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Topic: Open Source DVD-Audio project (Read 54351 times) previous topic - next topic
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Open Source DVD-Audio project

Not sure where the best place to post this is, but I want to announce the fact that I've started a project to develop a set of open source DVD-Audio tools.

I'm not interested in playing commercial DVD-Audio disks so I am ignoring MLP and the various copy prevention and watermarking schemes.

But what I am aiming to do is to try and publically document the format of the various files inside the AUDIO_TS directory and develop open source authoring and playback tools for uncompressed, unencrypted DVD-Audio disks.

The project home page is at http://dvd-audio.sourceforge.net and there is a mailing list there which anyone is welcome to join.

That site currently contains an in-progress "unofficial DVD-Audio specification" - which I would welcome contributions to.

Regards,

Dave.

Open Source DVD-Audio project

Reply #1
very nice

Open Source DVD-Audio project

Reply #2
Surprised this hasn't garnered any more commentary! If you can truly deliver, it will be a welcome bit of software.

  A few things to keep in mind:

  Some of the commercially available software does not enable "gapless" DVD-A authoring/playback. But without this feature, DVD-A would be little more functional than a high-bitrate MP3 player! Gapless is essential to a proper listening experience.

  The DVD-A specs allow for monophonic/single-channel audio, with the ability to select how that channel should be mapped in the authoring process (i.e., a single-channel *.wav could be used to author a DVD-A disc, with that channel being mapped to both the L and R). For collectors of early monophonic album mixes, this would be a God-send; a single-layer disc's capacity would easily exceed fourteen hours.

    - M.

Open Source DVD-Audio project

Reply #3
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Surprised this hasn't garnered any more commentary! If you can truly deliver, it will be a welcome bit of software.


Yes, I'm surprised at the lack of reaction as well.  Maybe in this age of portable hard-disk based digital audio players and PC-based hi-fi, there isn't any interest in another disk-based format.  Or maybe there just aren't very many DVD-Audio capable players in homes yet.

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  Some of the commercially available software does not enable "gapless" DVD-A authoring/playback. But without this feature, DVD-A would be little more functional than a high-bitrate MP3 player! Gapless is essential to a proper listening experience.


I completely agree - gapless is top of my priority list (I am mainly interested in DVD-Audio as a medium for storing live concert recordigns), so I'm fully aware of the issue.  My authoring software will default to gapless, and gaps will either have to be added to the source WAV files, or specified as a parameter.

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  The DVD-A specs allow for monophonic/single-channel audio, with the ability to select how that channel should be mapped in the authoring process (i.e., a single-channel *.wav could be used to author a DVD-A disc, with that channel being mapped to both the L and R). For collectors of early monophonic album mixes, this would be a God-send; a single-layer disc's capacity would easily exceed fourteen hours.


I'm not sure what you mean by "how that channel should be mapped".  Does that mean that there are alternatives to simply sending it equally to the left and right speakers?  If you have an example of a mono DVD-Audio, I would be happy to see it.

This is where I need help - identifying and documenting the various features of DVD-Audio.  Even if it's just high-level functional documentation - at least we then know what information to look for in the various files in the AUDIO_TS directory.

Regards,

Dave.

Open Source DVD-Audio project

Reply #4
Wow, that'd be great! Am I right expecting that with that software I could for example make a DVD-Audio disc containing several hours of Redbook quality PCM? How about the playback? If you ignore the MLP (can you do that and get a real DVD-A specs disc?), would the discs still be only playable on DVD-A players or also on DVD-V players? I assume the former.

Open Source DVD-Audio project

Reply #5
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Surprised this hasn't garnered any more commentary! If you can truly deliver, it will be a welcome bit of software.


Yes, I'm surprised at the lack of reaction as well.  Maybe in this age of portable hard-disk based digital audio players and PC-based hi-fi, there isn't any interest in another disk-based format.  Or maybe there just aren't very many DVD-Audio capable players in homes yet.
[a href="index.php?act=findpost&pid=279407"][{POST_SNAPBACK}][/a]

I have never seen a dvd-audio player and I believe that there aren't many people who really own one. That is likely to be the cause.

Open Source DVD-Audio project

Reply #6
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If you ignore the MLP (can you do that and get a real DVD-A specs disc?), would the discs still be only playable on DVD-A players or also on DVD-V players?


According to my "DVD Demystified" MLP _can_ be used to compress data - so I guess it is optional.

Open Source DVD-Audio project

Reply #7
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Wow, that'd be great! Am I right expecting that with that software I could for example make a DVD-Audio disc containing several hours of Redbook quality PCM? How about the playback? If you ignore the MLP (can you do that and get a real DVD-A specs disc?), would the discs still be only playable on DVD-A players or also on DVD-V players? I assume the former.
[a href="index.php?act=findpost&pid=279435"][{POST_SNAPBACK}][/a]


Yes, you can have over 4GB of 16-bit/44.1KHz uncompressed PCM audio on a DVD-R.  You can freely mix any of the six supported samplerates (44.1, 88.2, 176,4, 48, 96 and 192KHz) and sample sizes (16-bit, 20-bit and 24-bit).  The only limitation is the 9.6 Mbit/s maximum bitrate.

Yes, you can ignore MLP and still produce a 100% legal DVD-A disk - MLP is completely optional.  This follows from the fact that all apart from the very high-end commercial DVD-Audio authoring packages do not support MLP and can only produce disks containing uncompressed PCM.

The DVD-Audio specification only defines the content of the AUDIO_TS directory on a DVD.  Obviously, DVD-Video players ignore the AUDIO_TS "zone", and hence won't play any content stored in that directory.

If you want to author a DVD-Audio disk that will be compatible with a DVD-Video player, you will have to duplicate the content in the VIDEO_TS directory - either as 48KHz or 96KHz PCM or compressed using AC-3 or MP2 at 48KHz.

There are two ways of doing that - "legally' and "illegally".

The standards-compliant way (i.e. how commercial DVD-A disks are authored) is to produce a "linked" VIDEO_TS folder - this means that the navigation menus in the AUDIO_TS folder contain references to content in the VIDEO_TS folder.

The alternative is to simply author a standalone VIDEO_TS directory, and burn it to the same disk as the AUDIO_TS directory.  This is "illegal" according to the specs, but I can't see why it wouldn't work (with DVD-V players ignoring the AUDIO_TS content and vice-versa).

Dave.

Open Source DVD-Audio project

Reply #8
Shouldn't the video_ts also contain dummy video besides audio?

Open Source DVD-Audio project

Reply #9
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Shouldn't the video_ts also contain dummy video besides audio?
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Of course.  To be playable in a DVD-Video player, it needs to meet the DVD-V specs.

However, I don't think you can just use any DVD-Video authoring application to produce a "linked" VIDEO_TS directory -  I think they are only permitted to use a strict subset of the DVD-Video standard.  But I haven't really started investigating that area yet, so don't take my word as the truth.  Step 1 is to produce standalone AUDIO_TS directories.  Linking with the VIDEO_TS will come later.

Dave.

Open Source DVD-Audio project

Reply #10
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I'm not sure what you mean by "how that channel should be mapped".  Does that mean that there are alternatives to simply sending it equally to the left and right speakers?  If you have an example of a mono DVD-Audio, I would be happy to see it.

This is where I need help - identifying and documenting the various features of DVD-Audio.  Even if it's just high-level functional documentation - at least we then know what information to look for in the various files in the AUDIO_TS directory.

Regards,

Dave.
[a href="index.php?act=findpost&pid=279407"][{POST_SNAPBACK}][/a]


  Hi Dave. By "channel mapping," I mean that the specs allow for any single audio channel to be specifically directed to any available channel in the speaker setup. So, for example, if some esoteric leaning prompted you to position your STEREO audio in the "Rear-Left" and "Center" channel, it would be possible... just not very practical.

  I do not own a monophonic DVD-A (at the moment), although I have already seen some that have the monophonic content mapped strictly to the "Center" channel. For a 5.1 setup that might be just fine, but the majority of home theater systems still only have two speakers - so there's no true "Center" channel for the system to map! Monophonic content should, by default, be mapped to both "Left" and "Right" (and "Center" if available).

    - M.

Open Source DVD-Audio project

Reply #11
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  Hi Dave. By "channel mapping," I mean that the specs allow for any single audio channel to be specifically directed to any available channel in the speaker setup. So, for example, if some esoteric leaning prompted you to position your STEREO audio in the "Rear-Left" and "Center" channel, it would be possible... just not very practical.

  I do not own a monophonic DVD-A (at the moment), although I have already seen some that have the monophonic content mapped strictly to the "Center" channel. For a 5.1 setup that might be just fine, but the majority of home theater systems still only have two speakers - so there's no true "Center" channel for the system to map! Monophonic content should, by default, be mapped to both "Left" and "Right" (and "Center" if available).
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I haven't found any references confirming what you are saying.  My understanding is that DVD-Audio defines 21 preset channel mappings - and you have to choose from one of those 21 when authoring the disk.

There is only one channel mapping defined for a single-channel audio stream, and that is to map it to speaker "C".  I would expect that in a Stereo environment, the downmixing performed by the DVD-Audio player would map that channel equally to L and R.

Maybe what you are referring to are features of DVD-Audio authoring programs that let you assign any input mono file to any channel - but if you are only providing a single mono file, then your only choice is to map it to C.  Two channels can only go to L and R, and only with three or more channels do you get any choices (L,R,C or L,R,lfe or L,R,S)

The channel-assignment table listing assignments 1 to 21 can be seen here:

[a href="http://www.hodie-world.com/dvdtech2.html]http://www.hodie-world.com/dvdtech2.html[/url]

Dave.

Open Source DVD-Audio project

Reply #12
Actually, if you're looking for a standard DVD-video format that just plays audio, LPCM or AC3, there is a product called 'Goland Audio DVD Creator' that costs about $25 that takes non-conforming audio input, transforms them to either conforming LPCM or AC3 (stereo only), at a bitrate of your choosing, and creates a menu structure treating each Album as a Title and each Track as a Chapter. While the track is playing, it displays a still frame detailing the Artist, Album and Title.

This is obviously not DVD-Audio, but does have the merit of being playable on any DVD player. At 384kbps AC3, this allows you to pack 25+ albums on one DVD with full navigation.

I'm not trying to put anyone off Dave's project here, simply indicating that if you want to pack a lot of audio onto a DVD, DVD-Audio is not the only way to go, especially if you want compatibility with existing DVD players at all ends of the market!!  .

Open Source DVD-Audio project

Reply #13
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Actually, if you're looking for a standard DVD-video format that just plays audio, LPCM or AC3, there is a product called 'Goland Audio DVD Creator' that costs about $25 that takes non-conforming audio input, transforms them to either conforming LPCM or AC3 (stereo only), at a bitrate of your choosing, and creates a menu structure treating each Album as a Title and each Track as a Chapter. While the track is playing, it displays a still frame detailing the Artist, Album and Title.


I agree with what you are saying - for lots of people, DVD-V may be a better choice.

A big advantage of DVD-Audio is that it supports LPCM audio at multiples of 44.1KHz - so you can "losslessly" burn 4GB+ of Red Book CD Audio to DVD.    You can also create a DVD-Audio with no video content at all - giving all the space on the disc to audio content.

But as you say, the big disadvantage is lack of compatibility with the millions of existing DVD-Video players (unless you create a "Universal" DVD-A disk that duplicates the audio content in the VIDEO_TS directory).  This situation is only getting worse because manufacturers are still not building DVD-Audio compatibility into all their players.

Dave.

Open Source DVD-Audio project

Reply #14
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...but the majority of home theater systems still only have two speakers - so there's no true "Center" channel for the system to map! Monophonic content should, by default, be mapped to both "Left" and "Right" (and "Center" if available).

    - M.
[a href="index.php?act=findpost&pid=279527"][{POST_SNAPBACK}][/a]

The setup of your "DVD-A decoder" (or DTS or Dolby Digital for that matter), which is usually in your player's setup, should let you handle these things. There should at least be a speaker setup where you can indicate which speakers are available, so necessary remapping can be taken care of. (Many set-ups have no center or no sub-woofer or no rears). Would be silly to let someone enforce mapping to a non existing speaker and get away with it.
In theory, there is no difference between theory and practice. In practice there is.

Open Source DVD-Audio project

Reply #15
Dave, really interesting project here im sure this will become really useful when/if the DVD-A players become mainstream.

Im wondering, wouldnt it be cheaper to produce a DVD-A portible player, then say an I-Pod if all it has to decode is PCM ? It wouldnt be that intensive on hardware would it? Im suprised we havent seen any on the market yet.


Open Source DVD-Audio project

Reply #17
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Dave, really interesting project here im sure this will become really useful when/if the DVD-A players become mainstream.

Im wondering, wouldnt it be cheaper to produce a DVD-A portible player, then say an I-Pod if all it has to decode is PCM ? It wouldnt be that intensive on hardware would it? Im suprised we havent seen any on the market yet.
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A portable DVD-A player shouldn't be that much harder than a portable CD player.  You "just" need to replace the CD reader with a DVD reader and then the firmware will be slightly more complicated - but no more complicated than, for example, MP3-capable CD players.

EDIT: I forgot to add that a portable player would also need an MLP decoder and be capable of decrypting the disk.

DVD Audio disks have a special "Simple Audio Manager" (stored in the AUDIO_PP.IFO file) which provides a CD-like table of contents.  This allows navigation with only a simple LCD display showing the current Group and current Track numbers.

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[a href="http://www.amazon.com/exec/obidos/tg/detail/-/B00006AGPG/102-8505978-0724934?v=glance]http://www.amazon.com/exec/obidos/tg/detai...724934?v=glance[/url]
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Interesting product, but does anyone know if there are any DVD-A only portables on the market yet?  A full display isn't necessary to listen to DVD-A disks.

Dave.

Open Source DVD-Audio project

Reply #18
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I have never seen a dvd-audio player and I believe that there aren't many people who really own one. That is likely to be the cause.
[a href="index.php?act=findpost&pid=279436"][{POST_SNAPBACK}][/a]


Almost all DVD players these days accept DVD-Audio & SACD as well..

Open Source DVD-Audio project

Reply #19
This thing starts to fascinate me. Would it be possible to easily write a pcm-only player software for pc?

Open Source DVD-Audio project

Reply #20
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I have never seen a dvd-audio player and I believe that there aren't many people who really own one. That is likely to be the cause.
[a href="index.php?act=findpost&pid=279436"][{POST_SNAPBACK}][/a]


Almost all DVD players these days accept DVD-Audio & SACD as well..
[a href="index.php?act=findpost&pid=280075"][{POST_SNAPBACK}][/a]

Yes. Many new models include this ability but everybody buys €100 players here whereas dvd-a/sacd player costs €200.

Open Source DVD-Audio project

Reply #21
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This thing starts to fascinate me. Would it be possible to easily write a pcm-only player software for pc?
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Absolutely. 

With the documentation I've already published at [a href="http://dvd-audio.sourceforge.net]http://dvd-audio.sourceforge.net[/url] it would be almost trivial to write a simple player that played the contents of the DVD using the Simple Audio Manager (SAMG) - i.e. presented you with a simple CD-Player like interface to the contents of the DVD.

A full player which made use of the "normal" Audio Manager (i.e. video menus, slideshows, links to VIDEO_TS content) would be more work, but it would not be impossible for someone to adapt an existing open source DVD player to support DVD-Audio - most of the complications are already part of the DVD-VIdeo standard.

I'm planning to write a simple player using the SAMG, but am concentrating on authoring first.  So I would be more than happy if someone else did it.

Dave.

Open Source DVD-Audio project

Reply #22
When can we expect the first release?

Open Source DVD-Audio project

Reply #23
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When can we expect the first release?
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When it's ready. :-)  I'm working on this in my spare time.

But I hope to be able to release some early "proof of concept" command-line programs relatively quickly (i.e. within days rather than weeks/months).

If you want to help with testing of early versions, you should either have Linux installed, or Mac OS X (with the "developers tools") or Cygwin/Mingw if you're a windows user.  i.e. be able to download source code from a CVS repository and compile it yourself.

All development will happen in public CVS and binary releases won't be made very frequently (at least by me - others are welcome to distribute binaries subject to the GPL).

In the longer term, there will be binary releases for Windows/Mac OS X/Linux along with cross-platform  GUI versions of the tools (using wxWindows, as used by Audacity).

Dave.

Open Source DVD-Audio project

Reply #24
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A big advantage of DVD-Audio is that it supports LPCM audio at multiples of 44.1KHz - so you can "losslessly" burn 4GB+ of Red Book CD Audio to DVD.    You can also create a DVD-Audio with no video content at all - giving all the space on the disc to audio content.
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Hi!

Yes, I completely agree with this statement, I think this is a keypoint. A DVD Audio can store natively 44,1 kHz 16 bit audio. DVD Video can store only 48 or 96 kHz audio, so in order to store normal 44,1 kHz music, there is need to resample it, which is lossy.

I think DVD Audio capable players became cheap nowadays. (I purchased a Panasonic DVD-RA82 player in 2002, which was expensive at the time...) So I prefer DVD Audio!

I'm really glad to hear you are working on this, especially that it's open source. I have downloaded tons of music bootlegs, and I simply don't have enough space on my shelf to store hundreds of CDs. I would write these albums on DVD Audio!