Should the bit rate be the same converting mp4 to vob, and other ?s

[Redeemed]

I am one of those who has benefited in the past by the information on videohelp.com, but now need some specifics that i have not found, and which covers conversion as well as DVD authoring.

I received personal permission to copy and share some video files, and am trying a different authoring program than the Roxio MY DVD8 that i normally use. The files i am using are either .mp4 or .mov, and have various bit rates, according to Gspot, and using the Devede program (http://files.majorsilence.com/devede/downloads/312-2/devede3.12.2-setup.msi) allows me to choose the individual bit rate for each file, thus maximizing how much content can be placed. It can also "fit to disk," but which renders all the same bit rate. The question is will i lose quality if i choose the same bit rate for conversion as the original had?

Also, what is the verdict on mixing aspect ratios on the same disk? These videos are only 352x240 or 640x480, and I made up a DVD folder ("Create Disk structure"), all as NTSC, with "default" (i think) for the video format size, but when i played files with the VLC player that were formatted with a 4.3 ration then they were vertically squeezed and distorted, while some that were 16.9 were too narrow horizontally.

I then changed the former ones to 16.9 and the latter to 4.3, and chose 720x480 as the size for all, and which fixed the problem. I can see the VLC player (which also will now play ISO files) adjust the video to the correct aspect when it first starts, BUT what will happen
on a portable or stand top DVD player?

Finally, does anyone have an idea why some files (such as this .mov: http://dl2.cbn.com/RH7v2_WS_M.mov, or this .mp4: http://dl2.cbn.com/MW95v3.mp4 - downloads) are not recognized as a video file by this software while others ones with the same extension are? I did ask on the devede Google group forum but it has not responded.

I was able to convert the mp4 and some other mov. files from the same site to mpeg using other software, but not the first .mov - at least not without losing the sound.

Thank you and may God bless for any help.

[Case]

1/ The optimal bitrate is a function of the output codec, output framerate, output frame size, and to some extent: content. The bitrate of the source file is not relevant.
2/ A DVD-Video disc may have changes in aspect ratio for different Video Title Sets. A single VTS should have the same aspect ratio from beginning to end. E.g. a DVD menu could point to 5 clips, all of which can be either 16:9 or 4:3.
3/ The .mov file converts fine to DVD compliant .mpg (file) on my end...

[Redeemed]

Thanks so much for converting that file, and enabling it to be downloaded! It looks better than the smaller mp4 they also offered, and Devede recognizes it. What did you use to covert it? I had tried Super, Any Video Converter, iWisoft, and DVDVideoSoft Free Studio, but they left out the Audio or rendered a few seconds of it.

And as the Devede structure has only one VTS file, then i should leave it at 4.3, and 720x480.

But as for the bit rate, i am still unclear what would be the best way to retain the original quality without using up the whole disk. The original bit rate for them ranges from approx 600 to 1500 kbps, and which i thought indicated how good/poor the quality is.

[guns1inger]

Bitrate can influence quality, but is not the final arbiter. The problem you have is that different codecs use different methods of compression, and not all methods provide the same quality at the same bitrate. Mpeg-2 is not as efficient at compression as mpeg-4, and even within mpeg-4 there is a quite some difference. Part 2 (Divx/Xvid) is not a good at the same bitrates at Part 10 (AVC) for example.

Mpeg-2 requires around 3 - 4 times the bitrate in order to maintain approximately the same quality as mpeg-4 part 2, and up to 5 or 6 times the bitrate to match well encoded AVC material.

There are other factors that come into play as well, including the actually quality of the source (noisy material doesn't encode as nicely as clean material, and needs a higher bitrate), and the resolution of the source (upscaling usually results in a softer image). Upscaling VCD resolution material to full D1 will give a very soft image.

Ultimately, it all comes down to the universal rule of filesize = bitrate X running time. The lower the bitrate, the more you can fit on a disc, but eventually, the lower the quality. For DVD encoded with mpeg-2, you can get 65 - 70 minutes at the maximum allowable bitrate (and theoretically therefore, maximum quality - all else being equal), 90 minutes of high quality, 120 minutes of good quality, and after that it is all down hill. Of course none of these numbers are absolutes because of the factors involved, but they are a good rule of thumb.

[AlanHK]

. The original bit rate for them ranges from approx 600 to 1500 kbps, and which i thought indicated how good/poor the quality is.

It does, but the comparison only works for the same kind of file.

Newer, more complex, codecs are more efficient in giving you better quality at a given bitrate. (At the cost of more processing power needed to encode and decode.)

I'd say you need 2-3 times the bitrate in MPEG2 for an equivalent quality in DivX.

Anyway, by far the best way to determine this is to see for yourself: just encode some clips at various rates and see what you get.

[Redeemed]

Thank you guns1inger for the articulate, informative explanation, and AlanHK for your supplementary input, both of which help clarify the situation, and i am sure will help others as well. In my case i am taking files which were originally mp4 (avc1, H.264/MPEG-4 AVC codec) or mov (mp4v, ISO MPEG-4 codec) formats to make a DVD out of them, and can fit about 180 minutes without lowering the maximum bit rate and i think i could go further. Of course,i have found that just burning mpgs or mpg4 to a DVD allows a lot more, if the DVD players can read them, as newer ones can.

Thanks again for the help.