Keycode Access to play clips
image of the keypad used in the sample project
An interesting thread on the Apple Discussions recently talked about whether it is possible to use a menu screen with a number pad graphic so that users could type in a clip number to play a clip. In the thread, the requirement was for 550 clips, and the original poster referred to them as ‘tracks’. Clearly, you can only have 99 tracks, so you always put all of your material into a single track and use markers to set the start/end points between the clips. The only other constraint is that a track can only have 99 markers in DVDSP. With 550 clips you’d need 6 tracks, and to keep the number of markers lower, you’d put just 50 clips into each of the tracks you use.
So then came the scripting - how do you keep track of what the user typed, and send them to the relevant marker? It’s actually a lot easier than you might think, using the button values on the menu to determine the clip value. The harder part comes when you have to do the jumps to the clips. When you write a script you only have 128 commands at your disposal. With a jump statement that includes an ‘if’ clause, you’ll get through those very fast and need quite a few scripts for 550 clips. Additionally, the scripts would go through sequentially, making finding the right clip a chore, and probably creating quite a pause.
The answer is to create a script for each clip that has just a single jump statement to get to that clip. The genius part here is that you use a ‘Jump Indirect’ to get the right script and so massively reduce the time for the player to get from the selection script to the playback. Don’t forget that DVDSP has a pretty hefty abstraction layer and there are lots of ways to slow things down, so anything you can do to help reduce delays is going to be good.
The remainder of the job is to add menu calls and end jumps to the markers - in the sample project I just sent everything through a script that clears the GPRMs and goes back to the main menu. Additionally, I had to add some logic to deal with the user selecting clips that didn’t exist, and to allow them to use a leading zero in their number, for selecting clip numbers 1 through 9.
The sample project file is here. You’ll probably need to reconnect the images I used for the track when you open the project.
Creating Random Menus, or random anything!
Scripting Random Menus
A new tutorial on the site deals with a number of ideas for making random menus appear for the user. You might well ask what the point is in making this kind of thing, but it is all about enriching the user experience for your disc.
Consider the scenario where you want to reveal slightly different information each time the user visits a particular menu. Or how about adding an easter egg button to only one menu in a set of 10? What about just for visual interest, changing the background image every time that menu is accessed?
The tutorial shows you ways of achieving all of these things, and with your own ideas added in to the mix there is a lot that can be done to improve the quality of your projects. There are files available for download, and the scripting is all explained in the tutorial. It’s very short, and pretty simple, but does rely on using the ‘Item Values’ for menus. If you are not sure about this, you can find out more about item values on this site, too!
Click Here to get to the new tutorial, or follow the links on the left!
Comments Gone?
I am sorry to say that after a recent database upgrade the comments have sadly been deleted… we have lost all of those brilliant comments from the users. This is a bit of a tragedy, to say the least, and I apologise if your comment has now gone into the ether. Please feel free to add more if you can!
Video bitrate too high
I have lost count of the number of times this particular error message has been reported by authors using DVD Studio Pro, and how confusing it is to resolve.
By and large, the error reporting in Apple applications is fairly informative for most people, but like any other software there are some reports which just don’t make much sense, or inform you of what to do to fix the problem. Naturaly, when you see that your video bitrate is too high, you attempt to lower it and get stumped when no matter how low you go it still causes an error.
The maximum combined bitrate on a standard definition DVD, including all video, audio graphics and additional content, cannot exceed 10.08MBPS. The maximum rate for video alone is 9.8MBPS. There is no minimum bitrate above zero, as this is for you, the author, to decide given your footage and how it looks when it is encoded. However, the reduction of the video bitrate will also reduce your visual quality, and to an extent, raising the bitrate will help improve the visual quality (although there is a law of diminishing returns that you will get to). The lower the bitrate, the smaller the resulting file size and thus the more footage you can fit onto your disc. Raising the bitrate increases the file size and consequently you can fit less minutes onto your disc.
The trick is to balance the bitrate with the disc space available to get the best quality - in other words, to hit the ’sweet spot’. Since video is far more forgiving to compress, or rather your eyes are far more forgiving than your ears, it’s better to compromise on the video quality a little than it is the audio quality.
However, this is where the error message is misleading. Instead of decreasing your video bitrate, try re-encoding your audio. Yes, that’s right… re-encode your audio and convert it to AC3 (Dolby Digital) format. This is a much more efficient compression than you might realise, with the resulting files taking up a tenth of the space of the original, yet with almost no loss in audio quality. The bitrate for a stero based file can be as low as 192KBPS (yes, that’s kilobits), and you’ll still get a really good audio experience from that.
The best part is that the difference between AIFF and AC3 is that the bitrate of AIFF is around 1.5MBPS and AC3 can be vastly lower. In one step you’ll reduce the overall bitrate for the disc and give yourself more room for the video. You’ll also find your recorded discs are generally more compatible with a wider range of set top players, too.
There is no single bitrate setting that fits every situation, and each time you create digital footage to include on a DVD you need to look at it with a view to encoding it in the best way. The visual aspect of a disc is often the one that takes precedence for most people, yet it is the audio that will make or break your disc as an experience for the viewer.
When you make an AC3 file in Apple’s ‘Compressor’ you will find there is one setting that you have to change from default, and that is the dialog normalization value. It defaults to -27 but really ought to be set at -31. There are several really good reasons for this, not least of which is that you will almost certainly have spent time balancing the audio levels in your editor before encoding the video. If you don’t want any of that level setting to change for your audio, use -31.
So, the next time you see the dreaded ‘video bitrate too high’ error message, don’t change the video setting until you have looked at the audio more closely!
Quiz creation, subtitles and languages
It’s been a long time since the last update here, but there has beena lot going on in the background. One of the main pieces of interest is a DVD which has a language selection mechanism on first pay, and combines three audio tracks with three subtitle tracks and an alternative video track as well! Just thinking through the combinations of playback - a set up and resume system, shoing the right subtitles even if the user changes half way through and then switches to the alternate video track too…
Secondly, creating a four player quiz has been taking a lot of time, too. This has been a real challenge, making sure that the right player (or team of players) gets their turn, that scores are kept and that the questions are random. It has been incredibly interesting, to say the least.
As soon as practical, I’ll develop some sample projects and tutorials for these two scenarios and post them here for people to read.
