Streaming Media - December 2008/January 2009 - (Page 42)

THE HD SHOWDOWN Codec Vendors Battle It Out for SUPREME QUALITY By Jan Ozer I ’ve been spending a lot of time comparing codecs lately, and I always feel a little uncomfortable when I encode the test files since I assume that the actual codec vendors know how to wring the last bit of quality out of their respective codecs better than I do. So for this particular review, I asked the codec vendors themselves to encode the files. Specifically, I sent a test file to Microsoft (for VC-1) and On2 (for VP6), and each company preprocessed and encoded the clip to a standard set of parameters using their own tools and compression settings. Unfortunately, the company that had agreed to produce the H.264 files backed out. I was unable to find a replacement, so I encoded the files myself. In the past, for these types of competitions, I sent the participants a prescaled, prefiltered test file so I could isolate codec performance from the qualitative aspects of scaling, deinterlacing, and noise-reduction filtering. For this test, however, I felt that insight into the types of preprocessing performed by these companies to produce their “trophy footage” would provide some interesting perspective into the art of real-world preprocessing and encoding. So I produced the test file from seven different HDVsource scenes, edited together in Premiere Pro and exported in HDV parameters (1440x1080i) using the Lagarith YUV 12 lossless codec, which was as close as I could come to the original HDV format without imposing another layer of MPEG-2 compression by rendering back to HDV after editing. The rules were simple. The contestants could use any preprocessing and/or encoding tool available, irrespective of cost, as long as they disclosed the process to me so I could share it with you. Of course, I was free to do the same when I produced the H.264 file. The streaming files had to be delivered at an average data rate of 800Kbps video/128Kbps audio, which is insanely aggressive, but I felt that it was necessary to distinguish the quality of the three codecs. The companies could use the highest quality settings available (such as VP6E rather than VP6S, or the High Profile rather than Baseline for H.264) and either VBR or CBR, as long as the average data rate came in at about 928Kbps. Once I had all the files in hand, I compared the quality of each. I am reporting the results herein. Note that you can view the files and all preprocessing and encoding preset files at www.doceo.com/HDcomps.html. Preprocessing I’ve long believed that preprocessing is the key to high-quality streaming video, and that’s certainly the case with this test file, which is composed of footage shot over the last 12 months or so. Most of the sequences are on-location shoots or stage performances, and lighting is seldom optimal, which often results in noisy footage. In addition, we were working with interlaced source footage delivered in progressive streaming frames and 1440x1080 resolution video delivered at 1280x720, meaning that all contestants would need to scale and deinterlace their videos. Not surprisingly, all three contenders applied scaling, deinterlacing, and noise-reduction filters to the source video. What was surprising was that all three contestants used different tools to preprocess their file and that no contender used the tools integrated into their encoding program. But let’s jump in, starting with Microsoft. Microsoft Microsoft scaled and deinterlaced with AviSynth, a free program available under a GNU General Public License (www.avisynth.org). AviSynth is unusual in that there is no user interface; instead, you create a script that identifies the source file and any filters and configuration parameters applied to the file. Then, you load the script into an AviSynth-compatible program such as Expression Encoder 2, which executes the script, receives the processed file from AviSynth, and then encodes the file. If your encoding program isn’t AviSynth-compatible, you can use a different tool, such as VirtualDub, discussed later, to render a raw-processed intermediate file for inputting into your encoding tool. 42 STREAMING MEDIA December 2008/January 2009 http://www.doceo.com/HDcomps.html http://www.avisynth.org

Table of Contents Feed for the Digital Edition of Streaming Media - December 2008/January 2009

Streaming Media - December 2008/January 2009 Table of Contents User-Generated Politics Netflix Needs a Business Model Technology and Business Trends by the Numbers Improving Video Color Quality What Makes for Compelling Video? Game On: Bringing the NHL to IPTV Give! The New Era of Corporate Communications New Video Frontiers: Taking It Beyond the PC The HD Showdown: Codec Vendors Battle It Out for Supreme Quality The Ultimate Guide to Creating Online Video Content That Works, Part 2 Planning for Webcasting Success: Considerations for Deploying an Enterprise Video Communications Platform All Mobile Devices Are Not the Same Datmedia Datpresenter LSI Tarari Encoder Accelerator LCPX-6140 Gomez Active Streaming XF Transcoding for Global Reach Executive Visions 2009 The Revolution Is Being Televised

Streaming Media - December 2008/January 2009

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.