The video must also be all PAL or all NTSC. Multi-format discs are not supported, and most authoring applications prevent this mistake from being made. DVD players usually do not support playback of such discs.

Authorware variances. Each authoring program has it's own preferences and rules regarding the file types that are required and/or allowed for use. Your video and audio files must conform to the rules of the program, and this information is often found in the program manual or help files. It is imperative that you read the help files and manual of your authoring program.
- Example One: DVDit! PE. The DVDit! line of software requires that all files be the same resolution and format. This program does not support multiple VTS (see the multiple VTS authoring guide for more information on this topic). It only support 352x240 MPEG-1 between 1150k and 1856k and MPEG-2 at either 352x480 or 720x480 with bit-rates of up to 8000k for the video. It does not allow 352x240 or 704x480 video. It does not allow MPEG audio, only AC3 and PCM (WAV or AIFF only) sound files. It also requires closed GOP for the MPEG. It will not accept non-MPEG files. It requires video and audio to be imported separately.
- Example Two: TMPGEnc DVD Author: This program allows pretty much anything in the MPEG specification. It will not accept non-MPEG files. This program also allows multiple VTS.
- Example Three: Ulead DVD Workshop: This program will take MPEG source without transcoding it, and will accept multiplexed MPEG streams, a rarity for mid-level to high-level authoring software. It does motion menus and multi VTS. It will accept some non-MPEG files and will transcode them to MPEG-2 format.


Audio - AC3 vs. PCM vs. MP2  

The DVD format supports three types of audio: Dolby Digital (AC-3), uncompressed PCM, and MPEG Layer II. Each of them has advantages and disadvantages. All audio must be a minimum 48hz and stereo. It can also be surround sound. The most popular of them is AC3, as it is a small file that retains high quality. Dolby sound also allows for surround sound, most commonly the Dolby Digital 5.1 sound scheme.

AC3 audio
Dolby Digital Audio is a highly compressed audio format stored in an AC3 file. Dolby can be stereo or surround, and has allowable stereo bit-rates from 128k to 384k. Most commercials DVDs using stereo use 192k or 224k audio, having come from perfect sources and using hardware encoding. For home use, I suggest the 256k bit-rate in order to retain rich sound, especially if it is converted from AVI or MPEG captures. Surround sound must have at least 6 separate source channels. Do not use 5.1 unless you have a surround source. Taking a stereo or mono audio file and forcing it into Dolby 5.1 format will only waste space and provide no advantages. Most surround systems are able to emulate surround by translating the audio and feeding it to all the speakers, which is essentially the same as converting a 2/0 file into a 5/1 file.
Advantage: size and quality.
Disadvantage: none, really.

PCM audio
Uncompressed PCM audio is often stored as WAV or AIFF sounds files. PCM is merely uncompressed audio, and is enormous in size, often 10 times the file size of MP2 or AC3. Do not let the term "uncompressed" fool you, as most of the compression is being done on frequencies and information outside the range of human hearing. Compressed AC3 and MP2 audio can sound just as good as PCM, at a lower cost (in terms of disc space). In general, much like AVI video, the PCM audio format is honestly only good for editing. Final DVD audio should be AC3 if at all possible. Only leave it as PCM if final disc size is unimportant or if unusual distortion occurs from AC3 or MP2 compression. The bit-rate of PCM sound is set at 1536k or a close approximate.
Advantage: quality
Disadvantage: size

MPEG Layer II audio
The MPEG Layer II format (commonly using the .MP2 or .MPA file extension) is not the same as the MPEG Layer III (MP3) audio format. While both forms of MPEG audio, they are not the same. DVD and CD-based video does not use MP3 audio. For NTSC video, MPEG audio is not officially supported. This being said, also realize most DVD players can playback the MPEG audio. If the player can play S/X/VCD formats, then it will most likely playback the MPEG Layer II. Most MPEG video chips are also hard-coded to play the audio. For PAL users, MPEG Layer II is currently supported, though recent shifts in the DVD Forum has hinted that this will change in the future. The biggest advantage to leaving the audio as MP2 is to preserve it's quality, assuming it was clean sounding from the beginning. Encoding to PCM merely makes the file larger and encoding to AC3 can potentially harm the quality, especially if the MP2 was a low bitrate. In general, using 256k 48hz is optimal. And 192k is minimum. Most X/S/VCD formats used 224k.
Advantage: size and ease of conversion from XVCD/SVCD/CVD/VCD
Disadvantage: quality and player support


Multiple VTS  

The VOB and IFO files on a DVD are stored with a VTS naming structure. VTS stands for Video Title Set, though it is often referred to as "tracks". 

Example: VTS_01_0, VTS_01_1, VTS_01_2, VTS_02_0, VTS_02_1, VTS_03_0, VTS_03_1, etc
The first number following the VTS, as in "VTS_xx" is the VTS identification number, whereas VTS_01_05 would be VTS one part five. Each VTS can only hold one video format. All video within that VTS must have the same aspect ratio, resolution and MPEG type. 

Why is this important, you ask? Well, most consumer authoring software only allows one VTS for the whole disc. This means you are more limited in what your project can contain. It is important to remember this if your discs will contain multiples video, as they must all have the same specs. Multiple VTS does not require such limitations.

Advantages of multiple VTS. The advantages of multiple VTS are simple: it allows greater control over the content of the disc. The main movie can be 720x480 16:9 ratio MPEG-2 video, the disc bonus can be smaller 352x480 4:3 MPEG-2 and the trailers can be 352x240 MPEG-1 video. Or an episode disc can use several sources at different size and format. Or VCD material can be added to an existing DVD with no conversion being required. The possibilities of using multiple VTS are great. This also allows MPEG-1 and MPEG-2 to be put on the same disc. 

Multiple VTS software. The general rule is that professional software supports multiple VTS and that consumer software does not. 
- Home software. Most home-use software is single VTS software. The only real exception is TDA, which calls these "tracks". All you have to do is add a track and then a new VTS is created. Some of the newest mid-level authoring software like DVD Workshop 2 and DVDit! 5 also supports multi VTS.
- Professional software. Most professional software, like DVD Studio Pro, Sonic Scenarist, Sonic Maestro, SpruceUp and others, supports multiple VTS.

Please read the manual, the software help files or online support file in order to learn whether or not your software supports multiple VTS. 


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