If my source file is DV, where does that leave my audio?
thanks
-D

avgeek:
VBR will always get you a better deal, since then the encoder can drop way back and use a very low bitrate when it figures the extra bits aren't needed.

Also, as mentioned, you will need to compress your audio to maximize the video space. You could use MP2, and run the (slight) risk of NTSC player incompatiblility, or use AC-3. You can use a bitrate of 192kb/sec for the AC-3, or even lower if you don't mind slightly reduced high frequency response, which for a talking head shouldn't matter.

One other option to consider: why not build a VCD, using MPEG1? Then you're talking a bitrate of about 1.5mb/sec, and the quality is roughly comparable to VHS. I believe it's legal to build a VCD format on a DVD medium, and you'll get many hours of playback.

riredale.

I'd thought of going MPEG1, but we copy from these to VHS at the EP mode and I was afraid the quality would suffer too much. I would love to get 5-6 hours on a disc and we actually did the math, but I was too afraid of the quality loss.

If my source material is DV, what format is my audio in? I assume it's already compressed, but do I need to compress further to get the savings in bitrate?

-D

If you right click on your DV file & select properties you should be able to see on the summary page what format your audio is. I'll wager it is PCM @ approaching 1600Kbs. The format you can compress your audio to will depend largely on what authoring software you have as it is this that will need to accept & author the audio.

For 2.5 hours you can use the following to work out what rate you can use

600/(minutes of video) = average bitrate for video & audio combined.

600/150 = 4.0Mbs

If your authoring program will only accept PCM audio as already said you can only use about 2.4Mbs for video

If you can use Dolby @ 192kbs (Or MPEG-1 layer II audio) then you could do video at 3.8Mbs

When you are looking at encoding at these sort of levels you should use VBR to try & retain quality as it will be more efficient with bitrate managemnet. The figures I have given should be the average (you can still have the max at say 7.5Mbs & minimum at 2.0Mbs)

Vonhosen, thanks for the encoding tips. Just rendered a 1hr 18min video to MPG2 and got it in at 1.5 gigs. I figure a 2.5 hor should come in at around 3 gigs or so, which should be small enough for a DVD.

Playback on computer looks good, and I'm burning it to DVD to try it for real on my TV. My audio was PCM as you correctly guessed, so I'm not sure what avenues are open to me to compressing it within VV3. I use DVDit to burn and it takes straight MPG2 files and does all the authoring internally.

Thanks again!
-D

If you are using DVDit the thing that matters with audio is if you are using SE version or PE version.

Whichever version you are using the best thing to to with VV3 is to do seperate renders from the timeline.
1) creating a 16bit 48Khz .wav file
2) creating a DVD compliant MPEG video file .m2v

Load these seperately into DVDit themes and you can link them together in your project by loading your video file into the video placeholders to the right of preview. Then link that to button on menu. When you've done that drag & drop your audio file to the same button on the menu so that they are now linked. (You can check this by right clicking on menu & selecting show links).

It's best to do it this way because your build in DVDit will take much less time as it will not have to demultiplex your MPEG stream & then re-encode the audio from MPEG to PCM. (Your audio quality will be better preserved as well by not having gone from uncompressed to compressed to uncompressed).

If you have SE version PCM audio is all it will let you use.

If you have PE version you can then choose to have your .wav audio converted to AC-3 dolby digital stereo (giving you a big space saving & allowing the larger video bitrate I said in earlier post)

My DVDit came bundled with my DVD writer and it's the LE version. Not sure how far back that puts me. I'll give the separate audio and video streams a try. I'm wondering if this will make any difference in the encoding speed going from timeline (or AVI) to MPeg. I don't do menus since all we do is copy DVD to VHS for student use. I've been putting the video file in the first play section to all I have to do is drop in the disc and hit record on the machines. Can I link the two files together in this function as well with the LE version.

I've also just noticed that VV3 breaks the streams down into M2V and MPA files. Will the MPA act the same as a wav, or am I back to square 1.


thanks a million vonhosen. You rock!
-D

LE version means PCM audio only supported

(It doesn't do audio menus,chapter points,16:9,DLT support either)

For what you are doing those things don't matter much anyway .When you have dropped your video file onto first play just drop the .wav file on it after & they will be linked. To check right clieck on the movie placeholder, select properties & you should see your video & audio files listed.

I'm not sure how much time you will be saved if any in VV3 , but you will notice the difference in DVDit.

The .mpa audio is no good to you (it's compressed MPEG-1 layer II audio) When you select your DVD seperate streams template, click on custom, go to the audio tab, & make sure there is no tick in the "include audio stream" box. It won't waste time rendering the .mpa audio then.

I guess I can just render out the audio track separately as a standard wav file? I did a test render and DVDit took the mpa audio file with no problem, but I did notice a very slight synch problem when testing it with DVDit.

Thanks again!
-D

I didn’t read through all the responses so here is my two cents if you need more help:


For a two-hour DVD video here is the settings I use with the Main Concept MPEG-2 Plug-in:

Variable Bit rate

Maximum: 6,000,000 bps

Average: 3,750,000 bps (this is the one to lessen if you need more space)

Minimum: 2,000,000 bps

The longer the video the more you need to use VBR vs. CBR. VBR tends to be more suitable for longer recording times while it may give you some undesired characteristics in a fast motion video. Since your video is of a relatively stationary head that is talking. VBR would be your best choice in my opinion.

Good luck.

DVDit would accept the .mpa audio but it would cnvert it to PCM which is what you are trying to avoid. Sync issue could arise if you don't ensure correct sample rate. Make sure your file is 48kHz.