DVD Bitrate Question

[jntaylor63]

Whenever I use my bitrate calc. for DVD video that is around 70-80 mins, I get an average of approx. 8500 kbs and a max of approx. 9300 kbs. When I play back this video, it looks great on my TV. But if I calc larger time frames such as 140 mins, I get an average of 4100 kbs / Max 9300 kbs. Should I encode with such a large gap in the ave/max ? It seems that there would be highs and lows in video quality.

Does anyone know of a tool that can look at the vob files on my hollywood DVDs and see what the range is? The video looks good and if it worked for them, then it will work for me.

THX,JNT.

[EricB]

Well I'm sure you have read some of the discussions in here, but the concept is that when you want to make a longer DVD, you need to lower the bitrate to get it to fit. One way would be to run a constant bitrate and areas that really require a higher bitrate would suffer.

A second way is to allow the encoder to use higher bitrates when they are required, but conserve bitrate during low motion (VBR or variable bit rate). This gives better overall quality when additional time is required. By nature, the average bitrate moves farther and farther away from the max as you ask it to produce longer DVDs.

On your 70 - 80 minute versions, the max and the average are close together because you're not being very demanding on how much the disk will hold, so you are very close to a fixed rate which is virtually the max.

Is 4100 average too low? Try encoding a small segment and check the results. Are they good enough for you?

[mr2damn]

i use a great lil program called bitrate viewer 1.5 [google search it!] . its shareware...but u will get to see current, peak and avg bitrates along with a graph.. and some file info. Register it and u get even more info on the stream like GOP structure, modifying options, and a NICE BUILT-IN BITRATE CALCULATOR...! isnt life great! btw...keygens are available... try it... like it...BUY it! oh...and u might have to RENAME the vob to .mpg to see it show up in the OPEN box. piece

[jntaylor63]

I guess what I am getting at is, what's the lowest ave rate that you can get away with? I can make it look good on a 32" JVC with S-video.

But if I move up to a 65" wide screen HDTV what would I get? I would put at most is 156 mins with DD 5.1 on a back-up. (No menus or extras)

Has anybody hit a floor bitrate where the video looks poor? I know that its all in the eye of the beholder.

THX,JNT.

[DJRumpy]

I have a widescreen HDTV. SVCD still looks good, so I would guess that 2500kbs at 480x480 is a good starting point. Assuming that your using 720x480 for a resolution, you would need extra bitrate for the higher resloution, although not quite twice the 480 resolution. Say somewhere between 3500 and 5000 for acceptable quality. I usually encode using 3 pass VBR, 2000 min, 5000 average, 9000 max, and the picture looks fine.

[jntaylor63]

Thanks DJ

Learn from you, I will.