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DVD (or “Digital Versatile Disc”) is an optical disc format mainly used for storing video or data. There are many variations but the most common, and those supported by ContentAgent, are:
The – (“minus”) R/RW and + (“plus”) R/RW discs are competing formats but are both supported by the majority of burners and players so users shouldn’t be too concerned in choosing between the two. However, although DVD+R(W) is the newer, more reliable format, some older (pre-2004) players may only support DVD-R(W) exclusively, so if you are creating DVDs for distribution and are unsure of the age of the destination player it might be preferable to use the DVD-R format.
There are slight capacity differences between the DVD formats, but both can store approximately 4.7GB (gigabytes) or 4.38GiB (gibibytes) on a single layer disc.
Also available are Dual Layer discs which can almost double capacity to 8.5GB or 7.96GiB by writing to a second physical layer within the disc.
The specifications for video and audio requirements vary by global region but the most common are:
Video
The MPEG-2 can be either a Constant Bitrate (CBR) or Variable Bitrate (VBR) with a peak of 9.8Mbit/s but for maximum compatibility should not exceed 8Mbit/s.
Unlike Constant Bitrate (CBR), which uses a fixed bitrate, Variable Bitrate (VBR) varies the data rate within specified target minimum, maximum and average bitrates. Higher bitrates are allocated to the more complex segments of video (for example rapid motion) and lower rates to less complex segments (for example static shots). Therefore VBR can achieve a better quality-to-space ratio compared to a CBR file of the same size. However, the trade-off is that VBR encoding is slower, especially if multiple-passes are used – for example one pass to analyze the complexity of the footage and a second to encode it.
Audio formats
Mixing formats
Formats, video or audio, cannot be mixed on the same DVD. Aspect ratios can be mixed, but ContentAgent will default to playing them back at the aspect ratio of the first clip.
Length of video stored
The amount of video that can be stored on a DVD depends on the video and audio bitrates used and whether the disc is single or dual layer, so there is no fixed “record time”. However, as a guide, up to one hour of footage can be stored on a single layer disc using PCM audio and a video bitrate of 8Mbit/s CBR. If you need more help there are a number of good Bitrate Calculators online.