Song Analysis Task beaTlet

When you select a bunch of songs in beaTunes and then click Analyze, you are presented with the Analysis Options dialog, which lists all available analysis tasks. A SongAnalysisTask is such a task. Even though it's listed in the dialog, it's a non-visual component that allows you to analyze songs. It is intended just for the metadata, not for the audio.

A good example is a task that simply copies the key information to the comments field, so that applications like iTunes, that don't support the key field, can still display the information.

To create a new SongAnalysisTask, we should override a couple of methods:

Also, to make sure that the task is persisted correctly, we need to annotate it with @Entity. Unfortunately, Java annotations are not supported in JRuby, Jython or JavaScript, which leaves only Groovy.

That's all. Here's an example that copies the key in to the comments field using Open Key Notation.

// Groovy

import com.tagtraum.audiokern.*
import com.tagtraum.audiokern.key.*
import com.tagtraum.beatunes.analysis.*
import org.slf4j.*

import javax.persistence.Entity

/**
 * Copies tonal open key info to the comments field.
 * THIS TASK REQUIRES beaTunes 3.5.17 OR LATER!!!
 */
// =============================================================================== //
// It is *essential* for this class to be annotated as Entity.                     //
// Otherwise it will not be saved in the analysis queue and cannot be processed.   //
// Annotations are only available in Java and Groovy, but not in JRuby or Jython.  //
// =============================================================================== //
@Entity
class OpenKeyToComment extends SongAnalysisTask {

    static log = LoggerFactory.getLogger("OpenKeyToComment.groovy")
    static String KEY_START_MARKER = "KEY:"
    static String KEY_END_MARKER = ";"


    def OpenKeyToComment() {
        // this task does not take long - therefore we ignore it in per task progress bars
        setProgressRelevant(false)
    }

    /**
     * Returns a verbose description of the task in HTML format. This is shown in the
     * Analysis Options dialog (left pane).
     *
     * @return verbose HTML description.
     */
    def String getDescription() {
        "<h1>OpenKey To Comment</h1><p>Copies the tonal key (if it exists) to the comment field.</p>"
    }

    /**
     * This will be the displayed name of the analysis task.
     *
     * @return HTML string
     */
    def String getName() {
        "<html>Copy open key<br>to comment field</html>"
    }

    /**
     * This is where the actual work occurs. This method is called by beaTunes when
     * this task is processed in the analysis/task queue.
     *
     * @throws AnalysisException if something goes wrong.
     */
    def void runBefore(Task task) throws AnalysisException {
        // check whether we can skip this step altogether
        if (skip()) {
            if (log.isDebugEnabled()) log.debug("Skipped " + getSong())
            return
        }
        // get the song object
        AudioSong song = getSong()
        // get the new comment
        String newComments = getNewComments(song)
        if (log.isDebugEnabled()) log.debug("Setting new comments to: " + newComments)
        // store new comment - the new value is automatically persisted and the UI is updated.
        song.setComments(newComments)
    }

    /**
     * Indicates, whether this task can be skipped.
     *
     * @return true or false
     */
    def boolean skip() {
        AudioSong song = getSong()
        String comments = song.getComments()
        Key commentsKey = getKey(comments)
        Key key = song.getKey()
        boolean skip = commentsKey != null && commentsKey.equals(key)
        if (log.isDebugEnabled()) log.debug("Skipping " + song + " ...")
        skip
    }

    /**
     * Creates a new comment string.
     *
     * @param song song
     * @return new comment (with key, if the song has a key)
     */
    private def String getNewComments(AudioSong song) {
        String comments = song.getComments() == null ? "" : song.getComments()
        if (hasCommentsKey(comments)) {
            comments = removeCommentsKey(comments)
        }
        if (song.getKey() != null) {
            comments = addCommentsKey(comments, song.getKey())
        }
        comments
    }

    /**
     * Indicates whether this comment contains a key.
     *
     * @param comments comment
     * @return true, if the comment contains a key
     */
    private def boolean hasCommentsKey(String comments) {
        getKey(comments) != null
    }

    /**
     * Extracts a key out of a comment string.
     *
     * @param comments comment
     * @return key or null, if not found
     */
    private def Key getKey(String comments) {
        Key keyObject
        if (comments == null || comments.length() < KEY_START_MARKER.length() + KEY_END_MARKER.length()) {
            keyObject = null
        } else {
            int start = comments.indexOf(KEY_START_MARKER)
            if (start == -1) {
                keyObject = null
            } else {
                int end = comments.indexOf(KEY_END_MARKER, start)
                if (end == -1) {
                    keyObject = null
                } else {
                    String key = comments.substring(start + KEY_START_MARKER.length(), end)
                    // parseKeyCode() parses OpenKey notation keys
                    keyObject = KeyFactory.parseKeyCode(key)
                }
            }
        }
        keyObject
    }

    /**
     * Removes a key from a comment string.
     *
     * @param comments comment
     * @return comment without the key
     */
    private def String removeCommentsKey(String comments) {
        int start = comments.indexOf(KEY_START_MARKER)
        int end = comments.indexOf(KEY_END_MARKER, start)
        if (comments.length() > end) return comments.substring(0, start) + comments.substring(end+1)
        comments.substring(0, start)
    }

    /**
     * Adds a key to a comment.
     *
     * @param comments comment
     * @param key key
     * @return new comment with key
     */
    private def String addCommentsKey(final String comments, final Key key) {
        comments + KEY_START_MARKER + key.getOpenKeyCode() + KEY_END_MARKER
    }

}

Now, if you don't really care about plain metadata, but love dealing with audio signals, go on and learn how to integrate your own audio analysis code.

Other beaTlet samples:

All sample beaTlets are also on GitHub .