DVD Video Length?

mabas9395 wrote on 1/12/2007, 11:42 AM
Now I am aware that there are many things that will impact the file size of your project and I think a DVD disk limit is based on file size, not actual time. And I've seen bit rate calculators but I'm not looking for something that technical/specific at this time.

What I am looking for is a good "rule of thumb" for how long a typical project can be and still have good quality when played on a standard TV/DVD player (not hi-def). By typical project, I am working on a family style home move with stills, video clips, mp3 music background, basic transitions, no serious sfx, etc.

I am trying to plan out my project (allocate max time to each "chapter") but don't know if I can get an hour, 1.5 or two on the disk. I'm sure I can compress it to get many hours of footage, but realistically, what can I fit before I start to sacrifice noticeable quality?

I'm pretty new at this so I might not realize how dumb of a question this is, so just point me in the right direction if I'm way off base here.

Thanks.

Comments

ScottW wrote on 1/12/2007, 11:48 AM
The problem is you cannot get a complete answer to that question without getting a little technical. In addition, quality is a very "perception" thing - something that bothers you, may not bother someone else.

However, I would say a good rule of thumb would be:

1 hour, 15 minutes if using PCM audio
1 hour, 30 minutes if using AC3

And if you don't know what the difference is between PCM and AC3 then stick with 1:15.

--Scott
Chienworks wrote on 1/12/2007, 2:50 PM
It also depends very much on the material. I recorded a play that was over 3 hours that consisted almost entirely of people standing still on the stage talking. It fit on one 4.3GB DVD and no one noticed any quality degredation at all. On the other hand, if you were videotaping a basket ball game then you'd probably have a hard time fitting more than an hour without seeing lots of motion artifacts.
Siby wrote on 1/14/2007, 11:03 AM
For learning purpose what is the difference between PCM and AC3?.
Chienworks wrote on 1/14/2007, 11:46 AM
PCM is raw uncompressed audio, almost the same format that is used on Audio CDs. PCM audio uses nearly 11MB/minute.

AC3 is Dolby's compression scheme for reducing the amount of space audio requires. Depending on the bitrate specified it can take different amounts of space. Lower bitrates use less space but are lower quality. Higher bitrates sound better but take more space. The default value that SONY's AC3 encoder uses is 192Kbps which sounds quite good and uses about 1.4MB/minute, or less than 1/7 the size of PCM audio.
RMD wrote on 1/15/2007, 9:38 PM
On the Sony Website there is a Pro MPEG2 module for sale. Has anyone found this to improve the compression, say by allowing VBR compression. I agree that it would be nice to be able to get 2h on a DVD, but I have not been able to do that, only about 1:15 to 1:30. You can go down on bit rate to 6, but beyond that I personally find pixilation irritating.
Andy C wrote on 1/30/2007, 8:55 AM
Interesting topic.

Can anyone tell me if there's any advantage in AC3 encoding before submitting to DVDA? - I thought DVDA did a good job of compressing any PCM audio whilst compiling. Am I missing something?

BTW, I'm using VMS 6 Platinum, so I don't currently have the option of AC3. If I was to upgrade to VMS 7 Platinum would I actually gain anything with the AC3 compression compared to DVDA's native compression that I have now?

TIA,
Andy.
ScottW wrote on 1/30/2007, 9:03 AM
Keep in mind there's a difference between DVDA and DVDAS. DVDAS (studio that is) which ships with VMS did not include AC3 encoding capability until the 7.0 release.

So if you have DVDAS with VMS Platinum 6.0, you do not have AC3 encoding available to you.

--Scott
Andy C wrote on 1/30/2007, 9:12 AM
Scott, thanks for the reply.
I know VMS 6 hasn't got AC3. What I was asking is: if I upgrade, will I get any DVD space benefits by using AC3 compared to DVDA/S native compression?
ScottW wrote on 1/30/2007, 9:36 AM
DVDAS in 6.0 and earlier doesn't have any native compression; it only supports PCM which is uncompressed audio.

So yes, if you did upgrade to 7.0, you would have access to AC3 which is a compressed format and as such your audio would take up less room on the DVD. How much you gain depends on how much you decide to compress your audio.

--Scott
Andy C wrote on 1/30/2007, 11:02 AM
Scott, thanks. That's answered my AC3 question. However, when I prepare a DVD in DVDAS the summary screen always tells me:

'The audio on track 1 of 'XYZ MPEG Clip' will be compressed'

The same is listed for each MPEG clip that I've added to the project, clearly implying that the audio will be compressed. Please explain... Confused...

Thanks,
Andy.
ScottW wrote on 1/30/2007, 11:11 AM
You're probably using the wrong template when rendering out of VMS. You should be using a DVDA template for the video and then the WAV/PCM template for the audio to a seperate file. You then feed the 2 files into DVDAS which will multiplex them together as needed. If you are using the default template, then the audio and video are getting rendered together into a single file - DVDAS will then extract the audio from the video and then re-multiplex.
Andy C wrote on 1/30/2007, 1:49 PM
Scott,

OK, I understand you on the template process, however I think I tried that once before and it turned out to be a pain to have to render twice: once for video, once for audio. If it has to be, then I guess it has to be...

Unfortunately, the problem will always be the case for me, because I write a lot of MPEG files in DVDAS that are created and multiplexed on a TiVo-like system.

Thanks for your help anyway. It's helped to understand it a bit better.
A.