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| Xvid / Divx or transcoded mpeg - which is better? http://forum.linhes.org/viewtopic.php?f=6&t=17353 |
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| Author: | mogator88 [ Thu Nov 29, 2007 7:07 pm ] |
| Post subject: | Xvid / Divx or transcoded mpeg - which is better? |
Hi all, Lately I've been transcoding my recordings with the built-in transcoding feature to save space. I've been transcoding because its easier and I want to keep my "shrunken" recordings in with the current recordings, NOT in the videos folder. When I view transocded recordings on my HDTV I feel that I'm not getting the same quality I did from the xvid conversions I used to make with nuvexport. Am I correct? Or are there transcoding settings that will give me a quality and file size similar to an xvid conversion? If so, what would those settings be? Thanks for your input. I was going to add a feature request for an xvid conversion that replaces the original recording and updates the database but wanted to learn more about the practical differences first. |
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| Author: | tjc [ Thu Nov 29, 2007 7:30 pm ] |
| Post subject: | |
The MPEG-2 "lossless" commercial cutting transcoder preserves the initial quality since it _only_ transcodes the keyframe group/GOP on either side of the cut point and passes everything else through "as is". Getting high quality results (still lossy but the results look good) from a transcoder that is doing a more serious transformation (say MPEG-2 -> MPEG-4) can often take a lot of fiddling around with parameters which are often specific to a particular recording. (BTW - Both Xvid and Divx are MPEG-4 based.) |
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| Author: | Too Many Secrets [ Thu Nov 29, 2007 8:34 pm ] |
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I use the High, Medium, Low setting transcodings for all my stuff. High is set to lossless. Just for taking out commercials. Medium is set to transcode to mpeg4, size Auto, Auto. BitRate 3600, MaxQual 2, MinQual 15, MaxDif 3. Checked ScaleFrameSize, HighQualEncode, 4MV Enode. Low is set to transcode to mpeg4, same as above except for: BitRate 2200. The Medium settings works nicely for me when I transcode a large HD file. It leaves the quality very good, while really cutting down the file size. As always, YMMV. |
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| Author: | graysky [ Fri Nov 30, 2007 1:16 am ] |
| Post subject: | Re: Xvid / Divx or transcoded mpeg - which is better? |
mogator88 wrote: When I view transocded recordings on my HDTV I feel that I'm not getting the same quality I did from the xvid conversions I used to make with nuvexport.
It's probably all a function of your settings... are you keeping the full resolution (1280x720 or 1920x1024, etc.) while you transcode? Also, what bitrate are you using? Keep in mind that HD content requires more than SD content since there are roughly 3x as many pixels from 480p-->720p and another 3x from 720p --> 1080p. Also know that framerate will play a role in quality as well. Go to my website (url in signature), click the "DVD to video file (x264)" link, then click "information" from the top for a little more on this. On a side note, if you can transcode to x264, I would recommend you do that instead of either divx or xvid as it can give superior results at "low" bitrates.. for more on that, see the information link I wrote about above. |
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| Author: | mogator88 [ Sat Dec 01, 2007 12:57 pm ] |
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I don't think I was clear in my first post that I do need to reduce file sizes through compression. I'm recording digital OTA streams, and lossless isn't enough. I might consider transcoding to x264 at some point, however, I currently own several older network media devices that won't use 264 ,and I'd like to keep those "in the loop" and out of the landfill. Low quality transcodings have been at 2400 bitrate, 480x480 resolution, both HQ boxes checked. Medium quality has been 2400 bitrate, 720x480 resolution, and both HQ boxes checked. Oddly enough, some recordings GREW in size when transcoded at medium quality. These may have been 480i transmissions, I never went back to find out what they were broadcast at. |
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