CD Ripper Settings

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Revision as of 12:38, 5 January 2008 by Bernard S. Jansen (talk | contribs) (Audio compression: Started a table to compare encoding and rip quality options.)

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There are a number of parameters that affect exactly how MythMusic imports a CD to your MythTV system. This article provides detailed information about how to select the most appropriate CD Ripper Settings for your needs.

Ripping CD Music

Extracting the digital music information from a CD and putting it onto your Hardrive is referred to as Ripping. MythTV uses an Open source library called cdparanoia to achieve this. There is a common misunderstanding that this is a relatively error free process, as the music is held as a digital stream of numbers, and it should therefore be a simple matter of copying this information stream to the hard drive.

The real problem is that CD Audio is not a random access format like a data file. It was designed to be read from front to back in one continuous sequence. If you drop a bit in the transfer, it system can have moved on many more bits before it re-synchronizes the data stream. This can result in audio clicks. If you then throw in a modern pre-emptive multitasking operating system into the mix, the chances of getting that data off the CD in one piece is not as easy as it seems. Of course if you are then going to compress that music stream to a lossy compressed format such as MP3 or .ogg, then your less likely to care, because you are going to throw much of the music information away. A large click or skip in your music will be easily noticed however, even with lower quality compressed files. If you are an Audiophile then you will want to treat that CD data stream with velvet gloves, and cdparanoia is a good start. If you are using windows then you might look at DAE.

Paranoia level

The paranoia level tells cdparanoia (via MythMusic) how much care it should take in extracting the audio information. The general principle of "less haste, less waste" applies. The faster the extraction the more chance of dropping bits and having holes in your audio stream. This will lead to disappointing results, and the need to re-rip the track. A high paranoia level is very useful for ripping scratched CDs. Although a badly scratched CD can take literally hours to rip, the resulting files should be (almost) error free.


Audio compression

Once CD paranoia has extracted the Music data it will typicall write this out as a WAV, AIFC, AIFC or raw 16 bit linear PCM data stream. MythTV then compress this raw music stream into a compressed format that reduces the amount of space that music stream takes on your hard drive.


The following table details the difference between the different "Encoding" and "Default Rip Quality" options:

Quality mp3 Bitrate mp3 File Size (per hr) ogg Bitrate ogg File Size (per hr) FLAC Bitrate FLAC File Size (per hr)
Low  ?  ?  ?  ? N/A N/A
Medium  ?  ?  ?  ? N/A N/A
High  ?  ?  ?  ? N/A N/A
Perfect N/A N/A N/A N/A  ?  ?

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