environments, and network conditions.
Video Communication Technology Selection
Popular video compression standards used in the industry include H.264 Advanced Video Coding (AVC), H.264 Scalable Video Coding (SVC), VP8 codecs, and MPEG2/H.263 in some legacy devices.
Based on the applications, resource availability, and camera configurations supported on the mobile platform, H.264 provides profile configurations such as baseline, high, extended, and main. The baseline profile has been used for lower-cost applications with limited computing resources such as over-the-top (OTT) video conferencing solutions. But this is rapidly changing as mobile processors become increasingly powerful, supporting multi-core gigahertz processors and hardware video accelerators. These platforms are expected to support HD video conferencing.
Enterprise BYOD applications use the H.264 SVC technology, which allows multi-platform distribution using multiple layers. These include a base layer and enhancement layers such as temporal, spatial, and quality. In consumer devices, there is quite a bit of variation in technology choice. Examples include:
• Embedded: Embedded applications such as video over LTE (VoLTE) and Apple’s Facetime use H.264 as their video technology. The GSMA IR.94 VoLTE standard recommends support for H.264 Constrained Baseline Profile (CBP) Level 1.2 as the mandatory video codec in the user equipment or handset.
• Downloadable: The downloadable V.VoIP applications use a mix of H.264 and VP8 video technology.
• Web-based: VP8 has become the de facto standard for Web-based video conferencing applications, with Web browsers such as Chrome and Firefox being the early adopters.
• Social networking: H.264 video technology dominates social networking video conferencing applications.
Interoperability is another important consideration. Since transcoding can be expensive, interoperability is desired between the end points in a system. To keep costs low, the two end points should support the same video technology—H.264 and VP8.
We are also now seeing next-generation video standards such as VP9 and H.265/HEVC (High Efficiency Video Coding), which aim to reduce the bit rate required for a given quality of video by up to 50%, making it more feasible to support high-resolution video in mobile wireless environments.
Imagination Technologies, for instance, recently unveiled its PowerVR Series5 HEVC-enabled encoder and decoder families. For HEVC, the PowerVR D5500 decoder core is based on a new architecture designed for the higher resolutions, frame rates, and bit rates of 4K Ultra HD while optimizing silicon area and bandwidth usage.
In addition to video codec requirements, video conferencing needs appropriate voice codec and audio/video lip-sync algorithms. GSMA recommends the Adaptive Multi-rate (AMR) codec for video/voice over LTE calls. In addition, some OTT and Web-based applications use iLBC and Opus, as they are royalty-free.
Packet-Loss Mitigation
Compressed video is vulnerable to packet losses, especially in lossy wireless environments, to the extent that even minor errors can result in substantial degradation. Retransmission of video and voice packets is not an option in real-time video conferencing solutions, as it may result in latencies, jitter, and low network throughput, impacting the quality of service (QoS) and providing a very bad user experience.
Error resilience and error concealment are common traditional techniques used to mitigate the packet loses. While error resilience introduces redundant packets in the encoder, error concealment uses error recovery techniques at the decoder to mitigate packet losses. Also, available advanced in-band dynamic video quality management (DVQM) techniques can mitigate packet losses even up to 20% and enhance the user experience substantially.
Bandwidth Adaptation
While voice calling over the Internet needs only minimal bandwidth—less than 50 kbits/s to a maximum of 100 kbits/s, based on the voice compression standard used—video conferencing requires anywhere from 128 kbits/s for a basic call to up to more than 1 Mbit/s for an HD video call. These requirements can proportionally increase for multi-party conferencing.
Video quality must adapt to ever-changing bandwidth in dynamic wireless environments. As the bandwidth degrades, video should fall back to a lower resolution and fewer frames per second (fps). It also should upgrade to higher resolutions as bandwidth improves, providing a seamless user experience.
Other Considerations
All OTT clients today use a software video encoder/decoder for video conferencing, which can consume quite of bit of CPU resources if not optimized with DSP extensions for the target processor. Traditionally, mobile chipsets have video decode hardware for playback.
Due to the popularity of video conferencing, mobile chipsets are integrating video encoder hardware accelerators as well, enabling high-resolution video conferencing on mobile devices. The video resolution should also adapt to the varying screen sizes of the target devices.
Conclusion
Choosing a video conferencing technology best suited for the enterprise or consumer environment depends on a variety of factors. Bit-rate-efficient and compression-efficient video technologies such as H.265 and VP9 should significantly reduce bandwidth consumption. That could also help with battery life improvements when streaming video.
While mobile devices are becoming more computational-efficient, how video technology will play out in the marketplace remains to be seen. A lot will depend on the evolution of mobile broadband 4G/LTE networks and the allocation of dedicated bandwidth for video conferencing.
