Digital recording

1. DIGITAL RECORDING
Submitted By
Dhruv Upadhaya
Submitted to
Dr. (Mrs.) Ritula Thakur

2. Why digital???
• No physical limits for storage
• Can be accessed via the Internet
• 24/7 availability of access
• Great saving of space (example - library)
• Preservation of old texts/ manuscripts
• Easy retrieval of information using keywords
• Integrated online resource sharing
• It is cheaper to maintain digital library than book library
• Linking and networking possibilities
• Any number of times digital files can be duplicated with
exactness.
• Many can access a digital file at the same time

4. DIGITAL BASICS
• Sampling: An incoming analog signal is
sampled at discrete and precisely timed
intervals

5. Sampling
At each interval, this analog signal is momentarily
“held” while the converter goes about the process of
determining what the voltage level actually is, with a
degree of accuracy that’s defined by the converter’s
circuitry and the chosen bit rate.

6. (a) Whenever the sample rate is
set too low, important data between sample
periods will
be lost.
Effects of Sampling

7. (b) As the rate is increased, more frequency
related data can be encoded.
Effects of Sampling contd…

8. (c) Increasing the sampling
frequency further can encode the recorded
signal with an even higher bandwidth range.
Effects of Sampling contd…

9. Quantization
• The amplitude component of the digital
sampling process.
• Used to translate the voltage levels of a
continuous analog signal into binary digits
for the purpose of manipulating or storing data
in the digital domain.

11. The recording process
In its most basic form, the digital recording
chain includes
• A low-pass filter
• A sample-and-hold circuit,
• An analog-to-digital converter,
• Circuitry for signal coding and error
correction.

12. Following the low-pass filter, a sample-and-hold
(S/H) circuit
• holds and measures the analog voltage level
that’s present during the sample period.
This period is determined by the sample rate
computations are performed to translate the
sampled voltage into an equivalent binary word.
Sample and Hold Circuit

13. Low Pass Filter
At the input of a digital sampling system,
the analog signal must be band limited with a
low-pass filter so as to stop frequencies that
are greater than half the sample rate frequency
from passing into the A/D conversion circuitry

14. • Once the sampled signal has been converted into
its equivalent digital form, the data must be
conditioned for further data processing and
storage.
• This conditioning includes data coding, data
modulation and error correction.
• In general, the binary digits of a digital bit stream
aren’t directly stored onto a recording
medium as raw data; rather, data coding is used to
translate the data
Signal Coding and Error correction

15. Block diagram for Digital Recording
Analog
Signal
Low
Pass
Filter
Sample
and Hold
Circuit
Analog to
Digital
Converter
Error
Correctio
n and
Signal
Coding
Recorcdin
g Device

16. The playback process
The quantized digital signal is converted into analog signal using a digital to analog
converter
A stepped resistance digital to analog
converter

17. Digital recording devices
• Magnetic tape recording
– Hard disks
– Floppy disks
• Optical Recording Devices
– Compact disks
– Digital versatile disks
• Flash Drives
– Pen Drives
– SD cards