Dr. Satchin Panda on Time-Restricted Feeding and Its Effects on Obesity, Muscle Mass & Heart Health

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DVI - Digital Visual Interface

Digital Visual Interface (DVI) is a video display interface developed by the Digital Display Working Group (DDWG). The digital interface is used to connect a video source, such as a video display controller, to a display device, such as a computer monitor. It was developed with the intention of creating an industry standard for the transfer of digital video content.

The interface is designed to transmit uncompressed digital video and can be configured to support multiple modes such as DVI-A (analog only), DVI-D (digital only) or DVI-I (digital and analog). Featuring support for analog connections, the DVI specification is compatible with the VGA interface. This compatibility, along with other advantages, led to its widespread acceptance over competing digital display standards Plug and Display (P&D) and Digital Flat Panel (DFP). Although DVI is predominantly associated with computers, it is sometimes used in other consumer electronics such as television sets and DVD players.

Cable length

The maximum length recommended for DVI cables is not included in the specification, since it is dependent on the pixel clock frequency. In general, cable lengths up to 4.5 metres (15 ft) will work for display resolutions up to 1920 × 1200. Longer cables up to 15 metres (49 ft) in length can be used with display resolutions 1280 × 1024 or lower. For greater distances, the use of a DVI booster—a signal repeater which may use an external power supply—is recommended to help mitigate signal degradation.


The DVI connector on a device is given one of three names, depending on which signals it implements:

  • DVI-D (digital only, single link or dual link)
  • DVI-I (integrated, combines digital and analog in the same connector;
    digital may be single or dual link)
  • DVI-A (analog only)

Most DVI connector types – the exception being DVI-A – contain pins that pass digital video signals. These come in two varieties: single link and dual link. Single link DVI employs a single 165 MHz transmitter that supports resolutions up to 1920 × 1200 at 60 Hz. Dual link DVI adds six additional pins (located in the center of the connector) for a second transmitter increasing the bandwidth and supporting resolutions up to 2560 × 1600 at 60 Hz. A connector with these additional pins is sometimes referred to as DVI-DL (dual link). Dual link should not be confused with dual display (also known as dual head), which is a configuration consisting of a single computer connected to two monitors, sometimes using a DMS-59 connector for two single link DVI connections.

In addition to digital, some DVI connectors also have pins that pass an analog signal, which can be used to connect an analog monitor. The analog pins are the four that surround the flat blade on a DVI-I or DVI-A connector. A VGA monitor, for example, can be connected to a video source with DVI-I through the use of a passive adapter. Since the analog pins are directly compatible with VGA signaling, passive adapters are simple and cheap to produce, providing a cost-effective solution to support VGA on DVI. The long flat pin on a DVI-I connector is wider than the same pin on a DVI-D connector, so even if the four analog pins were manually removed, it still wouldn't be possible to connect a male DVI-I to a female DVI-D. It is possible, however, to join a male DVI-D connector with a female DVI-I connector.

DVI is the only widespread video standard that includes analog and digital transmission options in the same connector. Competing standards are exclusively digital: these include a system using low-voltage differential signaling (LVDS), known by its proprietary names FPD-Link (flat-panel display) and FLATLINK; and its successors, the LVDS Display Interface (LDI) and OpenLDI.

Some DVD players, HDTV sets, and video projectors have DVI connectors that transmit an encrypted signal for copy protection using the High-bandwidth Digital Content Protection (HDCP) protocol. Computers can be connected to HDTV sets over DVI, but the graphics card must support HDCP to play content protected by digital rights management (DRM).


Minimum clock frequency: 25.175 MHz

Single link maximum data rate including 8b/10b overhead is 4.95 Gbit/s @ 165 MHz. With the 8b/10b overhead subtracted, the maximum data rate is 3.96 Gbit/s.

Dual link maximum data rate is twice that of single link. Including 8b/10b overhead, the maximum data rate is 9.90 Gbit/s @ 165 MHz. With the 8b/10b overhead subtracted, the maximum data rate is 7.92 Gbit/s.

Pixels per clock cycle:

1 (single link at 24 bits or less per pixel, and dual link at between 25 and 48 bits inclusively per pixel) or
2 (dual link at 24 bits or less per pixel)

Bits per pixel:

24 bits per pixel support is mandatory in all resolutions supported.
Less than 24 bits per pixel is optional.
Up to 48 bits per pixel are supported in dual link DVI, and is optional. If a mode greater than 24 bits per pixel is desired, the least significant bits are sent on the second link.

Example display modes (single link):

SXGA (1,280 × 1,024) @ 85 Hz with GTF blanking (159 MHz)
HDTV (1,920 × 1,080) @ 60 Hz with CVT-RB blanking (139 MHz)
UXGA (1,600 × 1,200) @ 60 Hz with GTF blanking (161 MHz)
WUXGA (1,920 × 1,200) @ 60 Hz with CVT-RB blanking (154 MHz)
WQXGA (2560 × 1600) @ 30 Hz with CVT-RB blanking (132 MHz)

Example display modes (dual link):

QXGA (2,048 × 1,536) @ 72 Hz with CVT blanking (2 × 163 MHz)
HDTV (1,920 × 1,080) @ 120 Hz with CVT-RB blanking (2 × 143 MHz)
WUXGA (1,920 × 1,200) @ 120 Hz with CVT-RB blanking (2 × 154 MHz)
WQXGA (2,560 × 1,600) @ 60 Hz with CVT-RB blanking (2 × 135 MHz)
WQUXGA (3,840 × 2,400) @ 30 Hz with CVT-RB blanking (2 × 146 MHz)
Generalized Timing Formula (GTF) is a VESA standard which can easily be calculated with the Linux gtf utility. Coordinated Video Timings-Reduced Blanking (CVT-RB) is a VESA standard which offers reduced horizontal and vertical blanking for non-CRT based displays.

Digital data encoding

One of the purposes of DVI stream encoding is to provide a DC-balanced output link that reduces decoding errors. This goal is achieved by using 10-bit symbols for 8-bit or less characters and using the extra bits for the DC balancing.

Like other ways of transmitting video, there are two different regions: the active region, where pixel data is sent, and the control region, where synchronization signals are sent. The active region is encoded using transition-minimized differential signaling, where the control region is encoded with a fixed 8b/10b encoding. As the two schemes yield different 10-bit symbols, a receiver can fully differentiate between active and control regions.

When DVI was designed, most computer monitors were still of the cathode ray tube type that require analog video synchronization signals. The timing of the digital synchronization signals matches the equivalent analog ones, making the process of transforming DVI to and from an analog signal a process that does not require extra (high-speed) memory, expensive at the time.

HDCP is an extra layer that transforms the 10-bit symbols before sending through the link. Only after correct authorization can the receiver undo the HDCP encryption. Control regions are not encrypted in order to let the receiver know when the active region starts.

Clock and data relationship

The DVI data channel operates at a bit-rate that is 10 times the frequency of the clock signal. In other words, in each DVI clock period there is a 10 bit symbol per channel. The set of three 10 bit symbols represents one complete pixel in single link mode and can represent either one or two complete pixels as a set of six 10 bit symbols in dual link mode.

DVI links provide differential pairs for data and for the clock. The specification document allows the data and the clock to not be aligned. However, as the ratio between clock and bit rate is fixed at 1:10, the unknown alignment is kept over time. The receiver must recover the bits on the stream using any of the techniques of clock/data recovery and find then the correct symbol boundary. The DVI specification allows the input clock to vary between 25 MHz and 165 MHz. This 1:6.6 ratio can make pixel recovery difficult, as phase-locked loops, if used, need to work over a large frequency range. One benefit of DVI over other links is that it is relatively straightforward to transform the signal from the digital domain into the analog one using a video DAC, as both clock and synchronization signals are sent over the link. Fixed frequency links, like DisplayPort, need to reconstruct the clock from the data sent over the link.

Display power management

The DVI specification includes signaling for reducing power consumption. Similar to the analog VESA display power management signaling (DPMS) standard, a connected device can turn a monitor off when the connected device is powered down, or programmatically if the display controller of the device supports it. Devices with this capability can also attain Energy Star certification.


The analog section of the DVI specification document is brief and points to other specifications like VESA VSIS for electrical characteristics and GTFS for timing information. The idea of the analog link is to keep compatibility with the previous VGA cables and connectors. HSync, Vsync and three video channels are available in both VGA and DVI connectors and are electrically compatible. Auxiliary links like DDC are also available. A passive adapter can be used in order to carry the analog signals between the two connectors.

DVI and HDMI compatibility

HDMI is a newer digital audio/video interface developed and promoted by the consumer electronics industry. DVI and HDMI have the same electrical specifications for their TMDS and VESA/DDC links. However HDMI and DVI differ in several key ways.

  • HDMI lacks VGA compatibility and does not include analog signals.
  • DVI is limited to the RGB color model while HDMI also supports YCbCr 4:4:4 and YCbCr 4:2:2 color spaces which are generally not used for computer graphics.
  • In addition to digital video, HDMI supports the transport of packets used for digital audio.
  • HDMI sources differentiate between legacy DVI displays and HDMI-capable displays by reading the display's EDID block.

To promote interoperability between DVI-D and HDMI devices, HDMI source components and displays support DVI-D signalling. For example, an HDMI display can be driven by a DVI-D source because HDMI and DVI-D both define an overlapping minimum set of supported resolutions and frame buffer formats.

Some DVI-D sources use non-standard extensions to output HDMI signals including audio (e.g. ATI 3000-series and NVIDIA GTX 200-series). Some multimedia displays use a DVI to HDMI adapter to input the HDMI signal with audio. Exact capabilities vary by video card specifications.

In the reverse scenario, a DVI display that lacks optional support for HDCP might be unable to display protected content even though it is otherwise compatible with the HDMI source. Features specific to HDMI such as remote control, audio transport, xvYCC and deep color are not usable in devices that support only DVI signals. HDCP compatibility between source and destination devices is subject to manufacturer specifications for each device.

A female DVI-I socket

Color coded (click to enlargre)

Pin 1 TMDS data 2− Digital red− (link 1)
Pin 2 TMDS data 2+ Digital red+ (link 1)
Pin 3 TMDS data 2/4 shield
Pin 4 TMDS data 4− Digital green− (link 2)
Pin 5 TMDS data 4+ Digital green+ (link 2)
Pin 6 DDC clock
Pin 7 DDC data
Pin 8 Analog vertical sync
Pin 9 TMDS data 1− Digital green− (link 1)
Pin 10 TMDS data 1+ Digital green+ (link 1)
Pin 11 TMDS data 1/3 shield
Pin 12 TMDS data 3− Digital blue− (link 2)
Pin 13 TMDS data 3+ Digital blue+ (link 2)
Pin 14 +5 V Power for monitor when in standby
Pin 15 Ground Return for pin 14 and analog sync
Pin 16 Hot plug detect
Pin 17 TMDS data 0− Digital blue− (link 1) and digital sync
Pin 18 TMDS data 0+ Digital blue+ (link 1) and digital sync
Pin 19 TMDS data 0/5 shield
Pin 20 TMDS data 5− Digital red− (link 2)
Pin 21 TMDS data 5+ Digital red+ (link 2)
Pin 22 TMDS clock shield
Pin 23 TMDS clock+ Digital clock+ (links 1 and 2)
Pin 24 TMDS clock− Digital clock− (links 1 and 2)
C1 Analog red
C2 Analog green
C3 Analog blue
C4 Analog horizontal sync
C5 Analog ground Return for R, G, and B signals

Info Source: Digital Visual Interface Page
Image Source: Digital Visual Interface Image

Creative Commons Attribution-ShareAlike License and Terms of Use

VGA Port And Connector

Video Graphics Array (VGA) connector is a three-row 15-pin DE-15 connector. The 15-pin VGA connector was provided on many video cards, computer monitors, laptop computers, projectors, and high definition television sets. On laptop computers or other small devices, a mini-VGA port was sometimes used in place of the full-sized VGA connector.

Many devices still include VGA connectors, although VGA generally coexisted with DVI as well as the newer and more compact HDMI and DisplayPort interface connectors.

VGA connectors and cables carry analog component RGBHV (red, green, blue, horizontal sync, vertical sync) video signals, and VESA Display Data Channel (VESA DDC) data. In the original version of DE-15 pinout, one pin was keyed by plugging the female connector hole; this prevented non-VGA 15 pin cables from being plugged into a VGA socket. Four pins carried Monitor ID bits, which were rarely used; VESA DDC redefined some of these pins and replaced the key pin with +5 V DC power supply. Devices that comply with the DDC host system standard provide 5V ±5% and supply a minimum of 300 mA to a maximum of 1 A.

DE-15 has been referred to ambiguously as D-sub 15, incorrectly as DB-15 and often as HD-15 (High Density, to distinguish it from the DE-9 connector used on the older CGA and EGA cards, as well as some early VGA cards, which have the same E shell size but only two rows of pins). The video connector is an "E" size D-sub connector, with 15 pins in three rows, which is the high-density connector version (DE15HD).

The same VGA cable can be used with a variety of supported VGA resolutions, from 320×400px @70 Hz / 320x480px @60 Hz (12.6 MHz of signal bandwidth) to 1280×1024px (SXGA) @85 Hz (160 MHz) and up to 2048×1536px (QXGA) @85 Hz (388 MHz).

There are no standards defining the quality required for each resolution but higher-quality cables typically contain coaxial wiring and insulation that make them thicker. Shorter VGA cables are less likely to introduce significant signal degradation. A good-quality cable should not suffer from signal crosstalk, whereby signals in one wire induce unwanted currents in adjacent wires, or ghosting. Ghosting occurs when impedance mismatches cause signals to be reflected. However, ghosting with long cables may be caused by equipment with incorrect signal termination or by passive cable splitters rather than the cables themselves.

There are DVI to VGA adapters and cables. As neither DVI nor VGA carry audio channels, a separate path for audio should be used, if needed. Simple adapters from other modern outputs such as HDMI to VGA are also commonplace, again requiring a separate audio path.

To connect VGA outputs to interfaces with different signaling, more complex converters may be used. Most of them need an external power source to operate and are inherently lossy. However, many modern displays are still made with multiple inputs including VGA, in which case adapters are not necessary.

VGA to SCART converters can pass color information, because VGA — SCART RGB signals are electrically compatible, except for synchronization. Many modern graphics adapters can modify their signal in software, including refresh rate, sync length, polarity and number of blank lines. Particular issues include interlace support and the use of the resolution 720×576 in PAL countries. Under these restrictive conditions, a simple circuit to combine the VGA separate synchronization signals into SCART composite sync may suffice

A female DE15 socket.

15-pin VESA DDC2/E-DDC connector. Pin numbering is a female connector for graphics adapter output. Male connector, pin numbering is mirror opposite.

Pin 1 RED Red video
Pin 2 GREEN Green video
Pin 3 BLUE Blue video
Pin 4 ID2/RES formerly Monitor ID bit 2, reserved since E-DDC
Pin 5 GND Ground (HSync)
Pin 6 RED_RTN Red return
Pin 7 GREEN_RTN Green return
Pin 8 BLUE_RTN Blue return
Pin 9 KEY/PWR formerly key, now +5V DC, powers EDID EEPROM chip on some monitors
Pin 10 GND Ground (VSync, DDC)
Pin 11 ID0/RES formerly Monitor ID bit 0, reserved since E-DDC
Pin 12 ID1/SDA formerly Monitor ID bit 1, I²C data since DDC2
Pin 13 HSync Horizontal sync
Pin 14 VSync Vertical sync
Pin 15 ID3/SCL formerly Monitor ID bit 3, I²C clock since DDC2

Info Source: VGA_Connector Page

Evolution / Google Calendar Authentication Request

P ersistent Gnome Evolution requests to login to Google Calendar is an annoying bug. Each time you open dash or launch an application inside Gnome, Evolution pop-up window takes focus and demands logging in to Google account.

I don't use Gnome Evolution but it's still an annoying distraction. On Ask Ubuntu forums several solutions were offered, to users experiencing the same problem. It centered around deleting Evolution config files.

Remove the following:

rm -rf ./.config/goa-1.0/accounts.conf
rm -rf ./.config/evolution
rm -rf ./.local/share/evolution

One solution I found on the Google Calendar Forum, suggested the problem lay with 2-factor authentication, which requires generating a specific password for Evolution.


This solution was echoed on "Ask Ubuntu" tech help.


I didn't bother as I don't use Gnome Evolution for mail or calendar. My solution was to remove Evolution complete.

Ongoing Network Problem

H ad a network problem for a few weeks, on Linux Desktop box with the ethernet controller dropping connection when it goes into suspend. Coming out of suspend, there's no network connection, though ifconfig -a and ip addr show, indicate the network interface is UP. Giving the ifup command does not work and OS responds with an error message, the interface is not recognised.

Google offered solutions, many of which did not work. One suggestion to check /etc/network/interfaces and check if the interface is included.

# cat /etc/network/interfaces

Should contain:

# Loopback
auto lo
iface lo inet loopback

# network card
auto eth0
iface eth0 inet dhcp

My /etc/network/interfaces contained only the loopback address:

# Loopback
auto lo
iface lo inet loopback

I followed the instructions, by adding the interface data and restarted network service.

# /etc/init.d/networking restart

Still no network after suspend. More google. I found Debian Network Wiki which offered some hope. Here's what the wiki says:

Wired Networks are Unmanaged

As of Debian 6.0 "Squeeze", NetworkManager does not manage any interface defined in /etc/network/interfaces by default.

Unmanaged devices means NetworkManager doesn't handle those network devices. This occurs when two conditions are met:

The file /etc/network/interfaces contains anything about the interface, even:

allow-hotplug eth0
iface eth0 inet dhcp
And /etc/NetworkManager/NetworkManager.conf contains:



Enabling Interface Management

If you want NetworkManager to handle interfaces that are enabled in /etc/network/interfaces:

Set managed=true in /etc/NetworkManager/NetworkManager.conf.

Restart NetworkManager:

/etc/init.d/network-manager restart

I change the entry in Network-Manager from "false" to "true", as instructed in the Debian Wiki.


Changed to


Save file and restart network-manager:

/etc/init.d/network-manager restart

That appears to have fixed the problem.

What Are CHM Files?

C HM are Microsoft Compiled HTML files. A Microsoft proprietary compressed file format, consisting of HTML pages, index and navigation. Files are compressed in a binary format with CHM extension and sometimes used for software documentation.

If you are not running a version of Windows, you may experience problems opening or reading the CHM format. Linux offers GnoCHM for the Gnome Desktop,  Kchmviewer for the KDE Desktop, xCHM for anyone running X or you can opt for a Firefox solution using ChmFox, which allows reading in your browser.

CHM is an old, outdated, proprietary technology, Linux offers a solution to convert the format to PDF using chm2pdf or to HTML format using 7zip. Another option is Calibre which allows conversion to EPUB, PDF and HTML files.

To use chm2pdf, give the following command:

chm2pdf --book in.chm out.pdf

Check the man page for options.

To use 7zip, give the following command:

7z x file.chm

Check the man page for options.

To use Calibre, follow the onscreen instructions.