In Broadcast - May/June 2011 - 38

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Simultaneous Multi-Format Encoding for Efficient Content Repurposing
By Digital Rapids
Distributing content to multiple viewing platforms is commonplace for almost all content rights owners in today’s competitive and increasingly fragmented media environment. The expanding breadth of viewing devices is accompanied by divergence in the formats and parameters required for optimal presentation quality and device compatibility. While traditional production and distribution platforms used a limited range of formats, such as MPEG-2 in Transport Streams, little such consistency exists today. Even as H.264 has taken hold as a common thread amongst most audience viewing platforms and devices, exceptions remain, and variances in how the compressed media and metadata are ‘packaged’ for delivery continue to require distinct outputs for reaching these targets. IPTV, Internet TV (which itself might be viewed on a personal computer, a set-top box or a ‘connected’ TV), broadcast, mobile phones, personal media players – all of these targets have their own unique characteristics, and no one output comprehensively and optimally serves them all. For any multi-platform distribution strategy, encoding to multiple compression or packaging formats, resolutions and bit rates is an unavoidable requirement. Factor in non-distribution formats for acquisition, production and archive, and the types of deliverables number in the dozens. Even just looking at one distribution platform, playback on a personal computer from the Web, leads to an array of format considerations. Compression formats common on the web currently include H.264 (also known as AVC, or MPEG-4 Part 10), VC-1 (the SMPTE standard related to Microsoft Windows Media), On2 VP6, the open source WebM format introduced by Google in 2010, and Apple QuickTime. The different technologies for building web-based viewing experiences vary in which compression formats they support. For example, Adobe Flash technologies support H.264 and On2 VP6, while Microsoft Silverlight supports VC-1 and H.264. To reach the broadest audience possible across varying connection speeds and operating systems, and especially if syndicating your content, you may choose to offer your Web-based content in multiple resolutions, bit rates, and even compression formats. Even if only a single format is used, recent enhancements in web video delivery technology to dynamically adapt to variations in consumer bandwidth are dependent on the creation of streams in multiple bit rates and resolutions concurrently. (These technologies include Microsoft IIS Smooth Streaming, Adobe Dynamic Streaming and adaptive delivery to the Apple iPhone and iPad.) You will likely also want to create a full-resolution archive copy of the content for future transcoding into additional new deliverable formats as required.

Real-Time, Multi-Format Efficiency
Most file-to-file transcoding solutions can create multiple output formats from a single source, with varying degrees of performance, quality and efficiency when doing so. When capturing and encoding from a live

Efficiently repurposing content for these varying platforms and devices presents new challenges, and the encoding systems used to create these deliverables are critical points in the process. The quality, performance and efficiency of the encoders A) Single-format/resolution/bitrate and surrounding workflow have a significant impact on productivity, costs, the viewer experience and the timely availability of content. No longer is it enough for an encoding system to be able to output Encoder just a full-resolution and proxy version. Efficient multi-platform output requires encoding solutions that optimally support B) Single-format/multiple resolution/multiple bitrate multiple formats and the specific needs of each target device. Even better are solutions that can create these deliverables simultaneously in ‘real time’, where the total encoding time is the same Encoder as the duration of the content. Faster-than-realtime encoding can also be achieved when encoding from a non-live source such as existing mezzanine C) Multi-format/multiple resolution/multiple bitrate media files.
VTR VTR

source or tape in real time, however, solutions differ considerably. Some output only a single compression format, resolution and bit rate at a time; others can output multiple resolutions and bit rates concurrently but only in a single format; while the most flexible solutions can capture and encode to multiple formats and output parameters at full quality simultaneously in real time. This latter class of format-flexible encoding solution offers numerous benefits:

H.264 720x486 2 Mbps

H.264 720x486 2 Mbps H.264 320x240 600 Kbps

In this article, ‘encoding’ primarily refers to creating file-based deliverables. The inputs to the encoder could be ‘live’ sources (such as a video router), decks, or existing media files, while the deliverables could be used for subsequent on-demand viewing or download on multiple devices, Blu-ray or DVD authoring, archive, or a plethora of other purposes. Most of the same concepts also apply to encoding for real-time distribution (such as broadcast or live streaming), although the breadth of compression and container formats used in file-based production and distribution far exceeds that used for ‘live’ real-time delivery.

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H.264 720x486 2 Mbps Encoder H.264 320x240 600 Kbps VC-1 320x240 600 Kbps MPEG-2 720x480 5 Mbps

Diagram 1: Encoders can differ significantly in their real-time abilities when capturing and encoding from a live source or tape. (A) Encoder able to output only a single compression format, resolution and bit rate at a time. (B) Encoder able to output multiple resolutions and bit rates concurrently but only in a single format. (C) Encoder able to output to multiple formats and output parameters simultaneously in real time.

Uncompressed 1280x720

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