bitrate help

[loa909]

can anyone here help me on understanding video bitrate and this calc which I found on the internet i know you place in length of movie etc but whats this figure where it says kbits/s is this the video bitrate answer then

[steveryan]

Yes.

[thecoalman]

yes, that would the suggested maximum bitrate for length in time your video is. to fit on the size disc you seleceted.

[loa909]

so basicially you check movie in gspot 1st then just add figures from gspot to bitrate calc yes

also can anyone here place a snapshot of where i find all this info in gspot with arrows pointing to where these are please

many thanks it would be most appreciated

[redwudz]

As shown, it's just a product of playing time VS room on the media. You can set the size of your encode by adjusting the bitrate. Low bitrate=Low quality. Higher bitrate=better quality. On a DVD it is generally limited to about 9800kbps for the video. You also set the audio bitrate in the calculator to allow room for that on the disc.

Average bitrate is used for CBR (Constant Bit Rate) encodes. VBR (Variable Bit Rate) sets a maximum, minimum and average encode rate. VBR single pass encodes are difficult to get accurate encode sizes. 2 pass VBR or CBR will get you fairly accurate calculated sizes.

For maximum quality/bitrate, you can get about an hour of video on a DVD-5 (4.37GB) Lower bitrate will get you more time, even up to 8 hours or more, but with poor quality.

For more info on the DVD format, see 'WHAT IS' DVD to the upper left on this page.

We have several bitrate calculators in our 'Tools' section to the left. <<<<<<

And welcome to our forums.

[loa909]

I dont understand this as I entererd your gspot settings into bitrate calc like the length of movie plus the audio at 128 as it showed in your gspot settings and it said this but in your settings it shows bitrate as 1200 kbp/s but on bitrate calc it shows below 7662 can you explain why

[thecoalman]

First that's a xvid video and bitrates are typically lower from his example above and really has nothing to do with DVD... The information that Gspot will give you is really irrelevant except the time length of the video.

Secondly the calculator is used to maximize the bitrate....

You have x amount of space on a 4.7GB disc, the calculator will give you bitrate so that you utilize all of it. In other words it's going to tell you what the highest bitrate you can use for the space available on the disc. For example if you have 1 hour of video the typical bitrate is going to be about 8000kbs for 1.5 hours it's going to be 6000kbs.

Note as the you increase the length of time the bitrate drops...

[loa909]

I think i need to read up a bit more on understanding this bitrate thing as its a bit confusing to me

[thecoalman]

It's really not that hard to understand.... Let me put it another way.

If you encode a 1 hour video at 8000kbps the file size is going to be roughly 4GB's

If you encode a 1 hour video at 6000kbps the file size is going to be roughly 2.7GB's

If you encode a 1 1/2 hour video at 6000kbps the file size is going to be roughly 4GB's


As you lower the bitrate the file size decreases, so does the quality.

To maintain the highest quality you want to use the highest bitrate possible....

Now if you have a video that is 1 hour and 49 minutes long, what's the highest bitrate you can use and still fit it on a disc?

I have no idea myself that's what the calculator is for.

[loa909]

is it 9570 kbp/s but how do i know what audio size to put

[thecoalman]

No the 9570 is for setting the max and has no bearing on what the caluator is going to give you unless the bitrate it calculates exceeds that which is not going to happen unless you have a very short video. The number you are interested in is the one next to "Calculated bitrate"

The drop down box for the audio is for whatever you are going to select in the your encoder. For example if you are using PCM you would select 1536. MPEG and AC3 audio can have varying bitrates if you are using one of them.

[loa909]

5366kbits/s then is this right so when encoding this is what I put down for video bitrate then

[Pinstripes23]

If the bitrate calculator accounts for authoring overhead then yes use it. But if it's anything like videocalc (which I use), then I leave some extra room for the overhead.