Streaming Media - October 2008 - (Page 26)

tutorial Encoding for Screencams good, moving quality was twitchy, as if short sections were played back twice in the jump from 15 to 30 fps. I tried working from a 30 fps project and various other workarounds with the same results. That left two encoders standing: Episode and Squeeze. Here, I found that the results produced by Episode Pro’s Dicas codec were a clear step behind the MainConcept output from Sorenson Squeeze, which you can see in Figure 6. At the target data rate, Squeeze was nearly always visually perfect while Episode showed some artifacts. More importantly, during extreme scene changes, Episode exhibited severe and highly noticeable distortion that took several moments to clear up. I tried to analyze the file in Semaphore to diagnose the problem, but Semaphore couldn’t open the file. For the record, I should say that I tested Episode Pro 5.01 and was very impressed with the real-world video performance of the Dicas codec, which was commercially similar to video produced by the MainConcept codec for the first time. You definitely shouldn’t generalize the results of these screencams to real-world videos. Figure 6. The good, the fair, and the ugly Figure 7. Squeeze delivered the best quality among the three encoders that produced usable files. Windows Media Video If you’re producing screencam recordings with Expression Encoder 2, your best resource is the aforementioned article by Waggoner. The careful reader will note that I borrowed much of the discussion on B-frames (and the term “pixel perfect”) from his article, which I hereby acknowledge. None of the other encoders offered any of the advanced tweaking options available in Expression Encoder 2. In theory, if you’re not tweaking, you should get the same quality from both the Main and Advanced Profile. I tried both profiles using both Episode and Squeeze and found that the Advanced Profile delivered lower quality with both programs. Overall, if you’re not tweaking, don’t use the Advanced Profile. The only other noteworthy codec-specific option was the ability to set the number of B-frames. Interestingly, the quality leader, Squeeze, didn’t offer a B-frame control and didn’t use B-frames in the encoded file, according to Semaphore. In addition, when I used the max B-frame setting in Episode Pro (which was 4), the file didn’t play back normally; it essentially became stuck on the very first frame, and audio was distorted. When I scaled back to a B-frame setting of 2, the encoder skipped about 3 26 STREAMING MEDIA October/November 2008 seconds worth of frames at the start but otherwise played normally. In terms of quality, since a picture is worth a thousand words (and I’m running out of them) let me point you toward Figure 7, which shows Squeeze ahead of both Expression Encoder and Episode. This was consistent throughout the duration of the video. Some final caveats: Normally, when I encounter problems with encoding tools, I run them by the individual vendors before writing about them. Since I was testing so many tools in an admittedly fringe function, I didn’t contact the vendors in this case. Since most of the tools mentioned have trial versions, I would use my findings as a starting point. Once again, note that I’m not saying that you can’t produce high-quality results with the tools assessed as fair or poor. Rather, in my best judgment, you’ll most likely have to encode at a higher data rate than the higher-rated tools to deliver the same quality. Jan Ozer (jozer@doceo.com) is a frequent contributor to industry magazines and websites on digital video-related topics and is author and producer of the Critical Skills for Streaming Producers family of tutorials, available at www.streamingmedia.com. Comments? Email us at letters@streamingmedia.com, or check the masthead for other ways to contact us. http://www.streamingmedia.com

Table of Contents Feed for the Digital Edition of Streaming Media - October 2008

Streaming Media - October 2008 Table of Contents Standard Time Technology and Business Trends by the Numbers Encoding for Screencams Meeting the Enterprise Video Distribution Challenge Pulling Back the Curtain on Level 3 The 2008 Streaming Media Readers’ Choice Award Winners The Ultimate Guide to Creating Online Video Content That Works, Part 1 Brave New Platforms Video From the Democratic National Convention—Both Official and Unofficial—Made Clear That It’s No Longer Politics as Usual Creative Suite Turns 4 The Future of Internet Radio Decoding the Truth About Hi-Def Video Production Educating the Next Generation of Online Media Makers ViewCast Niagara GoStream SURF The Past and Future of Online Video: I’m Not Dead Yet!

Streaming Media - October 2008

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