4
Table Of Contents
- Compressor 4 User Manual
- Contents
- Welcome to Compressor
- Getting Started Quickly
- Ways to Use Compressor
- The Basic Transcoding Workflow
- The Compressor Interface
- Compressor Windows and the Transcoding Workflow
- Creating and Managing Compressor Layouts
- Working with the Compressor Windows
- Batch Window
- Settings Tab
- Destinations Tab
- Inspector Window
- History Window
- Preview Window
- Apple Qmaster Sharing Window
- Share Monitor
- Droplet Windows
- About Changing Values and Timecode Entries
- Keyboard Shortcuts
- Setting Compressor Preferences
- Importing Source Media Files
- Creating, Previewing, and Modifying Settings
- Finalizing Jobs and Submitting Batches
- Creating AIFF Files
- Creating Common Audio Format Files
- Creating DV Stream Output Files
- Creating Dolby Digital Professional Output Files
- About the Dolby Digital Professional Encoder Pane
- General Information About Creating Dolby Digital Professional Files
- Converting Stereo Audio Files to Dolby Digital Professional Format
- Assigning Files to Surround Sound Channels (Manual Method)
- Assigning Files to Surround Sound Channels (Automatic Methods)
- Assigning Files to Surround Sound Channels with Droplets
- Options for Spatial Mixing
- Creating H.264 for Apple Devices Output Files
- Creating H.264 for Blu-ray Disc
- Creating Image Sequence Files
- Creating MP3 Output Files
- Creating MPEG-1 Output Files
- Common Uses for MPEG-1
- MPEG-1 Specifications
- About the MPEG-1 Encoder Pane
- About the MPEG-1 Video Tab
- About the MPEG-1 Audio Tab
- About System and Elementary Streams
- MPEG-1 Transcoding Workflow
- Configuring the MPEG-1 File Format for Web Use
- Configuring the MPEG-1 File Format for DVD Use
- Creating the MPEG-1 Video for DVD Setting
- Creating the MPEG-1 Audio for DVD Setting
- Optional—Creating an MPEG-1 for DVD Group and Destination
- Creating MPEG-2 Output Files
- Creating MPEG-4 Output Files
- About MPEG-4 Part 2
- About the MPEG-4 Part 2 Encoder Pane
- Using Default MPEG-4 Part 2 Settings
- Customizing MPEG-4 Part 2 Settings
- Audio Podcasting Workflow
- Stage 1: Configuring the MPEG-4 Output for Audio-Only Output
- Stage 2: Including Podcasting Information
- Stage 3: Applying the Setting to a Source Media File’s Target
- Stage 4: Entering Annotations for the Output Media File
- Stage 5: Creating and Configuring Markers for the Output Media File
- Stage 6: Submitting the Job and Verifying the Output Media File
- Adding Additional Settings and Presets
- Creating QuickTime Export Component Files
- Creating QuickTime Movie Output Files
- Adding Filters to a Setting
- Working with Frame Controls
- Adding Geometry Settings
- Adding Actions
- Using the Preview Window
- Creating and Changing Destinations
- Using Droplets
- Apple Qmaster and Distributed Processing
- Distributed Processing Basics
- Basic Components of the Apple Qmaster Distributed Processing System
- Getting Started Quickly Using This Computer Plus
- Getting Started Quickly Using QuickClusters
- The Interfaces in the Apple Qmaster Distributed Processing System
- Apple Qmaster Sharing Window of Compressor
- General Information About Clusters
- Options in the Apple Qmaster Sharing Window of Compressor
- Managed vs. Unmanaged Services
- Turning Cluster Controller Services On or Off
- Using Virtual Clusters to Make the Most of Multicore Computers
- Setting a Service Password for Including a Computer in a Cluster
- Scheduling Service Availability
- Using Cluster Storage
- Defining Ports for Service Advertisements
- Recovery and Failure Notification Features
- Creating Clusters with Apple Qadministrator
- Setting Up for Part-Time Distributed Processing with Shake
- Appendix A: Keyboard Shortcuts
- Appendix B: Solving Problems
- Appendix C: Using the Command Line
GOP Structure
This setting specifies whether there will be two, one, or no B-frames between the reference
frames within a GOP. GOP structure, along with GOP size, determines the number of I-,
P-, and B-frames that will be used during transcoding.
The GOP structure you choose depends on how far apart P-frames should be spaced.
Since a P-frame is predicted from the previous reference frame (either an I-frame or a
P-frame), if there are one or two B-frames in between, the prediction must cover the
distance objects can move over the duration of two to three frames.
In principle, the less average motion there is from one frame to the next, the farther apart
P-frames can be spaced, and the greater the compression can be. For most video material,
the IBBP structure is a good choice. Material with unusually fast motion throughout the
entire sequence may benefit from an IBP or IP structure, but in such cases a relatively
high bit rate (6 to 8 Mbps for SD video) may be required for good quality.
GOP Size
This setting specifies the number of frames within a GOP. Because exactly one I-frame
exists per GOP, longer GOP sizes generally provide greater compression, because B- and
P-frames are smaller than I-frames.
For most media, spacing I-frames about 1/2 second apart gives good results. This equates
to a GOP size of 15 frames for NTSC and 12 frames for PAL. The DVD-Video specification
prohibits GOP lengths from being much longer than this. Generally, only material with
scene changes occurring less than 1/2 second apart frequently throughout the video will
benefit from shorter GOP sizes.
Open and Closed GOPs
Open GOPs are most efficient because they allow an extra B-frame in the GOP pattern.
Open GOPs start with a B-frame that is able to look at the last P-frame from the preceding
GOP as well as the first I-frame of its own GOP.
:06 :07 :08 :09
:09
:10 :11 :12 :13 :14 :15 :16 :17 :18 :19 :20 :21:04 :05
Open GOP
(IBBP, 15 frames)
I B B P B B P B B P B B P B B IB BP
:03
:06 :07 :08 :10 :11 :12 :13 :14 :15 :16 :17 :18:04 :05
Closed GOP
(IBBP, 15 frames)
P B B P B P B P B PI B BBB
210 Chapter 18 Creating MPEG-2 Output Files