Audio DVD Idea..

[sdsumike619]

Hi, I sell guitar audio lessons by mail on a website. There's 36 lessons in a series (3 years worth, 1 per month)
They're all on audio cassette and we use a high speed duplicator to run the copies, then have to print the sheet music, package it up and mail it. (time consuming)

Then I had the idea to drop all that audio into the computer, and sell the lessons on an "audio dvd"

Would it be possible to put all the audio files onto an authored DVD? And have a separate folder on the disc containing PDFs of each lesson the student could print out? I know I can put the folder on the disc. But my question is about the audio files. Can I author a DVD that just plays audio without video, or could there be just a picture on the screen while the lessons play that doesn't have to be encoded as video to conserve space?

Each lesson is approximately 30 minutes so my next question would be, can I fit 36 30 minute lessons of just audio and menu onto a DVD? What is the compression of AC-3? I think cd quality MP3 is 1 megabyte per minute, correct me if I'm wrong?

[daamon]

Would it be possible to put all the audio files onto an authored DVD?

Yes.

Can I author a DVD that just plays audio without video, or could there be just a picture on the screen while the lessons play that doesn't have to be encoded as video to conserve space?

You have two options:

1) Encode a static image and your audio together to get an MPG (containing MP2 audio) of that static image and lasting for as long as the audio runs. A variation on this is to still encode both the image and audio, but get seperate output files: video.m2v and audio.mp2

As you're in the US, MP2 audio isn't in the NTSC DVD spec and so probably isn't the best option.

2) Somehow, encode just the image to either video.mpg or video.m2v - both are valid, and neither have audio. I say "somehow" because I don't know of any tools that can take a still image and encode to a pre-defined period of time. The period of time is usually determined by the running time of the audio.

Based on this, I'd say encode to what are called "elementary streams" - video.m2v and audio.mp2 and then ditch the MP2 audio file.

You can then encode to AC3 audio from the same audio source (to make sure the running time is the same) using ffmpeggui. A bitrate of 224kbps will be fine for AC3 audio.

Each lesson is approximately 30 minutes so my next question would be, can I fit 36 30 minute lessons of just audio and menu onto a DVD? What is the compression of AC-3?

Here's the potentially good news: 36 x 30 minutes = 1080 minutes. Plugging this in to the VideoHelp Bitrate Calculator with an audio bitrate of 224 (from above) gives you a video bitrate of 335 to fit both a still image and AC3 audio onto a single layer DVD disc.

A video bitrate of 335kbps for a still image encoded at VCD resolution - 352 x 288 - may be enough. I'm guessing you don't mind too much about the quality of the encoded image - as long as it's readable. You'll need to experiment with an image and that bitrate at VCD - the lowest possible resolution, and so the one requiring the least bitrate. Having an audio file of something like 30 seconds will be OK for experiment purposes.

I think cd quality MP3 is 1 megabyte per minute, correct me if I'm wrong?

As MP3 and AC3 are different codecs, there's no meaningful comparison.

I hope that's of some use. Good luck!

[SingSing]

You can try using a DVD slide show program. It maybe able to take up to 6 to 8 30 minutes lesson per single layer DVD. All 36 lessons may fit into two Double layer DVDs.

[manono]

Hi-

I say "somehow" because I don't know of any tools that can take a still image and encode to a pre-defined period of time.

Of course it's easy (load the image and loop it for as many frames as wanted is one way), but you don't have to do that. You can take a 1-frame still image encoded to DVD specs, and when authored with the audio, it'll last the length of the audio. Heck, go to town and put a new pic to go along with each lesson. 36 pics. A very slow moving slide show. The pics and audio (DD 2.0@192 or 224) will all easily fit on a single layer DVDR (less than a GB).

[sdsumike619]

I'm definitely missing something here. I use Vegas 6 for my video editing. I was under the impression that if I take a still image and drop it onto the timeline, that it becomes video, since it has to be encoded to m2v (which I already use) Would I be able to pan and zoom on that image too so they could see up close? The image in this case would be a page of sheet music.

[MOVIEGEEK]

You can try using a DVD slide show program. It maybe able to take up to 6 to 8 30 minutes lesson per single layer DVD. All 36 lessons may fit into two Double layer DVDs.

I agree,the image quality is usually better than video.The only problem is you are limited to 99 chapters(photos) and 99 titles, Sonic MyDVD 6+ allows 999 photos per title by tweaking the DVD specs and it outputs to AC3.

[sdsumike619]

basically what I'm trying to determine is this:
It's not enough to be able to just put a still image on the screen because it is a full page of sheet music. Fitting that into a 4:3 frame is possible but they wouldn't be able to read the music. I would have to be able to pan and zoom in on the material which would be quite time consuming as far as editing all 36 lessons. I'm using Ulead DVD Workshop 2 for all my DVD authoring so maybe I can just use a slide show (never made one before) and have the slide just be an image that says "Lesson 1" and then maybe the filename of the PDF they can print out to get the sheet music. Would that work?

[manono]

I would have to be able to pan and zoom in on the material which would be quite time consuming as far as editing all 36 lessons.

Then you're talking about creating a regular moving picture DVD, and there goes the ability to stick all 36 lessons on a single DVD, not to mention the fact that the degree of difficulty and the amount of time involved increased exponentially. Originally you were talking about audio alone, without video, or with only a single pic. That, I say, is easy.

I was under the impression that if I take a still image and drop it onto the timeline, that it becomes video, since it has to be encoded to m2v (which I already use)

I don't know anything about Vegas, but you don't want to create 30 minute still videos for each lesson, especially since it's not even necessary, and takes up way too much space. I'm talking about creating a 1 or 2 frame M2V. Easiest thing in the world using AviSynth or DVDAuthorGUI. If you decide to go that route, just ask how.

[daamon]

Hi-

I say "somehow" because I don't know of any tools that can take a still image and encode to a pre-defined period of time.

You can take a 1-frame still image encoded to DVD specs, and when authored with the audio, it'll last the length of the audio. Heck, go to town and put a new pic to go along with each lesson. 36 pics. A very slow moving slide show.

Neat trick!!! I hadn't thought of doing it that way. I rarely work with stills - I'm 99% DV AVI as a source. Thanks.

It's not enough to be able to just put a still image on the screen because it is a full page of sheet music. Fitting that into a 4:3 frame is possible but they wouldn't be able to read the music. I would have to be able to pan and zoom in on the material which would be quite time consuming as far as editing all 36 lessons.

This is the kind of info that's useful to state up front, rather than "or could there be just a picture on the screen while the lessons play?"

Panning and zooming are certainly possible, but will require much higher bitrates which, in turn, will reduce the amount of audio you can fit on.

Your idea of having a simple image reading "Lesson 1" (that will require hugely less bitrate) and detailing to the relevant PDF file will work, but if you're planning to have the PDF files on the same DVD disc, they'll be taking up space and so reducing what's available for the audio and video.

How big are all the 36 PDFs in total? You may want to consider sending your material out on two DVD5's.

Disc 1: Lessons 1 - 18 and associated sheet music.
Disc 2: Lessons 19 - 36 and associated sheet music.

You could still put the two discs in one case.

In short, you have a finite amount of space to play with per DVD disc. Your contents are video, audio and PDF files. The size of the PDFs is fixed.

You can adjust the size of the video and audio by adjusting the bitrate. I'd say stick with no lower than 192kbps for AC3 audio and work on the video bitrate accordingly. Use the bitrate calculator I mentioned above to determine the end filesizes to help you.

[sdsumike619]

PDFs would be quite small I'm sure, not sure how small just yet... Let me ask if this is possible then:
Could I make the DVD so that the user simply selects say "lesson 1" from the main menu, and then he is taken to a submenu that IS an actual DVD menu with the words "Lesson 1" and utilize the background audio feature of the menu to play the lesson audio? I know typically background audio for menu for menus aren't more than 30 seconds to a minute or so, but is there an actual time limit to background audio? That way, everything is done from within the DVD menus. Would that work? Seems like it would be the simplest route for both the user experience as well as the amount of work I'd have to do to create it.

[daamon]

You need to think about navigation issues: what will happen after the sub-menu audio has finished? My guess is that it will either just stay where it is, waiting for a selection (as it's a sub-menu), or it'll loop. Neither are desirable. Unless of course you can set it up to go back to the menu - based on either you knowing how to do this and / or the authoring software allowing it.

A better option would be to link from the menu to an actual clip consisting of a static image with the desired audio. Default navigation here will be to go back to the menu once finished.

[sdsumike619]

Well I was assuming common sense would dictate that after the 30 minute lesson is over, they could push a "return to main menu" button... Then again, I thought about it more and realized that if it's menu audio, they probably can't fastforward and rewind...

"A better option would be to link from the menu to an actual clip consisting of a static image with the desired audio."

This is what I'm still unclear on, when you say "actual clip" do you mean a movie, i.e., an .m2v file encoded from my NLE? If so, is there a standard bitrate to use on still images only?

[daamon]

Well I was assuming common sense would dictate that after the 30 minute lesson is over, they could push a "return to main menu" button... Then again, I thought about it more and realized that if it's menu audio, they probably can't fastforward and rewind...

Exactly - navigation issues. It's best to spend a little more time delivering a better solution.

"A better option would be to link from the menu to an actual clip consisting of a static image with the desired audio."

This is what I'm still unclear on, when you say "actual clip" do you mean a movie, i.e., an .m2v file encoded from my NLE? If so, is there a standard bitrate to use on still images only?

In essence, "yes" - but I don't know Vegas 6 and whether this would be the most efficient way of doing it. If you did go this route, use the info I gave earlier - VCD resolution (352 x 240/288 for NTSC / PAL) and a bitrate that'll fit it onto your disc, something like 335 wasn't it?

I would come at this from a different angle: I wouldn't use my NLE - I would go straight for a dedicated MPEG encoder. The video source would be the still image encoded, as manono suggested, to valid DVD specs. Combine this with your AC3 audio during authoring. I've never tried this approach, but it sounds logical and manono says it works - I guess it may depend on your authoring program.

So, you need to find out how to encode a still image to a 1 frame MPG / M2V file that's to DVD specs. I know that an old freeware version of VCDEasy could do this - but I'm guessing that there's other tools.

[sdsumike619]

A one frame video? Wouldn't that just last for 1/30 of a second and then the screen goes black? I've used images before in encoding and you have to stretch them out on the timeline for however long you need them to be. If I stretch it to 1 minute, it will show on the screen for one minute and so on... I am a beginner really so the very idea of a one frame encoded video logically should play for one frame and then disappear.. *confused*

[daamon]

A one frame video? Wouldn't that just last for 1/30 of a second and then the screen goes black? I've used images before in encoding and you have to stretch them out on the timeline for however long you need them to be. If I stretch it to 1 minute, it will show on the screen for one minute and so on... I am a beginner really so the very idea of a one frame encoded video logically should play for one frame and then disappear.. *confused*

manono !!!! HEEEELLLLPPPP!!! You started this - you can tackle this one...

I say "somehow" because I don't know of any tools that can take a still image and encode to a pre-defined period of time.

You can take a 1-frame still image encoded to DVD specs, and when authored with the audio, it'll last the length of the audio.

My experience is pretty much all with DV AVI, so I'm not best placed to answer.

[sdsumike619]

ditto daamon! Vegas is pro software, so I'm pretty sure it can do what he's saying, but the concept just doesn't make sense since it's MPEG2 video when all is said and done

[AlanHK]

PDFs would be quite small I'm sure, not sure how small just yet

If you're scanning images, then not much to say. If you're authoring them on your computer, then for best quality and smallest size make the PDF including the fonts (including the symbol font you use for the music notes).

Also, most, but not all DVD players will play a disk with a bunch of MP3 files on it, presenting a simple menu of the filenames. Not a standard DVD video format, but a data disk. Files it can't play, like PDFs, it just ignores. Mine also plays raw jpegs, gifs and mpg files.

[mats.hogberg]

IMO, forget about PDF's and stuff for Video DVD. I'm with manono on this - Make a track, add your still image and accompanying audio to the track and you're basically done. The still should stay on screen for as long as the audio track is.
Time to get a little adventurous and try it maybe? I'd suggest DVD-Lab Pro as your authoring app for a project like this, as you can control in great detail what happens when a track starts, ends & cetera.

/Mats

[jimmalenko]

A one frame video? Wouldn't that just last for 1/30 of a second and then the screen goes black? I've used images before in encoding and you have to stretch them out on the timeline for however long you need them to be. If I stretch it to 1 minute, it will show on the screen for one minute and so on... I am a beginner really so the very idea of a one frame encoded video logically should play for one frame and then disappear.. *confused*

You would add your frame, then stretch it out on the timeline to match the audio duration.

Consider the concept of muxing a still with audio this way ....

You have one frame, played back over and over and over again @ 25fps or 29.976fps for the duration of your audio. Because of the way most video compression works, it only uses bitrate to detail when pixels in the image change from frame to frame. Now, since you have the exact same frame running for about 30 mins, the required video bitrate is just enough to represent the frame once, since the frame does not change for the duration of the audio. And of course in the grand scheme of things, the bitrate required to detail one frame is sweet FA

[manono]

Hi-

Now, since you have the exact same frame running for about 30 mins, the required video bitrate is just enough to represent the frame once, since the frame does not change for the duration of the audio.

That doesn't make a whole lot of sense. The bitrate may be enough to "represent the frame once" with decent quality, but since bitrate is also based on time, the filesize won't be the size of that frame represented just once. It gets redrawn completely every I-Frame at least, or roughly every half second. The video size will wind up much, much greater than the size of a 1-frame MPV (but maybe not enough to force him to 2 DVDs, don't know). There are a bunch of ways to do it using only a still, not making that still into a full-length video.

One is to create a BMP of DVD dimensions. For NTSC, one way might to be to create your pics at 640x480 and resize them in your picture editor to 720x480, disregarding AR, then encoding for 4:3. Take this BMP and open it in Muxman (Video->Usable Video Files). Add the Audio. Hit Start. That will give you your BMP in a VOB with the audio. Do that with all your 36 lessons and author them all together with a menu in an authoring app that accepts VOB input (TDA?). I tested this with a 2:46 AC3 file I had lying around. The audio was 3883 KB, the BMP was 1013 KB (converted to a smaller M2V of 75 KB in the process), and the final VOB size was 4684 KB. The extra space was taken by the muxing overhead. It played for the whole length with the pic showing.

If you want elementary streams, then make an MPV. I used a version of this AviSynth script:

ImageSource("C:\Path\To\Test.bmp",End=1,FPS=29.97)

That's 2 frames long at 29.97fps.

http://www.avisynth.org/ImageSource

You can make that same MPV automatically using DVDAuthorGUI. It has a facility for making M2Vs for use in menus, but you can use them for this project as well. It takes BMP or JPG input. Or you can demux the VOB you made earlier using Muxman by opening it in DGIndex and File->Save Project and Demux Video. That way you'll get the M2V and AC3 back again. Doing it this way will guarantee you all the space you need for your PDF stuff.

A one frame video? Wouldn't that just last for 1/30 of a second and then the screen goes black?

As I said before, when authored, it'll last the length of the audio. Instead of covering the same ground over again, now you know how to test it out yourself. I believe DVD slide shows are based on the same principle (he says, never having made a slide show).

[jimmalenko]

Hi-

Now, since you have the exact same frame running for about 30 mins, the required video bitrate is just enough to represent the frame once, since the frame does not change for the duration of the audio.

That doesn't make a whole lot of sense. The bitrate may be enough to "represent the frame once" with decent quality, but since bitrate is also based on time, the filesize won't be the size of that frame represented just once. It gets redrawn completely every I-Frame at least, or roughly every half second. The video size will wind up much, much greater than the size of a 1-frame MPV (but maybe not enough to force him to 2 DVDs, don't know).

I think you took what I said a little bit too literally

The point being that all other things being equal, high-motion clips require high bitrates due to the amount of information changing per frame or per second (whichever way you wish to look at it), low-motion clips requiring smaller bitrates and hence no-motion clips requiring very little bitrate at all.

[Cornucopia]

Yeah, but in a way he's right, jimmalenko:

Even no-motion clips you still want to have be DVD-compliant. That means maximum GOP lengths of 1/2 second. The I-frames will have to totally reconstruct the picture (which I agree will be small) AGAIN, and these small bits will add up.

For example, let's say you've got a still frame MPG (VCD hi-rez): 704x480.
The highest size you can put stills on VCD is 220kB. That's 1760kbits.

Played once and then "frozen" on the screen for the duration of the audio, it'll still have that same filesize, and quality.

To have that 1760kbits RE-DISPLAYED every 1/2 second (along with a very small amount of overhead for the extra P & B frames) would be ~3600kbps! Obviously, that is a waste of bitrate, unless you could somehow manipulate the "repeat 1st field" flag to repeat OVER and OVER again.

............

I recently did a test for a well-known national client for a digital display kiosk they were interested in using.

I tried a number of variation of muxing a still image with an audio clip.
A representative Still-EncodedAs-MPEGStill + Audio was 334kB.
A similar quality Still-EncodedAs-Video + Audio was 1610kB.

That's one reason why I was so excited about that VCD w/Audio tool that I recently found. (See my recent guide)

Scott