I have been a fan of Quentin Tarantino ever since I saw Pulp Fiction—on premiere night—in a movie theater with the woman who wound up marrying me. The director's particular combination of irreverent sensibility, cinematic flair and captivating dialog have frequently resulted in films that are among my personal favorites. I put Django Unchained squarely in that category. His rethinking of the spaghetti Western, set in the pre-Civil War South, is quite a brutal movie. I suppose that is something else you can always expect from Mr. Tarantino.
Christoph Waltz and Jamie Foxx in Django Unchained
Compression is also brutal, turning perfectly great cinematic footage into a scrambled mess of flickering pixels. At least that's the conventional wisdom about online delivery of high-definition movies. It is certainly what I believed, until just a few months ago when I purchased a copy of Skyfall from iTunes and watched the 1080p version on my home-theater PC. What I saw that night was a whole lot better than what I had seen previously, as far as streaming or downloadable movie formats were concerned. That is probably because I had sworn off online delivery formats after a number of negative experiences a year earlier.
Fast forward to April 2013. I am walking through my local neighborhood Walmart, and I spy a Blu-ray case for Django Unchained. It is a digital pre-release, and inside the case is nothing more than a piece of paper with a number on it. The number is a Vudu code, and since I already have an account with that service, entering the code granted me access to the digital early release of the film. It also automatically set up a shipment of the physical Blu-ray, which happened to arrive several days before the official release date. For a total of $20, I was able to watch the movie early and then receive the physical Blu-ray early. The only question is, was it worth watching the film on Vudu at all? Some would argue that only Blu-ray is good enough quality, especially for the first viewing of a great movie. Others would argue that Vudu HDX is more than adequate—not easily differentiated from Blu-ray in most cases.
A few weeks ago, I ran a poll about the suitability of online formats for home-theater usage. The results indicated that Vudu HDX has some fans, but not nearly as many as Blu-ray does. It also revealed that iTunes HD movie files are not at all popular for home-theater use.
From a practical perspective, this makes sense because Vudu does allocate more bandwidth to its HDX format than Apple does for its HD format. Blu-ray, Vudu HDX and Apple HD all use the same compression technology, so it comes as no surprise that the ranking in terms of quality has frequently been in line with the allocated bit rate. However, there are exceptions, based on the platform. Some movie releases have had restrictions, whereby the Vudu HDX version was not playable on a PC or Mac. Check out two examples of that approach in my recent comparisons of Wreck-It Ralph and Lincoln.
In the past, I have struggled to find a way to quantify differences in sound quality between formats. I have no way of performing double-blind A/B comparisons, and audio memory is notoriously unreliable. However, audio memory is all I have to work with. I needed a way to maximize what I was listening to, an audio equivalent to "pixel peeping." My solution: to listen to only the surround channels as if they were the front channels. That means turning my head around, turning off the mains, and turning up the volume. I chose the intense action scenes toward the end of the movie for a comparison—bullets and ricochet noises always make for good surround sound.
Blu-ray enjoys a significant theoretical advantage in terms of sound quality because it does not employ lossy compression. It is a remarkable fact—the highest-quality audio formats that have ever been available to consumers are on discs sold for only a few bucks in Walmart, Best Buy and Target across the country. The quality is so high, it would be impossible to improve upon in the context of human perception of dynamic range and frequency response.
The listening tests confirmed that the online versions suffered a significant loss in overall fidelity compared with Blu-ray audio. In addition to isolating the surround effects, turning off the mains also allowed me to hear the subwoofer channel. Uncompressed audio outperformed the online formats in a number of ways—each sound was more discrete, each sound had more impact at the same volume, and the accompanying bass impact for each sound effect was deeper. Listening to nothing but the surround effects really opened my ears to what's going on with the compressed formats. The same effects are there, but the soundfield is flatter. The sense of space, as well as the shock of a dynamic transient accompanied by strong deep percussive bass thump—those qualities were present in the Blu-ray version of Django Unchained.
Apple's iTunes HD offering does not fare well when compared to Blu-ray or even Vudu HDX—at least not in terms of specifications. Apple uses the exact same audio compression that was standard on DVD—Dolby Digital 5.1, with a bit rate almost 100 times lower than Blu-ray. Vudu claims that Dolby Digital Plus allows it to use a bit rate 40% higher than standard Dolby Digital, but that is still just a tiny fraction of the bandwidth used by uncompressed 5.1 or 7.1 audio. In some circumstances, Vudu also provides soundtracks in 7.1 audio, which is not available from iTunes.
Nevertheless, a funny thing happened as I performed my comparison. Listening to the iTunes version, I started to feel like it came close to the Blu-ray. In fact, I am not sure I would be able to pass a double-blind test. I do not know if this has anything to do with investments Apple has made in audio compression, but it seems to me like the company used its bandwidth better. I am a strong believer that good mastering trumps almost anything else when it comes to sound quality. I can say that I did not find iTunes to be lacking in the sound quality department.
Simply put, the online formats can never be as good as Blu-ray. They use too much compression, and as a result, fidelity is lost. However, an argument could be made that a highly capable 5.1 or 7.1 system is needed to hear the extra quality inherent in Blu-ray. After all, the sound available through iTunes is still the DVD standard—and I have thoroughly enjoyed many DVDs in the past. The fact is, the soundtrack is more than adequate in all the versions, but I did feel that Vudu was somehow not as good as iTunes for this movie. In some past comparisons, I have felt that Vudu's soundtrack was better sounding than iTunes'. In retrospect, each time that was the case, the soundtrack was actually 7.1 channel. This movie is 5.1, even though Vudu HDX uses Dolby Digital Plus, which supports 7.1 channels. HDX did not have extra surround channels to give it an advantage over iTunes. That made a real difference, and not in Vudu's favor.
This is the most intensive comparison of soundtracks that I have performed thus far, and I feel confident in recommending iTunes HD over Vudu HDX, at least for the soundtrack portion of Django Unchained. However, I also felt that all three soundtracks were acceptable for home theater use. Ultimately, discrete surround effects were present, and the bass was deep regardless of the version. Comparing sound in this manner is a completely subjective exercise, so please take my observations with a grain of salt.
Visual comparisons between formats are quite fascinating, and there is considerably less ambiguity than with any attempt to compare sound. Blu-ray, iTunes, and Vudu share the same underlying video compression, though iTunes and Vudu clearly take different approaches to processing video for compression. Sometimes, the processing can result in a change to the underlying character of the film. Specifically, Vudu HDX has a tendency to apply noise reduction. To some observers, the result is actually an improvement versus the original film grain—that happened with my Argo comparison.
In my last comparison, which was Lincoln by Steven Spielberg, a variety of factors combined to make online delivery versions of the movie unsuitable for home theater use. One big hint—Vudu HDX was not available on PC or Mac. As a result, I was not able to use screen captures, which resulted in less-than-ideal still-image comparisons. Django Unchained has no such restriction, which made it easy to use screen grabs to perform the comparison.
Django Unchained fared very well in my image-quality comparisons. Despite the many dimly lit scenes, and the often-monochromatic palette, all three versions were eminently watchable. While Blu-ray remains the reference for image quality, iTunes and Vudu both exhibited ample image quality. The differences were in the details; Vudu was more heavy-handed with noise reduction but also preserved slightly more fine detail. iTunes looked a little bit dirtier, but also potentially more authentic. With dark scenes and lots of action, both online formats struggled compared to Blu-ray.
With a bright scene and very little action, detail levels were close to Blu-ray in both online formats. In some dimly lit scenes, I witnessed Vudu HDX struggling with artifacts on occasion— but it required significant scrutiny. As far as I am concerned, the online-delivery versions of Django Unchained are very suitable for home-theater use. I hope that the following comparison images will help you come to your own conclusion.
All of these images are resized for web display. Please click within each image to view the original size. When viewed at the original size, you see the exact pixels taken from the screen grab. When viewed that way, the differences between the formats are considerably easier to see.
Dimly lit scenes tend to pose a challenge for compression algorithms.
To my eyes, iTunes 720p beats out the other two online delivery formats. I have seen this effect once before, in the movie Argo. The 1080p formats utilized too much noise reduction.
Artificially brightening the screen grab in Photoshop makes it easy to scrutinize the shadows. There are significant issues with Vudu HDX and both iTunes versions, but Vudu looks the worst by far.
This scene features uneven lighting. Because the camera is stationary, the lower bit rates of the online formats are not a significant issue.
Even though Blu-ray looks the best, the online delivery formats also look very good.
Artificially brightening the images in Photoshop once again reveals the inner workings of the shadows. In this example, Vudu HDX is not having any problems rendering shadow detail and looks remarkably similar to Blu-ray.
Diffuse outdoor lighting and a stationary camera make this a great scene for judging textures and detail rendition.
Blu-ray has superior detail in all of the rock textures, but iTunes 1080p does the second best job at rendering the scene. The noise reduction applied by Vudu HDX makes the scene look a bit fake, plus there is an issue with its color balance.
High key, outdoor lighting make this a relatively easy scene for the compression algorithms.
Among the online delivery formats, iTunes 1080p strikes the best balance between noise reduction and preservation of detail, coming the closest to the Blu-ray reference. Whatever slight gain in sharpness Vudu HDX provides is offset by the loss of texture detail that is a result of noise reduction. iTunes 720p continues to be the softest-looking, but it still looks very good.
The vibrant blue in Jamie Foxx's costume adds a colorful twist to a movie that is mostly painted in Earthy hues.
With ample daylight and a stationary camera helping to counteract limited bandwidth, iTunes 1080p once again performs the best among the online formats. Vudu's use of noise reduction is just too heavy-handed to retain a natural look.
This shot involved motion, and because the sun is behind the subject, there is a lot of shadow. It is the sort of scene that causes problems for online delivery formats.
Once again, the 1080p version of iTunes' HD format comes the closest to Blu-ray.
This artificially brightened version shows Vudu HDX struggling to render the shadows. iTunes HD 720p also seems to have a hard time with the shadows, compared to the 1080p version.
A scene like this—shot in broad daylight with a stationary camera and a wide-angle lens—possesses a tremendous amount of detail.
Blu-ray does quite a bit better than the online delivery formats, rendering detail right down to the individual pixel. iTunes HD 720p looks surprisingly good in this shot.
Leonardo DiCaprio lights a cigarette in this dim, amber-tinted scene. The lit match provides a spot of high contrast.
Both iTunes versions look remarkably similar to the Blu-ray, while Vudu's noise reduction continues to alter the image.
This indoor scene uses spotlighting to achieve a very high contrast, painterly effect.
Vudu HDX manages to preserve a bit more detail than iTunes. I was surprised by how similar these frame grabs look.
There is something about this scene that the online delivery formats liked—or rather, found easy to render.
Tarantino has a reputation for making movies that feature brutal, stylized violence. Of course, we all know it's just special effects.
Blu-ray renders more individual drops of fake blood than the online delivery formats, by a significant margin. Loss of detail during fast motion is one of the pitfalls of the relatively higher levels of compression used by iTunes HD and Vudu HDX.
Edited by imagic - 4/23/13 at 1:11am