Confusion over current position!

[wierdbeard65]

Hi,

I'm still to actually get my system installed, but spend a considerable amount of time surfing the site and planning my rig when I have both the time and money (at the same time!) to put it together.

I am somewhat confused about versions of the components and features supported, though. What version of Myth is being used? I ask because the latest version does cool things like linking in to IPTV and allowing you to pull off all the channels multiplexed onto a single transponder with only one sat tuner card.


Also, is HD supported or not? I've seen lots of posts asking questions about hardware and fixing HD, which would imply that it is, but I'm sure I've stumbled across pages saying "not yet" as well.

I have other questions, but will put them into other threads 

Thanks!

[colinjones]

0710RC2 (the current version) does not use the latest version of Myth. However, once the new version of LMCE (0810) is released, it will be using a more up to date version of Myth that supports many new features.

However, given that you are in the UK, you should consider the VDR option. VDR is a slimmer PVR that is specifically designed for DVB countries, whereas Myth is much more general and not as well intergrated into LMCE. Again, the new version of LMCE will include far better integration of VDR, however its current state is still quite useable. VDR already allows you to capture all channels in a DVB bouquet, record them or play them back. In fact, CHT (a company that produces fully managed and integrated LMCE systems as a product called Dianemo - http://www.dianemo.co.uk/ ), already produce core servers that have several multi-tuner DVB cards in them, and I believe can currently capture and record every terrestrial TV station broadcasting in the UK, continuously. Totallymaxed is one of the representatives from that company, here on the forum.

As for HD - depends what you mean by HD! If you just mean DVB-T/S in 1080i, then yes, as long as you have an HD tuner card, and your MD hardware is upto playing such a video stream back, then yes HD is not a problem at all. If you see HD as meaning BluRay or HDDVD, then that is more difficult - the implementation of these in LMCE is not good because of DRM and various odious US legislation that seeks to limit what you can do with media you have purchased, by preferring Microsoft, etc. So you can currently RIP some BD to your harddrive and play them on LMCE in HD, but it isn't guaranteed, especially for newer titles. Work, elsewhere, is being done to provide BD playback for Linux users, and ultimately this will be added to LMCE, but for now.... difficult...

[wierdbeard65]

Many thanks for your very rapid response! I will certainly look at VDR and the link you suggested as well.

HD, humm. Well, I want to be able to recieve broadcast HD and record / play it like any other channel. Blu-Ray, as you will see from other postings, I'd like a drive in my main MD, but I'm not sure if that will be to rip or just to use as a player - disks are not that expensive, but I don't want to fill them with loads of ripped movies and would hapily manage without that feature! Being able to stream the content to another MD in the house would be cool though!

Also, if broadcast HD is available, can MCE transcode it to SD easily, preferably in real time? I'm a bit of a novice with the whole HD/SD thing, so forgive me if it's a stupid question. My reason for asking is that I won't (certainly initially) have many HD-capable screens. If I record something on, say, the BBC that is available in both formats, I'm obviously going to want the HD version in case I'm watching on the higher-spec machines, but if I try to watch it on an older SD unit, what will happen?

Many thanks agai for your response 

[colinjones]

As long as you have an HD card, then yes, naturally, you can receive/record/play the HD broadcast. Screen isn't relevant - If you have a screen set for SD/ED and you try to play an HD piece of media or transmission, it will simply down-convert the image before it plays it back. Same the other way, play an SD piece of media on an HD TV it will up-convert it. This is trivial because it is just scaling - in fact TV's do this all the time on their own, after all, how could you watch an SD transmission on an HD set? It just scales the image up.

Note - none of this has anything to do with transcoding. Above we are talking about the video stream after it has been decompressed, thus there are no codecs involved to trans-code. Transcoding is what you do when you want to convert from one form of compression/coding to another. ie both compressed. The stream comes in, coded with say, MPEG2 codec - the MPEG 2 codec is used to decode the stream into uncompressed/raw form, then the transcoder uses another codec, say H264, to re-encode the stream back into a compressed format. This would commonly be done to further compress a stream - MPEG2 is not very compact, whereas H264 is. This is a different topic altogether - don't go there just yet, you don't need this immediately as it is nothing to do with viewing broadcasts, and it is much more complex. Concentrate on your base system... you have plenty to be getting on with as it is.

[wierdbeard65]

Thanks, Colin! A very clear and concise explanation 

I guess I was getting my wires crossed a bit. It makes sense that an HD television can show SD video as it is recent technology which was developed when both were around. I didn't realise that you could send an HD video signal to an SD television and it would work! I assumed it would be like NTSC and PAL completely incompatible!

[colinjones]

Sorry - clarification... I didn't say an SD TV, I said a screen set for SD... in other words, if you configure an MD for an SD resolution (because it happens to be connected to an SD TV) then when that MD is asked to play a piece of HD media, it will down-convert/scale the image to the right size for that screen mode (which in turn, happens to be the right size/resolution for the TV connected.... not coincidentally!)

This really isn't all that clever, it is just a computer after all ... if you play video on your PC, you don't worry about what the resolution is do you? The media player you are using will play it at something appropriate, or you can just zoom it to fill the screen. This is the same concept, its simply scaling/zooming the image. Because you set the MD to the resolution that the SD TV can handle, by definition, any media you play on it will be scaled to fill the screen at the right resolution. You certainly can't send an HD signal direct to an SD set for the reasons you assumed. The example of sending a signal to a set that it doesn't match was purely sending an SD signal (or actually receiving the SD signal on the set) to an HD set. Make sense?

BTW, PAL and NTSC are really not very different, and definitely not totally incompatible. The only material difference between them is the way they encode the colour information. PAL alternates the phase through 180degs of the two colour signals (yes, there are only 2 not 3), between alternate horizontal lines. This allows PAL to cancel out any atmospheric distortion of the signal giving accurate colour reproduction. NTSC cannot do this, it is static, which is why NTSC sets all have a Tint control, which you then need manually to adjust the phase angle to compensate the colour for changing atmospheric conditions. That's why broadcast NTSC looks so terrible, but NTSC delivered locally to a TV, say from a DVD player, looks fine! The subcarrier frequency of most NTSC colour signals is slightly different - so displaying NTSC on a PAL set or vice versa generally ends up giving you a black and white image, because it can't decode the colour. When this frequency happens to be the same, it corrupts the colour, but the image is still there.

Most people mistakenly believe that NTSC and PAL include a difference of refresh frequency - 50 or 60 Hz, that actually has nothing to do with PAL/NTSC, either can be broadcast in either frequency, and most modern sets will accept both. The frequency difference is derived simply from the power system frequency used in the countries that use the two standards ... convenience, which is now anachronistic. For NTSC this had the unfortunate, and coincidental side effect of making the conversion between film and TV, etc much uglier!

Thank goodness PAL/NTSC are a thing of the past, unfortunately, however, having multiple competing standards isn't. Now we have to deal with the ATSC vs DVB issues!

[totallymaxed]

Hi,

I'm still to actually get my system installed, but spend a considerable amount of time surfing the site and planning my rig when I have both the time and money (at the same time!) to put it together.

I am somewhat confused about versions of the components and features supported, though. What version of Myth is being used? I ask because the latest version does cool things like linking in to IPTV and allowing you to pull off all the channels multiplexed onto a single transponder with only one sat tuner card.


Also, is HD supported or not? I've seen lots of posts asking questions about hardware and fixing HD, which would imply that it is, but I'm sure I've stumbled across pages saying "not yet" as well.

I have other questions, but will put them into other threads 

Thanks!

Hi there,

Thought I'd just respond on a couple of UK specific things in your initial question & in the follow-responses. In the UK currently you have 4 ways to receive broadcast digital TV;

• Freeview (aka DVB-T) SD transmissions only
• Freesat (aka DVB-S) SD & some HD transmissions
• Sky (aka DVB-S) SD & many HD transmissions
• Virgin Media (aka DVB-C...kind of!)Sd and many HD trasnmissions

Freeview or DVB-T is currently only broadcast in SD in the UK due to bandwidth limitations until after the digital switchover due to complete in 2012. The other three all offer some HD channels now (with Sky leading in this area currently) and these services will expand greatly over the next few years.

If you use DVB-T tuners in your current LinuxMCE-0710 Core you will only receive SD DVB-T because that is all that is transmitted here in the UK. Secondly even if there were HD DVB-T tranmissions here in the UK it is very likely that todays DVB-T tuner cards would not receive the transmissions and the same would be true of your current Freeview STB too if you own one!

However we can expand the resolution of the standard DVB-T transmissions and this is called upscaling. If you configure your MD's to 720p or 1080i for example any video content they display, including DVB-T, will get upscaled to that resolution by the MD. If the source material is encoded well and was received, in the case of DVB-T, on a channel that transmits at a high enough data rate then upscaling can look very good indeed - many people actuall cannot differentiate between an HD transmission displayed at is native resolution and an good quality SD one that has been upscaled!

We at CHT are working on adding Freesat SD support to the next release of LinuxMCE, LinuxMCE-0810 and we have this working now on the 'test bench'. We are testing intermixing DVB-T & DVB-S tuners in a single core - this works now...but there is no user friendly way currently to combine the two types of channels into the channel list. Later we will upgrade the Freesat capability to HD when vdr 1.7 goes stable - this version of vdr support HD encoded channels.

Hope the above helps clear this area up for you :-)

All the best

Andrew

[wierdbeard65]

Many thanks to both Colin and Andrew! 

Just one thing, Colin, isn't NTSC 60fps and PAL 50? I thought that both (originally) used the mains frequency as a clock (or I may be mis-informed here!) also, isn't the number of lines different?

Anyhow, TV isn't my specialist area - I'm a network and VoIP person, although I'm gonna have to pick up Asterix

Andrew, useful stuff. If I get a DVB-S card (or cards) I can get freesat HD, right? Is there any way I can get Sky without an HD STB? I don't want to pay the premium for a STB with built in VDR (I believe it's Sky+ right?) to then plug it in to MCE 

I'll keep watching closely for news of the DVB-T / DVB-S integration, although for the time being, I reckon I'm going for a Quad LNB with one feeding a Sky STB attached to an MD (politics) and the other 3 feeding cards in my core.

Do you have recommendations for a good (UK) card and supplier?

TIA

[colinjones]

Read above - as I say, NTSC and PAL can work at either frequency. Indeed, there are some countries that used NTSC at 50Hz, and PAL at 60Hz. The standard focuses on the colour encoding only, the rest of the transmission relies on the older B&W standards. Yes, the lines are different, but that isn't a result of colour field, its incidental that that. As I said, the refresh rate is related to the power system frequency, but it is a misunderstanding to think that it is in any way a "clock". The power system frequency isn't anywhere near stable enough in the short term - putting a heavy, resistive load on the power network causes the system frequency to slow down. Over time the power company will regulate power output to bring the time-averaged system frequency back up again, because reactive loads depend on this being accurate, however such long term variation would be incompatible with microsecond level timing required for broadcast TV!

No, timing, such as it is, in TV is simply provided by the horizontal and vertical sync signals transmitted with the broadcast. This provides the "flyback" signal to the TV to tell it to return the trace either to the left of the screen, two lines down, or back to the top left, this is known as the vertical or horizontal blanking period. This timing area is also known as the "porches". Colour signal is handled differently, there is a timing/syncing pulse known as the Colour Burst transmitted when the trace gets to the far left, just before it begins scanning. This signal is used by (typically) a Phase Locked Loop to synchronise phase with one of the 2 colour signals (Red-Luminance and Blue-Luminance, from memory, there is no Green, that is derived) - as both colour signals are transmitted at exactly the same subcarrier frequency, but overlayed on top of each other with a 90deg phase shift, having a reference signal in-phase with one of these colour signals is necessary to be able to lock on to it and extract it from the other colour frequency. Otherwise they would be lost together forever So this is another part of the timing system, if you can call it that.

Andrew - sorry, was advising as generally as I could, but didn't realise that there were no HD DVB-T broadcasts in the UK yet... guess that explains why you guys have so many channels in a single bouquet!

[wierdbeard65]

Colin,

My mistake, I missed that part of your explanation. I guess a lot of the confusion comes from the view that most of us who are "not in the know" assuming NTSC=US and PAL=UK. SECAM=France. I guess all the standards get used elsewhere and with different parameters.

The analogy I was trying to make, however, stands and my question has been answered (a PAL tv won't playback an NTSC signal and I was worried that an SD TV when connected to an MD with an HD recording would similarly have "issues"). I now have it clear in my head (thanks to you) that the HD/SD issue when talking about the broadcast, recording and the link between the MD and the core is separate from the one when dealing with the display device and the link between it and the MD.

I was assuming that transcoding would happen on the core, whereas in fact that process (which is really rescaling) happens in real-time on the MD.

So......

If I install some kind of HD reception system in my core, I will be able to watch them on my current SD screens and, when I upgrade some to HD, I will see the benefit. My MCE system and my recordings are future-proofed and that's what I wanted to know 

Thanks, again, for taking the time to respond and clarify this for me.

I need to be VERY clear what I can achieve if I'm going to get the all-important sign-off from the management committee (AKA my good lady wife (chair) and our offspring)

[colinjones]

Yes, that should be fine... but I note totallymaxed's comments that your only HD broadcast source in the UK is likely to be DVB-S/S2 satelite for now.

[wierdbeard65]

That actually suits me fine as I don't currently have an aerial anyway  I'm sure that a quad LNB will provide enough for my family to go at for the time being!

[totallymaxed]

Many thanks to both Colin and Andrew! 

Just one thing, Colin, isn't NTSC 60fps and PAL 50? I thought that both (originally) used the mains frequency as a clock (or I may be mis-informed here!) also, isn't the number of lines different?

Anyhow, TV isn't my specialist area - I'm a network and VoIP person, although I'm gonna have to pick up Asterix

Andrew, useful stuff. If I get a DVB-S card (or cards) I can get freesat HD, right? Is there any way I can get Sky without an HD STB? I don't want to pay the premium for a STB with built in VDR (I believe it's Sky+ right?) to then plug it in to MCE 

I'll keep watching closely for news of the DVB-T / DVB-S integration, although for the time being, I reckon I'm going for a Quad LNB with one feeding a Sky STB attached to an MD (politics) and the other 3 feeding cards in my core.

Do you have recommendations for a good (UK) card and supplier?

TIA

...re NTSC/PAL/almost all TV's sold in the UK today (apart from the most basic models) will comfortabley handle all both tansmission standards... although your mileage may vary from manufacturer to manufacturer.

Freesat HD... Currently Freesat carries some HD channels (BBC HD channels, ITV and a few others) however to receive these we would need an updated stable vdr as vdr-1.6.0 does not support HD channels. Vdr-1.7.x is still in development and is not stable yet but this version will support HD channels and has many other enhancements that will be very exciting including using TS containers for its recording format. So shortly after vdr-1.7.x goes stable you should see an update for this version and this will deliver the basic HD capability we need (there will also need to be some other changes to manage SD/HD channels etc).

We (as in CHT/Dianemo that is) currently use Hauppauge Nova-S single tuner DVB-S cards and are about to make the changeover to Nova-S-HD cards which are S2 capable so that we can handle S2 formatted transmissions when they start to appear.

Further on the satellite side i would recommend that your install a MultiSat box (think of this as distribution amplifier for Satellite) that handles both Satellite and TV/RF down the same coax (CT100) cable. This enables you to bring all your Sat dish and RF Aerial feeds into the MultiSat box and then run a single CT100 run to each room where you need Sat/RF (giving you access to all four LNB's and RF in each location).

As to suppliers here in the UK for Sat cards... we buy from distributor...but do a search and find the best price you can is the recommendation.

All the best

Andrew