What should be the minimum Oscilloscope characteristics for DVB-ASI examination? - Page 1
Forum section: electronics / testgear

author: swartkatt
author_rank: Contributor
timestamp: March 01, 2015, 10:12:03 am
content: Dear Dave aficionado'sThis is a replicate of thehttps://www.eevblog.com/forum/beginners/what-should-be-the-minimum-oscilloscope-characteristics-for-dvb-asi-examination/post in the Beginners section of the forum. I posted my first post there because of being a beginner in the field.After i read the oscilloscope section rules. I decide to resend it in here also.I have a very few understanding of electronics and about oscilloscopes. I want to analyse and i want to process DVB-ASI streams (In years of a learning process).There has a good opportunity came up in my region to buy an TEKTRONIX TDS 540A 500MHz Digital Oscilloscope with a reasonable price.My question is if i can examine a full DVB-ASI stream with this oscilloscope? If it is not capable; what should be the minimum Oscilloscope characteristics for DVB-ASI examination?"DVB-ASI is carried at a 270 Mbps line rate. The 270 Mbps bit-rate on the link is derived from a 27 MHz byte clock multiplied by 10 bits. The carrier frequency of a DVB/ASI signal is 270 MHz. The maximum effective bit rate is 214 Mbit/s. An ASI signal is not like an uncompressed SD-SDI (270 Mbit/s) or HD-SDI (1.485 Gbit/s). It can carry one or multiple SD, HD or audio programs that are already compressed. Generally, the ASI signal is the final product of video compression, either MPEG2 or MPEG4"I just can not make a calculation and a meaningful conclusion from the information above - what kind of an equipment is sufficient to visualize this stream. How much bandwidth do i need, which sampling rate is enough, how much sampling memory is sufficient etc.I just presume that 500MHz bandwidth should be the minimum bandwidth because of the 270 MHz carrier frequency, and presume that 1GS/s Sample Rate should be enough because of the 214 Mbit/s payload and i do not have any ideas how much do "Recording Length of 50,000 points memory" play a role in my scenario?All of my assumptions might be incorrect because i am a beginner and i need guidance!Key Features of the oscilloscope which i would like to buy is listed below.TEKTRONIX TDS 540A 500MHz Digital Oscilloscope----------------------------------500 MHz Bandwidth1 GS/s Sample Rate4 Input ChannelsRecord Length to 50,000 points8-Bit Vertical ResolutionI already got some answers from:tautech: "I would imagine the Tek would do it with an active probe;"tggzzz told me that a low impedance Z0 probe might be sufficient (but not for differential signals) and post me very useful links likehttps://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/Neganur told that "if your bitrate is 270 Mbps and you sample at 500 MHz then your pulse width measurements will be with 2 ns resolution which is not enough to see anything meaningful.On top of that, if you want to conduct any jitter and rise time measurements I'd look for a 1 GHz scope with 2.5-5 GSa/s"SL4P: posted many useful informations.Thanks for them and the others i have not mentioned above.I just want to know if is there anything you can add top of their information.Thanks for your time!

author: nctnico
author_rank: Super Contributor
timestamp: March 01, 2015, 10:22:36 am
content: Judging from the original thread you don't need an oscilloscope but a device which can capture the data and then analyse with a PC. It won't be cheap. You could try and get a Tektronix TLA700 series logic analyser with a TLA7AA4 module (and hack it) to get 32M samples of storage. You'll also need a receiver which extracts the clock and data so the logic analyser has a clock source for synchronous clocking. From there you can read the data into a PC for further analysis.

author: swartkatt
author_rank: Contributor
timestamp: March 01, 2015, 10:43:33 am
content: Hi nctnico,Thank you for the information. There are many solutions out there which i can buy to capture the stream by a computer and they are almost at the same price point of the oscilloscope i want to buy.I just want to use this project as a learning curve of electronics.Is it possible to analyse the same stream with an Oscilloscope? Any Oscilloscope? I just want to understand, what kind of an Oscilloscope is needed for this kind of a job?Or isn't any exist?Thanks

author: swartkatt
author_rank: Contributor
timestamp: March 01, 2015, 11:28:16 am
content: Hi again nctnico,I looked for Tektronix TLA7AA4 136Ch Logic Analyzer Module and there are 4 Analog Probes Out on the module. Is that mean that it is an oscilloscope at the same time and is it possible to use the module without a mainframe?Thanks.

author: SL4P
author_rank: Super Contributor
timestamp: March 01, 2015, 02:28:22 pm
content: Just to add to comments on the other thread...If you only want to work on the buffered data - there are some outboard devices (I'll look for references) which will allow you to ingest the SDI /ASI serial streams at full rate, but if you specifically want to look at the serial waveforms - I think you're stuck with the expensive options.As a beginner project this is ambitious, but you'll end up with some cool test gear and knowledge when you're done in about 6-12 months time!

author: swartkatt
author_rank: Contributor
timestamp: March 01, 2015, 03:12:31 pm
content: Thank you very much SL4PI do not have enough knowledge about Logic Analysers. Is it possible to see the analog signal and the quantized signal at the same time on the screen? This Tektronix TLA7AA4 136Ch Logic Analyzer Module has 4 analog prob outputs on them and i really do not understand what do they intended for. Are they analog signal inputs or are they for some clock generation purpose outputs? I thought that the logic analyser's do only works and analyses for the positive voltages. In other words, i thought that before using a Logic Analyser i have to quantize the analog signal first and the quantized signals are always positive voltages in terms of 0's and 1's

author: TiN
author_rank: Super Contributor
timestamp: March 01, 2015, 03:27:45 pm
content: TLA Analog probe outputs are what they name implies,outputs. You can route any signal from LA inputs (those mictor input connectors) to outside by onboard high-speed mux circuitry in TLA7xx module.It's handy when having TLA+Oscilloscope, so you can just use TLA probe to both capture data by TLA, and send it to oscilloscope for more in-depth view of signal quality/levels. Also it's part of iView technology (which is in turn takes oscilloscope data and imports it into same TLA Application waveform window.So these are NOT analog inputs. For "oscilloscope" function there are special modules 7D2/4 and 7E2/4, but those are quite mediocre.

author: swartkatt
author_rank: Contributor
timestamp: March 01, 2015, 03:31:02 pm
content: Thank you very much for the explanation TiN.

author: SL4P
author_rank: Super Contributor
timestamp: March 01, 2015, 04:16:25 pm
content: A couple of ASI / SDI capture options...http://www.elecard.com/en/products/digital-tv-solutions/capture-cards/hdaccess.htmlhttp://www.dektec.com/A company I formed a whiel ago used both these suppliers, but I personally have been out of the loopforo a few years now.

author: tggzzz
author_rank: Super Contributor
timestamp: March 01, 2015, 06:11:49 pm
content: Quote from: swartkatt on March 01, 2015, 03:12:31 pmThe next, and arguably more important, question is "whatbenefitwill I gain from seeing analog signal and the quantized signal at the same time on the screen?". Personally I suspect you will only get any benefit if you are hunting down signal integrity problems on the links between two devices.You need to askwhat is my problemwhat do I need to find out in order to solve my problemwhat are all the possible ways could I find outwhat is the best way I could find it out, where best = easiest or fastest or cheapestI don't think you've understood (1), therefore don't know (2), have skipped to one possible answer to (3), and hence (4) is poorly understood and answered.

author: swartkatt
author_rank: Contributor
timestamp: March 01, 2015, 06:36:14 pm
content: Thank you SL4PI knew about Dektec but didn't know about Elecard has this type of cards.And there are Dveo versions of these cards available such as this onehttp://www.ebay.com/itm/DVEO-DVB-Master-FD-BR-Card-LS7643-ASI-C-Full-Duplex-PCI-Model-110-Rev-5-/271764945172?pt=LH_DefaultDomain_0&hash=item3f4673f914How pity that these days to invent something is nearly impossible and to reinvent the wheel is much more expensive.These boards are not exactly fully capable of what i intend to do. I intend to do is by using some FPGA's to decode the ASI data and use the decoded Mpeg-ts streams to make a standalone 16 multi channel display driver.It will be fun for me trying to do this project and i will learn much out of it even if i couldn't manage to accomplish the project.Some right instrumentation would be great to see the signals when things will go wrong.Thanks

author: andy_silicon
author_rank: Regular Contributor
timestamp: March 01, 2015, 06:49:51 pm
content: The 500Mhz scope won't have a long enough capture buffer to get much ASI data.A single transport stream frame is 204bytes ( 2040 bits as far as I recall )I'm curious - you seem to be suggesting you wish to take an ASI TS and decode ( presumably decrypt ) the stream - is this what you ae suggesting ?Or do you mean take the TS and extract 16 PS ( program streams ) and then send to a display ?If this is what you mean - how do you intend to convert the mpeg program stream to video ?

author: swartkatt
author_rank: Contributor
timestamp: March 01, 2015, 06:50:39 pm
content: Hi again tggzzzI do not have any problems yet tggzzz, but it will when i will begin this project.I want to learn electronics while doing something fan for me and i think this is the best way to learn things while having fan out of it.There are some ready to use equipments out there already doing the same job.Therefore i am looking for hardest (to learn much out of it) , slowest (matter of course) and cheapest solution for the project.Thank you

author: swartkatt
author_rank: Contributor
timestamp: March 01, 2015, 07:06:38 pm
content: Hi andyI have a MPTS - Multi Program Transport Stream of decrypted 16 channels and i want to process them and display them on a display in a multi-channel fashion.When i will find out the answer of your question "How?" it will be a huge process for me even by it's own.And never mind andy the 500Mhz oscilloscope has already been soldThank you

author: SL4P
author_rank: Super Contributor
timestamp: March 01, 2015, 09:33:19 pm
content: Quote from: swartkatt on March 01, 2015, 06:36:14 pmAha! - a noble cause.Go tohttp://www.mediaproxy.com/Products/LogServerIp/Overview/Monwall- and you can see what I put together until the product & company was stolen from me back in 2008...We originally used both Elecard and/or Dektec, as well as IP-based streams direct into the host box - demuxed and decoded in LogServer.

author: Neganur
author_rank: Unknown
timestamp: March 01, 2015, 09:44:14 pm
content: Quote from: nctnico on March 01, 2015, 10:22:36 amI'm not sure why you would need so much sample memory. What is the purpose of the measurement? An eye diagram on the 270 Mbps will most likely be observed at a 2 ns/div ... 500 ps/div time base. That's 2 ns/div x 10 div x 5 GSa/s = 500 points of sample memory required. With this setting you can observe- amplitude- rise/fall time- timing jitter- current jitter- alignment jitter- overshootIncreasing memory does nothing unless you want to capture a much longer time span. Say the scope has 4Mpts memory and can sample at 5GSa/s, that's some 80 us/div. I don't know if there is anything meaningful to see there (unless you want to process the data with external software). It is quite evident that you would rather want much much higher sample rate than more memory.

author: Neganur
author_rank: Unknown
timestamp: March 01, 2015, 09:46:37 pm
content: Quote from: swartkatt on March 01, 2015, 07:06:38 pmWhile it's a nice scope, it would not have done you any good for your application.

author: nctnico
author_rank: Super Contributor
timestamp: March 01, 2015, 09:50:39 pm
content: He doesn't want to look at the eye diagram but at the contents of the signal. For that purpose a logic analyser is much more suitable. The Tektronix TLA700 series would allow to develop a decoder and run it inside the logic analyser software (seehttp://dev.xdevs.com/projects/tla714/repository/revisions/1955faebc69b/show/tla700/Supports/I2C/src).

author: Neganur
author_rank: Unknown
timestamp: March 01, 2015, 10:15:14 pm
content: ahh gotcha.

author: SL4P
author_rank: Super Contributor
timestamp: March 01, 2015, 10:35:05 pm
content: Quote from: nctnico on March 01, 2015, 09:50:39 pmA logic analyser is useful - no question, but be prepared for a LOT of data, changing at field/frame rate.The container metadata tables, data frame structure, and video HANC/VANC blocks will berelativelystatic.Everything else will be running a lot faster than you can view it by eye - even when decoded.You will probably want to decode & render most fields if you're planning to 'see' much more than the stream's signal integrity.This means a lot of trial and error - or a strictly planned approach to your data harvesting.Also get hold of as many stream standards docs as possible - so you know where to look for what.n

author: swartkatt
author_rank: Contributor
timestamp: March 01, 2015, 10:53:53 pm
content: Quote from: SL4P on March 01, 2015, 09:33:19 pmHi SL4PWhat a shame to stole this kind of an intellectual propertyWhat a great piece of a tool. I want to try to put something together which is much easier than this multi-viewer. Without audio and without any information abilities. Just video.I know that this kind of a product costs really expensive. The broadcasting company i am working in (a regional small cable broadcasting company with 180000 subscribers) was asked a price for this kind of a multi-viewer solution in an expo and they gave up to buy because of the price. I do not know how much it was costed. After the expo i did an audio controlling unit with an arduino for free of charge which is still the way how we control the audio signal integrity. We also monitor both audio and video signals with the Snmp protocol management ability of the receivers with some software. If i can put a product together as in the link you sent, it would be great. That is what i am after, after all!

author: swartkatt
author_rank: Contributor
timestamp: March 01, 2015, 11:10:03 pm
content: Thanks all of you people, for your intellectual contributionsCan you tell me SL4P, what kind of an instrument i really need to look?Let say where i can analyse the signal in all the stages below:1 -) DVB-ASI as is after the transmitter2 -) DVB-ASI after the equalizer3 -) DVB-ASI after the deserializer4 -) Signal after the 8B/10B encoding5- ) When the signal is at the Fpga input stageetc..Is it possible to do all instrumentation with one piece of an equipment?Thanks

author: swartkatt
author_rank: Contributor
timestamp: March 01, 2015, 11:13:32 pm
content: Quote from: Neganur on March 01, 2015, 09:44:14 pmThank you very much Neganur this is a great piece of an information for me.

author: swartkatt
author_rank: Contributor
timestamp: March 01, 2015, 11:34:27 pm
content: Thank you nctnico for the information on Tektronix TLA7AA4 module. I am looking for the capabilities of the device.The main frame costs expensive from the point of the shipping concern. Do the Tektronix TLA704 main frame supports the Tektronix TLA7AA4 module?

author: nctnico
author_rank: Super Contributor
timestamp: March 01, 2015, 11:53:59 pm
content: Yes and no. With some hacking (search EEVblog for TLA704) you can run TLA application version 4.4 or 5.6 on a TLA704. I recommend using version 4.4 to run locally on the mainframe and version 5.6 remote but you will need a PCMCIA network card for remote access. I think it is better to get a TLA714 or TLA715 mainframe to start with.

author: swartkatt
author_rank: Contributor
timestamp: March 02, 2015, 12:01:31 am
content: Thank you nctnico

author: swartkatt
author_rank: Contributor
timestamp: March 02, 2015, 04:16:26 pm
content: Hi nctnicoIs it possible to hack Tektronix TLA7AA4 136 Channel 8GHz 450MHz 512K to make it 32M?if it is possible what is the hacking process; is it software based or hardware based?Thanks

author: nctnico
author_rank: Super Contributor
timestamp: March 02, 2015, 05:17:59 pm
content: That should not be a problem. See the TLA7AA4 hacking thread.

author: swartkatt
author_rank: Contributor
timestamp: March 02, 2015, 09:46:38 pm
content: Thank you i found the link nctnicohttps://www.eevblog.com/forum/testgear/tla-hacks-)/