Decoding the Truth About Hi-Def Video Production

Optimizing VP6 Playback
The first encoding decision with VP6 is whether to use VP6-E or VP6-S. Briefly, the VP6-S option produces a "simple" to decode file targeted at HD implementations while the VP6-E option produces "excellent" quality but may be harder to decode, so is better suited for SD files. Note that the simple and excellent monikers are mine to help remember the difference, not the official designations. Not all encoders enable both options, and in particular, you should note that encoding tools from Adobe only support the equivalent of VP6-E.

However, VP6-S is easier to decode and can make a significant difference on low-end Mac and Windows workstations. Specifically, the xw4100 dropped both audio and video when playing back the VP6-E file but played the 2Mbps VP6-S file without audio breaks and at a higher frame rate. On the iMac, using VP6-S meant the difference between 2 fps and full-speed playback. So, if you’re producing HD, you need a tool that supports both modes. These tools include On2’s own Flix Pro, Sorenson Squeeze, and Telestream Episode Pro but not On2’s Flix Exporter.

Beyond the VP6-E versus VP6-S decision, it appears to make sense to ship the lowest data rate stream possible, at least judging from the iMac results. The higher-bitrate streams required a greater CPU allocation to decode, though the iMac was able to play all VP6-S streams without frame drop. I’m not sure why the xw4100 dropped frames when playing back the 2Mbps VP6-S stream, since it played the 800Kbps and 3Mbps streams without a hitch.

For desktop playback, I used the Wimpy FLV player, which is a free decoder available on both the Windows and Mac platforms. Since the Wimpy player doesn’t use the GPU for decoding, it doesn’t have the advantage that we saw with the QuickTime and Windows Media Players. In fact, on both Macs, the Wimpy player required more CPU horsepower to play back the files than the Flash player. The bottom line is that if you use VP6-S video, offering a download-and-play option probably won’t be necessary and wouldn’t improve the playback experience over progressive playback in the browser.

You can view all the files mentioned in this section yourself at the following URLs:
—www.doceo.com/FLV_Tests/FLV_800K/test.html
—www.doceo.com/FLV_Tests/FLV_2M/test.html
—www.doceo.com/FLV_Tests/FLV_3M/test.html
—www.doceo.com/FLV_Tests/FLV_E_2M/test.html

Overall, if smooth playback on low-powered computers is a priority, you should choose encoding parameters with that in mind, particularly with VP6 and H.264, and always produce the lowest possible bitrate file. In addition, producers distributing HD videos in H.264 and Silverlight formats should consider making the video available for download-and-play.