The 2008 Encoder Shootout

In terms of encoding quality, Flash results were the best, with files that were visually identical to Flix Pro, the gold standard. New in version 4.4 is the ability to encode files with an alpha channel, a necessary addition.

With Windows Media Video, Episode performed well with low motion sequences, but during high motion sequences, either dropped frames or degraded quality beyond that evidenced by other encoders. Perhaps part of this related to scene change detection, since Semaphore indicated that Episode placed a key frame at only one of six scene changes that I tested.

Semaphore also revealed that though Episode generally stayed close to the target data rate, there were two data spikes up to 900 and 750Kbps; In contrast, the Windows Media Encoder peaked at about 590Kbps (all on a target of 468Kbps). This may be a concern for producers transmitting files over tight connections. Overall, these poor Windows Media results are surprising given that the WMV encoding plug-in tested in Compressor performed so well.

In the past, Episode's H.264 results were also frustrating. Not only was the data rate presentation confusing, as discussed above, but I ultimately had to reduce my target to 220Kbps to produce my 468Kbps target. Once there, video quality was acceptable during low motion sequences, but disastrous as motion increased.

With version 4.4, Episode changed to the Dicas H.264 codec, while adding 2-pass encoding to version 4.4.1. In my quality comparisons, this moved Episode to the middle of the pack, though this was only evident in high motion sequences. In less challenging low motion footage, all H.264 encoders produced similar results. Episode also added support for the Fast-Start playback, a critical feature for those producing H.264 files for progressive download.

Semaphore would not open Episode’s H.264 file, displaying an error message that read "Semaphore does not recognize this file type." Not sure what this was about, since the file was a standard MP4 file. However, I was able to load and include the file in QuickTime Player and my Premiere Pro productions without problem.

Overall, I wish Episode Pro was simpler to use, but I love its deinterlacing quality and workflow. Now that compression quality is at least reasonable in all formats, it’s a good choice for Macintosh producers, especially those who work in the advanced formats not supported by Sorenson Squeeze.

How I Tested
To compare deinterlacing quality, I started with a 1-minute DV file with lots of scenes with detail and diagonal lines and produced a 640x480 deinterlaced MOV file with each encoding tool. I then input these files into a custom 1920x960 Premiere Pro project that could display the same frame in six files simultaneously. Then I exported frames at various checkpoints, ending up with a comparative image like that shown in Figure 12 that made it easy to spot imperfections.

To test encoding quality, I produced identical files with the three codecs with all encoding tools, using a 6-minute test file comprising 42 different scenes. I scaled and deinterlaced the file in After Effects using Algolith’s now off-the-market scaling and deinterlacing filters. I produced all streaming files 640x480 resolution at 30 fps, at a target data rate of 500Kbps, divided 468/32 video and audio. I produced Flash using 2-pass VBR (when available) and Windows Media and H.264 using 2-pass CBR, with the audio configured as 44 kHz/16-bit/mono.

I compared still-frame quality by importing WMV and MOV files into Premiere Pro and duplicating the six-frame approach shown in Figure 12. Since Premiere Pro won’t load Flash files, I opened six instances of the FLV Player, displayed the same frame in each, and grabbed the entire stream using the screen capture function in Ulead’s PhotoImpact. Then I played each file in real time, side by side with the "native" encoding tool for each format (Flix Pro for Flash, Apple Compressor for H.264, and Windows Media Encoder for WMV) to identify any significant real-time playback issues such as dropped frames.I used version 2.1 of Inlet Technologies' Semaphore quality-control software to further analyze the H.264 and WMV files. I was looking for the general evenness of the data rate, which promotes smooth streaming, and whether the encoding tool inserted keyframes at scene changes. The tool also showed Quantization level, which measures the amount of compression applied to each frame, and identified dropped frames. Note that just after I handed in this article, Inlet released version 2.5, which can also analyze Flash VP6 files, a welcome addition to an already solid tool.

You can examine each file individually, or configure alerts that can scan files in watch folders, singling out those with these or other problems, like if audio levels drop below a specified level for a specified period. A bargain for large production houses at $995, it’s easy to see how this tool could quickly pay for itself in a production environment.