Important: On 19 February 2008, Toshiba announced that they would no longer continue with the development and production of HD DVD, thus ending HD DVD as a viable HD format. This page was relevant before this announcement, but is no longer relevant now that Blu-ray is the victorious format. However, it is here for legacy purposes, as a comparison between the formats and perhaps provide some explanation as to why Blu-ray was ultimately victorious. Please feel free to skip to the next page/chapter if you wish.
Chapter 3: Blu-ray vs HD DVD
This chapter will describe some of the differences between Blu-ray and HD DVD. It is not meant as a critique of either format, the differences described are just facts - you can make your decision as to which format is "best".
It might seem funny to start with bandwidth, but it affects audio and video quality, so it's worth a mention. Both Blu-ray and HD DVD have practically the exact same transfer speed ratings (that is, Blu-ray 1x speed is almost the same as HD DVD 1x speed). However, the Blu-ray movie specs require a throughput of 54 Mbps (of which 48 Mbps is available for audio/video, and the video bitrate peak cannot exceed 40 Mbps), whereas HD DVD only requires 32 Mbps (of which 30 Mbps is available for audio/video, and the video bitrate peak cannot exceed 30 Mbps). This means that theoretically, Blu-ray can transfer over more stuff at the same time than HD DVD with a greater video bitrate peak, which means Blu-ray can use less video and audio compress (or no compression at all for the audio). In reality, most Blu-ray and HD DVD releases use similar average video bitrates, which is usually just under 20 Mbps. And lossless audio tracks are usually around 5 to 6 Mbps (lossless audio is audio that is compressed for storage, but when uncompressed, it is exactly the same as the original uncompressed audio. Much like ZIP files for BMP images, as opposed to using "lossy" JPEG). Note that you will get diminished returns by increasing video bitrate during the encoding process - once you reach a certain bitrate, the improvement to quality is almost negligible (hence why typical encodings average less than 20 Mbps, even though much more is available for usage, especially on Blu-ray). The higher Blu-ray bandwidth was useful in Blu-ray's early stages when it relied on the less efficient MPEG-2 video compression codec. The higher bandwidth (and disc storage space) is now used mainly for Linear PCM audio tracks on Blu-ray discs. HD DVDs tend to use Dolby TrueHD to achieve the same quality audio without the need for higher bitrates. The HD DVD player then decodes the TrueHD soundtrack to Linear PCM, so the output is theoretically the same for Linear PCM soundtracks versus TrueHD soundtracks (again the "ZIP" file analogy stands, Blu-ray stores the files uncompressed, while HD DVD prefers to "ZIP" them up first).
There is a perception that Blu-ray offers better video quality, and this has to do with the first HD DVD player being 1080i only, while the first Blu-ray player was 1080p. For most people, the 1080i/p difference does not matter, and all HD DVD players other than the budget model has 1080p output anyway. All Blu-ray and HD DVD films are stored in the same 1080p/24 format, often using not only the same video compression codec, but having the exact same transfer as well (see Warner Bros. Blu-ray and HD DVD releases - their releases contain exactly the same video transfer, frame for frame). Both Blu-ray and HD DVD supports the exact same set of video compression codecs (H.264, VC-1 and MPEG-2). So quality wise, there is no practical difference between Blu-ray and HD DVD, and when the same transfer is used, no difference at all. Overall, both Blu-ray and HD DVD are equal in the video department.
As of December 2007, 36% of Blu-ray titles use H.264, 37% use MPEG-2 and 27% use VC-1. This compares to 87% of HD DVDs using VC-1, 10% using H.264 and only 3% using MPEG-2. For more statistics, please visit Blu-rayStats.com and HDDVDStats.com.
On a technical level, Blu-ray and HD DVD's supported audio codecs are the same, except that HD DVD requires both Dolby Digital Plus and Dolby TrueHD to be mandatorily supported by all players, while they are only an optional part of the Blu-ray specifications. Both formats have optional supports for DTS-HD. In reality, Blu-ray movies tend to prefer PCM (uncompressed) 5.1 audio, while HD DVD uses Dolby TrueHD to achieve lossless audio at lower bitrates. Listening tests have not really confirmed the advantage of using PCM over TrueHD or vice versa. In fact, the recent HD award gave the best audio category to the Transformers HD DVD that used the lossy Dolby Digital Plus format. When a format is a "mandatory" supported one, movie discs only need to provide one such mandatory track (for example, a HD DVD movie might only have one Dolby Digital Plus track). When it is optional, at least one of the tracks must use a mandatory standard (for example, a Blu-ray movie might have a Dolby Digital Plus track, but it also must have a separate Dolby Digital AC3 track to fulfil the mandatory requirements). Not that any of this makes too much difference to audio quality as it all depends on your AV amp/receiver - please refer to "Chapter 7: HD Audio" for more information. Overall, both Blu-ray and HD DVD are equal in the sound department.
Blu-ray is divided into 3 regions, with the US/Canada in one region, and Europe/Australia in another region (more details on the Blu-ray region breakdown in "Chapter 4: Blu-ray Buying Tips"). Note that not all Blu-ray studios use the region system, for example, Warner Brothers' releases are all region-free. Fox is the only studio where all of its releases are region locked. HD DVD, on the other hand, is completely region-free. This means you can import your movies from anywhere around the world without having to worry about playback problems. For the sake of comparison, HD DVD should be more favoured by consumers, while Blu-ray will be more favoured by studios.
Both Blu-ray and HD DVD use the same AACS copy encryption scheme. Blu-ray has additional support for two other DRMs called BD+ and ROM Mark. AACS also provides provisions for managed copy, which allows users to make limited copies of their discs for backup and portability issues. Managed copy if mandatory on HD DVD, meaning all discs must support it, while it started out as voluntary on Blu-ray before pressure from HP forced them to adopt it as mandatory as well.
For the sake of comparison, HD DVD should be more favoured by consumers, while Blu-ray will be more favoured by studios due to the extra levels of DRM.
Blu-ray has 3 hardware profiles (again, more on this in "Chapter 4: Blu-ray Buying Tips") - only the highest level of these profiles (2.0) has the same interactive features that HD DVD's single hardware profile supports. For example, Blu-ray profile 1.0 does not support dual video and audio decoders, which are used in picture-in-picture extra features such as those found in the 300 and Harry Potter and the Order of the Phoenix HD DVDs. Blu-ray profile 1.1 adds secondary video and audio decoder support, but is missing the Internet connectivity that most recent HD DVD releases carry.
There are also other technical differences. Many Blu-ray movies use the BD-50, 50 GB dual layer format. While HD DVD's dual layer format is limited to 30 GB (HD-30). This means Blu-ray has more storage space than current HD DVDs. HD DVD has reacted by releasing the triple layer 51 GB HD-51 format, but it is currently unknown how compatible it will be with existing HD DVD players. As of December 2007, roughly 50% of Blu-ray movies are BD-25 (25 GB) and the rest being BD-50. Nearly 86% of all HD DVD releases are HD-30. For more statistics, please visit Blu-rayStats.com and HDDVDStats.com.
As mentioned above, Blu-ray has 3 hardware profiles, while HD DVD has less confusing single profile. Only Blu-ray profile 2.0 (the highest of the 3 profiles) can compare with HD DVD in terms of the full feature-set (such as dual video/audio decoders, Internet and network connectivity), but Profile 2.0 includes more persistent storage than HD DVD's minimum requirements. There are currently no Blu-ray 2.0 players available for sale, and only a few Blu-ray 1.1 players as of December 2007 (one of them is the recently upgraded Sony PS3).
Blu-ray is supported by more movie studios with more new releases, while HD DVD has less studio support but the HD DVD studios have more catalogue titles available through Paramount and Universal (the effect of Warner Bros. going Blu-ray exclusive, see below, might affect the status of HD DVD having more catalogue titles). Warner Bros. is the only studio to support both formats.
Update (5th January 2008): Warner Bros. has just announced that from May 2008, they will only release movies on the Blu-ray format. This change of direction has firmly placed the advantage in Blu-ray's court. While this does not signal the end of HD DVD (there are still two large studios supporting HD DVD exclusively), it certainly will give Blu-ray a huge advantage in the format war and perhaps convince the HD DVD backers to change their mind.
Blu-ray is current selling better in movies than HD DVD, by about a two to one margin (December 2007). HD DVD claims to have more standalone sales (750,000, December 2007), but Blu-ray has more hardware sales overall if you include the Sony PS3 (2.7 million, December 2007). The Sony PS3 can play Blu-ray movies out of the box, but since its main function is gaming, it is hard to calculate how many people are not using the PS3's Blu-ray capabilities at all.
The table below sums up the above differences:
Video Codec Support:
MPEG-2, H.264, VC-1
MPEG-2, H.264, VC-1
Mandatory Audio Codec Support:
AC3, DTS, PCM
AC3, DTS, PCM, Dolby Digital Plus, Dolby TrueHD
Optional Audio Codec Support:
Dolby Digital Plus, Dolby TrueHD, DTS-HD HR, DTS-HD MA
DTS-HD HR, DTS-HD MA
AACS, BD+, ROM Mark
1.0, 1.1 and 2.0
Fox, Sony Pictures (including Columbia/Tri-Stars and MGM), Warner Brothers
Dreamworks, Paramount, Universal, Warner Brothers (only until May 2008).
Highest movie sales, highest number of hardware units
Lower movie sales, highest number of standalones, lower number of hardware units
Blu-ray has greater bandwidth, but it might not be needed
Blu-ray and HD DVD are equal in terms of video quality
Blu-ray and HD DVD are equal in terms of audio quality
Blu-ray has region control, while HD DVD is region-free