Video DVD basics & choosing Authoring software...
Video DVDs can vary a LOT in their complexity, & a very big part of choosing an authoring app is based on what you want/need to do -- it's really a lot like choosing the app you'll use for your image editor, e.g. can you get away with Windows' Paint or do you need Photoshop or The GIMP. And just like when choosing an image editing app, it's hard to judge just what you'll need when you're 1st starting out. It doesn't help that it's harder for the average person to choose a DVD authoring app than most other kinds of software because there's a really high level of abstraction -- if you actually saw the scripting & registers used it would be too complicated for many (most?) people to deal with without quite a lot of learning, so all that stuff's hidden & the novice has no idea what capabilities any authoring app has left out. What I'm doing here is telling you a bit about Video DVDs, & in doing that I hope to accomplish two things -- 1) make it easier to work with DVDs, & 2) give you enough knowledge about DVDs that you can decide what you want to be able to do, & knowing that, hopefully make a better choice checking out & deciding on authoring software. If all you want to do is play a video in your DVD player, that's easy. If you want to get into [especially more involved] menus, flying blind so-to-speak can get expensive in both time spent learning the app & the cost of the program. Just diving in can also mean dead ends & false starts as you try to learn & do more -- an authoring app's help files, manuals, & forums [usually stocked full of loyal fans] are based on what that software can do, & NOT on what DVDs can do or how it should be done... how DVDs work, & by extension how to author one, are covered by an NDA [Non Disclosure Agreement], so while a company can tell you how to use its software, they can't tell you really how to generally go about creating video DVDs. That said...
Everything you see when you're playing a Video DVD is DVD-spec mpg2 video -- mpg2 video encoded using a specific set of options -- though as this has almost become a standard in & of itself for mpg2 at DVD frame sizes, you often don't need to worry too much about your mpg2 being in-spec. In a DVD layout mpg2 video is contained in VOB files, along with audio tracks & optionally subtitles. Audio is usually AC3, & here you might have to worry about specs a little, since DVD authoring apps can seem a bit picky -- if your authoring app doesn't like the AC3 you want to import, you can often just import the original .wav files & let the authoring app do the encoding rather than lose quality (& usually volume) twice [once with each encode]. You can think of DVD subtitles as a transparent overlay track -- they have graphics shapes that act as masks, with the player coloring the area covered by those masks. Subtitles usually exist in 2 forms, as plain text an app will turn into an overlay track, or as those graphics overlay tracks saved to a separate file -- there are also OCR apps for turning graphics subs back into text. And there is software for stripping out the CC optionally embedded in mpg2 video, so that can be turned into subtitles -- since many DVD players &/or HDMI won't pass CC through to a TV that can be extremely useful [CC is rendered by the TV -- subtitles are rendered by the player, becoming part of the picture sent to the TV]. Subtitles in text files can be edited, & will play with some software players, but DVD players & player software will only handle the graphical version. Authoring apps for DVDs vary in their support for subtitles &/or multiple audio tracks -- sometimes you need to author the DVD to your hard drive, then add whatever you want/need using specialized software before burning to disc. Finally the media in VOB files is divided up into one or more cells -- these cells are time measurements that coincide with mpg2 video *I* frames. Cells are used for chapters, & any where/any time the DVD needs to jump to a certain time in a video. "I" frames are the Full frames in mpg2 video -- partial frames recording just changes fill the space in between -- I frames are usually 12 - 18 frames apart depending on the encoder. Usually you want to be able to add a chapter point [& cell] a couple of I frames into a new scene. More limited authoring apps might limit you to setting a chapter every "n" amount of time, which may not be a big deal to you if you'll just use the chapters as a sort of fast forward. Better apps will show you the I frames so you can be exact, though adding a chapter a minute or so into the new scene you're *usually* all right, as the closest I frame will usually be in the beginning of that scene -- add a chapter just when a scene changes & you'll often wind up showing just a frame or two of the previous scene, which is annoying to viewers.
The IFO files on a video DVD contain the directions for the DVD player -- they are where DVDs can get complicated, & are based on a somewhat primitive scripting designed for dumb hardware in the 90s to interpret. Part of what makes it complicated is some features were never commonly implemented in players, while other commonly used features are used in ways never envisioned when the spec was created. Most Video DVD authoring software uses a set of boilerplate scripting, & how well that scripting works varies from one app to the next, forming the basis for both the capabilities & weaknesses of any particular brand/model of authoring app. Often you can add to or edit that scripting in PgcEdit, adding features to a video DVD that it wouldn't have otherwise. Where the IFO files are most involved &/or more complicated is with any menus [if present on the DVD] as well as for special features, like DVD movies with more than one ending, or if the DVD contains simple games -- IFO files for DVDs with only a title movie or video are usually Very simple, so most any authoring app can handle those well. Menus are made up of mpg2 video, usually AC3 audio, & a type of subtitles. Buttons are really just rectangular areas, while button highlights [the part that changes color to tell you which button is selected] are any subtitle graphics shape(s) within that rectangular area. A pro-grade app lets you set those rectangular areas & import the graphics shapes used to define those highlights -- the further you move away from pro software the more limitations you'll have. What's called the Abstraction Layer in most video DVD authoring software hides the fact that any menu background, including what you *see* as buttons, any text, & any animation, is simply a mpg2 video file. If your Video DVD authoring software has or lets you place text, add animation, place buttons etc., it'll just render all that stuff to an mpg2 video file. Designing your menu in your authoring app can be a time saving convenience, but it also limits you to what that app allows or can do -- you can most always do better elsewhere, & better authoring software lets you import your own work. [In practice you often do what you can do in your software, & as possible learn tricks to force it to do what you want.]
One area where DVD menus get more complicated is with aspect ratios, i.e. 4:3 vs. 16:9... Generally you can get by matching the video, &/or using 16:9 since that'll look better to most people, even if letterboxed, than 4:3 with pillarboxing on a wide-screen monitor or TV. More pro-grade authoring software will let you include both. Another area where things get more complicated is having more than one menu cell... Video DVDs can have an intro video, plus you can use intro video's with any other menu or video -- this is what you see transitioning to the menu &/or playing before a menu or video plays. When you have menus with more than one cell the 1st cell can contain the DVD intro, & the 3rd cell (if present) can contain the intro to a video title, playing when you click that menu button, as opposed to including a separate video file on the DVD for each transition. I'm mentioning this mainly because some software companies make a bigger deal out of it than I think warranted -- in practice you won't usually see a huge difference... Using menu cells can help you control where on the DVD that video's physically located [you can have a delay if the DVD drive mechanism has to travel from one end of the DVD to the other], & it puts that video into another domain on the DVD [e.g. a concern if/when you reach the max number of titles]. OTOH if you have/use a menu with a looping audio &/or video track, multi-cell menus tend to cause a bigger delay at the point where it loops, so you may prefer not to use multiple cell menus, even if/when you can. Menus aren't just used for their designed purpose [letting the viewer make selections], but can be used just to hold scripting or used instead of a title for audio/video.
A title video is basically any video file that's not in a menu -- it's not just the main title on your DVD -- & both menus & title video's have End Actions you set to determine what happens once it's done playing. You can have a menu button start a short video file as an intro or transition, & that file's end action would normally be set to open another menu or play another video. Menu end actions are usually either loop or hold, but at a more advanced level for example you can have a menu end action set to activate a [often hidden] button -- with a multi-cell menu including the intro video, that auto-activated button can go to a duplicate of the main menu using a single cell with no intro video... that gives you the best of both methods, very slightly better continuity between intro video & main menu, plus slightly less lag when the menu loops, & doing it that way is pretty common for or with retail Video DVDs. And whenever thing's change, say a button's activated or a menu/title video ends, that's when/where you can change things like the audio or subtitle track, or even the video aspect ratio [though that one can get iffy because of player over-rides]. That's why you have separate setup menus -- when you change audio tracks using a menu the button you click goes to another menu page, though it may look identical. But the viewer, the person playing the DVD has a lot of those controls right in their hand -- the player's remote. A DVD author tries to control the viewer, not so much because of ego but because that's the only way to make sure of what they see on-screen, when, & to do that they prohibit operations -- you're probably became familiar with these DVD flags or switches when you tried to skip through the trailers at the beginning of a DVD & found out you couldn't. I think most authoring software adds these prohibitions when it makes sense to do so -- e.g. the results are unpredictable hitting the Next button with a menu on-screen -- & a lot of DVD related apps will remove them all by default. You should be aware that those prohibitions exist, that some apps will let you set them, & some other apps will remove them all unless you're careful... you don't want to spend time designing & creating a very nice DVD experience, & then run it through DVD Shrink, finding that all prohibited operations were removed because you didn't un-check the box in preferences.
Now, most authoring apps include an mpg2 encoder, & most of the time you want to avoid using it as possible... pro-grade apps assume you might have spent a whole lot more money on a separate encoder that they can't hope to match, while cheaper software is cheaper in part because they don't have to license or write a really good mpg2 encoder. Even in cases like the Sony apps where DVDA uses the same encoder as their Vegas editing app, they leave out most of the encoding controls/settings figuring you'd use Vegas if you wanted higher quality. You want a DVD Authoring app that passes through your already encoded video -- it used to be a sign of higher quality authoring software, but nowadays it's so common that only the really poor authoring apps won't let you. As a general rule of thumb, use VBR [Variable Bit Rate encoding] with a max bit rate of 9 [you can go higher but might have compatibility issues], & for single layer DVDs, an average of ~5 as you approach 2 hours length, ~6 as you get closer to 1.5 hours... rather than a bit-rate calculator what I've always done is open Windows Explorer so I could see the new file being written, opened Calculator at the same time, then regularly refresh the view in Explorer -- as soon as the encoder progress bar/window shows 4% I enter the new file's size in Calculator & divide by 4. If I'm in the ballpark I'll try again in a few minutes at 8 or 12 % for example, & if it still looks good I'll walk away & let it be. I'd also rather just be a hair over the limit & use DVD Shrink or Nero Recode to reduce the size than be too cautious & waste quality by having the video file turn out much smaller than it has to be. [If/when you're only slightly reducing size (in the 90 range), Shrink & Recode discard data from the in between frames ("P" & "B") in a way that is not very noticeable, & the overall result may even look better than the same video encoded at a reduced bit rate to fit.] If your encoder & source video support it, use pulldown -- a movie at 23.976 fps is used with special flags in the mpg2 file, telling the player to repeat certain frames to reach 29.976 NTSC, which allows you to use a higher bit rate for the same final file size, with no loss in quality compared to actually repeating frames in the video file. Note that you may or may not have better results encoding menus progressive or interlaced [assuming you have a choice], depending on the software you're using.
Audio & video tracks are separate things -- audio & video themselves use different timing [video is based on fps, while Video DVD audio is based on a sample rate of 48.000 Hz]. True, some containers like AVI may let you interleave audio & video, but that's just the way they're combined into a single file. Better Video DVD Authoring apps, encoders, editing software etc. let you work with the separate streams, indeed may only let you work with separate audio & video. Many, usually cheaper authoring apps & many converters only let you work with the two combined -- often you'll use a muxer/demuxer app to combine or separate the audio & video files as necessary. It can be confusing with mpg2 since muxed [multiplexed or combined] files usually have an .mpg file name extension & contain more timing info that separate .m2v files, which are the same thing, just without the audio & that extra timing data. Sony media apps [Vegas, DVDA] are an anomaly, working best with .mpg files without audio -- use a muxer on .m2v but don't supply an audio file.
Using more than one audio track means you need to be able to add audio tracks separately. When space is tighter, e.g. on a single layer DVD, a stereo AC3 file is smaller & more people can play them on their PC/laptop. When you have the room OTOH 5.1 AC3 sounds better, even down-mixed by a player to stereo. If/when you have room, e.g. on a double layer DVD, it's nice to include both -- again best of both worlds. There are apps/tools, both free & not that let you create fake 5.1 from stereo, & those often do sound better as 5.1 AC3.
Dual layer DVDs are necessary when you have too many extras to fit with the video on a single layer DVD, &/or when the video length exceeds 2 hours -- dropping the average mpg2 bit rate below 5 [which you need to do to get the video file small enough] noticeably downgrades quality. Most authoring apps consumers can afford do poorly when it comes to dual layer DVDs... What I do is open the DVD on a HDD in PgcEdit, then go to create an ISO, which tells me the layer break [split] should be between chapter X & chapter Y -- sometimes I get lucky & an existing chapter is ideal, but that's more rare than not. When I need another cell [chapter] I go back into my authoring app & add a chapter between "X" & "Y", since I can't just add a cell otherwise -- layer breaks are best placed when there's a minimum of anything going on, since reversing course the player's drive may hesitate/pause. Back in PgcEdit I'll remove the chapter from the cell, & then create the ISO, which I'll burn to disc with ImgBurn.
