Apple claims to have invented industry’s best Full HD 1080p video compression, which delivers High quality video & audio by using a very limited bandwidth. Lets dig deeper to find out the truth.
iTunes movie size reduces from 10-50gb (dual layer BD) down to 3GB. This is nothing new, several MP4 H.264 encoders can do similar job, without losing a lot of detail. iTunes downsamples the audio with AAC codec and offers audio in Stereo and Dolby Digital 5.1 track. The video resolution is 1920×798.
Sharpness can be best compared by comparing zoomed-in images head-to-head. They look very sharp on both BRD and iTunes 1080p. The iTunes image is always on top or to the left, the BRD image on the bottom or to the right.
For the ship scene, iTunes 1080p tries to compete with Bluray’s detail, and the margin is narrow. iTunes version loses a bit of sharpness & detail, and also ignores some noise that was present in original video.
Color Reproduction & Gamut
Both iTunes and Bluray have rich color definitiion and equivalent detail. Its hard to make out any difference here.
Detail / Highlights
iTunes movie does very well here too, but it loses lot of detail in the brighter areas of the video. Look at the picture below, all bright areas seem to have lost detail
Smoothness in Motion picture
The Blu-ray version of the telephone pole close-up shows much more detail—including noise or grain (which is present in the original video). iTunes video treats detail and noise identically, so loses noise along with detail. What needs to be noted is that you won’t have this noise on newer Blurays, hence difference to detail will be more pronounced.
iTunes video is pretty smooth but in cases of fast motion, it did seem to break apart momentarily. However, it was only noticeable with careful observation, unnoticeable for a normal viewer.
Contrast, Dark gradients Reproduction
Dark gradients are often a problem area with image compression. So it’s no surprise that iTunes falls behind at this. iTunes 1080p movie bands-out all over the image, however, BluRay does it smoothly.
You really have to be an audiophile to understand this part. For the tests, the fidelity was greatly affected by reducing 96khz HD audio to bare 44khz. There is an immidiate loss in ambiance, gun shots, and background music. iTunes 1080p’s audio was crisp, but not as much as BluRay.
I’ve been looking at compressed BluRays for several years, and have used all possible codecs to store my BluRay Dvd collection on PCs. From mkv to AVI, H.264, playing with bitrate, multi-pass and other advanced settings. The results have never been so close to the BluRay.
Apple has actually pioneered the BluRay compression by beating the open codecs by far. With High compression levels (50gb to 3GB) it really does a remarkable job. It does leave minor artifacts, which will in practice be unnoticeable by a normal user.
Sad part is BRDs can have uncompressed multi-channel audio, multiple audio language options, and special features. You’ll miss all those in iTunes 1080p movies, but the file size /download size justifies a lot of that. I rate the video compression to 9/10 and audio to 7.5. Overall it would score a 8/10, recommended!