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Introduction to DVD Authoring
What is DVD Authoring?
DVD authoring describes the process of collecting audio, video, menus, subtitles, etc into an interactive branching structure that will eventually be played on a DVD player. A DVD authoring software must be used to perform this task.
Encoding
What is MPEG-2?
MPEG-2 is the de-facto standard compression technology used for DVD video. This adaptive, variable bit-rate process is able to allocate more bits for complex scenes involving a lot of motion, while minimizing the bits in static scenes.
What is bit rate?
Bit rate measures the amount of compression needed to fit the complete video on a disc. Video must be highly compressed so programs can fit on one disc. Higher compression results in poorer video quality. Higher bit rates are not necessarily better, because certain DVD players cannot handle bit rates that are too high. A good rule of thumb is to keep it below 7 mbps (million bits per second)
What is CBR video encoding?
CBR (constant bit rate) video encoding would apply to a DVD title which contains shorter length of video content. For example, if your project only involves a short video clip, a bit rate is preselected and the video assets are encoded at that constant bit rate. If the total size of your project is 60 minutes or less, CBR will work for you.
What is VBR video encoding?
VBR(variable bit rate) video encoding would apply for example, if the title involved a 2 hour movie with subtitles, multiple language audio tracks, and a directors commentary. To make all of this content fit onto a DVD, you would need to use VBR encoding. VBR encoding varies the bit rate giving more information to complex images and less to simple less active scenes.
What is the difference between 2-pass and 1-pass encoding?
Since a VBR encoder will vary the bitrate depending on the complexity of the images, it does make mistakes from time to time. One feature found on professional encoders that helps reduce this problem is 2-pass VBR. The encoder will make a first pass at encoding the video, then start from the top and do it again. When finished, the encoder analyzes the results before finalizing. By using 2 passes and analysis, the encoder is less likely to make a mistake in choosing the appropriate bit rates.
Audio
There are three main types of audio: AC3 (Dolby Digital), PCM (uncompressed), and MP2 (MPEG Layer II).
AC3
It's a Dolby Digital Audio. AC3 supports not only stereo, but also surround. Audio bitrate range: from 128Kbit/s to 384Kbit/s. 192Kbit/s is the most common bitrate.
Surround sound must have at least 6 separate source channels. AC3 format has very good quality, surround sound support and very high level of compression. That's why the size of audio information is small.
PCM
The main advantage of the PCM audio is excellent quality. With PCM you can preserve all audio frequencies. The main disadvantage of Uncompressed PCM (WAV or AIFF) audio format is size. It stores all audio information without compression. It's a recommended format for audio editing. Do not use PCM in final versions of DVD. It causes problems in some DVD players.
MP2
Also known as MPEG-1 Audio Layer II. This format is not officially supported for NTSC video. It has good compression level but does not have very good quality, and lack of support by all devices.
DVD Menu
See our separate article on DVD menu creation.
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