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Audio formats, compression and Jitter

Discussion in 'Desktop & Laptop Computers Forum' started by Matty N, May 12, 2001.

  1. Matty N

    Matty N
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    We all have a good idea of the good and the less good as far as 24/96 passing PC audio interfaces go. Here's a few niggling points I'm intrigued by...

    * has anybody actually measured the Jitter from CD audio played via a CD/DVD drive in a PC which is output as SP/DIF to a preamp/poweramp without reclocking it after leaving the PC?

    * is it actually possible to achieve better sound quality using PCM stereo sourced from a PC than a high quality separate? What about RF interference from the PC/video hardware? (after all, CD transports are effectively just CD-ROM drives)

    * Has anyone come across a utility that will take 16/44 audio and i) convert it to 24/96 or 24/192 and ii) apply a waveform smoothing algorithm such that the quantization distortion is removed?

    * What is the best audio format for storing an archive of CD's on a PC whole house server?? Obviously MP3 is the most compressed but the quality is v.v.poor. I want severe audiophile quality, but also want to compress it - maybe use a compression algorithm on uncompressed files? But might this degrade the reproduction quality?

    With 100Gb drives on the horizon, we can store over 60 uncompressed CD's on a single drive, much more using some kind of compression so I think these questions probably need some informed answers!!

    Matt
     
  2. Branxx

    Branxx
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    A few months ago I tested de-jittering device called JISCO and ended up returning it as it produced no audible difference to my system. Music was played out of HTPC via Delta Dio2496 card digitally connected to Yamaha DSP-A1.

    There are several reasons for this:
    • DeltaDio 2496 produces very low jitter;
    • Yamaha DSP-A1 buffers and re-clock incoming PCM digital stream and minimises jitter by itself.
    • De-jittering device is effectively doing nothing.
    • My ears are indifferent to small variations.

    I am inclined to believe that Delta is a very low jitter card and it is hard to improve upon it.

    As for your second question, if you believe bit-are-bits (assuming low jitter) than a PC based player or a stand-alone player will feed the same information into digital processor and should therefore produce the same result.

    I thought initially bit-are-bits myself (computers being my profession), but there appears to be some other forces at play as well. As with the traditional home audio equipment more money buys more music, the same applies to HTPC, with the proviso that PC parts are generally much cheaper than the high-end audio.

    I have completely moved by CD collection onto HTPC using a number of compression techniques. My favourite is player is Sonic Foundry Siren using lossles Perfect Clarity Audio compression. It reduces the original WAV file to about 45%. Comparing the original CD and the Siren/PCA on my system yields no difference (DeltaDio 2496->Yamaha DSP-A1->Bryston 5B->M&K S-150THX+MX-350 Sub).

    Comparing MP3 and WMA (Windows Media Audio) I prefer WMA at the same bit rate. If compressing is necessary than I would recommend using at least 192Kbits. OggVorbis is also better than MP3.
     
  3. Branxx

    Branxx
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    I never looked into the subject of up-sampling, as it is beyond the capabilities of my Yamaha DSP-A1. It looks to me we are definitely moving toward an HTPC base DSP pre-processor, something like Lexicon MC-1, but all implemented as Windows executable.
     
  4. Matty N

    Matty N
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    Thanks for the info. Any ideas on the upsampling/interpolating software. Someone suggested that WinAmp had a plugin to do it, but I haven't found it yet. Not sure that WinAmp would offer the best solution either??
     

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