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AVI to DVD - 2 Pass VBR is it worth it?
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jumpjet
Newbie
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5. April 2004 @ 11:36 |
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Hi guys.
I realise the implications of converting from one lossy format to another, and the loss of quality, but I have a question.
Is the bitrate and the motion search options when using TMPGenc worth using to their full extent or at all?
Here is my scenario, I want to place 2 full avi movies on one DVD. I have already done this once with some success, getting a reasonable quality fully authored DVD with menus.
However, as normal, the actual conversion of the AVI to a MPG can take some time. So I want to know if I am wasting time by setting the bitrate and quality settings too high?
Most single disk AVI's have a bitrate of 800 - 900, with double that for 2 cd AVI's. As DVD video as a minimum bitrate of 2000, what is the point of using high encoder settings?
Using a bitrate calculator and the movie length, I calculate the average bitrate to fill the DVD, then half that average to give me the half a DVD figures. So typically for a full DVD I might calculate the average required as 5200, so set my encoder for about 2600.
This 2600 is way above the actual bitrate for the original AVI, and is above the minimum for DVD. So is there any point in using 2 pass VBR and a high quality motion search to encode the movie? Why not just use a CBR of 2500 - 2600 and a low quality (fast) motion search setting?
ANy advice would be much appreciated.
Cheers
Graham
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whassup
Member
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5. April 2004 @ 21:10 |
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Just my 2 cents...
Quote:
Most single disk AVI's have a bitrate of 800 - 900, with double that for 2 cd AVI's. As DVD video as a minimum bitrate of 2000, what is the point of using high encoder settings?
Quote:
So is there any point in using 2 pass VBR and a high quality motion search to encode the movie? Why not just use a CBR of 2500 - 2600 and a low quality (fast) motion search setting?
Well, the motion search (precision) settings really tell the proggy how precise you want the transfer to be. I have no idea what you're encoding. If it's anime, probably wouldn't make much of a difference. If it's actual video, there would be somewhat more of a difference. A big determinant would be the source. Is it of a very high quality or low quality?
Anyways, at 2600 kbps, that's extremely low for DVD and, unless it's ripped right from another DVD, probably will give you crappy results.
Why not just try encoding 30 sec intervals at different settings and decide what's acceptable for you? It's pretty subjective. Some people have higher standards for "watchability" than others.
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jumpjet
Newbie
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6. April 2004 @ 03:22 |
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Hi, thanks for your reply.
I am working with a high quality DVD rip of a standard movie (no anime), about 1.4 Gb in size. Naturally it's not my rip, or I wouldn't be doing this :)
I have done this movie now at 2500 CBR and minimum precision search, and the results are suprisingly pretty good, and took about 3 hours. Action scenes seem Ok, though there is some pixilation on wide angle shots, where the camera pans across the scene. Whether this will be noticed on an average TV screen when watching is debatable.
You are correct about the testing, I did go all or nothing, when I should have done some testing (no patience). I actually have some audio sync problems with the movie, so I will be probably be doing it again. This time I will pick a fast action scene and a wide panning scene, and test encode at differing qualities.
Cheers
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Manngo
Junior Member
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7. April 2004 @ 06:48 |
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Hi!
Let me add some hints.
1.) Comparing AVI bitrate and mpeg2 (DVD) bitrate is absolutly misleading. bitrate is how many bits are transferred during 1 sec, containing video data. Of course a better compression method will result a better qulaity on the same level of bitrate. in an AVI file usally mpeg4 compression is used nowdays (Xvid, DivX) that is much higher compression than mpeg2 (DVD). And I guess resolution is also different (of course the bigger needs higer bitrate). Let's say if you have an xvid AVI with 1000 kbps, you should not encode it under 4000 kbps DVD.
2.) bitrate is used to measure the data transfer speed. There are scenes in each movie, where more data is very useful, such as when camera position changes from one frame to an other. This case there is no connection between 2 frames (the one before change and the one after change), the latter has to be stored fully in video data. To be able to draw this fullscreen image sharply more bitrate is useful. If there is not enough, the 2nd frame will be blocky etc. In average we can say, where compessibility of a video stream is smaller, on that part higher bitrate is needed. This is true vice versa. Typically fast-moving scenes can not be compressed well (becouse frames are very different). So thats why VBR is better than CBR. Much more better. Using VBR your bitrate can reach even 8000-8500 where needed, while the average can remain only about 4000. Try to encode your AVI with VBR and check the difference on pixelised parts.
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jumpjet
Newbie
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7. April 2004 @ 07:33 |
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Thanks manngo, you have given me lots to think about.
I was particulary suprised that you equate 1000 kbs AVI to about 4000 kbs DVD. This has certainly blown what I was thinking, way out of the water!.
Essentially you are saying, that if I have a good quality, good bitrate AVI, then I should be re-encoding it as a high bitrate VBR, and therefore use a whole DVD per movie. With an average MPEG2 bitrate of around 4000 there would be no chance of getting 2 average length movies on one DVD.
And there was me, thinking I was being smart, squeezing 2 movies onto 1 DVD, and saving money on discs too!........ lol :-)
Cheers
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Manngo
Junior Member
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7. April 2004 @ 23:52 |
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I save 1 movie on 1 disc. In some cases it is still not enough (movies longer than 2,5-3 hours).
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AfterDawn Addict
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9. April 2004 @ 07:00 |
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hi there
with any conversion one to another looses quality! so he best you can get, and the final output will be the best you can get! maybe slower to code but its worth it!
Nothing here to see, move along folks.
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