video quality degredation after repeated conversions to wmv

[akuhl]

I'm converting a series of videos I took from a canon powershot A520 camera into ULEAD videostudio and then converting it to a WMV file (320 X 240) - for some reason each time I make minor changes and convert the file into a WMV file, the final file size gets much smaller and the video quality goes way down. Any ideas why this is happening and how I can prevent it?

Thank you very much in advance!

Andrew

[Black Lab]

Are you taking your WMV file, editing that, then rendering it again to WMV?

[akuhl]

Hi,

No, I'm going right from the editing panel each time - just clicking SHARE and then picking WMV 320x240.

Andrew

Gees Andrew, you have a lot to learn still. Going to SHARE >WMV renders a new file, compressing it again. That's why it is getting smaller in size.

[heinz-oz]

Yes Jeff, that is exactly what I think akuhl is talking about. Why the results surprise him surprises me too.

@akuhl
If you keep compressing an already compressed file you will end up with a file which is compressed again. Kind of logical isn't it? Compression works by dumping image detail (yes, your video consists of lots of images strung together) which the program considers redundant. We call that generation loss. Every compression performed loses another generation. That's just the way it is. That is also why serious video enthusiasts would never use your type of footage for editing except for streaming it from the web.

If you intend to continue to use your work flow, make all your editing steps in one process and only generate a new WMV file after you are done. That way you will lose less quality but you will still lose some.

[akuhl]

Hi,

Thanks for the reply, but I'm still a little confused (and yes this is for the web btw). I'm not saving a new WMV file, opening that WMV file, then resaving it. I'm working from the original UVS project file each time - that's what I'm making changes to, and then saving to WMV, and each time I'm still getting a smaller file size and lower quality video.

Thanks again for any feedback,

Andrew

[heinz-oz]

What do you intend to achieve with the intermediate SHARE steps? Are you saving under a different name in a different location? WMV is heavily compressed and no linear editor I know off does a good job editing these formats. After all, these are distribution formats not intended to be used for editing purposes.

If you save the SHARE result with the same name in the same location and reopen the project, VS will link to this file and incorporate your previous editing. If you keep compressing a lemon you will get juice for a while. A little less each time but over time all you will get is pulp, no juice. I hope you understand the analogy and do not take it as an attempt to belittle you. Video editing can be very confusing for the novice, that's why I try to give an analogy, no offence intended.

[akuhl]

I do the intermediate share steps because the video doesn't play smoothly from the editing panel - it runs slow and choppy so I need to convert to WMV occasionally to preview my final project as I go. But I thought that the UVS project file will NOT degrade as I go - I'm not re-importing the WMV file back into the editor each time. I just keep opening the UVS project file and making changes to that, then going back and saving a WMV, and the WMV is still degrading for some reason. Sorry I'm such a novice, and thanks again

Andrew

OH! So it's linking to my new WMV file when I reopen the UVS file - not the original video I imported from my camera??? If so, how do I get it to use the original video in the project file?

[heinz-oz]

The solution to that was already hidden in my last response. SHARE to a different file name/location.

[akuhl]

Ah great! So that's the problem I'll try that - thank you so much!!!

Andrew

[heinz-oz]

You are very welcome.

[Ken Berry]

I think there may have been a fundamental misconception from the start of this thread.

akuhl -- you have never told us what the format was of the files you have downloaded from your digital still camera. Normally, they are either .mov or some form of .avi. Right click on one of the *captured* files (i.e. before it has been processed) within Video Studio, and copy down ALL its properties here please.

Whatever the case, you are capturing highly compressed video in one format, then converting it to another highly compressed format, and I have to say that VS does not handle editing these highly compressed formats very well, particularly WMV.

But if, say, your original video uses the motion JPEG codec (MJPEG) the file size will be comparatively large. Converting these to WMV will naturally produce a smaller sized file, both because of the generational loss mentioned by Heinz, but also because WMV produces small files, period.

And be aware that the VSP file you mention is NOT a video file. It is a Video Studio Project (VSP) file which is rather like a road map. It merely tells the program what videos are included in a project, where they are stored, what format they have, and what editing has been done to them.

[today_on_ulead]

I just noticed this bug myself.

Videostudio 10 clearly corrupts my .wmv files on followup saves. (smaller filesize and poorer quality, even when using different filenames).

I have 2 workarounds until this gets fixed.

1) Close the Videostudio program and reopen the program where I left off and voila it works fine.

2) Make any slight color changes and voila it's fine.

There's probably more or better solutions but try this for now to see that your problem goes away.

[sjj1805]

I have noticed whilst working on DVD Workshop 2 projects, if I render a project and then later return to make some alterations to it. A re-render takes considerably less time than the original render.

This tends to suggest that the software is no longer using the original files but as a form of smart rendering is utilising the new files rendered from earlier.

If I delete all of the files that were created during the render process - such as a completed DVD burned to a hard drive folder, then if I again render the project it again takes a lot longer - more like the original time taken.

DVD Workshop is another Ulead product and so I assume that it shares many common modules with VideoStudio and other Ulead programs.
Based upon my experience with DVD Workshop - and as also suggested by Heinz-Oz it would appear that although you have opned your original VSP to make changes, it might be utilising those newly rendered files in subsequent edits. If so try deleting those files before making a new render.

[DVDDoug]

As the others have said, it's best to convert/compress once after all editing is done. It's good that you've found a work-around. Everybody's using different file formats from different sources, on different kinds of projects with different goals... You frequently have to find your own special procedure for your particular situation.

Videostudio 10 clearly corrupts my .wmv files on followup saves. (smaller filesize and poorer quality, even when using different filenames).

Weird! I can understand some quality loss, because most editing requires the file to be decompressed & re-compressed. But, I DO NOT UNDERSTAND the additional compression that's reducing the file size. File size is a function of bitrate... A one-hour 1500kbps WMV file should always be about 650MB... A one-hour 1500kbps MOV or DivX file should be exactly the same size too (assuming they also have identical audio-bitrates).

P.S.
As Ken mentioned, all of these highly compressed formats can be "difficult" to edit and/or convert. The only foolproof format seems to be 13GB per hour AVI/DV from a MiniDV camera. If you are thinking about getting a regular video-camera, this is probably the "safest" way to go at the present time. Even MPEG-2 (the DVD format) can sometimes cause trouble! A lot of people are having success with HD, but other people have problems. So, I suspect it's still somewhat on the "bleeding edge".

[heinz-oz]

...
I can understand some quality loss, because most editing requires the file to be decompressed & re-compressed. But, I DO NOT UNDERSTAND the additional compression that's reducing the file size. File size is a function of bitrate... A one-hour 1500kbps WMV file should always be about 650MB... A one-hour 1500kbps MOV or DivX file should be exactly the same size too (assuming they also have identical audio-bitrates).
....

I think you are looking at it a little bit too simplistic. I would agree if compression only had the one function, transfer data at a certain speed (kbps). However, that is not the case, the way I see it. Compression also has to do with discarding image information for subsequent frames where it is deemed redundant.

A certain duration of video at a certain bitrate should be a certain file size can only be true, if the source information is identical. Clearly, quality cannot be dependent on bitrate alone. Why would DiVX video still look so good even though the bitrate is so very low?

It's the compression of every frame of the video which causes the diminishing file size in the first place. That compression is applied every time you render a new file. The bitrate only determines the final file size for the output file.

That is my take of it. I could be wrong but my own experiences seem to indicate that I'm somewhat right with my understanding of it.