Compressor

K

Kandinsky

Active member
Hi everybody. I am now trying to export a video i've made with my DVX100a through Compressor so it can be burned on a DVD in the MPEG2 format. I would like you guys to share your past experiences regarding this matter.

Is is better to use Apple's compressor 2 or another program to have the best possible results in MPEG2 ?

Do you use a preset for compressing ? If yes, which one ?

What is the bitrate (min/max) that you generally prefer for a short film of 20 minutes (that offers both great quality and compatibility on DVD-R) ?

Do you use any of the other optional settings such as the noise reducer or some subtle edge sharpening ?

I have noticed in my first experience (where I have used a preset and didn't touch anything) that the footage looks considerably brighter once transfered on DVD in MPEG2 using DVD Studio Pro, and, partly because of that, it seems that the image becomes a bit more noisy. Do you guys use sometimes a +0.1 gamma on the whole sequence ?

Thank you.
 
While I own and have used Compressor it's not my MPEG2 encoder of choice. I use MainConcept on the mac.
However you will get results that are fine with Compressor. Below are some of the settings I would suggest for compressor.

Datarate settings are only an issue as you program lengths get up to and beyond 1 hour. A longer program requires a lower datarate to 'fit' onto a single layer DVD-r. At 20 minutes you need not worry about having to reducee your datarate to fit the program onto a DVD.

So all you need worry about with a 20 minute program is getting the higest datarate possible *without* going too high that you final DVD fails to play on DVD settop players.
The total allowed datarate for a DVD is 9.8Mbits - this includes audio... so when you encode the video portion of you program to mpeg2 you need to leave aside enough 'space' for the audio. The best way to ensure audio is not going to take up too much space is to encode it to AC-3.(using compressor). I suggest the audio datarate for AC-3 be 160Kbits.

If you used say 160Kbits for audio and the total datarate is 9.8Mbits (9800Kbits) that theoretically leaves about 9.6Mbits.
Unfortunately you can't be sure datarates that high will be able to be handled playing off DVD-r by all DVD players.
General consensus is that you want to aim for between 6 and 8Mbits total, Personally - to ensure compatibility - I use a total datarate of 6.5Mbits. You can go higher but be aware that compatibility may drop off the higher you go.

At a total of 6.5M bit with audio at 160Kbit leaves 6.34Mbit for the mpeg2 encode.

I would suggest not using things like noise reduction or edge sharpening. If your source footage looks good then no need to mess with settings that alter the look of the film. If there is a lot of noise or other issues with the film there are better programs than compressor to deal with them.

Try these settings in compressor:
mode: two pass VBR
Average bit rate: 5.3
Maximum bit rate: 6.3
motion estimation: best

as to which gamma setting to use - I don't really know - use google and search for 'compressor gamma settings' and see what you find.

kind regards

Steve Griffiths
Sydney Australia
 
Thank you very much Steve for your comments. I would love it if, like Steve did, many people could share their valuable experience in compression in this thread. It could become a source of reference for anybody who would like to learn more about DVD authoring.
 
Steve : How do you think MainConcept is superior to Compressor on the mac ? Because of the user-interface or maybe the results are significantly better ?
 
Kandinsky said:
Steve : How do you think MainConcept is superior to Compressor on the mac ? Because of the user-interface or maybe the results are significantly better ?
Click to expand...

It's faster and has very advanced controls (if you need them) and my personal opinion is it gives better results. However it's not very intuitive and the manual is lacking. Another mpeg2 encoder that is also very good on the mac is Bitvice - about the same price as Mainconcept and with a much simpler interface. It's also (in my opinion) better than Compressor.
... but compressor is not a terrible encoder by any means. You can get good results.
 
Kandinsky said:
I have noticed in my first experience (where I have used a preset and didn't touch anything) that the footage looks considerably brighter once transfered on DVD in MPEG2 using DVD Studio Pro, and, partly because of that, it seems that the image becomes a bit more noisy. Do you guys use sometimes a +0.1 gamma on the whole sequence ?
Click to expand...

Hi,
I was just wondering if you were comparing the before footage on your computer screen to the after footage on your TV. If you were, I'd suggest you to do the final review with NTSC monitor before putting it on DVD. If you weren't, please forget about my post.
 
This is what I posted under FCP couple days ago.

This is what I posted under FCP couple days ago.

Well, I had tried Compressor 1 for a good while to come out with a watchable video, but never made it, so I stopped using it and made a move over to Sorenson Squeeze, instead. During my experience with Sorenson Squeeze, I'd talk real bad things about Compressor.

Just a few weeks ago, I was asked, again, about Compressor by a friend who just bought and installed FCP Studio. I went over to his place to show him how to export a .mov file to compress with Sorenson Squeeze. After that short lecture, I decided to show him how bad compress was. However, Compressor 2 gave us a good quality video! So I told my buddy, *well, I guess they've done a good upgrade.* However, I later figured out that it wasn't Compressor's problem, but mine. The first time I used Compressor 1, I didn't really have proper knowledge on video compressing.

Anyways, there are a few things, if not more, to consider and tell Compressor to perform. Please correct me if I'm wrong or there's more.

1. Keyframe: this is basically how compression's done. Compressor compresses what's between two keyframes. For example, if you put 24, it will compress based on the movements in between every 24 frames. The smaller number you give, the better quality you will get, but the larger the size of file you will get. It's recommended to start with 10, and go from there.

2. Method of calculation: Either 1 or 2 pass, and either CBR or VBR. This is to tell the compressor how many times to calculate before actually compressing. There's no doubt 2 pass gives you better result. If there's more movement than static image on your video, it is highly recommended to perform 2 pass so that it carefully looks through your footage. CBR is recommended if there's less movement or no-movement at all. I, personally, recommend not to use it if there's any movement at all, either camera's or objects'. VBR, Variable BitRate, compresses based on how heavy the movement is at any given moment of your video.

3. Maximum size of data per second: Even though Compressor is supposed to does all the calculation for you, you should be the one actually calculates to make the best possible video. For example, if you're compressing for DVD, you should calculate so that it comes out to be less than the amount of data your DVD accepts. Also, there's a certain number that you shouldn't exceed, but I can't think of the exact number right now. I think it's somewhere around 700,000bps. Don't quote on me and look up on either FCP or Compressor manual. If you exceed that number, it won't play right. It's also one of the causes which makes DVD Studio Pro fail to burn.

These three things are the basic elements that you need to be aware of to make compression happen. To further make your video look the best (and who doesn't wnat to?), you should use Compression Markers on FCP during editing. By putting markers at the beggining and the end of where you see any heavy movement, you tell compressor to compress less so that there won't be any artifacts. You can do so by typing *<compression>* in where you make notes about makers by hitting keyboard *M* one more time after hitting *M* to put a marker. There are a couple of rules that I don't really remember, but it's like there should be at least two frames in between two compression markers, and so on. Also, if you bring out Compressor in FCP, Compressor automatically puts compression makers, which is keyframes, on every cut there is.

Please bare with my english since it's not my first language. I'm sure I forgot to mention something, so reply if there's any other questions. This should give you good results. FCP itself does a wonderful compressing job, too. Happy comression!
 
janghos said:
Hi,
I was just wondering if you were comparing the before footage on your computer screen to the after footage on your TV. If you were, I'd suggest you to do the final review with NTSC monitor before putting it on DVD. If you weren't, please forget about my post.
Click to expand...

Hi Janghos. No, I'm always linked to my NTSC widescreen television while editing and my settings are the same for this video input and for my DVD input. But I believe that most televisions are set up to be brighter than normal in default mode. That's why I thought that it might be a good idea to reduce the gamma a little to compensate (most people would not see the difference, but i'm a bit of a maniac when it comes to my images).

I also think that the compression marker advice is definitely the solution to my problems even though I didn't try it yet. Most of the footage looked fine, except for some dissolves and one voluntarily underexposed shot. I will try the markers on those. Hopefully it will solve my problem.

I might also try SteveG's suggestion regarding the Mainconcept encoder.

Thanks guys.
 
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