jumpy jittery video

greenspun.com : LUSENET : Video CD : One Thread

hi, I have video files that i've made into mpg2 files and they play ok on the computer. I've made these into vcd mpg1 standard files and written to vcd which plays fine on a dvd player. These files are also smaller and easier to download than the mpg2 version. all files played smoothly on the dvd player and also when played on the computer. Following along the smaller file goal, I wanted to make even smaller files for online download, so i slowed down the video rate just to make the files as small as possible. vcd is bit rate of 149 so i went smaller down to 50 which is the lowest setting. the files were much smaller but the video playback was jittery or jumpy. every 10 seconds or so it would pause briefly then jump ahead a number of frames. It is very annoying. i tested on my computer, pentium 4 2.4gh, by not slowing down the bit rate as much. i tried every setting slower than the 149 for vcd down to bit rate 68. the 68 actually played smootly on my machine (not much bigger file than the 50 setting so it was ok with me). other people downloaded these files at the 68 setting but complained they were jumpy and jittery and unwatchable etc. so now i do not know why. they claim they have fast computers etc. i just don't know why the video is jumpy etc at a low bit rate rather than just playing smoothly at a lower quality etc. My goal was simply to offer the same video clip at a lower quality/smaller file size so people could download the high quality mpg2, mpg1/vcd, or the lowest quality mpg1 etc but i need the smallest file to NOT be jumpy. Point me somewhere that i can learn about what is causing the jumpy jittery video. Thanks:) -=

-- teresa davis (teresa690@yahoo.com), October 02, 2003


I don't recommend using bit rates that low. Actually, the bit rate for VCD is a constant 1.115 Mbps for video and a constant 224 Kbps for audio. Combined this is 1.339 Mbps. The video bit rate for VCD can not be changed and still have a true VCD. Yes, it is possible to make the bit rate lower, but you are violating the VCD standards. You don't say what you used to convert the bit rate, but jumpiness could be a result of the conversion. I really don't recommend that you use lower bit rates on MPEG-1 video than VCD uses. The final result may be smaller, but it's not really going to be watchable. I've seen MPEG-1 video at bit rates of about .6 Mbps (about half the normal rate for VCD) and what I saw was garbage. The image was fuzzy and quality was terrible. If you just absolutely have to have smaller video clips, you can try converting them to Real Media. Real Media is terrible quality even on those postage stamp sized resolutions it uses, but it does produce pretty small files that are easily downloaded. I would recommend you convert your highest quality MPEG-2 source to Real Media if you decide to use it. http://www.vcdhelp.com has some guides on converting between various video formats.

-- Root (root@yahoo.moc), October 03, 2003.

Moderation questions? read the FAQ