My nephew showed me a DVD one of his university professors gave out at the end of the semester because he know of my interest in video/DVD authoring, and I was floored - here's my description, and assumption of how it worked, but with questions.
The DVD had a menu with 18 items on it. The very first and last are normal video captures, about 10-15 minutes of video of the professor speaking while being filmed (I did not watch the full 17 hours or so on the DVD, I was kind of guided through it). The remainder consisted of videos that were one hour long, but the video portion actually looped every ten minutes, while the audio continued. Unfortunately, I wasn't able to keep it or copy it (although I've requested that he copy it for me) so that I could really study the DVD itself, but we played with it on his player a little bit & I think I see at least the theory.
It appears that each "hour long" segment is actually only a 10 minute track with 6 audio streams (from watching the display and toggling the audio stream setting on his remote). So say for the first track of this sort, it would play the first "chapter" (although it didn't seem to change chapters, it continued to show the same chapter/track), not hiccup or pause, then switch to the next audio stream and play the same video stream again. He did show me one segment that the audio only went to about 53 minutes, and there is 7 minutes of video with no audio at the end of the section.
I spent a number of hours today searching here and all of the other places I know and saw a lot of posts on topics I already knew fairly well, putting 50 hours of audio by using a single black frame or image, etc, but nothing that compares to this. What I couldn't find was any information regarding essentially looping video. Although I don't have a pressing need for someone requesting this, I have several things I'd like to use this for myself, then possibly offer to others.
Any ideas? I don't necessarily have to use the exact same technique, but would love to be able to utilize some idea of this, with possibly a somewhat longer video that loops in the same manner. I don't think it could have possibly been done by use of super-low bit rates, because the video (computer animations and diagrams) looked *way* to clean to be low bit rate.
Thanks in advance for any suggestions!
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Theoretically it is possible to do this. Essentially you would be doing as you described - a short video track with multiple, low bitrate, audio tracks. With simply talking only tracks you could easily get away with 128 kbps. You would then author each title to play repeatedly in sequence, but with a different audio track each time, until all the audio tracks had been played. Not doable in most authoring tools, but certainly doable within the DVD spec.
So you are looking at
15 minutes video intro
15 minutes video outro
17 10 minute segments
Total video is around 3.5 hours. This is pushing it for full-D1, but quite acceptable for half-D1. If it is mostly talking heads and static images then even full-D1 might look OK. On an in-car system you wouldn't know anyway.
I could probably author something like this using a combination of DVD Lab Pro and PGCEdit. Create a series of title playlists that repeat the same title 6 times. One playlist for each set of audio. Compile the disc, then use PGCedit to change the audio track that was played on each call so that the audio played through almost seamlessly. Because the player sees the playlist as a title in it's own right, the player display would show the loop as a continuous title, even though behind the scenes it is not.
Any authoring tool that supports title playlists should be a good starting point.Read my blog here.
Originally Posted by doctor
Set audio to a register value.
In Post command advance register by one and go to top. Than on next loop it will play same video with new audio track.
I appreciate your help, both of you... I will research this some this coming weekend or so when I have time. I didn't even ask if the disk was dual layer or not... that might account for some additional quality.
Regardless, I myself have a number of spoken-word audio discs that I frequently listen to either as-is, or I've made several DVDs with HOURS of audio, simply using 352X240 video (which gets pretty bad as the bitrate keeps dropping) or taking advantage of the mpeg-stills, but I really liked this idea. The videos were basically examples of what the entire lecture was about, and although I think it would get pretty boring to stare and focus and give it your full attention, it certainly seemed like a fantastic plan for this material and reinforced the memory, and I would like to do it.
Guns1inger, I appreciate your answer - I'm going to start here; it's clear and sounds very doable to me. I've played some with IFO edit in the past, so I think this will work for me
tinker, thank you very much, but admittedly I'm not so good at this that I understand all of the terminology - this does give me a great place to research using these terms however, and will see if I can follow it.
My current plan is to split a one hour talk into a series of 5 min audio clips, make the video I want in After Effects (which is usually what I'm doing, and the DVD creation is typically a small part of any project for me) and see if I can get this to work at all before I get into the big steps of adding additional menus & video that doesn't have to be on the disc.
Again, thank you both for all of your help. I get the feeling that I have enough to go on here; I didn't have a clue how to get it to loop the video, but I'll look into any authoring apps that supports "title playlists".
Just FYI in case you are subscribed to this - I had pretty good success with this in my tests, and learned a lot in the process. Using the "SetSTN" command to change the audio stream choice just prior to the start of the new playlist, this worked pretty good. A very slight pause, so that you could hear it if it was mid-word, but generally not during a normal speaking pause. Although I didn't review the original in depth, it may have some of those (it's not enough to prevent listening, although it is noticeable), or they may well have segmented their original audio to the closest point prior to the end where it wouldn't be noticeable. What else did I learn? That using this same command, it would be possible to add multiple subtitle tracks and have them shown throughout as well, changing with each cycle. Although I don't think I would do this often (It took quite a while to just get 1 hour ready between seqmenting the audio, converting to AC3 and changing the commands) it is nice to know it's available! I am going to go ahead and create a longer project, and I think I can get about 20 hours of audio that I'd like. Some of the disadvantages? The audio gaps, and trying to fastforward or seek a specific place. Although my DVD player remembers where you were when you left it, it defaults back to the original audio layer if you turn it off. Anyway, advantages outweigh disadvantages for my purposes.