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24p NTSC DVD Creation using Sorenson Squeeze

(Windows versions only)

Michael Phillips

One of the advantages of working on a native 24p project (or 23.976) is the ability to create what is referred to as a "progressive DVD." DVD has the ability to payback material that is 24p native and insert the 2:3 pulldown for NTSC viewing. This allows for 20% more program to fit on a DVD for the same bit rate, or a higher quality bit rate for the same length program. The MPEG2 encoding process adds a 2:3 pulldown flag to the frames telling the player how to create the NTSC signal. This allows for very clean still frame advance (no interfield motion twitter) as well as a smooth playback on either progressive or interlace monitors. Working progressively also allows the frame to retain its full vertical resolution throughout the process and the steps outlined here for Sorenson Squeeze are also valid for 30p and 25p except for the references to the NTSC pulldown from a 24fps frame rate.

Step 1

Export sequence from the Avid bin using the "Send to" command. This is available via a "right click."

Once the send to process is done, a new dialog box appears with the "Send to" command and other settings. Applications can be added to the "Send to" by clicking the menu and selecting the "Add Item." The operating system navigation will open. Select the application of choice ­ in this case "Sorenson Squeeze."

Once OK is clicked, a "master" QuickTime reference movie is created as well as an audio file. All effects for picture and sound are rendered (mastered) and the Sorenson Squeeze application is launched. The user just needs to drag the QuickTime reference movie to the window for the MPEG2 encoding processing to begin.

Step 2

You can select NTSC LARGE as a preset and then tweak the MPEG2 settings, or create a new custom setting and select MPEG as your desired output. Once "custom setting" is selected, you are presented with all the outputs available:

Select MPEG from the TABS at the top of the window. In order to prepare MPEG2 for DVD authoring applications, most of them expect "elementary" streams where the picture and audio are treated separately and joined in the authoring application for the final DVD multiplexing process. Select ELEMENTARY from the stream type:

The select MPEG2 as the video output format:

Once selected, click on the options button and be sure to select "progressive" as your source:

The pixel aspect ratio is dependent on your source media. If your source media is 4:3 or has any type of letterboxing, select 4:3. Only select 16:9 if your sources are 16:9 anamorphic (appear tall and thin on a 4:3 monitor). Selecting this will indicate to the DVD player to "squeeze" the image down on a 4:3 monitor, or display full frame on a 16:9 monitor. Now make sure that the FORMAT is set to NTSC (PAL sources will select accordingly) and this sets the rate to 29.97. Even though the sources are 23.976 or 24p, this step indicates to the encoding process that the 2:3 flags need to be inserted into the MPEG2 stream to be decoded later by the DVDV player.

Select either constant bit rate or variable frame rate depending on your own needs. If you need more room on the DVD for longer programs, select "variable." Also the data rate needs to be entered as required. DVD specification cannot be more than 9.8Mbs and that is only in bursts. Most "Hollywood" style DVD's are encoded to an average of 6.5 ­ 8Mbs variable depending on length of movie, single sided, dual layer DVD etc. Now make sure that 720 is selected for the "Frame Size":

Once selected, 480 will automatically be selected as the NTSC DVD frame size of 720x480. Select a low I frame as most DVD authoring applications do not deal with higher numbers. I also like to select an "I frame" that is evenly divisible by the source frame rate (24fps). In this case, 6 is selected:

Please select audio settings as supported by the authoring application. PCM is the most basic and is supported by all applications but also takes up the most space on disc so plan accordingly. Save these settings and they will now be available as a preset for all future MPEG2 encodings.

Step 3

This step is very important and it is not saved as part of the MPEG settings. You need to select from the main menu bar the "Filter settings" to finalize the last setting needed to create "progressively encoded MPEG2."

In the "Filter Settings" window, go to the "Auto Remove Interlacing" menu pick and select "NONE." Even though "Auto Remove Interlacing" is the default setting, this

assumes that there the source is still interlace regardless of the "progressive" setting in the MPEG2 options and try to remove interlacing by playing with field order and pulldown cadence.

You are now ready to encode the files. At the end of the process you will have a video and audio mpeg file ready to be used by the DVD authoring application. There are cases when working with anamorphic sources, there can be a half line of black in the visible picture. When viewed on a 4:3 monitor, the ½ line is visible as part of the "letterbox" area. If this is an issue, Select "custom" from the Cropping menu and enter 1 or 2 for the "B" (bottom) and it will be cropped accordingly.


Microsoft Word - 24p DVD creation v.2

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