MPEG-2 Transcoding Workflow

This section includes step-by-step instructions for setting your MPEG-2 attributes prior to creating MPEG-2 output files with Compressor. Make your MPEG-2 settings from the MPEG-2 Encoder pane by either modifying an existing setting or creating a new one in the Settings tab.

See the following steps for working with the MPEG-2 output file format. For example values for each of these settings, see Example MPEG-2 Settings.

Stage 1: Choosing Video Format Settings

It’s important to match the video format, aspect ratio, and field dominance to those of your source media file. See Video Format Tab for a more detailed description of each of these settings.

Note: The easiest way to make sure you are matching the source media file is to activate the Automatic buttons. See About the Automatic Settings for more information.

To open the MPEG-2 Encoder pane and choose Video Format settings
  1. Open the Settings tab, then choose MPEG-2 from the Add Preset (+) pop-up menu button.

    The MPEG-2 Encoder pane opens in the Inspector window with the default Video Format tab displayed.

    Figure. Stream Usage pop-up menu and Video Format tab of the MPEG-2 Encoder pane in the Inspector window.
  2. Choose the setting from the Stream Usage pop-up menu that matches how you intend to use the encoded video. This ensures that the MPEG-2 encoding options are restricted to those that are supported by your intended usage. The options include:

    • Generic

    • SD DVD

    • Blu-ray

    • HD DVD

  3. Choose a format from the Video Format pop-up menu or select its Automatic button:

    • NTSC (default)

    • PAL

    • 720p

    • HD 1440x1080

    • HD 1920x1080

    • 640x480

    • 640x360

    • 640x352

    • 640x384

    • 640x320

  4. Choose an aspect ratio from the Aspect Ratio pop-up menu or select its Automatic button.

    You must determine whether the intended shape of your source video is 4:3 (normal) or 16:9 (widescreen) before you can choose your aspect ratio.

  5. Choose a field dominance setting based on your source media type from the Field Dominance pop-up menu. For example, for DV choose Bottom First. Or choose the Field Dominance Automatic button to let Compressor determine the correct setting.

  6. If you want to use the timecode from your source video, leave the “Choose start timecode” checkbox unselected. Otherwise, select this checkbox and enter a new timecode.

  7. If you have selected the “Choose start timecode” checkbox, and if your video format is NTSC, select the “drop frame” checkbox if you want to use drop frame (rather than non-drop frame) timecode.

    See Video Format Tab for more information.

Stage 2: Choosing Quality Settings

In the Quality tab, you set the MPEG-2 encoding attributes that have the greatest influence on the resulting quality of your MPEG-2 video output file: encoding mode, average and maximum bit rate, and type of motion estimation.

To open the Quality tab and choose the Quality settings
  1. Click the Quality button in the MPEG-2 Encoder pane to open the Quality tab.

    Figure. Quality tab.
  2. Make a selection from the Mode pop-up menu.

    For best image quality, choose “One pass VBR Best” or “Two pass VBR Best.” For faster encoding, with excellent image quality, choose “One pass VBR” or “Two pass VBR.” For HD sources, choose either “One pass VBR Best” or “Two pass VBR Best.”

    With two-pass modes, the source media file is examined on the first pass and transcoded on the second pass, with bit rates tailored to the video content. Alternatively, one-pass modes transcode the material more quickly, but allocate bits less optimally than do the corresponding two-pass modes.

    Note: If you are using two-pass VBR with distributed processing enabled, you may want to deselect the “Allow Job Segmenting” checkbox in the Encoder pane. See Job Segmenting and Two-Pass or Multi-Pass Encoding for more information.

  3. Choose an average bit rate using the Average Bit Rate slider or field.

    Choose an appropriate bit rate based on the content and length of your source video and the intended size (in bytes) of your output file. In DVD authoring, the entire video must fit on the DVD disc—the lower the bit rate, the more data you can store. However, the higher the bit rate, the better the image quality will be.

    As you change the Average Bit Rate value (with the slider or the field), the bit-rate calculator at the bottom of the Quality tab dynamically shows the maximum number of minutes of video on a DVD-5. The calculator assumes 1.5 Mbps for audio (two-channel AIFF).

    See the table below for some average bit rates and corresponding footage times for a 4.7 GB DVD.

  4. If available, use the Maximum Bit Rate slider or field to set a maximum bit rate.

    Because SD DVD players support peak bit rates of up to 10.08 Mbps for video plus audio, you should set the maximum video bit rate between 8.0 and 8.5 Mbps if you are using a 1.5 Mbps (two-channel AIFF) audio track.

    Note: For best results, make sure the maximum bit rate is at least 1 Mbps higher than the average setting. Larger differences can produce better results.

  5. Choose one of the following settings from the Motion Estimation pop-up menu:

    • Good: The fastest motion estimation setting—sufficient when there is relatively low motion between frames
    • Better: A good general-purpose motion estimation setting—provides very good results even in the presence of complex interlaced motion
    • Best: The highest quality setting to handle the most demanding and complex motion for interlaced sources—somewhat slower than the Better mode

    See Quality Tab for more information.

The following table shows some average bit rates and corresponding footage times for a 4.7 GB DVD:

Average bit rate1
Approximate duration for 4.7 GB DVD
3.5 Mbps
121 minutes
5.0 Mbps
94 minutes
6.0 Mbps
82 minutes
7.5 Mbps
68 minutes
8.0 Mbps
65 minutes

For a DVD clip with video, audio, and subpictures: assumes 1.5 Mbps for audio (two-channel AIFF).

Note: When “One pass VBR or “One pass VBR Best” is chosen for very short clips (less than a minute or two in length), the resulting MPEG-2 output file size may not accurately reflect the average bit rate you specified. If the MPEG-2 output media file is larger than you want, you can try transcoding it again at a lower average bit rate.

Stage 3: Choosing GOP Settings

Select a suitable GOP structure and size and decide whether you want the GOPs to be open or closed.

Note: These settings are not adjustable if you chose an HD video format in the Video Format tab.

To open the GOP tab and choose GOP settings
  1. Click the GOP button in the MPEG-2 Encoder pane to open the GOP tab.

    Figure. GOP tab.
  2. Choose a GOP structure from the GOP Structure pop-up menu.

    For the majority of MPEG-2 encoding jobs for DVD authoring, choose the IBBP GOP structure.

  3. Choose a GOP size from the GOP Size pop-up menu.

    For the majority of MPEG-2 encoding jobs for DVD authoring, choose GOP size 15 for NTSC and GOP size 12 for PAL and 24p.

    The options available in this menu are determined by the GOP structure you choose and by whether or not the GOP is open or closed.

  4. Decide whether you want the GOP pattern to be open or closed and click the appropriate button.

Working with MPEG-2 I-Frames

The Compressor Preview window offers additional MPEG-2 transcoding flexibility by allowing you to manually insert I-frames into your output MPEG-2 file at any frame location, regardless of your chosen GOP pattern and size. These are known as forced I-frames, and may be useful for improving the quality of the MPEG-2 file in the vicinity of the scene change. See Understanding GOPs and Frame Types for more information on I-frames.

In addition, adding I-frames to your clip allows you to create chapter markers that DVD Studio Pro can understand and use. See Adding Markers to a Clip and Adding Chapter or Podcast Markers to a Clip for more information.

See Understanding GOPs and Frame Types, Things to Consider When Choosing a GOP Setting, More About GOPs and Markers, and GOP Tab for more information about GOPs.

Stage 4: Choosing Extras Settings

You can control the inclusion or exclusion of specific MPEG-2 authoring information in the Extras tab.

To open the Extras tab and choose Extras settings
  1. Click the Extras button in the MPEG-2 Encoder pane to open the Extras tab.

    Figure. Extras tab.
  2. Select the “Add DVD Studio Pro metadata” checkbox if you want Compressor to parse specific MPEG-2 authoring information rather than parse the information later in DVD Studio Pro.

    Important: Selecting this checkbox may make your MPEG-2 files incompatible with any DVD authoring tools other than DVD Studio Pro 2 (or later).

  3. Select the “Include chapter markers only” checkbox if you want to exclude automatic compression markers from the stream but still retain the chapter markers.

  4. Select the Multiplexed MPEG-1/layer 2 Audio checkbox only if you need to create transport or program streams. See About Elementary, Transport, and Program Streams for more information.

    See Extras Tab and More About GOPs and Markers for more information about settings in the Extras tab.

    Also, to make it easier to use the output files created by these presets in DVD Studio Pro, create a destination that ensures the video and audio output files have the same name, only with different file extensions. See Creating Destinations for Use with DVD Studio Pro for more information.