What is an OK bit rate setting for computer videos?

[johnharlin]

I want to convert some of my videos from dvd to avi to 720 by 480 h264 format for just computer use. I don't need fancy high quality video for the computer, just average reasonable quality. I have noticed that the bit rate can effect the size of files considerably and I want to keep them relatively small.

Recently, I converted 3 gig, one hour 30 minute dvd film, 704 by 480 with a 59.9 frame rate to h264 29.9 frame rate, 192kb mp3 audio which resulted in just under 700mbytes. I used 800kbytes for the bit rate and it seemed to come out fine. But I don't know what the hell I'm doing, I'm just doing it and what comes out, comes out. I don't know if I ruined the film or not but it looks OK and runs OK. The thing is that if I put the bit rate higher at 2,000kbytes, the file size gets way too high. So what do you experts recommend for computer video bit rate size for conversions like this.


Also, can I convert such a computer video with the bit rate of 800kbytes back to reasonable quality DVD format or has it lost the bit rate level for good once you downsample it. I thought that if I keep the videos at 720 by 480 that there won't be as much deterioration if I remade a dvd out of them but I don't know about the bit rate issue.

I'm still working on the other project but this is a loose end I want to tie up as well.

[Hoser Rob]

I'm afraid that you can't convert a 1 1/2 hour 700Mb video back to dvd resolution. When you lower bit rate you lose information. It can't be put back in. Any encoding loses quality, and if you made a dvd out of it you'd be reencoding twice.

"Average reasonable quality" isn't easy to define but you don't seem 100% happy with it. I wouldn't be satisfied with it either. I find about 1 Gb per hour of video is needed for good quality. With 700-800Mb files I have to use the add noise filter in SMplayer to make it watchable.

I never encode my dvd rips to avi. I use handbrake or vidcoder (handbrake with a different interface and, since it's an older version, they still have target file size mode) with .mkv output and h.264 encoding. h.264 is much better. I've tried reencoding an h.264 clip to xvis and had to significantly increase the bit rate to get decent quality.

Actually my recommendation for ripping dvds if you want to keep it simple and reasonably fast is handbrake or vidcoder, using high profile (very important unless it's for watching on a mobile) and constant quality mode set from 18 to 19.25.

19.25 won't necessarily be as good as 18, but many can't tell the difference, and it'll be significantly smaller. For some dvds I more fussy than others.

[jagabo]

If you're going to output to AVI you'll probably be using Xvid. Try using Target Quantizer mode (constant quality in a mathematical sense) with the quantizer set to 2, 3, or 4. At 2 you'll hardly see any difference between the source and encoded video, even looking at enlarged still frames. At 3 you'll see some blocky artifacts if you look at enlarged still frames but you usually won't notice them at normal playback speed. 4 will give even more blocky artifacts. The higher you set the quantizer the worse the quality gets, but the smaller the resulting file.

[Cornucopia]

If you were using h.264 vs. MPEG2, you can get by with much less bitrate for similar quality. However, you've got to remember that if you are going MPEG2_on_DVD -> h.264_on_AVI/mkv/mp4 -> MPEG2_on_DVD, you are doing at least 2 conversions with LOSS generated on each conversion. If you want to remain h.264 that could be ok, but it wasn't meant for use as an intermediate format. Go back to your originals, in that case.

Scott