Online Video Production Blog

One of the questions I am often asked is about when and how to compress videos for encoding to DVD.  While the "how" will have to wait for another post, I intend to discuss the pros and cons of compressing files prior to authoring and during authoring.

Just a little of background information. Most video editing applications edit videos at the best quality they can handle, for SD typically using a DV CODEC which is the same as the digital information stored on a MiniDV or DVCAM tape.  Other CODECS are used but this is by far the most common.  For HD, at a prosumer and domestic level this is typically (although becoming less so) in the HDV format.  Other HD CODECs are used but this needs to be saved for another post.

DVD's are compiled using the MPEG 2 CODEC using strict guidelines for the structure of this file and its bitrate, they need to be "authored" using software to meet the stringent standards set to ensure compatibility across a range of DVD players.

Some DVD authoring packages include; DVD Studio Pro, Adobe Encore, DVD Workshop, Pinnacle Studio.  All these packages will import a video file or an already converted MPG file as well as a range of still picture formats and audio files.  Once imported these files can be arranged to create a DVD you can burn using your DVD burner. (Freeware alternatives exist I just don't use them all that much)

There are two trains of thought when it comes to whether you should create MPG's first or just use the software itself to burn and encode the entire DVD. The first is to use a high quality encoder and create DVD compliant MPEG 2 files of your edited videos with specialist encoding software and then use the MPEG's in your authoring software. The second is to export full size files (or Quicktime reference files) of your edited videos and then get the authoring software to encode everything then burn the final product.

Lets look at the pros and cons of the first method, it will allow far more advanced configuration of the encode and to the experienced user I can suggest this is a good thing.  The files can be optimised for quality and size ensure the best balance of both. Stand alone encoders are built for the task of encoding and may present better encoding results.  The longest part of any build process after DVD authoring is always the encoding step, this method bypasses that resulting in a quicker result out of your authoring package. Of course you will still have had to encode the files prior to authoring but this may have been done during "downtime".

With larger files this method can present problems, the files you create need to be compressed enough to fit on your burnt DVD and while you can get bitrate calculators that allow you to calculate the right bitrate to fit your files duration on a burnt DVD, these calculators cannot presume how much space Menus and other DVD data may take up.  The result is that you usually compress the file a little more than needed to allow for "headroom" on the disk resulting in a less than optimal size vs quality ratio.

This method is great for experienced users who understand files sizes, bitrates and duration of video files and how they all interact with each other.

The second method of letting the DVD authoring software make the encoding calculations is one I would recommend to beginners. After authoring the disk the software makes a calculation based on all the content and starts encoding as required.  This ensures larger projects fill a disk,which should result in better picture quality.  The truth is the supplied encoders often aren't as good as specialised software so any benefits gained by this are often offset by the encoder quality. After completing the the authoring the encoding process can take a long time, this can be disappointing for those around you as they expect a DVD straight away.

I like using this method for long form editing etc as I have on more than one occasion used the first method and then had to re-encode an entire file (hours of time by the way) as my calculations weren't correct or I had more menus  or still than I imagined.  Due to this fact alone this method can save you time and minimise annoyance levels.

In conclusion I use both methods, certainly any videos under 20 minutes I use the first method as I am not able to max out the file size and maintain DVD compliance and the encoders do a better job.  For long form DVD I typically use the second method just so I save myself the annoyance of the ONE time where I get a calculation wrong. (It happened to me this week andheld up a projectby half a day...annoying!!)  Tread your own path and good luck with your authoring!!

How do you go about encoding your files?

NB  I have had issues with the Adobe Encore CS3 Encoder with Avid HD compressed Quicktime Reference files, it seems the bandwidth/filesize causes the encoder to hang sometimes.