Review: Rhozet Carbon Coder 3

Examining my newly encoded Flash files in Inlet Semaphore, I noticed that Rhozet’s default parameters used a key frame setting of 30 and showed no "auto-key" frame feature and that the encoded files had some dropped frames. I dropped the key frame rate down to a more reasonable 150, which reduced but didn’t eliminate the dropped frames.

Though I didn’t notice the dropped frames during real-time playback, if you’re a purist, either bump your data or use the On2 codec, which you can still do via Carbon Coder’s QuickTime export component interface. You’ll also need to go that route to produce Flash video with an alpha channel, which the Adobe implementation cannot do.

Comparing the output quality from Adobe’s single-pass Flash encoder with On2’s 2-pass encoder, I noted that in extreme high-motion sequences, On2’s codec delivered slightly higher quality but nothing you would notice without side-by-side comparisons. The flip side is that in scenes with backgrounds that weren’t very suitable for streaming—such as light, shiny, reflective walls—Adobe’s encoder produced less noticeable noise and banding-type artifacts.

H.264 Encoding
For H.264 encoding, Carbon Coder uses MainConcept’s H.264 codec, which Carbon Coder can use to output F4V files for the Flash Media server as well as MPEG-2 transport streams; MPEG-4 system streams, which I used for testing; or raw H.264 streams. Rhozet provides access to all relevant encoding parameters, including profile, level, entropy encoding modes, search shape, B-frame interval, pyramid B-frame coding, sub-block motion estimation, and the like.

Rhozet might want to tone down the techno-jargon a bit—perhaps replacing "Size of Coded Video Sequence" with the more familiar "I-Frame Interval." Speaking of that, I found the default of 60 too low for my tests and suggest most users dial that up to 150 or higher. Though there was an enable-scene-change-detection checkbox, it didn’t work in my tests, which turned out to be a bug that Rhozet was aware of. Note that this didn’t seem to impact quality negatively, as Carbon Coder ranked at or near the top in all comparisons, which included files produced by Apple Compressor and Anystream Agility.

Windows Media
Rhozet’s new VC-1 export function supports all the standard encoding parameters as well as the new tweaks previously enabled only via the WMV 9 PowerToy. Rhozet even uses the same descriptive language as the PowerToy, simplifying the transition.

For Windows Media Encoding, I compared Carbon Coder with Microsoft’s Windows Media Encoder and found the two streams very similar. Analyzing the file in Inlet Semaphore revealed a file that hovered closely to the target data rate line (which was 468Kbps) with one spike up to 780Kbps. During encoding, Carbon Coder correctly identified and placed a key frame at nearly all scene changes, which was impressive.

That turns out to be a good adjective for the version 3.0 update in general, which significantly improves an already highly competent product.