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QDesign Music Codec
The QDesign Music Codec (QDMC) is one of the best technologies available for
encoding music at very low data rates.
It does an outstanding job on instrumental music, allowing very high quality
reproduction even when streaming over a 14.4 or 28.8 modem.
The QDesign Music Codec is also very good at vocal music, although more complex
clips may require slightly higher data rates.
In general, QDesign Music Codec provides comparable or superior quality to RealAudio and MPEG layer
III audio at low data rates - below 5KBytes/sec. (See the news archives at
David Renelt's audio page).
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For more QDesign demos,
check out:
CBC Records
MouseJam
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Even though the codec's name refers to music, it can reproduce any type of material. For anything other
than simple speech clips, QDesign Music Codec is the best low data rate QuickTime codec. It is important
to point out that QDesign Music Codec is not like MIDI. Rather than require music to be stored as a
series of notes, it works with sampled audio files... just like IMA or other QuickTime codecs. This
takes more data rate than MIDI, but avoids the need to transcribe the music, and produces higher quality
audio.
Architectures Supported
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Basic vs. Professional Edition
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There is only one version of the decoder, and it is built into QuickTime 3 for both Mac and Windows.
There are no licensing requirements or per-title fees for playback.
The Basic Edition of the encoder is built into QuickTime 3.
It allows compression to 8-48kbits/sec; any sample rate; mono or stereo.
It supports batch processing only where all clips have exactly the same parameters.
The Professional Edition of the encoder is intended
for media producers who need improved performance and quality. The main advantages of the Professional Edition are:
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Free demo of Professional Edition
Download the demo and try out the advanced
features for yourself.
Get the Challenge Phrase.
Then purchase an unlock code from Terran.
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- Encodes at twice the speed of the Basic Edition
- Full support for batch processing
- Supports higher (up to 128kbits/sec) and lower (4 kbits/sec) bitrates
- Advanced control over compression parameters can allow higher quality in some clips
Pros
- Excellent musical reproduction
- Allows full bandwidth, 16-bit, 44.1kHz stereo playback over a 28.8 modem
(with some material)
- Better audio quality than MPEG layer III at low bitrates
- At top quality (128Kbits/s, 16 KByte/s), allows a CD-ROM to store 10
hours of very high quality audio
Cons
- Places moderately high load on CPU. May not work in conjunction with demanding video tracks.
Playback of 44khz stereo audio-only clips requires 100mhz+ Pentium or PowerMac.
Tips
- There is often a long delay when encoding begins, especially on long clips. This does
not mean your computer has hung; in this case, patience is a virtue.
- The best results are acheived on "clean" intrumental music: 44khz stereo at 16kbit/sec can
be acheived
- When encoding music with vocals, expect to use higher data rate, and/or lower sample
rate: 22khz mono at 24kbit/sec may be more realistic
- Samples which reach 100% amplitude are likely to cause artifacting. We recommend normalizing
the audio to 70% before compression. You can do this automatically with
Media Cleaner Pro 3.0.
- Bit rate You may compress the audio down to a range of bit rates,
regardless of the frequency. Of course, the wider the frequency response you wish to accurately
reproduce, the higher the bit rate will need to be. Stereo clips generally require higher
bitrate than mono to acheive the same level of quality, but not twice as high.
| Ideal source material |
Best on instrumental music; also does a good job on wide range of music |
| Compression Ratio / Datarates |
Basic: 8 - 48 kbits/sec (1 - 6 kbytes/sec)
| Pro: 4 - 128 kbits/sec (0.5 - 16 kbytes/sec)
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| Compression time |
Basic: Approx 14 min to compress 1 min of material on 180mhz PPC, 133 mhz Pentium
Pro: Twice as fast as basic (approx 7 minutes in this example), approx. realtime compression of 22khz mono
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| Encoder requirements |
Any PowerPC or Pentium |
| Decoder requirements |
Any PowerPC or Pentium |
| Encoder availability |
Basic: included with QuickTime 3
Pro: Download demo of Pro for free;
Purchase unlock code from Terran |
| Decoder availability |
Built into QT 3.0 |
| Manufacturer |
QDesign |
If you have any comments or tips & tricks to share
about the QDesign Music Codec, please contact us at
info@terran-int.com.
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