Design and Development of aMulti Format Converter for Target detection systems

Scope:This project aims at design and development of a Multi format video converter for converting the analog video data to digital format used for target detection applications.The digital converted data is then compressed and transferred to the computing device such as a personal computer through USB/ Ethernet port.Objective:The transmission and storage of analog signals is tedious and time consuming process. Where as it is easier in digital signals. Also analog signal processing is difficult compared to digital signal processing.The recent development in DSP leads to easier data manipulations. Hence these factors influence in design and development of this module.

Video Conversion &

Compression

USB Controller

Ethernet Controller

Analog Input

Digital Video

LAN Port

USB Port

Fig: Block representation of the proposed module.

Analog Video

• Analog video standards followed worldwide are:

• NTSC• PAL• SECAM

NTSC

• NTSC stands for National Television System Committee.

• It is the analog television system used in most of North America, most countries in South America, Burma, South Korea, Taiwan, Japan, Philippines, and some Pacific island nations and territories.

• It was the first widely adopted broadcast color system.

• It is encoded in the YUV color space, which provides a mathematical equivalent of red, green and blue.

• It uses a luminance-chrominance encoding system .

NTSC: Frames and Resolution

• NTSC broadcasts 60 half frames per second, which is known as 60 "fields" per second.

• NTSC uses 525 lines of resolution: the first 480 lines in each frame are the image, and the last 45 are the "vertical blanking interval" (VBI).

• In NTSC, chrominance is encoded using two 3.579545 MHz signals that are 90 degrees out of phase, known as I (in-phase) and Q (quadrature) QAM.

• These two signals are each amplitude modulated and then added together. The carrier is suppressed. The result can be viewed as a single sine wave with varying phase relative to a reference and varying amplitude. The phase represents the instantaneous color hue, and the amplitude represents the instantaneous color saturation.

4.5 MHzSound Carrier

4.2 MHzVideo Bandwidth

3.579545 MHzColor Subcarrier Frequency

60 HzVertical Frequency

15.734 kHzHorizontal Frequency

525/60Lines/Field

N T S CNational Television System Committee

• In NTSC, chrominance is encoded using two 3.579545 MHz signals that are 90 degrees out of phase, known as I (in-phase) and Q (quadrature) QAM.

• These two signals are each amplitude modulated and then added together. The carrier is suppressed. The result can be viewed as a single sine wave with varying phase relative to a reference and varying amplitude. The phase represents the instantaneous color hue, and the amplitude represents the instantaneous color saturation.

PAL

• PAL, short for Phase Alternate Line, is an analogue television encoding system used in broadcast television systems in large parts of the world.

• The name "Phase Alternating Line" describes the way that the phase of part of the color information on the video signal is reversed with each line, which automatically corrects phase errors in the transmission of the signal by canceling them out, at the expense of vertical frame color resolution.

• The basics of PAL and the NTSC system are very similar; a quadrature amplitude modulated Subcarrier carrying the chrominance information is added to the luminance video signal to form a composite video baseband signal. The frequency of this Subcarrier is 4.43361875 MHz for PAL, compared to 3.579545 MHz for NTSC.

PAL Signal detailsFor PAL-B/G the signal has these characteristics

Parameter Value

Clock frequency 14.8 MHz

Bandwidth 5.0 MHz

Horizontal sync polarity Negative

Total time for each line 64.000 µs

Front porch (A) 1.65 µs

Sync pulse length (B) 4.7±0.20 µs

Back porch (C) 5.7±0.20 µs

Active video (D) 51.95 µs

Parameter Value

Vertical lines 313 (625 total)

Vertical lines visible 288 (576 total)

Vertical sync polarity Negative (burst)

Vertical frequency 50 Hz

Sync pulse length (F) 0.576 ms

Active video (H) 18.4 ms

PAL B PAL G, H PAL I PAL M PAL D PAL N PAL Nc

Transmission Band VHF UHF UHF/VHF UHF/VHF VHF UHF/VHF UHF/VHF

Lines/Fields 625/50 625/50 625/50 525/60 625/50 625/50 625/50

Video Bandwidth 5.0 MHz 5.0 MHz 5.5 MHz 4.2 MHz 6.0 MHz 5.0 MHz 4.2 MHz

Sound Carrier 5.5 MHz 5.5 MHz 6.0 MHz 4.5 MHz 6.5 MHz 5.5 MHz 4.5 MHz

Channel Bandwidth 7 MHz 8 MHz 8 MHz 6 MHz 8 MHz 6 MHz 6 MHz

Active lines 576 576 582* 480 576 576 576

PAL broadcast systemsThis table illustrates the differences:

• The most widely used system of color television, PAL, employs a chrominance Subcarrier, frequency interleaving of luminance and chrominance components, the constant luminance principle - all taken from the NTSC scheme.

• The major differences are that, in PAL, the phase of the color components is reversed from line to line, with corresponding reversal at the receiver, and that simple color-difference signals are used in place of the NTSC I and Q signals.

4.5 MHz4.5 MHz5.5 MHzSound Carrier

4.2 MHz4.2 MHz5.0 MHzVideo Bandwidth

3.575611 MHz3.582056 MHz4.433618 MHzColor Sub Carrier

60 Hz50 Hz50 HzVertical Freq.

15.750 kHz15.625 kHz15.625 kHzHorizontal Freq.

525/60625/50625/50Line/Field

PAL MPAL NPALSYSTEM

P A LPhase Alternating Line

SECAM

• SECAM is the Sequential Color with Memory system of analog encoding.

• The SECAM system requires the receiver to memorize the content of each line, successive line signals being transmitted in the two color components.  The color signals are sent on a chrominance subcarrier by frequency modulation, thus precluding the use of frequency interleaving.  Both PAL and SECAM require somewhat more complex receivers and have somewhat lower vertical color resolution, but highly satisfactory reception is achieved by each system.

6.5 MHz5.5 MHzSound Carrier

6.0 MHz5.0 MHzVideo Bandwidth

50 Hz50 HzVertical Frequency

15.625 kHz15.625 kHzHorizontal Frequency

625/50625/50Line/Field

SECAM D,K,K1,LSECAM B,G,HSYSTEM

SECAMSequential Couleur Avec Memoire

or Sequential Color with Memory

Differences

• The major difference in performance among NTSC, PAL, and SECAM is the superior horizontal resolution of the latter systems.  o This arises from two causes:

more fundamentally from the wider channels (7 and 8 MHz) used, with correspondingly wider video bandwidths (variously set at 5.5, 6, and 6.5 MHz);

less fundamentally from the lower frame rate (25 frames per second) which in turn has the deleterious effect of increasing their susceptibility to flicker problems. 

The Video Signal

• A composite video signal is a signal in which all the components required to generate a video signal are embedded in a single signal. The three main components that together form a composite signal are as follows:

• The luma signal (or luminance) — contains the intensity (brightness or darkness) information of the video image

• The chroma signal — contains the color information of the video image

• The synchronization signal — controls the scanning of the signal on a display such as the TV screen

The Composite Video Signal

• The monochrome composite signal is built of two components: luma (or luminance) and synchronization. This signal, which is usually called the Y signal, is shown in figure below.

Figure 1. Monochrome Composite Video Signal (Luma Steps from White to Black)

Figure 2. Color Information Signal for a Color Bar Line (Including the Color Burst)

The composite color video signal, often called the Color Video, Blank, and Sync (CVBS) signal, is the sum of Y and C, is shown in Figure 3.CVBS = Y + C

The two components Y and C can also be distributed separately as two independent signals. These two signals together are called either Y/C or S-video.

Parts of the Video Signal

• The signal for a single horizontal video line consists of a horizontal sync signal, back porch, active pixel region, and front porch, as shown in figure below.

• The front porch is a brief (about 1.5 µs) period inserted between the end of each transmitted line of picture and the leading edge of the next line sync pulse.

• The horizontal sync (HSYNC) signals the beginning of each new video line.

• HSYNC is followed by a back porch, which is used as a reference level to remove any DC components from the floating (AC coupled) video signal. This is accomplished during the clamping interval for monochrome signals, and takes place on the back porch.

• Back porch is followed by color burst, which provides information for decoding the color content of the signal.

• Vertical sync (VSYNC) pulse is actually a series of pulses that occurs between fields to signal the monitor to perform a vertical retrace and prepare to scan the next field.

H Sync & V Sync

Video Levels

• The video levels define the levels and ranges for the different parts of the video signal.

• The unit used to define video levels is the IRE (Institute of Radio Engineers).

• The blanking level refers to 0 IRE and the white level refers to +100 IRE. The blanking level, which is the reference level for the video signal (usually 0 V), is different from the black level if a setup is applied to the signal as shown in figure below.

Figure: Analog encoding from R'G'B' to CVBS.