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MPEG-2 Encoders, Part 1

Table 1. MPEG-2 encoder overview.

The last time I remember writing about MPEG-2 encoders was back in 1996, the year the Olympics was held in Atlanta (and what a time that was). But just last week, I got a random call about MPEG-2 encoding for DVD from Emmy Award-winning producer Connie Simmons. By way of background, Simmons produced a PBS Series entitled Landscapes through Time with David Dunlop, which began airing nationally in June 2008. The series was shot using two Sony CineAlta HDW-F900s and edited using the Apple ProRes HQ codec. When she originally produced DVDs of the series, her ProRes HQ HD Quicktime movies were downconverted to SD and compressed for MPEG-2 using Sonic Scenarist by a the postproduction house Pillar to Post. Now she was reproducing the DVDs, and wondered if the hardware downconvert and encoding process delivered the best encodes for the next DVDs. Her question was simple: What’s the best tool for encoding HD footage to MPEG-2 for DVD distribution?

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Though DVD sales are dropping, they still totaled $8.8 billion in the U.S. for the first half of 2010, and almost all event shooters like myself still deliver on DVD, making Simmons’ question very relevant for many Apple Final Cut Pro producers. Connie donated some test footage, and this month’s Final Cut Pro Insider will try to identify the highest-quality Mac-based software encoder for converting HD footage to DVD-compatible MPEG-2.

Tested encoders will include Apple Compressor, Cinema Craft Encoder MP, Innobits BitVice, Sorenson Media Squeeze, and Telestream Episode Encoder. In this issue, I’ll discuss features, usability, and performance. In two weeks, I’ll discuss comparative quality and what happened when I tried to import the files into DVD Studio Pro.

By way of background, during the encoding speed trials, I encoded standalone files with all programs to the highest possible encoding parameters, which in all cases involved at least two-pass variable-bit-rate (VBR) encoding. My target data rate was 4Mbps total, with a minimum of 2Mbps and maximum of 7Mbps. For consistency, I encoded with a GOP size of 15, with a closed GOP and two B frames (when this option was configurable). When search or other quality-related options were presented, I always chose those that produced the highest possible quality. I produced the files on a dual processor, 2.93GHz quad-core Mac Pro running OS X 10.6.4 with 20GB of RAM.

Figure 1. Compressor’s MPEG-2 encoding options.

Apple Compressor

Apple Compressor is easy to use, works fast, and is free with Final Cut Studio. If the quality compares well, it might be the only MPEG-2 encoder you’ll ever need.

Let’s face it: Few of us know MPEG-2 encoding parameters well enough to tinker without potentially causing more harm than good, so an MPEG-2 encoding tool with just a few, easily understandable encoding options is better than one with multiple options that would take many hours of testing and reading to fully understand. Compressor’s MPEG-2 encoding configuration options are very consistent with this philosophy.

The easiest way to encode to MPEG-2 is to apply and configure a preset, of which Compressor has two classes: highest quality and fastest encode. The differences between the two are both in the Quality tab, the second tab from the left in Figure 1. Specifically, the higher-quality option uses two-pass VBR Best, while the faster option uses one-pass VBR. In addition, the higher-quality option uses Best for Motion Estimation, while the faster preset uses Good. I used the configuration options shown in the figure.

Working through the other tabs, if you leave the automatic buttons enabled, Compressor will analyze the source video footage and choose the proper options, which you can see in the Video Format tab. That is, the video that Simmons supplied was NTSC, with a frame rate of 29.97, 16:9 aspect ratio and shot in interlaced mode. Compressor properly determined all that, so this tab needed no changes. In the Quality tab, I set my average and maximum bit-rate targets, and left the Mode and Motion Estimation fields as set by the preset. I touched nothing in the GOP or extras tabs.

Compressor produced our single 2:52 test file in a snappy 3:35 (min:sec), while encoding our five 1-minute test files in parallel in 1:37.

Figure 2. Cinema Craft Encoder MP’s cryptic and under-documented MPEG-2 encoding features.

Cinema Craft Encoder MP 1.0.39

In price, encoding options, and usability, Cinema Craft Encoder MP ($695) is best-suited for professional and knowledgeable users. Unless quality is extraordinary, it’s probably overkill for most casual producers, and nontechnical users may be put off by the breadth of cryptic options.

Encoder MP functions as a Compressor plug-in that you access by clicking the Create a New Setting drop down list in Compressor’s Settings window, and choosing Cinema Craft Encoder MP. This loads the preset in Compressor’s Inspector pane, and you click the Options button to see the configuration options shown in Figure 2. Step one is choosing a template (Figure 2, Screen 1), and this dictates which encoding parameters that you’ll see in the first main screen (Screen 2). For example, click the Film radio button, and you’ll see a screen with pulldown controls. Click Video, and you’ll see the Screen 2 in Figure 2. This screen will have links to two other screens: Advanced, which takes you to the Advanced screen (Screen 3), and Compromise, which takes you to the DVD player issues screen with options that maximize DVD compatibility.

For the most part, Encoder MP does a good job explaining what the multiple parameters actually do and when to use them, though there are a couple of very significant lapses. Most significant is that the latest manual on the website is for version 1.09, not version 1.0.39, which I was running. In several instances, this meant that screens in the manual didn’t match the program screens that I was seeing, which is definitely an uncomfortable feeling. In addition, not all encoding options are detailed. Sure, I could figure out that the DF next to Frame Rate in Screen 2 stood for Drop Frame, but a mention in the manual would have been nice.

My other big beef related to the Multipass feature, which the 15 page manual describes as follows:”If Multipass is selected, Cinema Craft Encoder MP uses multiple passes to generate an MPEG-2 file.” Hmm, thought so. What it fails to tell you is that you can select up to 99 passes, or what an optimal number of passes might be, an important consideration given that boosting the passes from two to eight increased single-file encoding time from 5:12 to 15:13.

On the plus side, there’s a good range of features that advanced compressionists will appreciate. For example, Fix GOP Structure is required for multiple angle video, as appropriately detailed in the manual. The manual also does a good job telling when not to use features, with comments like “because it affects picture quality, do not use this option unless you really need it,” which is included on multiple options.

As mentioned, performance related to the number of encoding passes. The table contains the results for two encoding passes, while the figures for eight encoding passes are 15:13 for the single longer HD file, and 3:35 for the five 1-minute SD files. I’ll update the chart once I determine the amount of passes required to produce optimal quality video.

Figure 3. BitVice’s encoding parameters are well documented and available on one screen.

Innobits BitVice 2.9.6

Innobits BitVice is an affordable ($196) standalone Mac MPEG-2 encoder with a bit of a nontraditional user interface and workflow, though nothing that can’t be easily learned in a matter of minutes. The program posted the fastest single-file encoding time in the roundup, though the lack of parallel encoding pushed its multiple-file encoding time back to third place.

BitVice has no File menu, and you run it primarily via drag-and-drop, dropping multiple files on the program icon or program to set up a batch. You can save and retrieve encoding settings, and save them into a droplet you can use to encode up to 200 files in sequence.

BitVice presents all encoding parameters on one single screen, which is nice, with a 37 page manual that competently details most of them. Notable features include the Video Purifier, which is a temporal filter that reduces interframe noise. Theoretically, this will produce higher quality than simple blur filters, which most other encoding tools offer. If your footage is particularly noisy, BitVice’s Spatio filter also offers blurring.

Overall, BitVice is our cheapest third-party tool, our fastest single-file encoder, and reasonably straightforward to use. This makes it my favorite coming into the quality and compatibility trials.

Figure 4. Sorenson Squeeze’s totally undocumented MPEG-2 encoding parameters.

Sorenson Media Squeeze

Like Telestream Episode Encoder, Sorenson Squeeze is a multiformat primarily streaming file encoding tool that also produces MPEG-2 files for DVD and Blu-ray. Squeeze’s MPEG-2 configuration options are completely undocumented in the program’s manual, not surprising since it totals all of 15 pages. When I pointed this out to the ever-patient product manager, he let me know that Sorenson had hired staff to improve the company’s documentation, so additional description should be forthcoming. I used the DVD preset pretty much as is, adjusting data rate options to meet my target, and setting Field Encoding to Top Field First to match my source footage. Most of the important parameters are there, like the ability to close all GOPs, but some documentation would have been nice.

Though Squeeze was one of our slowest single file encoders, it made up some ground in the multiple file encode, using its ability to encode multiple files in parallel to encode five one minute DV files in a very respectable 1:52. Going into our quality and compatibility trials, I doubt I would buy Squeeze solely for DVD encoding, but if you’re currently using Squeeze to produce other formats, it still might be an acceptable option for DVD encoding.

Figure 5. Episode Encoder’s MPEG-2 encoding options.

Telestream Episode Encoder 5.3.2

Episode Encoder ($495 and up) is a multiple-format batch encoder that you can access either as a plug-in to Compressor or as a standalone program, though all my quality and speed tests were performed using the standalone tool. I found Episode’s presets and some encoding options more confusing than I’d like, and multiple-file encoding speed was slow.

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MPEG-2 Encoders, Part 2

In the first half of this month’s article, I looked at the usability and performance of five MPEG-2 encoding tools: Apple Compressor, Cinema Craft Encoder MP, Innobits BitVice, Sorenson Media Squeeze, and Telestream Episode Encoder…

Episode presents two sets of DVD encoding templates, HD to SD and SD, both in three data rates: 3Mbps, 5Mbps, and 7Mbps. Both sets of templates make sure your video is scaled to the proper 720×480 target, and convert your footage to 29.97fps (more on this below); the difference is in the Field Order configuration. Specifically, in the HD to SD presets, the Field Order option is selected, and set to detect the input field order and convert the footage to bottom-field-first. If your goal is bottom-field-first interlaced video, that’s OK, but if you’re working with progressive source, or interlaced video produced top-field-first, you may want to reconsider this option. My PBS footage from Simmons was top-field-first, so I switched the order.

Regarding the frame-rate option, if you’re working with 24p source, chances are that you want to encode in 24p, and let the DVD player convert the video to 29.97 interlaced if not connected to a TV or other device than can play 24p. So be sure you disable frame-rate conversion to 29.97 if that’s your goal.

Otherwise, Episode’s General MPEG-2 configuration options options are easy to understand, and preselected options logical. I ran into a bit more confusion in the Advanced tab, where the default Frame Encode Type was Progressive. This is confusing for several reasons. First, I thought I’d selected field order in the eponymous configuration option—always confusing when you have two configuration options that cover the same item. Second, I’d prefer to see same as source as the default, but this wasn’t an available option—just progressive or interlaced.

Trying to get a read on what the programmers were thinking, I checked the Help file, which stated: “Processing and storing interlace fields independently may give slightly better compression, but transcoding is slower and the format is not supported by most players. Use the option Interlaced for this.” As far as I know, all DVD players support interlaced playback, which was around long before producers started shooting in progressive (and most film-based content was telecined to 29.97 interlaced for VHS/DVD playback). I spoke to Telestream about this, and apparently this option relates to how the frame is packed, not encoded. It will be interesting to see what DVD Studio Pro says when I try to import the files that Episode produced.

Fortunately, other options on the Advanced tab were clearer. In most instances, you should always check the scene change detection checkbox, and Episode is one of the few MPEG-2 encoders that can support closed captions, though I didn’t test this capability.

In terms of encoding speed, Episode performed well during the single-file encodes, but suffered compared to other encoders in multiple-file trials because it encodes serially, not in parallel. I’m happy to report that this is likely the last time I’ll have to report negatively on Episode’s multiple file performance, since Version 6 will feature parallel encoding, not to mention a switch to the MainConcept H.264 and MPEG-2 codecs, two moves which will certainly smooth my relations with Telestream’s PR folks.

So, those are the basics. Come back in two weeks for more on quality and compatibility. Time-permitting, I may also encode some 24p source footage and look at both the 24p pulldown issue and the ability to perform inverse telecine.