Video/Audio settings and how much video fits on a DVD

Arcsoft's Showbiz 2 is the first PC software package that combines video capture, editing, and DVD authoring into a single program with a consistent user interface.   Prior to its introduction, it was necessary to learn to use a multitude of products to produce DVD videos.  The combination of the HP DVD Movie Writer with Arcsoft's Showbiz 2 is "beginner-friendly" for those who simply want to migrate their home videos to DVD using the HP Transfer Wizard and yet also includes features that are "expert-friendly" for those who want to exercise some of their creativity. 

This page is intended to help users who are curious about all the video and audio settings available from inside the Showbiz application.  The dc3000 allows the adjustment of bit rates and resolutions for the video as well as the audio.  If you are using the Transfer Wizards, you really don't need to worry about these settings because the software chooses them for you automatically.  These settings are available in the Capture menu of Showbiz by clicking the 'Setting' button down in the left hand corner next to the HP DVD Movie Writer dc3000 as shown in the image below.

I should mention here that the the 'Input' button will allow you to choose between Composite and S-video.  The primary differences between these two sources is that S-video has the color (chrominance) and brightness (luminance) signals separated whereas they are combined on Composite.   S-video usually allows for a better quality video image, although the quality difference between S-Video and Composite can be subtle.  You'll still need to connect the red/white audio connectors even if you're using S-video.  Some people think that S-Video includes the audio, but it does not.   You can also select this option in the 'Video Properties' page which is shown below.

Once you click on that the 'Setting' button, you will see a  properties page that look like the following:

Video Decoder

The Video Decoder settings above allow you to select between NTSC, PAL, and SECAM.  In general, this will happen automatically because the HP DVD Movie Writer tries to figure out the type of video source by the signals it sees.  The VCR Input and Output Enable have no effect and should be left with the default checkmarks.  So this page isn't very interesting.

Video Proc Amp

The Video Proc Amp page can be used to modify the properties such as Brightness, Contrast, Hue, etc.  In general, you won't need to make any changes to this page.  The values are optimized for the HP DVD Movie Writer.  If you have a video that has some problems with brightness, contrast, hue, etc., you can experiment to see if making changes to these settings improves the image quality.   You cannot make changes when the video is being previewed.  Whenever you access these controls, the video will stop which makes it a bit of a challenge to select the optimum values, but, like I mentioned, the defaults work fine for most videos.  All of these settings, except sharpness, can also be adjusted when you edit a project but if you do it during the edit, Showbiz will have to re-encode each and every frame.  I'll address this re-encoding later in the SmartRendering topic.
 

Video Properties

The dialog box above is the one that causes most confusion.  The motivation behind providing the capture video bit rates is to adjust the size of the .mpg file so that it has the desired quality and yet can still fit on a single DVD.   You'll notice that you can change the capture resolution, video source, and whether you capture in constant or variable bit rate.   The advantage of Variable Bit rate is that you can have a smaller overall file size since it allows the bit rate to increase when the motion in the video increases and fall back to a lower rate with the video doesn't have much motion.  If you set the minimum and peak rates to be 3000 and 7000 Kbps respectively, you might find in some videos that the overall file size will be smaller than setting it at 7000 Kbps constant, particularly if there isn't a lot of motion in the video.  However, it's impossible to predict what the size of the resulting video will be when you use variable rate, so you could push things a little too far and end up with a video that is just a little too big to fit on a DVD.   I used to try to squeeze as much video as I could on a DVD using variable rate, but after a few times found that I missed by a few percent which meant I had to start again.  So I began to use a constant bit  rate, which results in a very predictable file size.

It would be useful to point out the difference between the capacity of the DVD disk and how it relates to the size of the .mpg file captured with Showbiz.

A single layer writable DVD+R/W disk can hold 4.7x10^9 bytes of data.  In the case of DVD writable disks, this is advertised as 4.7GB.  However, 1 GB is  not always  1x10^9 bytes.  The reason for this is that a long time ago, some engineer noticed that 2^10 bits was very close to 1000 bits (it's actually 1024 bits).  He decided to refer to this quantity as 1 Kilobyte or 1KB even though it wasn't exactly 1000 bytes.  After all, this error is only off by 2.4% and since computers use binary, it was convenient to refer to 2^10 bits as a 1 KB.  However, the error gets compounded if you use a definition that 1MB is 1024 KB.  Then you have an error of 4.9%.   This error grows to 7.4% when you apply it to 1 GB being equal to 1024 MB.  So when you look at a file size on the Microsoft Windows operating system and it says a file is 4.37GB, it is actually 4.7x10^9  bytes and if you try to write a file that is larger than 4.37GB, you'll find it won't fit on a DVD.  So it's important to know when you're writing files to a DVD how its size is defined.

In addition, some of the disk is used to hold the file system directory and other information so you may find that you can't fit a set of files that takes up the entire 4.7x10^9 bytes on to a single DVD disk.  In the case of a DVD video, there are also the files that hold the chapter points, images, and audio information, so an MPEG file that is 4.37GB as defined by the Windows OS will not  fit on a single DVD.  It's best to allocate 10% of the disk as overhead for the file system and menu files.  But more importantly, you need to take into consideration the extra space required for the audio.

DVD Transfer Wizards

The dc3000 has two separate Video Transfer Wizards available that attempt to hide complexity from the user and automate the task of converting video tapes to DVDs.  Both of these Wizards will choose a  video capture rate that will ensure that the video will fit on the to the DVD by knowing in advance the length of the captured video file.  This allows the Wizard to adjust the video bit rate for optimal video quality that is still guaranteed to fit on to the disk.  In the case of the HP Transfer Wizard, which is the one that launches when you push the button with the red dot on the dc3000, these are the constant video bit rates it selects:

Video Length      Video capture bit rate

1 hour or less    7 Mbps
1 to 1.5 hours    4.8 Mbps
1.5 to 2 hours    3.2 Mbps

In the case of the Showbiz DVD Wizard, the bit rates are similar, except that it only allows a maximum of 1.5 hours (at 4.8 Mbps video rate) of video on a single DVD.  Please note that these values have changed over time as Showbiz has added support for other video resolutions and Dobly audio which now allow more video to be fit on to the DVD.

As you can see, the more video you want to fit on to a single disk, the lower the video bit rate that must be used.  In the case of 1 to 1.5 hours, you may not be able to tell the difference between the original video tape and the resulting DVD.  However, when you go beyond 1.5 hours, which means the video will be captured at 3.2 Mbps, you may see a kind of 'blockiness' in the higher motion scenes.  These artifacts will be most noticeable in higher resolution displays.  If you have a 13" TV, you can probably use the lowest rate  and still not detect the difference in video quality.  However, the trend in the future will be for larger, higher definition displays, so you shouldn't try to squeeze too much video on a single DVD unless you know that it will not be viewed on a high resolution display that will show the motion artifacts.   It's important to recognize that these motion artifacts will be more noticeable on a large computer monitor viewed from 2 feet away than they will be on a TV viewed from 10 feet away.  So you should use a TV at a normal viewing position to help determine whether the DVD video quality is sufficient.

One way to reduce motion artifacts is by reducing the screen resolution, but there is a downside to this.   The version of Showbiz that is included with the dc3000 only allows 'full D1' resolution to be written to the DVD disk.  Full D1 resolution for NTSC is 720x480 pixels.  It looks good on even a large screen TV and is the native format of commercial DVDs.   If you go to 1/2  D1 (352x480), the image quality will be reduced, but the motion artifacts will also be less  noticeable.   Some consumer electronics DVD recorders even allow 1/4 D1 resolution, which is 352x240 and if you're viewing them on a 13" TV, they might look OK and you can actually squeeze up to 6 hours of video on to a single 4.7 GB DVD disk (with Dolby audio), but on a large screen TV, video at this resolution will look very, very bad.  Incidentally, 1/4 D1 is the native resolution that VCDs use (which are recorded on to CDR/W disks) and if you want to experiment with 1/4 D1 resolution, try making a VCD of your video and it will help you determine if that's a viable way to permanently store your treasured memories.

Audio Properties

Now that we've talked about video bit rate, it would be worthwhile to discuss audio bit rates which are shown in the dialog box below.

You'll notice on this box that there is a way to change audio bit rates and sampling rates.  The audio bit rates that are available on the dc3000 are: 64, 96, 112, 128, 160, 192, 224, 256, 320, and 384 Kbps.   Since the audio rate on the DVD will be expanded to be 1500 Kbps, there's really no reason to set it any lower than the default of 224 Kbps.  In fact, it's probably better to adjust it higher, since  that has been beneficial in solving audio echo issues that some users have experienced.  Also, the sampling rate can be selected to be either 48KHz or 44.1 KHz.  You should leave it at 48 KHz since that is the native rate of the DVD specification so if you set it at 44.1 KHz, it will have to go through a sample rate conversion which requires time and has the potential for loss of audio quality.  The dc3000 may exhibit audio echo problems with rates below the default of 224 Kbps so it's best not to select audio rates below the default.  The audio encoding rate will always be much, much smaller than the video bit rate, so there's not too much incentive to fiddle with it to try to save space on the DVD especially since it will be expanded to 1500 Kbps PCM anyway.  On a DVD where you are trying to preserve maximum video quality, the audio rate won't be too much of a consideration since it will only represent a small fraction of the video rate.  It's only when you're not concerned with the video quality that the amount of space taken up by uncompressed PCM becomes an issue.

The DVD standard has several ways that audio data can be stored.  The most universal way to store audio is as uncompressed audio  known as PCM (pulse code modulation) which at  48KHz sampling, 16 bits per channel, will take an extra 650MB of disk space per hour (48000 samples per second * 16 bits/sample * 2 channels * 60 seconds per minute * 60 minutes per hour / 8 bits per byte = about 650MB/hour).  The audio that is captured with the dc3000 is compressed using a technique called MPEG Layer 2, which is similar to the MP3 (MPEG Layer 3) files we are all so familiar with when storing music on a PC.  However, compressed MPEG Layer 2 audio isn't compatible with all DVD players.   Showbiz automatically expands that compressed audio out into uncompressed PCM when it writes the DVD.  So even though you may be capturing your compressed audio at 224Kbps, the expanded audio will be 1500Kbps, which is how we end up with an extra 650MB per hour required to hold the audio data.  Therefore, you have to take into account this extra space requirement when writing a DVD.

As a side note, Dolby Digital (AC-3) is another form of audio compression which is part of the DVD specification in all regions.  Dolby Digital audio can range from 1 to 5.1 channels.  The bit rate for it can be from 64Kbps to 448Kbps.   The versions of Showbiz that shipped with the dc3000 and dc4000 did not have the capability to convert the MPEG Layer 2 to Dolby Digital, so we were limited to PCM as the default audio storage method.  The version of Showbiz that shipped with the dc5000 does have the ability to use Dolby audio as well as MPEG audio.  That version is available on the dc5000 installation CD which can be ordered through hp.com and will work with the dc3000 and dc4000 DVD Movie Writers.   With Dolby Audio, you won't have to allocate an extra 650MB/hour to store the audio information.

SmartRendering

I would like to discuss the Showbiz feature of SmartRendering which comes into play when you are editing your videos in Showbiz prior to making DVDs.  Basically, SmartRendering tries to avoid the re-encoding the unedited portions of the captured .mpg video file.  If you are using either of the DVD Transfer Wizards, SmartRendering will have no effect.  When you use either the HP Transfer Wizard or Showbiz QuickDVD, the .mpg files are not re-encoded using the software MPEG encoder inside Showbiz.  The advantage of not re-encoding the video is that it results in a higher quality video image since converting an MPEG image twice will reduce its video quality.  SmartRendering will attempt to use the .mpg video frames as captured from the HP DVD Movie Writer (with the exception of edited frames, which have to be re-encoded in software) and thus will be faster and produce a better overall image quality on the DVD.   To access SmartRendering, you can select it from the Options menu when you are either exporting files to the hard drive or creating a DVD in the 'Create' menu.

You can see above that the bit rates are grayed out when you use SmartRendering.  As long as you have captured the video at 7000 Kbps or less constant or  8000 Kbps Variable or less (peak rate), SmartRendering will only re-encode those frames that are edited, i.e., have added text, transitions, or effects.   You will need to upgrade to Showbiz 2.0.0.130 if you haven't done so already in order to take advantage of SmartRendering.  The Showbiz version that shipped with the dc3000 (2.0.0.124) had a bug which caused it to crash when writing the DVD when SmartRendering was enabled.  But now that it's fixed, I'd highly recommend you use it when authoring a DVD to make things go faster and have maximum video image quality.

There is also some confusion about how a 2-hour movie that your purchase on DVD can look so nice, yet it's difficult to get a video you capture to look as good.  First I'll mention that a video which is captured can never  look better than the source from which it is captured.  However, the main reason is that commercial DVD movies looks so good is because most of those disks use two layer recording, so they can hold up to 9GB.  The first layer is semi-transparent so after the player finishes about half the movie, it can focus down on to the second layer and play the other half of the movie.   Without the dual layer feature, it would be hard to record more than an hour of high quality video on to a DVD.  Only the dc5000 supports writing to dual layer DVD+R media.  The limitation is dependent on the hardware of the drive, so the dc3000 or dc4000 drives cannot be updated to write to dual layer DVDs.

I hope that this page has been useful and has taken some of the mystery out of the various settings and features in making your own DVDs.

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