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mpg quality not as good as original avi
The phrase ‘leave well enough alone’ springs to mind.
I have never been totally happy with the ‘sharpness’ of my dvds, and have recently been taking a step back to try and understand more of what is going on under the hood. I will also be upgrading my camera shortly, and before doing so want to get a better understanding of what is going on.
I have some footage, shot on a Sony HC1000e. It was captured from DV tape into AVI using the sony capture tool. According to gspot, it’s settings are 720×576, PAL, interlaced, with an average bit range of 25083 kbps
When I view the original AVI directly in vlc or media player, it looks sharp and clear. I import the AVI into Vegas, and render a short 30 second section. No fx are added. I choose main concept mpeg2, with a CBR of 8M. I leave everything else at its default. if I view the rendered mpg it is softer than the original – quite noticeably.
Choosing to render the same section into an avi the quality of the rendered avi is again soft, and certainly not a sharp as the original.
Some questions:
1. If I render an imported AVI out to AVI, should there be any loss? I understand that avi is more of a container.
2. What settings are likely to cause rendered mpgs to be ‘soft’ compared to their source materials?
3. Is it possible that codecs might be an issue. It is possible that the machine may have some codes that ‘should not be there’ – I know – there should only be the ones that are needed, but it seems that some applications seem to install their own. For example, I still have Pinnacle 11 and 12 on the machine (I moved to VMS from Pinnacle about 2 years ago). In the preferences, I thought there was an option to tell vegas to only use its own codecs, but I cannot see it anywhere…
For my source, gspot says the codec is dvsd (DVC/DV video) but I am not sure if this is a Vegas-supplied one, or something else…
I am a techie, so would like to understand more about how and the why!!
Many thanks,
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7 Replies
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1. As log as you don’t add any FX, the render will be a duplicate of the the original.
It’s only when you add FX of any kind (fades included) that the new video will decrease ever so slightly in quality AND only at those points.
As a matter of interest, a test was done a number of years ago ( sure wish I still had the link to the original file) and it showed quite conclusively that, even after 100 generations (i.e. copies), the 100th copy was identical to the original.2. Any time you render to mpeg, the quality will suffer.
For example, a recent video I did (all stills) was 14 min. long.
As an AVI, it was just under 4 GB. in size.
The mpeg-2 file was only 1 G. in size.
When you reduce something by a factor of 4, something has to suffer and that something is overall image quality.
The reason that DVDs from the “big guys” looks so good is that they start with pristine footage and then encode it for DVD using hardware and software that costs a LOT more than you and I will ever be able to afford.
I had the chance to sit in on a (Hollywood movie) film-to-tape transfer at a post house one time and watched the operator colour-correct the film one scene at a time.
The settings were stored in a computer and, when it was time for the DVD encode, it was sent to a multi-pass encoder that extracted every bit of information possible.We’re also tied to inferior technology with 4:1:1 cameras going to 4:2:0 DVDs.
DV Pix – Sampling Methods, courtesy of Adam Wilt, does an excellent job of explaining what these numbers mean. -
Mike,
Many thanks for the detailed responses here and to my other questions. I really do appreciate the time you and others take to give detailed answers and explanations. The info (especially the link re the sampling method) is really interesting..
With regard to your answer re the AVI rendering, if I understand your post, the AVI should be rendered with the same quality as long as there are no fx. I have no fx on the event (or track) at all – I simply dropped the file on the timeline, selected a 30 second region and rendered to AVI again, and the difference is noticeable.
I have no doubt it is something I am doing but can you suggest any possible areas to check?
Is it possible that third-party codecs could be an issue here? According to gspot (which I am only starting to understand), when I point it at the AVI there appears to be a number of different chains, but from the details I am not sure which ones come with Vegas, and which ones are from other applications (e.g. I can see one chain referencing a Pinnacle file, and one referencing a Roxio file).
If it is a possible codec issue is it possible to have vegas list the actual codec/dll files it is using?
I did see a reference in one post on the forum which said that in the Preferences/general tab there was a box to tell vegas to use its own codecs, but I cannot see it in VMS10…
Thanks again for all the help.
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“I simply dropped the file on the timeline, selected a 30 second region and rendered to AVI again, and the difference is noticeable.”
Stewart, that makes no sense whatsoever.
Just to confirm, are you rendering from and to a DV-AVI file?
How are you viewing the rendered file? -
Mike,
Too busy looking for the small things… Did not notice that within the avi template I had selected PAL/DVD – I changed it to ‘Default template – uncompressed’ – and rendered the loop – and on WMP (which is what I had been using) the quality looks like the original…
Starting to make sense now… thanks again for all your help. That link you gave me earlier on sent me off on about 3 hours reading…
Stewart
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“…I had selected PAL/DVD…”
I didn’t know that option existed as it doesn’t show up in Vegas Pro (7, 8 or 9).
“I changed it to ‘Default template – uncompressed’ – and rendered the loop – and on WMP (which is what I had been using) the quality looks like the original…”
The only drawback doing that is the huge file size.
Assuming your video came from a standard definition camcorder, then PAL DV or PAL DV Widescreen are the usual choices. -
Not sure whether you have spent a lot of time with this camera and other NLE’s, but DV on these ‘lower end’ cameras (although the camera is a 3 CCD camera it is a higher end consumer camera), the quality is never going to look as good on the final render as it does on the small LCD on the camera, nor on perhaps the smaller screen size you use with WMP. (at least that’s been my experience). And with HD footage all around you to compare to, it’s easy to be disappointed. You might try rendering out to BluRay in as uncompressed as possible, as I’ve seen DV become better looking on B.R. But not dramatically. Ultimately, the footage is probably going to look best displayed small on a monitor, like YouTube, rather than large. It likely won’t hold up as you ramp it up in size. With all the inexpensive HD cameras around, it may be that you want to consider moving to a better camera. Even your smallest HD cams like the Kodak is going to outperform that camera, I figure. I’ve seen footage from helmet cams for $200 USD that outperform my old SD Sony. Best of luck! Hope you find the right setting for your use. It always is a pain to have to upgrade cameras. And with 3D around the corner!
Alf
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Mike,
first, a typo on my part – should have said PAL/DV. If I set the option to that the quality was not exactly the same as the original, but if I choose ‘uncompressed’ it is…
In any case, I understand a lot more now, and experimenting has taught me a lot. I also have been adding a small amount of sharpening and it makes a difference.
Alf – thanks for the comments – I do of course understand that the camera is more a high-end consumer – but for a beginner the quality has been fine. I will be updating, but I really wanted to spend some time learning about what to look for in a camera first before rushing out any buying one, and the best way for me to learn is to try and work with its output to try and get it to its best, then at least I know what to look for in a camera..
Many thanks to all again for the advice and info..
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