For more information:
e-mail: enquiries@singmai.com
Tel: +66 (0) 36 275465
Previous issues:
We are currently working flat out for the release of our first two standalone products, the SM01 and SM03, at the Broadcast Asia exhibition. If you are in Singapore between 21st and 24th June please come and see us at stand 4C4-04.
Our compact microprocessor, the PT13, is now available as a free download for Altera FPGA users. Just send us an e-mail to sales@singmai.com and we will send the license and encrypted IP to you. The free editor and assembler are available from our website, http://www.singmai.com/PT13.htm, together with further information on the PT13 . At just 374 logic elements and potentially memory-less operation PT13 is a real alternative to NIOS for small control applications.
The last two months have seen the re-release of two existing IP cores with a host of new features and improvements.
PT2 provides a 60x32, (30 character for 525 line), video character/text overlay and is ideal for displaying subtitles or closed captions, time code, user menus, status or error information and channel identifiers.
PT2 is pre-programmed with 112 characters including 0-9, A-Z, a-z and various punctuation marks and symbols and has 16 user programmable characters. Each character has a 12x16 pixel size and is shaped using a raised cosine filter to comply with the system bandwidth requirements.
PT2 accepts a compliant BT656 video stream, (both 625 and 525 standards), and it's associated 27MHz clock and it produces a BT656 output with the overlay. The user can choose to have a background to the characters which is programmable in colour; the luminance level of the character is also programmable.
For more information: http://www.singmai.com/PT2.htm
PT6 is a line based SD video pattern generator IP core
The PT6 IP core provides all of the timing required to provide a 525 or 625 line BT656, 10 bit pattern. The core is priced separately so the user may choose which of the following standard patterns he wishes to use. He may choose either a single pattern or the full suite or anything inbetween. In addition the core can be programmed to accept non-standard clock frequencies and custom patterns are also available. The patterns may be multiplexed on a line basis, (e.g. SMPTE bars), or on a frame basis, (e.g. field bounce tests)
The standard patterns available are:
- 75%/100%/SMPTE Colour bars
- Black/White/50% grey flat fields
- 75%/100% Red fields
- 2T, 20T and Pulse bar
- CCIR17/18/330 and 331
- FCC Comp and FCC MB
- N7C MBF and N7C MPF
- Ramp
- Multiburst
- Sweep
- 10 step linearity
- Pathological (SDI test)
- Gamut
- Bowtie
- Sinx/x
Large screen displays and the use of video compression is putting increased demands on the performance of standard definition analogue decoders.
The comb filter is a key element of today's analogue video decoders. But there is a lot more to designing a comb filter than just a line of memory and an adder or subtractor. The comb filter for our soon-to-be-released PT5 video decoder is our best yet.
A comb filter utilises the phase relationship of the colour component of the NTSC/PAL video standards to remove cross-colour/cross-luma components and help restore the full luma bandwidth.
Usually a 2D line comb filter is used as this requires the least memory and most off the shelf video decoder ICs use this method.
However even the basic 2D comb filter can be improved on. The line comb filter will not always be able to be used, for example it will fail on diagonal structures, and this has to be detected otherwise artifacts will be produced. Detection is usually done using luminance amplitude differences but that does not detect all instances; different colours with similar luma amplitudes will be undetected.
The SingMai comb filter uses both luma and chroma amplitudes to detect comb failures ensuring we do not introduce artifacts into the decoded image.
The NTSC line comb filter uses the line above and below the pixel being combed, (3 line comb), but because of interlace these lines are actually 4 lines apart. For PAL the problem is worse as the PAL line by line phase shift means a 5 line comb is used.
The SingMai PAL line comb uses the same 3 line aperture as the NTSC line comb which means the comb can operate more of the time.
The frame comb uses spatially exactly the same pixel for combing and therefore offers better rejection of artifacts (although the 25Hz PAL offset means perfect cancellation is never possible).
Most video decoders offering 3D comb filters only provide a symmetrical frame tap. This means the apertures are very wide temporally, especially so for PAL which needs a 2 frame interval tap, again because of the 90deg line based phase shift.
The SingMai PAL frame comb uses a novel comb architecture, similar to the line comb, to use a single frame tap, reducing the time interval and meaning the frame comb can operate for longer when there is motion.
Additionally, instead of dropping from frame comb to line comb when there is motion, we offer an interim field comb tap which is closer still in time. Each of the 3D comb filters are asymmetric which means there is no need for a compensating audio delay. The image below shows a frame of video in which there is motion. The green shows the frame comb and the orange the field comb. You can see that nowhere in this image was it necessary to use the line comb, (magenta), the field comb was still usuable even though the frame comb was failing.
Other comb filter features are reduced chroma bandwidth in the notch mode which helps reduce cross colour effects in this mode and improve the luma bandwidth, and individual assessment of each comb failure including the notch filter so the best comb mode and the image with the least artifacts is chosen at all times.