Why Blu-Ray is better than HD DVD

I've decided to create this page since I grew tired of constantly re-writing this information on forums trying to make my point as to why Blu-Ray is a better format than HD DVD. I will try to point out the technical limitations of HD DVD. For the time being, I'm going to ignore studio support, since that doesn't really have anything to do with each format's specifications. Studio support can and will change over time. In the end it would be great if all studio's released movies on both formats, so that the consumer could decide what format to get a movie on, rather than being forced to choose the format that has most of their favorite movies. My two main arguments are Blu-Ray's superior capacity and bandwidth.

1. Capacity

Blu-Ray is the superior format mainly because it supports a greater capacity of 50GB on a Dual-Layer disc vs. the 30GB available on a Dual-Layer HD DVD Disc. Many people believe 30GB is enough space for High Definition movies, and the extra 20GB which Blu-Ray provides is simply not necessary. This is simply not true.
With all other things being equal, picture quality is determined by bitrate. A higher bitrate will result in better picture quality. However, there is a point where the video is close to perfect and increasing the video bitrate will have absolutely no visible effect on picture quality. This point varies from movie to movie depending on many factors such as the codec used for encoding, and the amount of action/movement in the movie. For the sake of argument let's take a conservative number and say an average video bitrate of 20Mbps is the ceiling where increasing the bitrate will no longer improve visual quality. Let's assume there is an additional 2Mbps of bandwidth usage, for audio and overhead. Let's also assume there are no extras on the disc and the menu and other files take up a negligible amount of space.

HD DVD size: 30GB
Bitrate: 22Mbps

HD DVD size in Mb = 30 000MB * 8 = 240 000Mb
Length of Movie (in seconds) = Size/Bitrate = 240 000/23 = 10909s
Length of Movie (in minutes) = 10909/60 = 182min

As you can see, The size of HD DVD discs effectively limits a movie to approximately 3 hours at the best possible quality. Of course, it IS possible to fit movies longer than 3 hours on a HD DVD, but the longer the movie is, the more noticeable the drop in quality will become. A low bitrate will result in a softer picture or visible macroblocking, or pixellation.
This lack of space also limits the amount of extra content available on the disc because the more content that is added, the lower the bitrate must be for the video.
This lack of space will no doubt prove to be a problem for longer movies such as the Lord of the Rings Trilogy where Lord of the Rings: Return of the King Extended Edition is over 4 hours long. It will be impossible to fit the movie with regular audio and all the commentary tracks on a single HD DVD with an average video bitrate much higher than 12MBps.

Some people will argue that HD DVD has a Triple layer 51GB disc which is supposed to work in all existing players with a firmware update. The truth is, until a movie is released on such a disc, for all intents and purposes, it is just a prototype and will never be released. Besides, Hitachi has developed a quad-layer Blu-Ray disc capable of holding 100GB which is supposed to be compatible with all existing Blu-Ray players. Since these discs were not in the original disc specifications for either format they can effectively be ignored for the time being.

2. Bandwidth Limitations

HD DVD is limited to a total data transfer rate of 36Mbps, with Blu-Ray Maxing out at 54Mbps. This includes any overhead. When playing a video, HD DVD can allocate a maximum of 30Mbps for video,audio and subtitles while this limit is 48Mbps for Blu-Ray. HD DVD supporters argue since there is no noticeable difference between video at 20Mbps and video at 30Mbps, the extra bitrate on Blu-Ray is simply wasted and not needed. Let's assume, this is true (although in reality, there are movies which can benefit from a bitrate higher than 20Mbps). The 30MBps is the total for ALL Video, audio and subtitles.

Since audio and video use variable bitrates, When it comes to bandwidth issues, it's the maximum bitrate that matters, not the average. For example, lets say a video is encoded with an average bitrate of 20Mbps which fluctuates between 15Mbps and 25Mbps, and an average audio bitrate of 4Mbps which fluctuates between 2 and 6 Mbps. When a huge explosion occurs on-screen most likely the video and audio bitrate will peak, in this case, video at 25Mbps, and audio at 6Mbps. Since the player will not be able to read at 31Mbps without stuttering the Maximum bitrate will have to be limited so it never goes above 30Mbps.

Dolby TrueHD supports 8 channel 24-bit/96Khz lossless audio at a maximum of 18Mbps. You'll probably never see such a high quality audio track on a HD DVD since it would leave only 12Mbps for video. So Let's assume a more realistic 8 channel 24-bit/48Khz Dolby TrueHD track with a max bitrate of 6.6 Mbps. Subtitles take up very little bandwidth, so lets say with 13 or so language subtitles, about 0.2Mbps are taken up. That leaves a maximum bitrate of 23.2Mbps for video. This is not a problem, and would probably make an excellent quality movie.

The problem happens when you want to add extras and more content to the disc. What happens if the studio wants to add audio tracks in other languages, or a director's commentary? All of this will eat into the discs bandwidth. Let's assume these are Dolby Digital tracks. Each track would use an additional 0.5 Mbps. Let's assume 4 additional tracks for a total bitrate of 2MBps. Both Blu-Ray and HD DVD support picture-in-picture. To use PiP, the disc would need a second video track. This would probably be a standard definition video, with a max bitrate of about 5Mbps. With these additional features the maximum bitrate for the main feature drops to 16.2Mbps. As you can see the lower bandwidth limit on HD DVD does come into play and can limit the amount of content available on the disc.Also note that these are somewhat conservative numbers, if Dolby TrueHD tracks were used instead of the inferior Dolby Digital, a lot more bandwidth would be used for each additional track.

One thing that may need some explanation is why everything must fit within the 30Mbps available bandwidth since the player doesn't need to read all the audio, subtitle and video tracks at once. Optical discs have a single track which winds from the center of the disc to the edge and then to the second layer of the disc. This can be pictured as a single piece of string containing multiple threads. When playing video, the player is moving along that string at the fastest speed possible. Let's say 1mm of that string represents 1 second and the string is made of 30 threads each representing 1 Mb. The player is incapable of moving to different parts of the disc and reading video at the same time, so all content that will be played at the same time as the video has to be on that same 1mm section of string. All that content has to fit within those 30 pieces of thread.

Blu-Ray myths:

This is simply not true. Blu-Ray players are completely capable of playing back existing standard definition DVD's. They also upscale DVD's to High Definition resolutions just like HD DVD players do.

This is just BS spread by HD DVD fanboys when they run out of valid arguments. If Sony studios ever released a movie on HD DVD you would be just as likely to get a rootkit.(Even though those chances are close to nil.) This has absolutely nothing to do with the Blu-Ray disc format. Content on the disc is something the individual studios control.

Blu-Ray movies will always be playable in all players. The only thing to look out for is special features. Some optional Bonus View special features will only be available on players which support them. Of course, if special features are important to you, simply buy a player which supports them. The main feature on Blu-Ray discs will always be compatible with all existing players.

It is completely up to the device manufacturers on what features to support. Some special features were optional until Profile 1.1 was mandated October 31, 2007. The profiles simply guarantee all players released after a certain date support a specific set of features. It does not mean that Profile 1.0 players do not support special features. In fact the Samsung BD-P1400 is a profile 1.0 player and supports Picture-in-Picture as well as BD-Java.

The Blu-Ray specifications have been finalized since early 2006. Some people don't seem to understand that profiles 1.1/2.0 simply make certain optional features mandatory in players. The profiles are all about optional features which are supported by Blu-Ray players. They have nothing to do with specifications being unfinalized. If you belive Blu-Ray is an unfinished format, by the same logic you would have to belive DVD is still an unfinished format since not all DVD players today are capable of playing DTS audio.

-Last Updated:19/11/2007

If you want to argue with me I can be found on the neowin.net forums with username Marty2003. Just send me a PM.