Copyright © 2003 Paul Hoadley
2003-07-11
Abstract
This document describes how to partially automate the
process of ‘ripping’ an audio compact disc
(CD) to the Ogg Vorbis compressed
audio format under FreeBSD. This is very much a
work-in-progress: there are bound to be better ways to do it.
The main goal, however, is to describe a non-GUI-dependent
process: the instructions in this article do not rely on any
desktop environment. The only pre-requisite, of course, is
physical access to the machine's CD-ROM drive. There should be
no other constraints on the system (for example, the X Windows
System is not required).
Table of Contents
The process of ripping an audio CD into any compressed audio format usually involves (at least) the following steps:
Sampling the CD audio data and dumping it into an uncompressed format on disk
Encoding the uncompressed format into a compressed format.
In this document, we will consider some refinements, including:
Automatically consulting an online database to retrieve metadata relating to the CD (including album title, artist, and track names)
Automatically encoding, renaming and adding the metadata to each ripped track.
There are certainly more potential refinements. Ideally, one should be able to insert a CD, type a command, and have the tracks added to a music collection with no further intervention.
The audio data on a CD can be extracted track-by-track to
uncompressed .WAV sound files using the
cdda2wav utility. This is part of the
cdrtools port, and can be installed by
executing the follwing as the root user:
#cd /usr/ports/sysutils/cdrtools#make install
You obviously need to have read access to the CD-ROM drive
on your machine. Depending on the permissions set for the device
in /dev, this may require you to remain as
the root user for the
next step.
The cdda2wav has many options, and you should read the manual page thoroughly. For the purposes of this document, the following will suffice to rip an entire CD to individual tracks. Create a directory for each disc, as the created filenames will be the same as the last run by default. Change to that directory and run:
#cdda2wav --device /dev/acd0a --cddb 0 --bulk
In this example, the CD-ROM drive is at
/dev/acd0a—this
may be different in your system. The option
--cddb 0 tells cdda2wav to
consult the default online database for CD metadata and prompt the
user if there is a choice. --bulk ensures the
whole disc is ripped track-by-track into separate files.
cdda2wav will print out some informational messages about the disc and the tracks it finds. It may pause while contacting the online database. If the database contains more than one entry for a given disc ID (presumably because more than one person has submitted a slightly different track list—often just capitalisation or genre differences), cdda2wav will provide you with a list of options, for example:
3 entries found:
00: rock 9b0a410c Violent Femmes / Violent Femmes
01: rock 9e0a410c Violent Femmes
02: newage a00a410c Violent Femmes / Violent Femmes
03: ignore
please choose one (0-3): 0At this point, choose one of the options. There is often
nothing separating the options, other than the ‘genre’
field, which is information we will not be using anyway. In this
case, I would type 0.
cdda2wav should then print out some preliminary
information, and a track list:
CDINDEX discid: f4QJf7DxjEZlH5XvdcfkAwIghPc-
CDDB discid: 0x9b0a420c CDDBP titles: resolved
CD-Text: not detected
CD-Extra: not detected
Album title: 'Violent Femmes' [from Violent Femmes]
Track 1: 'Blister In The Sun'
Track 2: 'Kiss Off'
Track 3: 'Please Do Not Go'
Track 4: 'Add It Up'
Track 5: 'Confessions'
Track 6: 'Prove My Love'
Track 7: 'Promise'
Track 8: 'To The Kill'
Track 9: 'Gone Daddy Gone'
Track 10: 'Good Feeling'
Track 11: 'Ugly'
Track 12: 'Gimme The Car'The sampling process will take a few minutes, and cdda2wav will keep you informed of its progress.
This part of the process involves the
oggenc program from the
vorbis-tools port. As the root user, install the
vorbis-tools port:
#cd /usr/ports/audio/vorbis-tools#make install
We will also be performing an XSLT transformation on the XML data retrieved from the online database, so you will need an XSLT processor. The libxslt port provides the very fast xsltproc:
#cd /usr/ports/textproc/libxslt#make install
Having installed the tools, the next step is to transform
the XML data in the file
audio.cdindex into a standard shell script
that will perform the encoding work for us. Save the following
simple XSLT code as makesh.xsl in the same
directory as the ripped .WAV files:
<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
version="1.0">
<xsl:output method="text"/>
<xsl:strip-space elements="*"/>
<xsl:param name="quality" select="'6'"/>
<xsl:template match="CDInfo">
<xsl:text>#!/bin/sh
# Generated by makesh.xsl
# Album: </xsl:text>
<xsl:value-of select="Title"/><xsl:text>
</xsl:text>
<xsl:apply-templates/>
</xsl:template>
<xsl:template match="SingleArtistCD">
<xsl:for-each select="Track">
<xsl:text>oggenc</xsl:text>
<xsl:text> --quality=</xsl:text><xsl:value-of select="$quality"/>
<xsl:text> --output="</xsl:text>
<xsl:number value="@Num" format="01"/>
<xsl:text>_</xsl:text>
<xsl:value-of select="translate(Name, ' ', '_')"/>
<xsl:text>.ogg</xsl:text>
<xsl:text>"</xsl:text>
<xsl:text> --artist "</xsl:text>
<xsl:value-of select="../Artist"/>
<xsl:text>"</xsl:text>
<xsl:text> --title "</xsl:text>
<xsl:value-of select="."/>
<xsl:text>"</xsl:text>
<xsl:text> --album "</xsl:text>
<xsl:value-of select="//Title"/>
<xsl:text>"</xsl:text>
<xsl:text> --tracknum </xsl:text>
<xsl:value-of select="@Num"/>
<xsl:text> audio_</xsl:text><xsl:number value="@Num" format="01"/>
<xsl:text>.wav</xsl:text>
<xsl:text>
</xsl:text>
</xsl:for-each>
</xsl:template>
<xsl:template match="*">
</xsl:template>
</xsl:stylesheet>The stylesheet is fairly primitive, and really just serves
to re-arrange the information we already have into a series of
shell script lines. Only the --quality option is
parameterised here, so it could be over-ridden at the command
line. Track numbers are encoded into the filenames—I like
this because it preserves album ordering in a directory listing.
Spaces are converted to underscores in filenames.
Now that access to the CD-ROM device has concluded, you can
work as any non-root
user again. To generate the shell script, type:
>xsltproc -o script.sh makesh.xsl audio.cdindex
This command tells xsltproc to transform
the XML in audio.cdindex into the shell
script script.sh using the XSLT in
makesh.xsl. Before proceeding, take a look
at the generated script to ensure it is satisfactory:
>more script.sh
Occasionally, for example if the data returned by the online database is incomplete, the script can be generated with missing parameters. You should see a series of command lines beginning with the oggenc command, and including information such as the song and album titles, the artist and the track number:
oggenc --quality=6 --output="01_Blister_In_The_Sun.ogg" --artist "Violent Femmes" --title "Blister In The Sun" --album "Violent Femmes" --tracknum 1 audio_01.wav oggenc --quality=6 --output="02_Kiss_Off.ogg" --artist "Violent Femmes" --title "Kiss Off" --album "Violent Femmes" --tracknum 2 audio_02.wav
The lines are split here for readability, but will be continuous, long lines in the script itself.
If script.sh looks good, change it to
be executable, and run it:
>chmod u+x script>script.sh
This will start the encoding process. It will take a few
minutes per track, dependent on the speed of your CPU. When the
encoding is finished, you should have correctly named
.ogg files in the directory:
>ls -l *.ogg-rw-r--r-- 1 paulh paulh 3070070 Jul 4 14:20 01_Blister_In_The_Sun.ogg -rw-r--r-- 1 paulh paulh 3583998 Jul 4 14:22 02_Kiss_Off.ogg -rw-r--r-- 1 paulh paulh 5288692 Jul 4 14:25 03_Please_Do_Not_Go.ogg -rw-r--r-- 1 paulh paulh 5782202 Jul 4 14:29 04_Add_It_Up.ogg -rw-r--r-- 1 paulh paulh 6940948 Jul 4 14:33 05_Confessions.ogg -rw-r--r-- 1 paulh paulh 3182951 Jul 4 14:35 06_Prove_My_Love.ogg -rw-r--r-- 1 paulh paulh 3283854 Jul 4 14:38 07_Promise.ogg -rw-r--r-- 1 paulh paulh 4786760 Jul 4 14:41 08_To_The_Kill.ogg -rw-r--r-- 1 paulh paulh 4130547 Jul 4 14:43 09_Gone_Daddy_Gone.ogg -rw-r--r-- 1 paulh paulh 4728298 Jul 4 14:46 10_Good_Feeling.ogg -rw-r--r-- 1 paulh paulh 3220215 Jul 4 14:48 11_Ugly.ogg -rw-r--r-- 1 paulh paulh 6402192 Jul 4 14:52 12_Gimme_The_Car.ogg
They should also contain the correct metadata from the original album:
>vorbiscomment 01_Blister_In_The_Sun.oggtitle=Blister In The Sun artist=Violent Femmes album=Violent Femmes tracknumber=1
You can now safely delete the .wav
files:
>rm audio_*
You may wish to keep the files
audio.cddb,
audio.cdindex and the generated
script.sh for future reference.
There is certainly a lot of scope for enhancing this process. At least the following spring to mind:
Certainly the XSLT script should be kept somewhere more
central. For example, I rip my CDs to
audio/cds as a subdirectory of my home
directory, so makesh.xsl resides there on
my system. Placing it in the working directory of the ripping
process was a simplification for this article.
The process seems ideal for further automation, perhaps via make. The sequence:
>cd ~/audio/cds; make rip encode clean
would be ideal. There should be nothing preventing the automatic creation of the whole directory hierarchy based on the metadata received about the album. However, on occasion the online database has no record for a particualr disc ID. A make-based approach would need to be able to handle this, and may want to check that a sane script has been generated in the case of poor metadata being received. Just off the top of my head, I suspect that a double quote character in one of the title fields, for example, would break the simplistic approach described above.
The author of this document is Paul Hoadley. This document only describes what I did to rip some audio CDs to disk. Your mileage may vary. If you notice any errors in this document, or, better still, you have a system that is far superior to this, please let me know. I am interested in refining the general process described above, with the proviso that any refinements don't require use of the X Windows System or any X-related applications.