Liberty Recorder Multi-Channel dcr Files



Introduction

The Liberty Recorder creates audio files with a "dcr" extension. A dcr file is a multi-channel audio / video file with the audio data saved in standard compressed audio file format. The .dcr files could not be given a .wav extension, because other .wav players such as Windows Media Player are not designed to recognize the multi-channel data tracks found within the dcr files.

Both .wav files and .dcr files save the audio data in a compressed PCM (.wav) format. Saving the audio data in a standard, compressed format allows any Windows PC to playback the audio using the Liberty Player.

Compression

The Liberty Recorder can use any standard compression algorithm installed onto the PC. This includes any algorithm provided by the Windows Operating System and any compression algorithm that might be added to the PC. Various compression algorithms have been a standard component of all Windows Operating Systems since Windows'95 and any of these may be used with the Liberty Recorder. These algorithms include, but are not limited to Microsoft ADPCM, and D.S.P. Group Truespeech.

Speex is another compression algorithm that will work with the Liberty Recorder. SPEEX is an Open-Source, patent-free compression algorithm specifically written to record the spoken word, not music. It delivers a high compression rate with very good sound quality. The Speex algorithm may be downloaded using this link. If the Speex codec is used, then please use of one of the Q4 mono (Quality 4) or higher recording attributes. We suggest recording with the Attributes set at "16.8 kBit/s, 16.0 kHz, Mono Q5". Further information about Speex may be obtained from www.speex.org.

The following chart provides details on disk space requirements for 4-channel recordings:

# of courtrooms ; Compression Algorithm

1 courtroom 4-ch; Microsoft ADPCM

1 courtroom 4-ch; Speex

1 courtroom 4-ch; D.S.P. Group Truespeech

per 6 hr day

480mb

180mb

120mb

per 5 day week

2.4gb

900mb

600mb

per 50 week year

120gb

45gb

30gb

* The MS ADPCM and D.S.P. Group Truespeech compression algorithms have been a standard component of all Windows systems, since Windows'95.


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