This is how nPSK works...
We made some television history the other night: in a test for the NFL International Distribution, Adrian from TV2Go and us folks at IMG Mediahouse have successfully brought a 32APSK encoded signal across the Atlantic, with a datarate of 30Mbps using a 9MHz carrier!
Since the start of the current NFL season in 2009, part of my job is to bring in feeds that originate in the US for an uplink in stateside to NSS7. Our clients then downlink these feeds in Europe. Using MPEG2 and H264 encoding, QPSK and 8PSK modulation are commonplace in satellite transmissions.
Ray was looking after this year's NFL season (I was behind the camera of my mobile phone)
However satellite bandwidth is expensive, and we’re dealing with ever increasing datarates. Data compression alone will only get us so far, so the only other way to increase throughput would be to increase phase modulation on the TX path. Lucky for us, the DVB-S2 spec has another trick or two up its sleeve.
Using 32APSK modulation and Newtec equipment, Adrian, Ray and I successfully brought over a stable 30Mbps connection using only a 9MHz carrier. With our 5.6m dish, carrier to noise was 18dB – which is not too shabby. Newtec kindly provided an NTC 2263 receiver for this, which provides an ASI output – so we had to wire it into a Tandberg 1290 IRD to decode the signal into SDI.
The results are gooood! In laments terms: 32PSK increases the amount of data that can be sent in comparison to 8PSK by about 30%: with 8PSK modulation on a 9MHz carrier, we’d be getting a maximum data rate of 20Mbps. In 32APSK we’re getting 30Mbps!
8PSK Gray Coding - imagine this x3 for 32APSK
As I understand it, 8PSK sends all bits in one phase revolution, or orbit. 16APSK uses twice as much using two orbits, and 32APSK uses THREE orbits. How exactly this works is beyond me – but it’s sure as hell exciting to see the results!
On the transmission front, Adrian was using an Adtec Encoder for this project. Although MPEG2 is commonly used in satellite transmissions, we were utilising MPEG4/H264 compression which is more efficient than MPEG2 – so that’s TWO new technologies in one fair swoop!
The Newtec seems to be the only demodulator that can currently cope with 32APSK downlinks. Even though the Tandbergs have 16APSK and 32APSK as an option in the Licensed Features list, I understand these are hardware upgrades, not software upgrades.
And speaking of Tandberg 1290 receivers, we encountered a slight problem: every once in a while (say every 10mins or so), the 1290 would glitch for a couple of seconds, as if it’s not coping with error correction (at least that’s what it looked like). Apparently this phenomenon happens because of i-frames sent at irregular intervals from the encoder. I understand that due to different on-board chipsets, the Tandberg motherboards 3.x are NOT causing these glitches, whereas the version 2.x do (at the time of writing, we currently have the latter ones here at IMG).
“But what’s the application, Jay? Why go through all that trouble and pay for a new infrastructure?” I hear you ask. Simple really: saving money. If you can use the same satellite space for more data, then you’ll be able to use a 6 MHz carrier instead of 9 MHz or provide more services in the same space. Adrian suggests carriers as narrow as 3MHz for decent broadcast quality – superb for news gathering.
We’re hoping to utilise 32APSK with MPEG4 for the forthcoming NFL season 2010/2011 starting in September. Let’s keep our fingers crossed!
Newtec NTC 2263 demodulator wedged between two Tandberg 1290 IRD's
- My own notes, invaluable in times of severe panic
Sometimes a feed comes in, gets an English voiceover and is put straight to air on ESPN UK. But on Sunday, we pulled various aces from our sleeves to bring the Serie A “Milan Derby” to an expecting UK audience.
The feed comes in from Eutelsat W3 in HD, the studio for pre match presentation is SD, the commentators are on site in Milan and come in via ISDN. Question is: How do we synchronise comms with pictures, and how do we create HD graphics during the match?
We use pretty much EVERY piece of kit IMG Mediahouse has to offer, that’s how.
In this article, I’ll explain some of the challenges my dayjob in MCR has to offer. My colleagues and I feel like rockstars when a feat like this can successfully be pulled off, and I’m happy to say we did it once again. We’ve never done this particular route before, so it deserves a mention here.
First of all, the audio commentary will reach us instantly via 128 kbps ISDN circuit. Even though we have our man Paul Ryan on site, we have no influence on the picture circuit. It’s provided by Infront Media, who do a similar thing to the Italian Serie A football that we (IMG) do for the English Premier League: international distribution. This involves getting a feed from the stadium (either via fibre or satellite) to a dedicated facility, add graphics and potentially commentary and send it out for further satellite uplinks around the world.
- more notes…
Here’s the snag: By the time we see the signal, it could potentially be bounced off two satellites, each path taking roughly one second. Take into consideration compression and decompressions along the way, the pictures could arrive roughly 2-4 seconds later than the commentary reaches us – how long exactly requires a sync test. At this point, we’re not sure if the host broadcasters will let us step in front of the camera.
Even so, one delay unit alone won’t be able to provide a full 4 seconds or longer should we need it, so we’ll have to plan for TWO units. Here’s the signal path:
- ISDN commentary comes in as analogue audio
- pass through a BEL delay unit (we’ll set this to 1000ms or one second for now – maximum here is 2400ms)
- delayed output needs to be converted via Proc Amp into embedded SDI audio for distribution around the building
- Proc goes into yet another Proc with option to delay a maximum of 2600ms
- this delayed Proc is onpassed to the Studio so commentary can end up on air eventually
- in addition, an UNDELAYED version straight from the ISDN unit is passed to the Studio so the presenters can interact with the commentators in real time
That’s audio sorted. Now let’s have a look at the video signal:
- The clean pictures come in off satellite in HD
- a downconverted version is sent to the Studio
- the HD feed is sent to a HD capable gallery, which is connected via TBU to the Studio Gallery (they’re in different buildings, and we’ve run out of tie lines by this point)
- we’ll create the HD graphics in one gallery, while audio gets mixed in the main studio
- we then take this dirty HD video feed and combine it with the audio from the SD Studio via an interesting bit of kit known to us as Shuffler 4
- Shuffler 4 (HD pictures plus Studio’s audio) are sent via HD SDI to ESPN TX at Arqiva Chalfont on dedicated fibres. We’re also providing an HD ASI feed via direct line to Arqiva Newman Street, and a downconverted SD backup feed is sent via BT Tower
Confused? That’s nothing! Various requests for recordings at various stages of the process require further audio shuffling and downconversions, but let’s not mention this here.
All that counts is that all went very well and our clients were happy.
Join me next week when I’ll tell you about an interesting 32APSK downlink test we did for NFL football.
If you’ve recently passed through Oxford Circus Station, you will have noticed only ONE advert on all billboards at the platform: Google Chrome, and how you desperately need it in your life. In fact, this ad is currently plastered all over the UK, and one must ask the all too obvious question:
Why advertise for a FREE product that won’t make any money?
[read full article…]
Particularly rubbish for a shocking rip-off price: £7.99 for “The Big One”. Includes disgusting scrambled egg, terrible sausages and squidgy bacon. Hash browns and beans were OK, but then what can go wrong when all you’re doing is heat up the contents of a can. “Overpriced Shit” sounds way too positive.
Verdict: no matter how desperate you are – AVOID at all costs!
