General Questions on Smart Render & MPEG Optimiser

[glbpro]

Hello everyone, greetings from Singapore.

I've been a user of Corel Video Studio for several years now, having purchased X2 and recently upgraded to X4. I have a couple of general questions about smart render and the MPEG optimiser. I have searched the forums and have not been able to find posts addressing these exact issues. I have also looked in my online owner's manual and in the knowledge base on the Corel website.

First of all, is smart render still considered a no-no when working with HD video files? I came across one post from one of the list admins advising against using smart render with HD files.

Secondly, am I correct that smart render is designed mainly for use when doing 'draft' renders, ie as a time saving device? As a rule, when doing my final rendering of a project (using HD files), should I keep it off?

Thirdly, I notice that when creating a file with and without smart render, the file created without smart render is substantially bigger, even though it has the same resolution, frame rate, length etc as the other one. Why is this? I am rendering from AVCHD files to MPEG files.

Finally, what is the relationship between the MPEG optimiser and smart render? Will switching off smart render defeat the MPEG optimiser?

Thanks and regards,

Bruno Goh Luse

[Carroll]

I too would like to have the answers to Bruno Goh Luse's questions.

Carroll

[lata]

Hi

Sorry you haven’t had any replies, I must admit I stayed clear because of the reference to HD which I don’t use, still to upgrade the camera from standard definition. Besides being quite a challenging subject.

Ok my thoughts on Smart Render.
I work mainly with DV Avi, if I edit my video removing the unwanted frames, add a few transitions and titles, the normal stuff, then Smart Render will recognise the edited portions and fully render them, the untouched sections renders much quicker. That’s assuming I am rendering from Dv-Avi to Dv-Avi.

If I render from DV-Avi to say Mpeg2 then all frames have to be rendered, so in effect smart render would have little or no effect. At least that’s the way I interpret it.

So if you are using AVCHD 1920 x 1080 and rendering to standard Mpeg 720 x 576 (480) then again SR would have little effect as all frame s have to be altered.
I think it was Ken that disabled SM when working with HD, so guess we will have to wait for his comments.
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As for file size, very surprised that Smart Render affects the file sizes, generally the Bit Rate is responsible for file size, given time I will run a few test renders.
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Mpeg Optomiser
Has nothing to do with Smart Render, the optimiser is purely an auto template that the program suggests you use, in the same way that you could create your own or in fact use any option from Share Create Video File. Choosing the Optimised template then opens the Create Video File window, the properties used to render are shown in the lower panel in the same manner as any other template.
The options button allows you to disable Smart Render.
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Draft or not----Smart Render is just a tool to reduce the render times, rendering some video types does cause some reduction in quality, however I doubt if you will see any reduction with the first few renders, most users only render the once anyway,
As Smart Render does not affect the un-edited portions which I suppose are copied rather than rendered, the edited bits being fully rendered, so most of the video is as original.

Unfortunately there have been some quality issues when using Smart Render for some types of video file, disabling has cured this. Nobody said it was magic.

Draft / Final Renders, some users say that the Resampling Quality should be set to Best for your final render, (F6) Preferences-Edit tab.
In my view I only do one render and that is for the final output, so its always set to Best.

[Natal]

Draft or not----Smart Render is just a tool to reduce the render times, rendering some video types does cause some reduction in quality, however I doubt if you will see any reduction with the first few renders, most users only render the once anyway,

If you are using a highly compressed format, and then re-render that, you most certainly will see a reduction in quality. The reason being is that the original compression reduces space by making "like" areas more "like" and thus compressable. When you rerender that, you effectively decompress those frames, then recompress it again, making those "more like" areas even more "more like" in local areas. So some parts of the frame have high resolution and other parts extremely low resolution, which is very obvious and disconcerting, particularly in footage that has highly detailed backdrops. That is what creates the mobile giant pixels you see in the background of some edited footage.

That is the point of Smart Render - to avoid that. Your camera will almost certainly do a vastly better job at rendering a scene than VS.

[Carroll]

Thank you Trevor and NATAL for the help.

[glbpro]

Dear All,

Thank you for your replies, much appreciated.

From what you have said, it sounds to me like smart render will only save time when your output format is the same, ie when only some of the frames need to be re-rendered. Seeing as I a always rendering from AVCHD to MPEG, it looks like smart render will not be of any use to me. The same would apply to MPEG optimiser, seeing as I am rendering to MPEG from another format.

Does Corel Video studio have an option to output AVCHD files? I am under the impression that this format is only for use by video cameras.

On the matter of file size, you're right that what changes is the bitrate - on one file that I did, the bitrate using smart render was 9000+ and without smart render was over 22000. Any idea why this is?

Regards,

Bruno

[lata]

Hi Bruno

First Smart Render is something I don’t worry about, it is on by default and unless I have I problem that’s the way it remains.

AVCHD
Yes Video Studio can edit and create these video types, go to Share Create Video file, in the list is Avchd.

There are many different types of video files using a variety of settings, AVI, Mpeg2, Avchd, HDMV, Div X, Mov etc
Frame sizes, rates may vary, Each type packing the information a little differently, some are highly compressed.
The bit rate also varies depending on the type, Mpeg 2 is used for standard DVD and uses a max bit rate approx 9000kbps
High definition 25000kbps depending on the type of HD
WMV is relatively low in the hundreds.

Right click the video file in the library or timeline and select Properties, note the Compression type and bit rate?

Your Mpeg files use 9000kbps, this allows you to fit approx 60 minutes to a disc.
Reduce this to 6000kbps and you will fit 90 minutes to the disc, the quality will reduce a little whether this is noticeable is in the eye………

Hope that helps a little

[glbpro]

Hi Bruno

AVCHD
Yes Video Studio can edit and create these video types, go to Share Create Video file, in the list is Avchd.

Sure enough! I wonder why I never noticed that option in the list before... I guess I just wasn't looking properly.

I see that there are two types of AVCHD files listed, one with a P and one without eg 1440 x 1080P and 1440 x 1080. The only difference between them appears to be that one is upper field first and the other is frame based. Could I ask what this means? The footage from my camera is upper field first.

I just did a test render of a project that I recently completed to see Smart Render in action - I rendered from AVCHD to AVCHD, and the render time was definitely reduced, from real time to about 10 mins for a 28 min video. I didn't notice any reduction in quality or problems with the audio so that's great. Comparing the rendered AVCHD file to an MPEG rendering with smart render turned off, the results were interesting:

AVCHD rendering: 1.56GB, bitrate 7971kbps
HD MPEG rendering: 2.20GB, bitrate 11248 kbps

This makes quite a bit of difference when it comes to upload time! Is the higher bitrate of the MPEG file due to the fact that it has to be converted?

My main purpose when rendering at the moment is to upload to youtube - would that be MP4 HD? Would it be better to upload in AVCHD and let YouTube do the conversion or convert to MP4 and then upload?

Many thanks for your help! Your answers have really helped to explain a topic that should get much more extensive coverage in the user's manual.

Regards,

Bruno

[lata]

Hi
I will try to give you a quick answer……..

Interlacing, well we perceive our video as having individual frames, just like a series of Jpeg images representing the frame. For Pal there are 25 per second

Interlacing was developed to reduce flicker when viewing on a TV. This literally split the frame into two sets of individual lines, each being transmitted separately then put together. They were identified as Frame A and Frame B aka Upper and Lower fields. (lower field being A)

All analogue video used Upper Field as does HD video.
DV-Avi from a mini DV camcorder used Lower Field.
Just to confuse things HD can also use Frame Based, known as Progressive.

The basic rule is if your original video uses Upper then you should keep using “upper” for your final render, do not use Lower, with the exception of the internet.

The internet uses Frame Based, this is a full frame.

Video Studio gives the option to upload to the Web, choose Mpeg4 HD 16:9 and you will render a suitable video for You Tube. However Video Studio limits the size of video, Using Make Movie Templates Manager you can create the same template allowing you to render video for YouTube, overcoming the limitation of the Web Upload approach.

The frame size is 1280 x 720, using a calculator you will see that this is 16:9 ratio.

If you wish to reduce the size for uploading then you reduce the bit rate, this in turn reduces the quality
A bit of a juggling act.

Hope this helps a little, the interlacing subject is quite involved but the above should give you a feel of what’s going on.

[glbpro]

Thanks for the reply and explanation, they were very helpful and all help add pieces to my understanding of how the programme works.

I've been doing lots of trial renders this week and it looks like it's better to upload to YouTube in MP4 if possible, because sometimes YouTube messes up the videos - this week I had a video which I had to upload three times - the first two attempts the length of the video doubled - the playback speed slowed to half but the audio was unaffected. No idea how that happened...

Thanks for sharing your knowledge!

regards,

Bruno