Posted: Sat 17 May 2003, 5:56 Post subject: Learning from the masters
Does anyone knows what parameters are used in commercial (professional) DVDs? I'm talking about avg. bit rates, GOP structure, etc.
Does anyone knows of a way to scan a DVD (I have plenty of those ) and get that information? I have a Sony DVD player, and it can show the video and audio bit rate while playing. It looks like the video bit rate is usually around 5Mbit. How can they put 2 hours on a single side DVD when all the conversion routines I see on the net say that we should use around 6Mb/sec for the video, which yields about 90 minutes per DVD?
Joined: 04 Feb 2003 Posts: 587 Location: Lisboa, Portugal
Posted: Sat 17 May 2003, 6:11 Post subject:
The GOP structure of commercial DVDs is usually hand-tuned for each scene. They usually start with 1/5/2 or 1/7/1, then watch the result and change the settings for scenes that did not encode properly.
Nearly all commercial DVDs are VBR, with the maximum set to (approx.) 8 Mb/s, the minimum set to (approx.) 2 Mb/s and the average set to a value between 4 Mb/s and 6 Mb/s. Film transfers to MPEG better than video so, for film, an average of 5 Mb/s usually produces good quality. For video, you should generally use an average of 6.5 Mb/s or more.
Regarding the size, commercial DVDs are dual-layer (8.5 GB, instead of 4.3), so they have enough room for the full movie plus the extras.
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