PDA

View Full Version : DVD video bitrates?


MheAd
2005-01-27, 11:14 AM
Hi!
Can anyone tell me the exact bitrate of a SP/120 minutes DVD-R disc?
Is it based on VBR or CBR values?

Thanks in advance!

4candles
2005-01-27, 11:26 AM
Hi!
Can anyone tell me the exact bitrate of a SP/120 minutes DVD-R disc?
Is it based on VBR or CBR values?

Thanks in advance!

MPEG-2 video is normally (possibly always) VBR. The audio (in whatever format) must be CBR.

The main useful bitrate when talking about video is the average bitrate (ABR). The DVD specification also limits discs to a maximum bitrate of about 10Mbit/s (for both video and audio) which is how fast DVD players are required to be able to read the data from the disks. So the "peak bitrate" can never exceed that limit.

I'm not 100% sure, but I think that generating a DVD with an average bitrate of about 4.5Mbit/s (including the audio stream) will give you 120 minutes of on a 4.7GB DVD.

MheAd
2005-01-27, 11:47 AM
Hi and thanks for the reply!
Well, I was also thinking that ABR should be somewhere around 4.5 Mbps, but that doesn't tell us the exact "peak" of the maximal bitrate.

sharemydog
2005-01-27, 07:18 PM
112min pal video + 448kbps ac3 no subtitle no extras 12 frames per gop:

min 1926kbps
avg 5033kbps
max 9185kbps

for 29.97fps ntsc use avg of 5022kbps

calculation is nearly perfect...incl muxing overhead ect. if filesize exceed lower the avg by maybe 10.

New Homebrew
2005-01-27, 07:26 PM
Hi and thanks for the reply!
Well, I was also thinking that ABR should be somewhere around 4.5 Mbps, but that doesn't tell us the exact "peak" of the maximal bitrate.

There is no program to tell you what max bitrate you should use based on space. That is up to you and your encoder decides where to spend the bitrate.

bitrate calculator is here: http://www.videohelp.com/calc.htm

Yes, mpeg-2 can be CBR. 120min length for a 4.7GB DVDr is only a suggestion for moderate quality. For max quality use maximal video bitrate at constant level and LPCM audio. With these settings you can fit about 1 hour on a 4.7GB disc.