When to switch to Half-D1

[rbautch]

When encoding a video long enough to require a relatively low avg bitrate (1500-3500kbps), at what bitrate would I want to switch from from Full-D1 to Half-D1? I know it would depend on the source, so how about two answers for: 1) low motion family video and 2) action-packed movie.

[jimmalenko]

http://members.dodo.net.au/~jimmalenko/AVI2DVD.htm

Sometimes the bitrate determines what frame size we should use, other times the source. It is best to choose the nearest resolution to your source, always rounding down where possible. Choose between 352 * 240/288, 352 * 480/576, or 720 * 480/576 (there may be times when you have a resolution smaller than 352 * 240 - that is OK, you'll just have to use 352 * 240).

Given a perfect (DVD quality 720 * 480/576) source, I use the following:

(where ave is the value you've calculated using a bitrate calculator)

If ave is < 1000kbps, I'd use 352 * 240/288 2-Pass VBR (min 100 ave ave max 2000)
If ave is > 1000kbps & < 2000, I'd use 352 * 240/288 ave CBR
If ave is > 2000kbps & < 5000, I'd use 352 * 480/576 2-Pass VBR (min 1000 ave ave max 6000)
If ave is > 5000kbps & < 7500, I'd use 720 * 480/576 2-Pass VBR (min 1000 ave ave max 9000)
If ave is > 7500kbps, I'd use 720 * 480/576 ave CBR

If a resolution is "forced" because of the source, keep this in mind when perusing the above chart (ie. if your nearest resolution is 352 * 240/288, there is no point using a bitrate > 2000kbps).

[ronnylov]

With progressive letterboxed movies I use full D1 down to 3000 kbit/s average bitrate with VBR, which equals around 3 hours on a single layer DVD. That is my absolute minimum bitrate with full D1 resolution.

But for full screen interlaced home videos shot with a handheld camcorder I switch to half D1 when the average VBR bitrate goes below 5000 kbit/s.

But normally I encode all my home videos with CBR at 8000 kbit/s and PCM audio to get max 1 hour per DVD.

In your case with family videos and action packed movies at bitrates below 3500 kbit/s I would probably not use anything above half D1 and for quality reasons I would not use anything below half D1 and never go below 2000 kbit/s either...

[rbautch]

Great advice. Thanks.

[junkmalle]

Unless you used a tripod, your "family videos" probably don't qualify as low motion because of camera shake.

[Phoebos]

IMHO 8000 is too much for VHS home videos, no noticable difference with 5500 or mabe less bitrate.

[FulciLives]

Half D1 hits the MAX bitrate around 5000kbps ... it might be just a tad lower but it really isn't as low as 4000kbps which is the often quoted bitrate MAX of Half D1.

However, having said that, a CBR at 4000kbps is usually good enough with a clean source.

Although I did use to do some TV captures at Half D1 using a VBR with 2000kbps MIN, 4000kbps AVG and 6000kbp MAX and that worked really well.

Now though I think that is overkill unless it's a low quality source like a videotape.

- John "FulciLives" Coleman