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Bitrate for DVD's

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argoc
Bitrate for DVD's
on Nov 10, 2002 at 10:41:37 pm

I use a DV500 capture card and the average data rate of my video upon capture shows as 3.61 MB for all of my DV AVI clips. My question is that upon authoring the DVD and transcoding to MPEG2, will a bitrate higher than 3.61 MB result in an increase in quality, will it stay the same, etc? Simply, is there a relationship between bitrate of MPEG2 and the average data rate of DV-AVI Clips?

Thanks

Chris Argo


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John Q
Re: Bitrate for DVD's
on Nov 11, 2002 at 5:20:35 am

DV is a special MPEG2 format at a fixed datarate of 3.6 megabytes/second. DVD is variable format MPEG2 IBP limited to a maximum of 9.8 megabits/second. Thus DVD video is compressed 3 times more than DV. The compression techniques differ, so you're talking apples and oranges. You can edit DV. You really can't edit DVD format. With some software, you can do simple cuts, but you can't do anything sophisticated.

Basically, shoot in DV. Capture it. Do your editing. Then export it for DVD and do your DVD authoring.


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newguy
Re: Bitrate for DVD's
on Nov 13, 2002 at 6:06:25 pm

Hi,

===
"My question is that upon authoring the DVD and transcoding to MPEG2, will a bitrate higher than 3.61 MB result in an increase in quality, will it stay the same, etc? "
=======
If you don't set the bitrate (MPEG 2 format) higher than 3.61 MB, then you will get a 'decrease in quality' Cool
there is no way you can get "an increase in quality".


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John Q
Re: Bitrate for DVD's
on Nov 14, 2002 at 5:07:36 am

Actually the point is that 8 bits make a byte. DV is about 25 megabits/second versus DVD's maximum video+audio 9.8 megabits/second. Two hours of DVD uses about 26 GB of disk space, where a DVD only has 4.38 GB of space for the same video/audio. You always lose information when transcoding from DV to DVD format.

With PCM audio, your DVD video (MPEG2 IBP) would have to be a maximum of about 4.4 megabits/second variable bitrate (VBR) for it to fit on the DVD. AC3 Dolby Digital audio is typically 1/8 the size of PCM audio, so you could budget more bits to your video.



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ProDVD_Authoring
Re: Bitrate for DVD's
on Dec 18, 2002 at 5:49:55 am

Hi Argoc:
At our facility, we encode using a software solution. We use a double pass veritable bit rate encoding scheme. Typically, in DVD authoring and our tests and experimentation bears this out, the best data rate - quality trade off is to use the 4 mb per second data rate for your delivery codec MPEG 2.
A double pass variable bit rate encode provides the highest quality possible result with the smallest file size. Your DV data rate is almost irrelevant at this point. Whatever your DV data rate is - it is. However, whatever your resulting MPEG 2 DVD compliant file data rate is matters much.
Some folks like to encode MPEG DVD at higher rates such as 6 Mb per second, but the higher data rate you use, then the greater chance there will be that the disc will stutter at chapter points and even some really cheap table top players may not play ther disc at all ! (Usually, this is not a problem with data rates from 4 Mb to 6 Mb, but look out after 7 Mb per second ! The DVD Forum specifies a maximum playback possible with an MPEG 2 compliant stream as high as 9.78 Mb, but if you have a complicated menu hierarchy with multiple animated splash screens or animated buttons, then you're best advised to keep MPEG data rate at 4 Mb.
The ultra high end hardware DVD encoder boards use a 1 Pass VBR encode to remain real time and they yield spectacular results, but you pay big time for this level of quality up to 40 K $ US !!!


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