Why enforce simultanous recording limit?

sarumbear

Novice Member
Hi

I cannot understand the reason behind the limit of recording 'only' two channels at the same time. I tried and failed to find an answer in the forums. If I failed please point me to the relevant link.

At any place in UK where you can receive FreeView you can tune to just six multiplexes (MUX). These broadcast all FreeView TV, Radio and Text services multiplexed into a single data stream. MUX are often known as frequencies in FreeView box/PVR parlance.

In the case of a twin tuner PVR, one can record two channels at the same time, but why just two? As each MUX transmits five or more channels and the PVR has two tuners and hence can receive two data streams at the same time, you should be able to record ten or more channels at the same time WITHOUT any limitation to the hard disk capacity or capability.

In fact if you configure a Windows Media Center or use NextPVR to do exactly that. Heck, you can even select the channels AFTER you have recorded the program. That is because you have recorded the data stream that carries multiple channels. You can demultiplex that data at playback and chose the channel you want. Which means, a five tuner PVR system can record EVERY FreeView channel there is. As each data stream is about 15Mbps, the current hard disks will have no difficulty to record five channels simultaneously.

If what I have explained above is correct why does EVERY PVR manufacturer on the market limit us to two channels? Am I missing something?

All the best

Riz
 

grahamlthompson

Distinguished Member
Some PVRs allow you to watch another when recording two already (with twin tuners).

Perhaps its a hardware limitation? Hard drive write rate? Processing Power?
It's not a HDD limitation. A Toppy with a TAP can record a whole mux. It eats up your hdd at a prodigious rate. :D
 

sarumbear

Novice Member
It eats up your hdd at a prodigious rate.
But, you don't have to record the whole MUX. You can select what you want to record. Yes, it consumes more disk space, but you record more programmes. Surely, the consumer will understand -- and accept -- that the more programmes you record the more disk space it consumes.

I still do not understand the 'logic' of the limitation of just two. Of which I'm sure one, otherwise all manufacturers won't be obeying to it.
 

grahamlthompson

Distinguished Member
But, you don't have to record the whole MUX. You can select what you want to record. Yes, it consumes more disk space, but you record more programmes. Surely, the consumer will understand -- and accept -- that the more programmes you record the more disk space it consumes.

I still do not understand the 'logic' of the limitation of just two. Of which I'm sure one, otherwise all manufacturers won't be obeying to it.
For the average punter being presented with a prodigous list of channels you want to record to choose which would be a pain in the neck. There are some satellite boxes that let you record up to 4 at once based on transponder limitations (The Humax Icord). The Humax HDR FOX T2 will in effect let you record 3, by rewinding the timeshift buffer after the recording sharing the same mux is completed.

The firmware complications would be horrendous, imagine trying to resolve the clashes arising from recording lots from the same transponder with different start and ends with follow on recordings.

Which leaves out series and accurate recording capability. It ain't going to happen.
 
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noiseboy72

Distinguished Member
Doesn't somebody sell a MUX recorder that can record everything at the same time ? Pretty darn expensive and eats HDD space like nobody's business.

I gather that a number of broadcasters and police forces use them to capture all channels for future analysis.
 

grahamlthompson

Distinguished Member
Doesn't somebody sell a MUX recorder that can record everything at the same time ? Pretty darn expensive and eats HDD space like nobody's business.

I gather that a number of broadcasters and police forces use them to capture all channels for future analysis.
If I remember correctly, around £1000.00 and SD only :eek:. There's an old thread somewhere.
 

sarumbear

Novice Member
For the average punter being presented with a prodigous list of channels you want to record to choose which would be a pain in the neck.
What list? I cannot see any need for a UI change. Am I missing something?

They will see the same programme list as normal. The only difference is they will not get the "you are already recording two channels" message as often.

The firmware complications would be horrendous.
Why would there be complications?

trying to resolve the clashes arising from recording lots from the same transponder with different start and ends with follow on recordings.
We are talking of two data streams at the speed of 15Mbps each. Modern day computers -- which PVR is one -- handle orders of magnitude more data routinely. The data complexity and throughput of FreeView signal is nothing compare to what happens when you do a Save As on Excel.

Which leaves out series and accurate recording capability.
Not correct. NextPVR can record series while simultaneously recording any number of channels transmitted on the same MUX, using just one tuner.

Doesn't somebody sell a MUX recorder that can record everything at the same time ? Pretty darn expensive and eats HDD space like nobody's business.
You can buy a 3TB disk for £70 wholesale, that is £20 more than a 500GB disk. That £20 extra translates to around £80 retail value. I.e. by simply increasing the cost of your PVR by £80 you can say:

Records up to five channels at the same time (depending on the selected channels)

Wouldn't you pay the extra?
 
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mike7

Distinguished Member
When would you find the time to watch all this extra Freeview stuff, most of which is repeats anyway? I have a Virgin Tivo box which records three channels at once, but I seldom, if ever, use it to that extent.
 
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Gavtech

Administrator
If what I have explained above is correct why does EVERY PVR manufacturer on the market limit us to two channels? Am I missing something?
Not quite 'every'

See here.
 

Trollslayer

Distinguished Member
You can buy a 3TB disk for £70 wholesale, that is £20 more than a 500GB disk. That £20 extra translates to around £80 retail value. I.e. by simply increasing the cost of your PVR by £80 you can say:

Records up to five channels at the same time (depending on the selected channels)

Wouldn't you pay the extra?
With this audience, yes.
If you say it can make five recordings the general public want five recordings.
They don't care about the details.
 

grahamlthompson

Distinguished Member
I fail to see what the Excel save as function has to do with it. There's no effort in simply saving a copy of an existing file with a differrent name, a totally trivial operation.

As it happens I wrote an Excel application for the Foxsat-hdr that calculates the recording possibilities using one or two cables including the ability to identify when switching to a different transponder can make recording and third viewing possible when using one or two lnb connections. So I do know a bit about the subject.

Try it for yourself. Foxsatrecordcheck11 from here

https://skydrive.live.com/#cid=7A85DB0B139861D6&id=7A85DB0B139861D6!106

Every time you add an extra recording to the same tuner from the same mux with overlapping times you are going to generate multiple and complex clashes. Just identifying and asking the user to choose which to cancell to resolve the clash is far from simple. Imagine adding a simple reservation and generating say a list of 6 clashing existing reservations and having to choose to cancell more than 1.

A very simple example

Tuner 1 is currently set to record say 4 channels at once all finishing at say 21:00. Tuner 2 is set to record say 6 starting at 20:00-21:00 on a different mux. You try and add a new recording on a 3rd mux starting before 20:00 and after 21:00. You get a 10 channel clash message :eek:

Pvrs don't just stop you making a reservation they identify the clash and suggest ways to resolve the issue. (Have you ever used one ?)

Coping with a AR generated overrun message with a clash message of multiple channels would be pretty daunting.

Have you never had a clash come up at run time thanks to Accurate Recording ?

Humax won't enable the 4 channel recording capability of the Foxsat-hdr because they get enough calls already about the limitatations of the existing arrangement especially for single cable users.

I can imagine the calls if they were to say a whole mux.
 
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sarumbear

Novice Member
Not quite 'every'

See here.
There you are. Thank you! You have proven that what I thought possible is indeed possible and the 2 channel limit is artificial.

There is after all at least one manufacturer who does the logical. Shame that it is a small manufacturer with little to no marketing budget, hence you cannot see them on major retail channels. :-(
 

sarumbear

Novice Member
I fail to see what the Excel save as function has to do with it. There's no effort in simply saving a copy of an existing file with a differrent name, a totally trivial operation.
I respectfully disagree. You are ignoring what is going on at the OS level. Data is recorded on multiple sectors of the disk and the application along with the OS has to gather the data and put it back on various other sectors to make an alterred copy of it. That happens in an instant but the data involved is not much different than it is at a PVR.

Can you really tell me that demultiplexing a couple of 15Mbps data channels, stripping programme start and end flags is a complicated matter for today's computers? Just imagine what happens on your home router and its firewall. Imagine what happens on a big Cisco firewall with multiple 10 GIGA bps connections. Trust me, I wrote code for those boxes, I know what I'm talking about. I'm also a video broadcast engineer but I do not practise that these days.

Every time you add an extra recording to the same tuner from the same mux with overlapping times you are going to generate multiple and complex clashes. Just identifying and asking the user to choose which to cancell to resolve the clash is far from simple. Imagine adding a simple reservation and generating say a list of 6 clashing existing reservations and having to choose to cancell more than 1.

A very simple example

Tuner 1 is currently set to record say 4 channels at once all finishing at say 21:00. Tuner 2 is set to record say 6 starting at 20:00-21:00 on a different mux. You try and add a new recording on a 3rd mux starting before 20:00 and after 21:00. You get a 10 channel clash message :eek:

Pvrs don't just stop you making a reservation they identify the clash and suggest ways to resolve the issue. (Have you ever used one ?)

Coping with a AR generated overrun message with a clash message of multiple channels would be pretty daunting.
Yes, I have used a PVR, I use them daily. I do know what you are talking about but cannot see why it is the case. As I tried to explain above, the computation power is huge. What you explained in the above paragraph is nothing for a computer. It is an engineering problem only and we all know that engineering problems are solvable -- always!

Humax won't enable the 4 channel recording capability of the Foxsat-hdr because they get enough calls already about the limitatations of the existing arrangement especially for single cable users.

I can imagine the calls if they were to say a whole mux.
Is that why Promise.TV is not generally available at the shops? Is that because their PVR is not working as advertised?

Or, they can do what I think can be done but Humax cannot?
 

mike7

Distinguished Member
There is simply no market for an expensive device to record multiple channels. It would not have mass appeal. People use various 'catch-up' services if they miss something. No market place, no market for a niche product. No manufacturer is going to invest in such a product. If you want to record more then why not buy additional PVRs ?
 

grahamlthompson

Distinguished Member
sarumbear said:
;17356264Yes, I have used a PVR, I use them daily. I do know what you are talking about but cannot see why it is the case. As I tried to explain above, the computation power is huge. What you explained in the above paragraph is nothing for a computer. It is an engineering problem only and we all know that engineering problems are solvable -- always!
Pvr's don't have programmeable cpu's like a PC. They are based on dedicated large scale chips mostly by Broadcom, which provide the basic pvr functions. They have limited memory and use relatively modest clock speeds. They can't be described as having massive computational power.

Most can't even record two channels from the same mux using a single tuner let alone more than two. Streaming a whole mux to disc is relatively simple as it's a straight data copy of the original broadcast data stream. You don't get a fancy list of individual recordings just a single file. It's then down to the box in effect extract the channel you want to watch from the recorded mux just as it would have been if viewed recorded in the first place. This must have implications for viewing such recordings while making others.

If you want such a minority product you will have to make one using a htpc, with lots of memory, ooodles of Hard Disc space and a fast multicore processor. It won't be cheap :eek:

Expecting this capabilty from a £300.00 mass produced pvr is a pipe dream.

Perhaps the most prolific pvrs in use in the UK are the Sky+/Sky-HD ones. With these you can't even view a 3rd channel while recording two.
 
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sarumbear

Novice Member
Pvr's don't have programmeable cpu's like a PC. They are based on dedicated large scale chips mostly by Broadcom, which provide the basic pvr functions. They have limited memory and use relatively modest clock speeds. They can't be described as having massive computational power.
I do realise that, you can see some examples here and here.

If you want such a minority product you will have to make one using a htpc, with lots of memory, ooodles of Hard Disc space and a fast multicore processor. It won't be cheap :eek:

Expecting this capabilty from a £300.00 mass produced pvr is a pipe dream.
Once again I respectfully disagree. Have you seen the price and specs of the Raspberry Pi? US$25 can buy you a RISC CPU running at 1GHz with onboard GPU. Smartphone technology offers you immense computational power for very little cost. It is the same technology that runs the iPhone and iPad which can act like a PVR easily.[/QUOTE]

Price is directly proportional with scale. There is no reason I can see that stops one to design a PVR that record tens of channels while costing almost the same as the major PVRs on the market. If a small family firm like Promise.TV can offer such a device for £599, you can bet that price can be halved when the device is mass manufactured. Stop using a wooden box for starters, there's your £40 retail value gone!

I'm an engineer and I do not see any reason why we should be limited with the number of channels we can record at one time. All your kind replies so far proven to me that engineers who designed the PVRs were lazy and/or were trapped into the chip manufacturers offerings.
 

Rodders53

Distinguished Member
As each data stream is about 15Mb/s,
A post-DSO 8k, 64QAM mux has 24Mb/s capacity, or 27Mb/s for the two Arqiva ones. The HD mux is 40 Mb/s.

So you could have to record quite a bit more than 15...

{The 2k, 16QAM mux was 18Mbit/s capacity.}

Digital terrestrial television in the United Kingdom - Wikipedia, the free encyclopedia

Don't some Home Theatre PC's allow more flexible recording options?

My view is that this is a niche market product. Most of us cope with the two simultaneous recordings limitation. I use +1 and repeats to cover the odd time when I need more (virtually never watch live)... and I have two PVRs but still only fire up the one!! :facepalm:
 

sarumbear

Novice Member
A post-DSO 8k, 64QAM mux has 24Mb/s capacity, or 27Mb/s for the two Arqiva ones. The HD mux is 40 Mb/s.

So you could have to record quite a bit more than 15...

{The 2k, 16QAM mux was 18Mbit/s capacity.}
Still in the ball park of the figure I wrote. Disk data rates are almost an order of magnitude more that FreeView MUX data rate. That was my point.

Those data rates are not a problem since 200+GB disks became available. Today a cheap 5400RPM disk has 40MBps (around 400Mbps). DV video data rate is 3.6MBps (around 36Mbps) and you can stream multiple DC streams using current disks even when connected via USB2/FireWire 400. (Don't confuse Byte per second with bits per second.)

Don't some Home Theatre PC's allow more flexible recording options?
Yes they do, as I have said in my initial post.

My view is that this is a niche market product. Most of us cope with the two simultaneous recordings limitation. I use +1 and repeats to cover the odd time when I need more (virtually never watch live)... and I have two PVRs but still only fire up the one!! :facepalm:
Before iPhone came most said the same for smartphone. Look what happened to Nokia who thought as much and to Apple who begged to differ.

You cannot make such a decision before you offer the product to the masses and teach them the virtues with marketing. Like Apple did with iPhone.
 

mike7

Distinguished Member
You cannot make such a decision before you offer the product to the masses and teach them the virtues with marketing. Like Apple did with iPhone.

I really don't see what 'marketing' has to do with this. True people can be talked into anything, but look at the numbers of people who have bought into 3D and SMART TV only to find it is not quite what it cracked up to be, and largely abandoned it. I think you would have to be a very clever marketing man to convince a substancial number of customers that they need a product that will record hundreds of hours of television that they would either have to store or struggle to find the time to watch.

As you say there are technical problems that could be overcome,at a price, but since no-one has mass produced such a product I can only conclude that manufacturers have decided that it is hardly likely to attract any serious interest amongst the public. Lets face it for many years the single channel recording VCR met the needs of most of us, and that was before iPlayers and +1 channels.
 

Gavtech

Administrator
Price is directly proportional with scale. There is no reason I can see that stops one to design a PVR that record tens of channels while costing almost the same as the major PVRs on the market....

Snip

..I'm an engineer and I do not see any reason why we should be limited with the number of channels we can record at one time. All your kind replies so far proven to me that engineers who designed the PVRs were lazy and/or were trapped into the chip manufacturers offerings.
Is not the issue here that you are looking at this entirely form an engineers perspective.

You are not taking any account of marketing, or price point fixing, which has a great deal to do with why the marketplace is the way it is.

It has always been the case that the technological capability is way ahead of what is actually offered in the marketplace, except in niche product areas that typically cost tens or hundreds of times a 'standard' product.

Your argument suggests that economies of scale could make a difference here... but why would manufacturers want to go down that road? They struggle enough for profits in high tech areas.

The product you would wish for already exists - but clearly will not sell much... and I have some puzzles myself in regard of just how such a machine could usefully function in day to day use.
Take the 7 day recorder for example. I presume it amounts to a 7 day retrospective time shifter for the whole of SD freeview.

I presume all its resources are thrown at this problem, and that it will operate on a steady self-replenishing cycle.
So I doubt there is much storage left available to do what many users tend to do which is use their PVR's as semi- archiving devices.

Again, you may argue that it is just a case of throwing yet more resources at it... but if that is the case you need to know just how much manufacturers will baulk at putting in an extra chip never mind more or larger drives.

This really is an economics issue, not a technical or engineering problem.
 

sarumbear

Novice Member
You cannot make such a decision before you offer the product to the masses and teach them the virtues with marketing. Like Apple did with iPhone.

I really don't see what 'marketing' has to do with this. True people can be talked into anything, but look at the numbers of people who have bought into 3D and SMART TV only to find it is not quite what it cracked up to be, and largely abandoned it. I think you would have to be a very clever marketing man to convince a substancial number of customers that they need a product that will record hundreds of hours of television that they would either have to store or struggle to find the time to watch.
If you re-read your comment above you will see that you admit it is all about marketing. :)

As you say there are technical problems that could be overcome,at a price, but since no-one has mass produced such a product I can only conclude that manufacturers have decided that it is hardly likely to attract any serious interest amongst the public. Lets face it for many years the single channel recording VCR met the needs of most of us, and that was before iPlayers and +1 channels.
You can also conclude that manufacturers are lazy and as you said, thought from a VCR to a twin tuner PVR is enough of development jump. Let's face it. The market for non-subscription connected units, which are almost free (Sky+ and Tivo), is minuscule. There is no market sense to try to just match their capabilities if you are in the market. If I was Humax/Vestel/Beko/Thompson I would try to offer extra so that people are attracted to my offering.
 

sarumbear

Novice Member
Is not the issue here that you are looking at this entirely form an engineers perspective.

You are not taking any account of marketing, or price point fixing, which has a great deal to do with why the marketplace is the way it is.
Marketing starts with capabilities of a device, which is an engineering process. A modern day engineer works with designers and marketers, through a product manager.

Your argument suggests that economies of scale could make a difference here... but why would manufacturers want to go down that road? They struggle enough for profits in high tech areas.
So that they have a product that is demonstrably better than the competition. How can you differentiate a Humax PVR from a Topfield PVR? You can't and that is a marketing faux-pax.

Again, you may argue that it is just a case of throwing yet more resources at it... but if that is the case you need to know just how much manufacturers will baulk at putting an extra chip never mind more or larger drives.

This really is an economics issue, not a technical or engineering problem.
I will again give the iPhone example and how back in 2007 thought Apple is mad.

Capable products sell and will increase profits - period.
 

Rodders53

Distinguished Member
Well I look forward to seeing you get your product into production soon. It must be HD capable, of course and have a remote with full AV amp control capability (another of your ideas). Ideally serving streams to other, simpler, decoders in the rest of the house. {You View compatible would be good, but not essential}.

I'd happily pay £500 or thereabouts (as I did for a VHS HiFi stereo VCR - not Nicam - back in the 80s).
 

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