What is this and why is it important?

Surround formats primarily refer to the number and placement of speakers.  While there are many surround formats, 5.1 (6 speakers) is the most common.

Large panner views are used to represent and change the 360-degree placement of the surround panning.  They normally also contain other surround-related controls such as width dispersion and center-channel volume.

The Low Frequency Effects (LFE) channel is used to enhance the bass.  There are several different formats which differ primarily in the frequency cutoff.  Some products take the position that since the surround specification stipulates that the audio reproduction system is responsible for bass management no frequency cutoff is necessary.

This category refers to the capability of applying FX plug-ins to a surround bus.  Ideally you would want to be able to control the FX separately for each channel (or channel pair). 

There are many cases in which a surround mix will need to also be exported in a stereo format.  Thus facilities for mixing the additional surround channels back to a 2-channel format are useful.

Surround mixes must be exported either as multiple mono channels or in a format, such as Windows Media Audio which supports surround.  None of the products support DVD formats.

What is this and why is it important?

There are a variety of video formats, so the more formats a product can handle the more functional it is.  As noted in the ratings explanation, the Windows products usually use the codec's available on your computer.

A video viewer is used for playing back video and for displaying the video frame at any given point on the timeline.

Since video is measured in frames, being able to display the timeline and current pointer position in frames is useful.

The Video Frame Strip is a track which displays video frames on the timeline.  This is useful in navigating to various points in the video.

Video editing in this case refers to simple cut, copy, paste and trim functions.  

What is this and why is it important?

There are several standards for software synthesizer plug-ins, all of which are proprietary.  VST is probably the most widely accepted.

A Freeze Synth function creates an audio track from the output of a synth and its associated MIDI input.  Being able to do this reduces CPU utilization.

It has become a standard practice to bundle third-party software synthesizers and rewire clients with music production products.  The type and quality of these synths varies greatly.  Some are available separately for free.

An Instrument Track is a MIDI track which also supports a software synthesizer.  This allows you to use a single track instead of two when you are routing MIDI to a soft synth.

Instrument layering is the ability to route MIDI tracks to multiple virtual instruments.  This feature allows you to layer different patches to create richer and more complex sounds.

Rewire is a real-time software interface between two products.  A rewire host can use a rewire client (or slave) as a plug-in.

What is this and why is it important?

WAV files can contain metadata specifying the tempo, number of beats and root note using the conventions popularized by Sony Acid.  This information is necessary for tempo shifting and pitch shifting.  Pro Tools recognizes Acid looping segments ("slices").  However, only some Acidized files contain this data.

REX is a file format popularized by Propellerhead Reason that embeds "slice" data corresponding to the beats in an audio file.  This format is useful for facilitating tempo changes.  Pro Tools and Cubase accommodate  REX clips in audio tracks and match the time slices with the timeline tempo.  Sonar uses MIDI events to trigger time slices in a sample player modeled after Propellerhead's Dr. Rex.

Alternative sequencing encompasses any paradigm of creating music other than arranging MIDI or audio clips serially on a timeline.  Cubase and Ableton receive higher ratings than Sonar because their methods apply to all types of tracks whereas the Sonar Step Sequencer is limited to drums.

Mirrored editing allows you to automatically apply changes to one clip to all other clips that have been replicated.

With this function you can change the tempo of your project at any point on the timeline and time tempo of all clips after this point will be adjusted on the fly.  Pro Tools provides real time tempo shifting for "sliced" files which is primarily useful for drums.

Logical event slicing means that logical time slices are created for an event which correspond to the beats within that event.  Physical time slicing means that the event is physically separated into multiple events.  Some people maintain that physical time slicing produces better results for drums.

Using batch time stretching can produce higher quality results than real time and does not increase CPU utilization during playback.

Automatic beat detection means that the product can automatically identify hitpoints in an audio file based on the transient peaks.

No automatic beat detection algorithm identifies the beats correctly all of the time.  It is essential to be able to add, delete, and change the timing of hitpoints manually.

Time stretching can produce artifacts and other undesirable results that make the clip sound unnatural.  Some products compensate for this by using different time stretching algorithms for different types of sounds--drums, vocals, etc.

Tempo extraction allows you to extract the timing from an audio clip and then apply the timing to a variable tempo track.  This function is useful when you have an audio clip with variable timing and want to sync other tracks to that clip.

With this function you can change the tempo of your project at any point on the timeline and time tempo of all clips after this point will be adjusted on the fly.

Using batch pitch shifting can produce higher quality results than real time and does not increase CPU utilization during playback.

Project key means that you can define an overall key or root note for a project.  It is unrelated to a MIDI key signature.  Root note means that you can identify a key or root note for each clip.  Both of the concepts are basically documentation since you can do pitch shifting with them.  However, they greatly facilitate managing pitch changes.

This function allows you to change the pitch of an individual clip in real time without changing the overall root note of the timeline.

Audio groove detection allows you to create a groove based on the beats of a clip which then  be applied to change the timing of the beats in another audio and/or MIDI clip (depending on the product).

MIDI groove detection allows you to create a groove based on the beats of a clip which then  be applied to change the timing of the beats in another audio and/or MIDI clip (depending on the product).

Groove pattern editing allows you to edit a beat pattern once it has been extracted from an audio or MIDI clip.

Audio groove mapping means applying a particular beat pattern to an audio clip in order to change the beat pattern.  Quantizing, for example, is a special instance of groove mapping.  Beat slicing chops the sample up into physically separate events based on the hitpoints.  Virtual groove mapping adjusts the hitpoints to change the beat using real-time time stretching.

MIDI groove mapping means applying a particular beat pattern to MIDI clip in order to change the beat pattern.  Quantizing, for example, is a special instance of groove mapping.

Many times your goal in applying a groove is to adopt the feel of an existing style--swing, hip hop, rock, shuffle, etc.   Having these styles readily available is a big plus.

A good library of audio and MIDI loops  increases the value of a product since otherwise you would have to purchase or create loops separately.