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Channel 4 HD blips

S

SemiRamis

Member
I had sometimes in the past experienced short fragments of either live/recorded tv where the picture would pixelate and sound would disappear. These were becoming more frequent indicating tuners failing. I got a "new" T2 out of storage and the perfect picture returned on all hd channels. Except on channel 4hd. The picture stays perfect, no pixeling, but a milisecond break in the sound.

The question is. Can a tuner fail on just one channel?
 
All the HD channels are now broadcast on a single multiplex so your box is tuned to the same thing. All that changing from BBC1 HD to 4HD does is causes the box to pick different digital data out of the stream it is already receiving. So it is very unlikely this is caused by the tuner.
 
Black Hole said:
I find sound-only issues are more likely to do with HDMI.
Click to expand...
I occasionally have to force a Humax and my TV to re-negotiate the HDMI connection to cure sound (or vision) problems.

Obviously not directly connected to C4HD, but I've found that sound problems on UKTV channels are more likely to be :poop: equipment at their end. Fingers crossed, no current problems, but clicks, pops and other noises (plus unconnected vision disturbances) have occurred on most U& channels irrespective of multiplex, Humax device and connection method.

It may be a C4 fault, trog is reporting problems on some StdDef C4 channels on the Aura - https://hummy.tv/forum/threads/arq-a-com-5-problems.11337/post-177227.
 
As the recorded stream of a channel is identical to the live... any inherent stream problems would (or should) be seen on both live and recorded instances of an identical stream.

Of course there are multiple sets of encoders, duplicated at two sites and an issue on one set of encode and mux may not be seen on another set of code and mux... So London C4 HD vs Newcastle can easily give different results in the event of a fault or setup issue. Even, potentially if a switch from one to another (coder, input stream, location, output stream to the transmitters) were to happen.

C4 HD on Sat is advert regionalised... not sure if that's true for Freeview HD (it is for SD, derived from the HD streams of course) but either way all (5/6?) incoming streams will be available within the Code & Mux centres for input to the relevant coder set that the OP will be watching...

So it is not such a simple question: Which Channel 4 HD version is this exhibiting a regular issue?

Then, such sound and vision issues are equally likely to be caused by other factors within any viewing location. High pressure propagation weather interference, electrical thermostat interference, mobile phone interference, for example, can all give varying and unpredictable issues. Only noticed on the most watched channel(s), of course.

BBC did have an issue with their kit many years back that gave rise to similar brief audio breaks - something to do with a large multiple of 2 (binary) frames and the Dolby E embedded audio signals and different brands / versions of kit en route to the coders from playout.
 
Rodders53 said:
As the recorded stream of a channel is identical to the live... any inherent stream problems would (or should) be seen on both live and recorded instances of an identical stream.
Click to expand...
Indeed that is the case on both live/recorded streams as I said in the opening.
This is the south east version of ch4hd
I will record on two machines to see if the blips coincide.
In the meantime if anyone recorded any of the Indiana Jones movies over Christmas we can compare with a different region.
 
SemiRamis said:
This is the south east version of ch4hd
Click to expand...
That's a big advertising region for C4: it covers:

BBC East (ex Norwich)
BBC Southeast (ex Tunbridge Wells)
BBC South (ex Southampton)
BBC Southwest (ex Plymouth)
BBC West (ex Bristol)
BBC Wales (ex Cardiff)
Channel Islands ITV, not sure if BBC opt still or cover from Plymouth?

So it could be any one of seven sets of kit with an issue (if the problem is not in playout itself). *Assuming C4HD is regionalised on Freeview as it is on Satellite.
 
That's not insurmountable – use a file sharing site and link through. You can even embed it in a post using the media tool.
 
For such a small file all you had to do was disguise it as a .txt :rolleyes:

Why is this a .mp4 and not a .ts? It's not the unmodified off-air recording, so the rest is just speculation. It seems like you're being obstructive. The sound track is very quiet (-35dB), so there's something wrong with that for a start.

Look at the 'blip' profile - it's not the clean cut-off we might expect of a fault:

Screenshot from 2025-01-20 12-39-17a.jpg
 

Attachments

Black Hole said:
Why is this a .mp4 and not a .ts? It's not the unmodified off-air recording, so the rest is just speculation
Click to expand...
Both the resolution (848 X 478) and FPS (30) are wrong for C4HD - probably should be 1920 X 1080 at 25fps. Not sure about the sound. Difficult, if not impossible, to comment on the possible causes of a sound dip without hearing it from the original recording.

Edit: FWIW the audio looks the same as a current C4HD recording - AAC LC 46.875fps.
 
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Black Hole said:
For such a small file all you had to do was disguise it as a .txt :rolleyes:

Why is this a .mp4 and not a .ts? It's not the unmodified off-air recording, so the rest is just speculation. It seems like you're being obstructive. The sound track is very quiet (-35dB), so there's something wrong with that for a start.

Look at the 'blip' profile - it's not the clean cut-off we might expect of a fault:

View attachment 7349
Click to expand...
Wow. You do seem to make up all sorts of traits and assumptions. You definitely need to calm down.

Firstly
Two people have wrongly assumed above that I posted the actual ts recording. Not correct.

Secondly
Black Hole said:
It might be instructive if the OP were to make a short recording available which demonstrates the problem.
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I posted EXACTLY that. A recording made with my phone of the playback including the problem. IE the blip. Exactly as I said earlier.
SemiRamis said:
The picture stays perfect, no pixeling, but a milisecond break in the sound.
Click to expand...
 
General comment: I do my best to help or at least research a problem presented. I get exasperated if I spend time and mental effort (irreplaceable commodities which could be applied more usefully elsewhere) but the recipient is uncooperative through ignorance, stupidity, or deliberate action (it's very hard to tell the difference). I swear some people don't read their own posts, or more particularly are unable to read their own posts with a view to how another reader would understand them (see Newbies Guide).

Serial offenders make my blood boil, and the best thing in a situation like that is to click the "Ignore" button. That means posts, threads, and even quoted parts of posts by that author, are hidden from my view when I browse the forum. The OP is now on my ignore list, so will have to rely on forum users who have not ignored him to answer his queries. Good luck with that.

I'm sure I am not alone.
 
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