Buyers' Guide to Transcoders 2017
Open source transcoders have increased in both quality and performance, but the very nature of using open source software means that some assembly is required. Due to limitations around licensing, most tools like HandBrake or ffmpeg require a number of additional modules to be downloaded and installed in order to transcode to still-popular legacy formats like MPEG-2 or VC1.
Bundled transcoding tools are geared toward assisting in the job of converting a very high-quality master file—such as 4K UHD or even RED 5K content, edited on a nonlinear editing (NLE) system—down to a bitrate and resolution that can be delivered as VOD on an over-the-top (OTT) device such as a mobile phone or streaming set-top box. Examples of these include Compressor from the Apple Final Cut Pro X NLE bundle or Adobe Media Encoder from the Adobe Premiere Pro NLE bundle.
Server-Based Transcoding
For production workflows in which the NLE machine needs to be actively engaged in editing, server-based transcoding has become a much more affordable alternative.
Essentially, the server-based transcoding tools are the same software as their less-powerful desktop counterparts, but they include options such as watch folders (to assist in automated workflows) as well as some form of quality control and scheduling or prioritization of rush jobs. Open-source server-based transcoding tools, riding on Linux operating systems, have found their place in large media environments, thanks in part to the robustness of x264 and ffmpeg.
Appliances
A number of companies make transcoding appliances, especially for higher resolutions (such as 4K Ultra HD) or live streams (including IP-to-IP transcoding). Some of the appliances also allow a number of files from a playlist—such as video ads, primary content, and secondary content that wasn’t encoded in the desired streaming format or protocol—to be stitched together in a single on-demand (VOD) asset.
Another reason to use a transcoding appliance is the sheer amount of processing power, which is critical for doing faster-than-real-time transcodes of VOD assets. In the earlier playlist example, an hour’s worth of content on a desktop transcoding software tool could take 3–4 hours to convert. On an appliance, though, it should take 15–20 minutes. Converting in one-fourth the time is a huge gap, and it may be worth paying the extra dollars in order to get optimized hardware assistance from a transcoding appliance.
Even companies that have traditionally been involved in cable TV signal modulation, such as Blonder Tongue Laboratories, Inc., are now offering transcoders that not only convert from cable standards such as ASI and QAM to IP-based ATSC formats, but they can also package and output HLS or even MPEG-DASH.
Cloud-Based Transcoding
Assuming that the production pipeline includes a fat pipe to the outside world (i.e., a robust internet connection) then cloud-based encoding is a viable option. The master file, sometimes referred to as a mezzanine file, is uploaded to a transcoding service, and the various versions of streaming-ready files are converted in a scalable cloud-based environment.
Some cloud-based transcoding options include a desktop application that will segment large video files into smaller segments—although these segments aren’t to be confused with stream-ready segments like those created by a packager for Apple HTTP Live Streaming (HLS) or MPEG Dynamic Adaptive Streaming via HTTP (DASH)—to make the overall mezzanine file uploading process go more smoothly. Be aware, though, that some of these desktop helper applications also do a bit of transcoding or transrating behind the scenes, potentially impacting the quality of your mezzanine file.
Conclusion
As we continue to see new video codecs (e.g., H.265, AV1) and new resolutions (e.g., 4K UHD or even 8K), the use of transcoding applications and appliances will continue to be relevant.
Desktop open source and bundled software transcoding applications are good for small transcoding jobs, but to really scale up and automate a workflow, careful attention should be paid to server or cloud-based transcoding solutions. Appliances—dedicated to the task of transcoding, transrating, and repackaging VOD and live streams—continue to meet mission-critical transcoding needs, especially when it comes to new resolutions, compression formats, or faster-than-real-time transcoding requirements.
This article appears in the March 2017 issue of Streaming Media magazine.
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