Streaming Media - December 2007/January 2008 - (Page 68) Since the presets were handcrafted by the selfproclaimed “World’s Greatest Compressionist” Ben Waggoner—who was helpful and very responsive while writing this article—I’m a bit loath to criticize them, though I will say that they tended to be a bit audio-heavy. For example, all presets included 44.1KHz, stereo audio, often at comparatively high data rates, like 64Kbps of audio in the 256Kbps preset, compared to 150Kbps video. For most talking head videos, stereo adds no value and you can drop the data rate to 32Kbps, mono, perhaps even to 22KHz, and allocate the extra bits to video. Note that this isn’t always possible because all VBR modes are stereo only. Otherwise, the presets were standard best practice, with CBR for files destined for streaming servers and VBR for standard web servers. The 256Kbps preset dropped to 15fps, while all others used the source frame rate. For those of you messing with the buffer size of your streaming files, note that Ben used a 5-second buffer in all streaming presets. Of course, you can tweak all presets as desired, as we’ll see in our next step. express yourself Figure 3. Constant bitrate video encoding controls Figure 4. Variable bitrate video encoding controls Let the Customization Begin After choosing a preset, you can click a small white arrow beneath the preset to expose most relevant encoding controls. Interestingly, as shown in Figure 3, the Expression Encoder calls all video codecs “VC-1,” while the Windows Media Encoder calls the same codecs “Windows Media Video” codecs. Waggoner explained this in his article “Best Practices for Windows Media Encoding” (2007 Streaming Media Industry Sourcebook, pp. 122–128). “There’s been some confusion on the relationship between the Windows Media Video codecs and the SMPTE (Society of Motion Picture and Television Engineers) VC-1 spec. VC-1 is the SMPTE designation for their standardization of WMV 9. In essence, you can now think of Windows Media Video 9 as Microsoft’s brand for our implementation of VC-1, as implemented for advanced streaming format (ASF) files.” In an email exchange related to this article, Waggoner explained further: “Basically, just think of ‘WMV 9’ and ‘VC-1’ in a WMV file as synonymous. Using WMV 9 and using VC-1 have the same MPEG-LA implications, since they’re the same thing (and have virtually the same implications as H.264). But bear in mind that anyone with fewer than 50K customers/year or producing clips under 12 minutes doesn’t have to deal with MPEG LA at all. Its terms are crafted to only apply to big commercial content publishing companies.” Note that Waggoner is a compression guy, not an attorney, so if you’re a large 68 STREAMING MEDIA December 2007/January 2008 Figure 5. Video Complexity controls Figure 6. A/B Compare mode lets you compare different encoding parameters.
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.