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Travel Channel and Film4+1 comes to Freeview, Film4 to Freeview Light

Two welcome developments for Freeview today. The popular Travel Channel (already on Freesat 405 and Sky 251) starts an evening service, and Film4 moves to all UK transmitters, bringing more choice to homes with the limited Freeview service.

Two welcome developments for Freeview today.   The popular Trav
published on UK Free TV

42 isn't just the Ultimate Answer to Life, the Universe and Everything, it is where you will now find the Travel Channel on Freeview, from 6pm-10pm.

Scripps Networks (who half own UKTV with the BBC) also broadcast the Food Network on Freeview.

Scripps Networks Jon Sichel told Broadcast "The launch on Freeview represents another milestone in the expansion strategy for Travel Channel as a world-class brand. We want to continue to build awareness of our award-winning content and global brands, and this trial block with Freeview is a great partnership that helps us fulfil that goal" (Travel Channel heads to Freeview Broadcast).

Scripps sister-channel Food Network is currently available via Freeview.

Film4 - Great news for Freeview Light

Homes with Freeview Light will be very pleased indeed to hear that they now have Film4 to watch, as the channel has moved to multiplex PSB2.

Freeview Slot 45 is now allocated to Film4+1, which is on the Full-Service-only multiplex of COM6.

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Friday, 2 August 2013

4:30 PM

Mick_Dawn: it's an extra stream. ITV+1 and c4+1 have better resolution too

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Briantist's 38,915 posts US flag
Mike Dimmick

6:38 PM

Tim: No, that's completely wrong.

The signal/noise/interference profile is governed by the low-level modulation. You can trade off the multiplex capacity in megabits versus the signal-to-noise+interference ratio required (effectively the coverage). The PSB multiplexes have approximately the same required SNR for reliable performance: PSB1 and PSB2 use the same DVB-T mode and have the same SNR requirement, PSB3 (HD) uses DVB-T2 and has slightly different requirements, but less than 1 dB difference in the most difficult conditions. The COM multiplexes started out using the same mode as PSB1 and PSB2, but chose to trade off a little less coverage for a little more capacity. The rollout of that change completed last year.

Changes to compression efficiency only affect the round-trip accuracy of the result. MPEG-2 Visual and MPEG-4 AVC get most of their compression from predicting where a block is going to move from one frame to the next. (MPEG-2 Visual can only encode moves in whole-pixel units; AVC can encode moves in quarter-pixel units.) Where motion prediction is used, all that needs to be sent to the receiver is the list of block movements, plus the differences between the resulting reshuffled old picture and the actual new one. The better the prediction, the less difference data needs to be sent. With more computing power available, more effort can be expended on the prediction in the same amount of time. The encoders have to work in real-time - i.e. a fixed, small duration from the frame arriving at the encoder to the encoded content coming out - because many of the channels are live, or can have live programmes, and even if a multiplex only contains pre-recorded programmes, the effort to co-ordinate all the channels to do the encoding off-line is impossible.

Different content requires a greater or lesser amount of multiplex capacity to encode with equal quality (and equal computing capacity). In order to keep quality consistent over a range of content and allow extra capacity momentarily where needed, the multiplexes use 'statistical multiplexing' - another device, the 'statmuxer', looks at the bitrates that the various channels on that multiplex are currently using, and what they're asking for, and makes decisions about reducing the rate on one in order to increase it on another. Again, the better the computing power, the better decisions it should make.

The other source of compression is how a full picture, and the differences between prediction and actual, are encoded. This is the same as JPEG: the picture is divided into 8x8 pixel blocks, then the brightness and colour are converted from a sequence of values (scanned diagonally across the block) into frequencies, using the Discrete Cosine Transform. The encoder then uses a quantizer to say how large the contribution from each frequency is. The more compression is required, the fewer bits are allocated to each frequency, which means fewer values are available. The quantizer selects the nearest available value to the true value, which means it's a little bit wrong. The fewer levels available, the more wrong it will be. But if it's fairly close to the 'right' value, the viewer won't notice.

Primarily, when not enough bits are available for a channel, the block edges become visible. This is because the quantization in one block doesn't match that in another, so a continuous tone across two blocks ends up as one level in one block, but a different level in its neighbour. The decoder has a 'deblocking filter' to correct this, but the bigger the difference, the less effective it is.

Yes, one way to increase the compression ratio is to increase the length of the Group of Pictures (GoP). A GoP contains one full picture (the 'Intra' or I frame) and then any number of either Predicted (P) frames (motion-prediction from the I frame only) or Bi-Predicted (B) frames (motion "prediction" from an I frame and a future P frame, or between two P frames - the frames can be sent out-of-order and the receiver puts them back in the right order). As you say, a longer GoP also means it takes longer to start displaying the video stream after switching channels, and if you're directly cutting the data stream, it gives you fewer cut points, since you can only start a cut at the start of a GoP, and only end it after an I or P frame (since the B frames don't make sense if you remove the P frame they depend on).

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Mike Dimmick's 2,486 posts GB flag
Kim Smart
6:47 PM

The Wednesday evening of the 31st 2013 film 4 disappeared from my freeview its not there today either..I have tried to retune but to no avil ...Could you tell me has film 4 stopped broadcasting to freeview customers?

Kim Smart

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Kim Smart's 1 post GB flag
Dave Lindsay

7:15 PM

Kim Smart: It is still available and is in the process of changing multiplex. At present it is (according to my receiver) available on its old multiplex and on the new one.

See if it is on logical channel number 791 or in the 800s.

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Dave Lindsay's 5,724 posts GB flag

7:27 PM

Kim Smart: To add to that said by Dave Lindsay, Film 4 is still using LCN15 but is now being broadcast from the ITV1 transmitter hence why nothing is being received as your programme guide has not been updated to accommodate this change.

Try carrying out a "first time installation" before making another attempt at retuning, "factory reset" or "default settings" being other terms used depending on the brand of equipment.

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jb38's 7,179 posts GB flag
Saturday, 3 August 2013
Morris Woodberry
11:51 AM

Will the constant retune of channels ever STOP... It would not be so bad if the TV companies did it all together... I retune five neighbours TVs each time a total of 11 televisions

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Morris Woodberry's 2 posts GB flag

11:53 AM

Morris Woodberry: basically no. The platform is going to be constantly updated with me channels and improved compression.

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Briantist's 38,915 posts GB flag
8:05 PM

This is good news. Thanks to Google I found your explanation. We're afflicted with Freeview Lite but suddenly today Film 4 appeared. As far as I know we didn't manually retune, but the EPG doesn't yet show any programme details. We're on BT Vision - might be worth doing a rescan? I wonder if it's a hangover from when we lived in London and we had all the channels (albeit on different channel numbers).

Anyway, no matter, we have one more reason to hold out getting Freesat, as we generally stream the other Freeview channels online.

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Andy's 2 posts GB flag
Monday, 5 August 2013
Peter Young
8:58 AM

I am with Morris Woodberry here. The first I heard of the disappearance of Film4 was a phone call froma friend in the middle of a programme I was enjoying on Saturday. Non-technical folk can be very distressed when their TV isn't working normally on their favourite channels.
Last night my internet search only pointed me to channnel 4's site and I e-mailed them. They e-mailed me this morning referring me to digital UK's site and don't seem to care at all that millions of viewers could be experiencing problems! Digital UK site doesn't suggest any problems or retuning needed - Just e-mailed them too. Only just now found your site - keep up the good work.
Why is this retune such a well kept secret?

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Peter Young's 3 posts GB flag
Peter Young
9:18 AM

Oh yes and I forgot. Everytime I retune, it takes ages to delete all the subscription, shopping and adult channels that clutter up the EPG. If I manually retune, it can affect the prog+/- button(s)depending on the box/tv model concerned.

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Peter Young's 3 posts GB flag
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