ScottW,

I'm not talking about PCM...Im talking about ac3 stereo and 5.1...The thing is, it was my understanding that DVDA only accepted one format per dvd (ie stereo ac3, 5.1 ac3 or pcm for all videos...) Well either my player is taking some form of digital drug or it DVDA encodes various types of audio formats on the same disk!!! anyone else see this?? or am I hallucinating!!!!!!!!!!!!!!!!!!!!!!!

Ok. try this...slap a stereo ac3 and a 5.1 ac3 into DVDA 2 an see whether the player sees both differently..(mine does)..so Am I seeing things ???

You aren't seeing things. DVDA will accept mixed audio formats.

If you've got a movie in Stereo AC3, then you can have another movie in 5.1 AC3 and a third one using PCM, all on the same DVD. You could even have a 4th one with DTS if DVDA supported that format (and you wanted to spend a couple of thousand on the encoder).

The audio format is associated with the program material, not the DVD.

--Scott

I think you can mix them if you create a menu based DVD. However, if you put Sereo and 5.1 into a Music Compilation, DVDA won't allow this, because in a Music Compilation it combines all the assets into one VOB file sequence. I learned this by actually trying to do this with DVDA 2.0. This is not a huge deal, and I understand technically why it must be so.

Not to be confrontational, but it technically isn't because all the audio is in one VOB that is the limitation, but the audio (for a music compilation) would all be put in one title set. The dvd spec doesn't allow for mixing of audio types within a specific stream within a specific title set. IE, in a title set you can have a video asset with ac3 stereo in stream position one, and PCM wave in stream position two, and ac3 5.1 in position three, etc.; all the rest of the assets within that titleset will have to have audio that matches each audio type in the specific streams to be compliant. You couldn't have a PCM file in audio stream position one because it wouldn't match the ac3 stereo already there. In addition, you not only have to have the same audio type, but the bitrates much match.

The reason you can 'mix' the audio types is because DVD-A treats another video asset/slidehow/etc as a completely different title set. You can change the audio type in any of the stream positions without regard as to what order and type of audio was in another asset.

DVD-A treats all the music files in a particular compilation as one title set, therefore, all the audio types have to match or be converted. If you create another music compilation, you could change the audio to be different than your first compilation because they are in different title sets. However, whatever audio you choose for your first file will dictate what all the rest will need to be within that compilation.

Jim

JSWTS,

Thanks for the explanation. That is more than I knew about the subject.

Interesting that the spec is so particular about the audio, but apparently not as particular about the video. I have now authored many "music compilation" DVDs where I use MPEG2 video that was encoded at different times, each with a different bitrate. The AC3 audio is always at the same bitrate and is always stereo. These combine together perfectly into a seemless DVD where I can use fast forward and reverse right through chapter points (something that you cannot do if you use the menu compilation, because that form treats each MPEG file as a separate titleset). In fact, I am not certain that I will ever use the menu compilation again when I am assembling pre-existing MPEG files, or re-authoring from VOB files (something I do almost all the time now because much of my work involves cutting and pasting from work that I have already done, and it is really fast to just grab the video from the disc rather than re-capture from tape and then re-encode).

Mixed audio has been possible since DVDA 1.

Rob

The video requirements are not as stringent in terms of bitrate, because you can mix VBR with CBR, and varying bitrates. You can't mix different frame sizes (like half D1 and full D1) or aspect ratios (4:3 and 16:9) in the same title set, but as with audio, you can have differences between title sets. Within a particular titleset the video bitrates can vary (even within the same file using VBR you would expect to have bitrate fluctuations). The only for sure no-no is that you can't mix PAL and NTSC on the same disc, regardless of title set.

Jim

The only for sure no-no is that you can't mix PAL and NTSC on the same disc, regardless of title set.

There is apparently a hack where you edit the video's header so that the authoring program (and the DVD player itself??) thinks the video is PAL instead of NTSC or vice versa. Haven't tried it, not sure I plan to. From what I hear, DVDA is not fooled by this hack, and it will re-encode the hacked video to match the project settings.

Rob