DVD Resolutions with low bitrate

[akrako1]

When making a long-play DVD (lets say 4 hours..) what is an appropriate resolution to pick? I'm using Ulead Movie Factory 2, and you can custom select the bitrate, resolution, etc, for your converted video (assuming you need conversion). Now, I'm trying to put lets say 4 hours of video on a disc, so I chose a bitrate of something like 2000. Now... here's where the question is. I have the opportunity to choose multiple resolutions for the converted video. Since I'm using a low bitrate, will the output look better if I'm using a lower resolution (like 320x240) instead of full DVD resolution? My general thinking would be that requiring there to be lots of pixels would cause more blocking or crappy looking encoding. Whereas using 320x240 at a bitrate of 2000 (lots more than the standard VCD bitrate) should look great on a non-HD TV. What do y'all think?

[adam]

If you are going to lower bitrate that much then yes you need to also lower resolution otherwise you will get lots of blocking. At 2000kbits I would try 352x480/576 first and see if you are satisfied with it, which you probably will be. If you find that you need to go lower then use 352x240/288. The resolution you typed is not dvd-compliant, but that might have just been a typo.

Compliant DVD resolutions are listed in the What Is DVD section on this site.

[bottle-necked]

The rule of thumbs I learned... 720x480 then 8Mbps, for 352x480 then 4Mbps, and for 352x240 then 2Mbps, and for MPEG1 (352x240) then 1.850Mbps max bitrate. (NTSC)

For 4 hours on 1 DVD I'd say use 352x480, VBR 4Mbps. If the project comes out a little too big then run it through DVD Shrink before you burn it.

4.350 / (4*60) / 60 = 3.02 {3.02Mpbs average}

Good luck.

[akrako1]

Thanks! I'll check it out!

[adam]

Those numbers look extremely conservative bottle-necked. Commercial DVDs use full D1 (720x480) and with the exception of SuperBit DVDs they almost never have an avg of 8mbits. Actually, even SuperBit DVDs probably don't go that high. Most commercial DVDs have an avg bitrate of between 5 and 6 mbits, and personally I think 4mbits is more than enough for most sources.

Also, 2mbits is plenty for 352x480. That is actually one of mpeg's famous sweet spots. Of course this is all very subjective and will vary according to the source, but personally, I'd half everything you said.

My general rule: 720x40 use at least 4mbits. 352x480 use at least 2mbits. 352x240 for anything less.

[bottle-necked]

The rule of thumbs I learned... 720x480 then 8Mbps, for 352x480 then 4Mbps, and for 352x240 then 2Mbps, and for MPEG1 (352x240) then 1.850Mbps max bitrate. (NTSC)

For 4 hours on 1 DVD I'd say use 352x480, VBR 4Mbps. If the project comes out a little too big then run it through DVD Shrink before you burn it.

4.350 / (4*60) / 60 = 3.02 {3.02Mpbs average}

Good luck.

You're assuming I said "Average"... Read it again. ok
lol

[edit] and my calculation is showing an 'average' allowed of around 3.02Mbps. So, 4max, 3average, w/352x480 (NTSC). Actually pretty standard numbers if you read many of the archives here.

:::
8,000,000 / (720x480) = 23.14
4,000,000 / (352x480) = 23.67
2,000,000 / (352x240) = 23.67
:::
Good luck.

[adam]

You're assuming I said "Average"... Read it again. ok
lol

[edit] and my calculation is showing an 'average' allowed of around 3.02Mbps. So, 4max, 3average, w/352x480 (NTSC). Actually pretty standard numbers if you read many of the archives here.

:::
8,000,000 / (720x480) = 23.14
4,000,000 / (352x480) = 23.67
2,000,000 / (352x240) = 23.67
:::
Good luck.

Yes I did assume you meant average because otherwise it wouldn't have made sense. You'd keep the same avg but adjust max bitrate according to resolution? I don't see what that would accomplish.

And there would never be any reason to change your max. Your max is always the highest that the standard allows after factoring in overhead (audio + subs + etc..) Otherwise, there's not much point in using VBR encoding when your bitrate can only fluctuate by 1mbit.

EDIT: Those calculations you just added ARE for avg bitrate.

[thor300]

I would not go below half D1, coz 352x240/288 is so low that the picture will suffer badly just because of the resolution. The only reason to use 352x240/288 would be if your source was already in that resolution or lower.

[FulciLives]

I would not go below half D1, coz 352x240/288 is so low that the picture will suffer badly just because of the resolution. The only reason to use 352x240/288 would be if your source was already in that resolution or lower.

Yes I agree the hit you take by using half height resolutions (240 instead of 480 in the case of NTSC) is just too much of a hit picture quality wise. In effect you are throwing out one field of your frame and a frame is made of of two fields. So you are streching one field to fit a single frame and this results in a very "jaggy" picture no matter WHAT bitrate you throw at it.

So unless you are working from a source you somehow obtained that is already crippled with a resolution of 240 height ... well as thor300 said that is the ONLY time you probably would ever want to use that low of a resolutoin.

- John "FulciLives" Coleman

[bottle-necked]

You'd keep the same avg but adjust max bitrate according to resolution? I don't see what that would accomplish.

That's not what I ment. My calcs show that the allowed will be around 3Mbps if they want that much time (4 hrs). (yet to be proved and will depend on many factors). I also ment that 'by the rule of thumbs that I learned' then by looking at a dvd with a 3 average then it fits into the 2-4Mbps range so I suggested the 352x480, and by this same rule of thumbs, the 4 max. That's how I came up with 4max, 3 average, 352x480.. lol

Those other numbers are ratios. Available pixels verses bitrates. They pretty well equal out at those sizes. lol


Good luck.