Pulling Back the Curtain on MPEG-4

We expected this encoder to crunch, and it didn’t let us down. The WebCine Encoder is capable of encoding MPEG-4 AAC audio from 16Kbps to 288Kbps, CELP speech from 3.6Kbps to 24Kbps, and video from 10Kbps to 1.5Mbps. We ran an action-packed 320x240 resolution, 64-second clip through the WebCine Encoder for 1.5Mbps, 750Kbps and 300Kbps encodes. Encoding took less time than the actual run time of the file — 42 seconds in all three cases. (Faster-than-realtime encoding would be mandatory for WebCine Encoder 1.1’s ability to multicast live feeds, but it’s already here with this version.)

Quality was decent on all three bit rates, too. Compressing the file to fit a 1.5Mbps bit stream, the encoder reduced the file size from 445,162KB to 12,467KB, a mere shadow of its former self. Even so, we didn’t notice much difference between the original file and the MP4 encoded one. Detail looked good, color gradients were still intact; nobody would complain about viewing this encoded file.

As we moved the bit rate bar down to 750Kbps, outlining detail around objects in motion began to get lost and the frame rate began to drop. The average frame rate came to 26fps, which was a lot cheaper on bandwidth than the original 30fps. To do this, however, the encoder had to drop a few video frames — 277 out of 1,928 original frames. The encoder made quick work out of which frames were key (intraframes, or I-frames, in MPEG-4-speak) and which were hosts to extraneous difference information. The quality remained consistently good and we could experiment with sequencing I-frames, P- (predictive) frames or B- (bi-directional) frames for the most desirable effect.

As we continued to slide the bit rate bar down, we didn’t pick up any discernable herky-jerky motion, even at 300Kbps. But we did begin to notice "blockiness," or pixelization. Gradient changes in colors started to disappear as the encoder assigned a single shade representing all shades of a color in order to fit the file to the stream. Still, for 300Kbps and a 130:1 compression ratio, the WebCine Encoder did a pretty good job.

In our final test, we ran a corporate training video complete with PowerPoint presentation through the encoder — the kind of media businesses and schools would likely run through it. These sources typically have a lot of chroma noise from the camera, which can play tricks on MPEG-4 (and on other Discrete Cosine Transform (DCT) codecs, for that matter). We noted some "shimmering" effects at the 1.5Mbps rate, resulting from coded blocks of video that essentially resonated to the noise. At 300Kbps, text also appeared out of focus at the start of a scene change, although detail was recovered after several frames passed.

Overall, the encoder — and to a lesser extent, the server and player — convinced us that there’s more function than fiction to this MPEG-4 package. You can see some of our video results by downloading a zip archive of encoded video, unhinted to allow local playback, for each of three sources: talking head/business presentation (320x240, 4:2:2 source), fast motion animation (320x240, 4:2:2 source), and a fashion show (DV25 source). This zip archive is 32MB with self-identifying file names for each clip at each of three resolutions (30Kbps, 252Kbps, and 604Kbps) for video with no audio. You’ll need to get Philips’ player at Philips WebCine Home (www.mpeg-4.philips.com). The archive can be downloaded from (www.streamingmedia.com/reviews/webcine10/webcine10results.zip. (Special thanks to TV Taxi, at www.tvtaxi.com, and ActionCAM Films, at www.actioncamfilms.com, for providing source files for our comparison.)

Pros

• First complete ISO MPEG-4 solution product on the market
• Reliably yields beautiful video and high quality audio streams
• Lots of encoder source inputs and settings via great user interface

Cons

• First complete ISO MPEG-4 solution product on the market
• Server lacks administrative tools at the application layer, and its simplicity is lost on those not familiar with Linux
• Expensive at $40,000 for server and encoder

The Bottom Line

This is the sort of server/encoder system we expect to see in streaming houses with high-volume production schedules because it is faster than real-time, somewhat foolproof, and it builds on the universal MPEG-4 standard. Still, the price of admission is steep: $40,000 for the WebCine Server and WebCine Encoder. Undoubtedly, these prices will drop over time and, although we cannot be certain, it seems likely that as competition blossoms and price competition comes to bear, the software will eventually be unbundled from the hardware.

For those wondering about getting WebCine 1.0 now versus waiting for WebCine 1.1, Philips notes that WebCine 1.1 will include a program to update files (to ISMA 1.0/WebCine 1.1). Either way, there’s a premium on this first-of-its-kind system, and it’s really for organizations that want to standardize on MPEG-4 beginning today, or that must have MPEG-4 for other reasons. Others may want to investigate other solutions or wait for the MPEG-4 market to become a bit more populated and less expensive. However, for those willing to pay the price, this is a professional, stable, powerful system that yields and serves excellent video and audio streams in ISO compliant MPEG-4 right now today.