1 / 9

CD player components: Processors, Buffers …

CD player components: Processors, Buffers …. Walid El jebbari. Oversampling using a DSP. Oversampling means using a sampling frequency greater than that dictated by the Nyquist theorem

tanek
Download Presentation

CD player components: Processors, Buffers …

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CD player components: Processors, Buffers … Walid El jebbari

  2. Oversampling using a DSP • Oversampling means using a sampling frequency greater than that dictated by the Nyquist theorem • It results in great performance gains; an increase in signal-to-noise ratio and a decrease in the quantization noise • Done using a digital signal processor (digital filter) which takes in audio samples, performs an operation on them, and then outputs audio samples. • Oversampling can be viewed as interleaving zeros between each sample with additional samples

  3. Oversampling using a DSP • i

  4. Oversampling using a DSP • i

  5. Output Filtering • The role of the output filters is to smooth out the waveform from the digital-to-analog converters • the output filter stage has witnessed a great deal of improvement since 1982 • Early 16-bit players used brickwall reconstruction filters • These filters had a very sharp cutoff characteristic and held the signal gain close to unity • The problem was that they had “big” phase nonlinearities at high frequencies, and high-frequency group delay (change in phase shift with respect to frequency)

  6. Output Filtering • current players have taken advantage of digital oversampling filters placed upstream of the DAC along with a gentle analog reconstruction filter • These filters have a gentler cutoff characteristic than the brickwall filters, because the oversampling filter shifts noise outside the audio band • Its design is noncritical and low-order--which guarantees excellent phase linearity • phase distortion can be held at ±0.5° over the entire audio band

  7. Buffer memory • CD players incorporate a buffer memory that “reads ahead” on the disc stores up to 45 seconds of audio as a CD plays • When the player is bumped or jostled, it interrupts the laser’s ability to read the data from a CD • The buffer memory temporarily reads the contents of the buffer so playback can continue uninterrupted while the laser assembly regains its bearings

  8. The ability to read different formats • CD-R was designed to be read by an infrared 780nm laser • DVD uses a visible red 635nm or 650nm laser, which aren't reflected sufficiently by the organic dye polymers used in CD-R media • As a result, many DVD players can't read CD-R media • Some DVD players come with two lasers so that they can read CD-R; one infrared for CDs, one visible for DVDs

  9. References • www.tc.umn.edu/~erick205/Papers/paper.html • www.answerbag.com/c_view.php/2012 • www.bestbuy.ca/learnmore/AskTheExpert/en/portable_cd_players_faqs • www.cdrfaq.org/

More Related