loss of quality in rendered MPEG-2 files

[linwc]

I'm using VideoStudio X2 (12.0.98.1 Pro). I'm having some problems with a loss of quality when I export my projects to MPEG-2 files. I imagine that there are already some threads covering this subject. If so, please point me to them.

I'm trying to edit out the commercials from some DVDs I¡¦m creating with my DVD recorder. The imported (captured) MPEG-2 files look fine. The properties of these files are:

File format: NTSC DVD
Video Type: MPEG-2 video, Lower Field First
Attributes: 24 bits, 720X480, 16:9
Frame Rate: 29.970 frames/s
Data Rate: Variable bit rate (max. 9800 kbps)

The exported MPEG-2 files just don¡¦t look as clear or well defined. The properties of the exported files are exactly the same as the imported ones, except that the data rate has a maximum of 9632 kbps. I¡¦ve tried using the MPEG optimizer, making sure that all the settings are consistent with the properties of the imported clips. I¡¦ve also tried using the ¡§Custom¡¨ option, favoring quality over speed as much as possible in the ¡§Compression¡¨ tab. In all cases SmartRender is enabled. Is there anything else I can do?

Also, I¡¦ve read in these forums that MPEG-2 files do not edit well. So I¡¦ve tried converting the imported files to AVI format prior to editing. The results were pretty disappointing though. Is it best to convert MPEG-2 files to some other format before the project is edited?

Thanks, I appreciate any help you can offer.

[Ron P.]

Welcome to the forums,

Is it best to convert MPEG-2 files to some other format before the project is edited?

Very simple enough, No! When you convert to another format from a DVD compatible MPEG-2 for editing, you will have to recode it back to DVD MPEG-2 for burning to disc. This will most likely cause problems such as a drop in quality.

One other option you might try is to use 2-Pass encoding with the Variable Bit Rate. This will take a lot longer than single-pass encoding, however VS will make better use of the Variable bit rate encoding, as on the first pass it just finds the fastest and slowest parts of the video. The faster parts are given the highest bitrate, while the slow or static given the lowest. This may help improve your quality, however I think it is meant more for trimming down file sizes so that more can fit onto a disc.

You want to be careful on setting the bitrate too high, because there needs to be enough room for the audio. Some DVD players tend to choke on burned discs that use very high bitrates, nearing the maximum of 10,000kbps, which is the total for the combined video and audio..

[renx]

I'm not a big fan of Ulead video conversion options. I haven't been able to find the option to set the bitrate for conversions to mpg, hence, the quality is degraded from the original source. I use several programs to finalize and edit programs. Maybe I'm doing this the hard way. First I convert my edited video to mpeg using the HDV - 720p setting in Ulead. Unfortunately, this will resize the video to a 16x9 format. Unchecking the "Perform non-square pixel rendering" in the options, will stretch the image to fill the 16x9 frame. The resulting video is very nice and clear (large high bitrate file). Then, I use other software to resize and encode. I use VDubMod for most avi file ecodes using the Lanzcos resize filter (640x480). Or, a nice little program called Total Video Converter will resize and convert to mpeg-2 and allow you to select your own bitrate or chose from the default settings.

[linwc]

One other option you might try is to use 2-Pass encoding with the Variable Bit Rate. This will take a lot longer than single-pass encoding, however VS will make better use of the Variable bit rate encoding, as on the first pass it just finds the fastest and slowest parts of the video. The faster parts are given the highest bitrate, while the slow or static given the lowest. This may help improve your quality, however I think it is meant more for trimming down file sizes so that more can fit onto a disc.

Ron, thanks for the response. I have tried using the 2-Pass encoding option and I did not notice any improvement in the quality of the video. Is a loss of quality simply unavoidable when working with MPEG-2 files? Also, since apparently it's not a good idea to convert MPEG-2 clips to another format, should I try to limit the amount of editing I do?

I'm not a big fan of Ulead video conversion options. I haven't been able to find the option to set the bitrate for conversions to mpg, hence, the quality is degraded from the original source. I use several programs to finalize and edit programs. Maybe I'm doing this the hard way. First I convert my edited video to mpeg using the HDV - 720p setting in Ulead. Unfortunately, this will resize the video to a 16x9 format. Unchecking the "Perform non-square pixel rendering" in the options, will stretch the image to fill the 16x9 frame. The resulting video is very nice and clear (large high bitrate file). Then, I use other software to resize and encode. I use VDubMod for most avi file ecodes using the Lanzcos resize filter (640x480). Or, a nice little program called Total Video Converter will resize and convert to mpeg-2 and allow you to select your own bitrate or chose from the default settings.

Renx, thanks. I'll try the HDV-720p setting and see what happens.

[skier-hughes]

I don't use VS but doesn't it have the smart render feature, so it will not render parts of the file that haven't been altered?
If so, you want to use this.

I can't see any reason for taking an SD file and converting it to a HD progressive file, unless the outcome is going to be HD and progressive.

Mpeg compression is lossless. It was made originally for watching not editing. Any changes made will cause a loss in quality. Once lost, you cannot regain quality.

[Black Lab]

I think Graham meant to say MPEG compression is lossy.

As for renx not being able to find the options to change the bitrate, when you go to Share>Create Video File, choose Custom. Or, if you go to Share>Create Disc, click on the cogwheel icon then choose Change MPEG Settings. These will allow you to change the bitrate.

[skier-hughes]

First of all I thought I'd typed lousy, but lossless, bit of a brain storm there, it is indeed lossy which mean each time you save it, the mpeg compression algorithm is used and you lose detail.

[linwc]

I don't use VS but doesn't it have the smart render feature, so it will not render parts of the file that haven't been altered?
If so, you want to use this.

I can't see any reason for taking an SD file and converting it to a HD progressive file, unless the outcome is going to be HD and progressive.

Mpeg compression is lossless. It was made originally for watching not editing. Any changes made will cause a loss in quality. Once lost, you cannot regain quality.

Graham,

I always enable SmartRender whenever I export my projects to MPEG-2 files.

Since learning that MPEG-2 files are not meant to be edited, I have tried exporting unedited MPEG-2 clips. Though I did not alter the clips at all, there was still the same noticeable loss of quality compared to the imported MPEG-2 files. Is this drop-off normal, or am I doing something wrong?

[sjj1805]

.....
Since learning that MPEG-2 files are not meant to be edited, I have tried exporting unedited MPEG-2 clips. Though I did not alter the clips at all, there was still the same noticeable loss of quality compared to the imported MPEG-2 files. Is this drop-off normal, or am I doing something wrong?

Your message reads
1. Import MPEG2 file
2. Do nothing to it
3. Export MPEG2 file.

Which begs the question why have you done ANY of the above steps.
Whatever it is you have "Exported" to could simply be given the original untouched MPEG2 file mentioned in step 1.

OK ignoring that point. Even though you have not EDITED the video (i.e. cut stuff out, put stuff in, added titles, overlays or anything else) when you then "Export" this file is it an exact replica of the original?
Bit Rate, Frame Size, Audio format so on and so forth?

[linwc]

Your message reads
1. Import MPEG2 file
2. Do nothing to it
3. Export MPEG2 file.

Which begs the question why have you done ANY of the above steps.

Steve,

Mainly, in that instance I was just experimenting. I wanted to see if not editing an imported MPEG-2 file would yield the same results as an edited project. From what I could tell, it did not seem to matter whether I edited the MPEG-2 clips or not. The exported file is still unsatisfactory.

OK ignoring that point. Even though you have not EDITED the video (i.e. cut stuff out, put stuff in, added titles, overlays or anything else) when you then "Export" this file is it an exact replica of the original?
Bit Rate, Frame Size, Audio format so on and so forth?

Yes, as I said in the OP, I've made sure that the properties of the exported MPEG-2 files match those of the imported clips. The only difference is that for the exported file the bit rate has a maximum of 9632 kbps instead of 9800 kbps.

Let me ask you: if you were doing a project using MPEG-2 clips (as I must apparently, since I want to edit out commercials from DVDs I've created), what are the steps you would take? I figure I've got to be doing something wrong, because I can't believe anyone would be happy with the results I'm getting.

[skier-hughes]

If you change any property, then the mpeg will be re-encoded to meet the new properties, so changing your bitrate will mean that the whole file will be encoded and thus as mpeg is lossy, each save will give you a slightly lower quality end result.
Changing the output to 9799 from 9800 will result in total encoding, so giving you a poor result.

Try your unedited mpeg and use exactly the same settings.