Add gstreamer-less flac encoder and tagging (#121)

* Add encoding using Xiph.org 'flac' program.

This adds a FlacEncodeTask that encodes wave files to flac files.
This commit also replaces morituri's EncodeTask with FlacEncodeTask, however, in
morituri, EncodeTask also does the tagging.

FlacEncodeTask will not perform the tagging.
So we will need an extra task for the tagging - this will be added soon.

Meanwhile, do not merge this commit to master yet.

* Add tagging using mutagen.

Replace the gstreamer tagging code with mutagen tagging code.
getTagList is rewritten to return a dictionary of tags, which are then simply
passed to mutagen.

The way it is set up right now is not the best - I don't think it makes sense
for tagging to take place in program/cdparanoia.py ; but this is how the current
code did it.

I suggest that, when we rip out all the gstreamer code, we also move the tagging
to a more sensible place; and then also make the tagging not be an actual
'task.Task'.

* Add gstreamer-less CRC32 version

Only works on wave files at this point. Should not be a problem, I think.

* Use proper musicbrainz tags and ALBUM tag.

* Add mutagen to .travis.yml

morituri/program/cdparanoia.py

@@ -490,12 +490,18 @@ class ReadVerifyTrackTask(task.MultiSeparateTask):
         # here to avoid import gst eating our options
         from morituri.common import encode
 
-        self.tasks.append(encode.EncodeTask(tmppath, tmpoutpath, profile,
-            taglist=taglist, what=what))
+        self.tasks.append(encode.FlacEncodeTask(tmppath, tmpoutpath))
+
+        # MerlijnWajer: XXX: We run the CRC32Task on the wav file, because it's
+        # in general stupid to run the CRC32 on the flac file since it already
+        # has --verify. We should just get rid of this CRC32 step.
         # make sure our encoding is accurate
-        self.tasks.append(checksum.CRC32Task(tmpoutpath))
+        self.tasks.append(checksum.CRC32Task(tmppath))
         self.tasks.append(encode.SoxPeakTask(tmppath))
 
+        # TODO: Move tagging outside of cdparanoia
+        self.tasks.append(encode.TaggingTask(tmpoutpath, taglist))
+
         self.checksum = None
 
     def stop(self):

morituri/program/flac.py

@@ -0,0 +1,18 @@
+from subprocess import check_call, CalledProcessError
+
+import logging
+logger = logging.getLogger(__name__)
+
+def encode(infile, outfile):
+    """
+    Encodes infile to outfile, with flac.
+    Uses '-f' because morituri already creates the file.
+    """
+    try:
+        # TODO: Replace with Popen so that we can catch stderr and write it to
+        # logging
+        check_call(['flac', '--silent', '--verify', '-o', outfile,
+                    '-f', infile])
+    except CalledProcessError:
+        logger.exception('flac failed')
+        raise