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DTMark

Tv And Blu-Ray Questions

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Inspired by the thread about a TV playing up... couple of questions that our resident experts might be able to help with:

1. Blu-Ray player crashing

This is a cheap Panasonic one which we were bought as a gift. Does everything OK except that it crashes quite often. Film will be playing along quite happily and the whole thing freezes. Needs turning off and on again at the socket to get it back again. How "normal" is that for Blu-Rays?

2. TV picture glitching

Also a Panasonic but not a cheap one. About 6 months old.

The quality of the TV picture is very good to my eyes and often looks stunning. When you're watching a Blu-Ray (and only then) which has exceptionally high definition and a lot going on in the picture, just occasionally it glitches with the movement. It's almost imperceptible but not quite.

e.g. Mission Impossible Ghost Protocol - the scene where the camera pans across an overhead shot of the city in stunning detail - it looks like something isn't quite "keeping up". Doesn't visibly "stall", hard to describe, but assuming the camera is moving at a consistent speed left to right the picture doesn't move quite as consistently. The perception is that the movement isn't "uniform".

It's as if something isn't quite keeping up with the demand. Could this be the HDMI lead, the TV trying to "reframe" the picture, that Blu-Ray player again?

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With regard to the Blu Ray player, I had similar problems with a two year old Samsung that came free with the TV (3D package). I replaced it with a Sony BDPS490 which I recommend highly for the money (£69.95 at Richer Sounds).

The picture "glitching" sounds like it could be a scaling issue which can affect panning scenes, causing jerkiness. This could well be resolved by the new Blu Ray player.

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My blu-ray player was a bit buggy at first, it let me do firmware upgrades through an ethernet port on the back which sorted things out.

Have you looked into if the firmware can be updated? Maybe burn a disc or something?

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I'm very surprised that a Panasonic is crap at all! :huh:

Mind you there is a difference between a £80 one and a £250 one! ;)

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Have you tried updating the BR player firmware?

I connect my Panasonic BR player to my router every so often and check for firmware updates. However, if the crashes appear to be random, firmware might not be the answer - but possibly overheating - is the unit well ventilated?

I get the panning issue in some cases (also with a decent Panasonic TV), and haven't found a solution for it. Luckily it's not often a problem. It might be worth experimenting with the frame creation/refresh rate/24p settings on the TV, and seeing if the BR player has any options toggling 24p output. I doubt it will eliminate the issue, but it might improve it.

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I get the panning issue in some cases (also with a decent Panasonic TV), and haven't found a solution for it. Luckily it's not often a problem. It might be worth experimenting with the frame creation/refresh rate/24p settings on the TV, and seeing if the BR player has any options toggling 24p output. I doubt it will eliminate the issue, but it might improve it.

Movies will always judder a bit with panning - 24 Hz is just too slow to get good panning, but it's what is used for filming movies, so it's here to stay.

However, there is a problem, in that TV broadcasting is done at either 50 Hz or 60 Hz. On DVDs, UK films were played back at 104% speed - barely noticeable, but it would shave a few minutes of running time, unless the film was a musical and you are a musician with perfect pitch (in which case it is a disaster as all the music is out of tune).

However, with Blu-ray, 50 Hz is reserved for UK/Europe/Aus sourced TV. Movies will be played back at the correct speed, and this means that 24 Hz has to be forced into 60 Hz. This is a problem, as the 2 speeds are not directly compatible. The only way to do it, is to vary the time each movie frame is shown, alternating between 30 Hz and 20 Hz. This gives a horrible juddering experience, which is almost certainly what you've spotted. The trouble is that once you've seen it, you can't unsee it.

HDTV and Blu-ray does have a way around this. Blu-ray players can produce a 24 Hz signal, and HDTVs are capable of accepting a 24Hz (also called 24p) signal. If all is well, this should work fine, with each movie frame being shown for exactly the correct time. In practice, this isn't always the case, especially with cheap TVs; the TV may be able to accept a 24 Hz signal, but cheap TVs will often convert it to 60 Hz internally (using the uneven time method). Better TVs will take the 24 Hz signal all the way to the actual screen.

Unfortunately, there is no easy way to check that a TV works properly without testing it. All the specification sheets will say 24p compatible - but that means nothing, what matters is the internal processing in the TV. This usually means testing it out with a Blu-ray disc that you know shows the problem up. (I know I ended up buying a very expensive TV a couple of 3 or 4 years ago, specifically looking for 24p compatibility, and I was furious when I found out after a lot of fannying around that the TV juddered horribly with 24p because of the internal processing).

You may find that your blu-ray player, if it is a modern one, has better internal frame rate conversion than your TV. In which case, you may get better results, by choosing "always use 60 Hz" or whatever the option is called in your blu-ray player's settings.

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Movies will always judder a bit with panning - 24 Hz is just too slow to get good panning, but it's what is used for filming movies, so it's here to stay.

Actually, there's a panning rate below which stutter isn't noticeable and a panning rate above which it's too fast to be noticeable; you should only see stuttering pans when the people making the movie were incompetent and went into the middle range between the two (which does happen fairly often, even in Hollywood movies).

I believe you'll find actual numbers in cinematography manuals.

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2. TV picture glitching

Also a Panasonic but not a cheap one. About 6 months old.

The quality of the TV picture is very good to my eyes and often looks stunning. When you're watching a Blu-Ray (and only then) which has exceptionally high definition and a lot going on in the picture, just occasionally it glitches with the movement. It's almost imperceptible but not quite.

e.g. Mission Impossible Ghost Protocol - the scene where the camera pans across an overhead shot of the city in stunning detail - it looks like something isn't quite "keeping up". Doesn't visibly "stall", hard to describe, but assuming the camera is moving at a consistent speed left to right the picture doesn't move quite as consistently. The perception is that the movement isn't "uniform".

Is it noticeably jerkier than the other (crash-prone) player? Have you compared the two with the same disc and the same telly?

I ask because it could simply be a limitation of the disc. I'm not an expert (and am open to being told that I'm talking cobblers :P ), but as I understand it variable bit-rate video compression works by identifying scene changes (the details of which are recorded in full, as a 'key frame'), and then identifying which parts of the scene move in subsequent frames; the changes are then recorded, with the rest of the scene still being filled in from the original 'key frame'. Obviously, the more data space and bandwidth you've got available, the more key frames you can afford to use, and so on a DVD or Blu-Ray they'll generally refresh often enough (like several times a second) that the human eye won't perceive any jerkiness.

Blu-Ray has a lot of data space and bandwidth (30-50mpbs I believe?) but that's still not anything like enough to stream 24 1920x1080 frames a second in anything like photo quality, so they still use key frames. A smooth pan across a very detailed picture is obviously the nightmare scenario- there's a lot of detail in the picture, and it's all moving from one frame to the next. So the person mastering the disc has a Hobson's choice- they can either reduce the effective frame rate, preserving the picture detail but resulting in a noticeably jerky pan, or they can have a nice smooth pan at noticeably reduced resolution, resulting in a soft picture, possibly with JPEG-typle blocking effects. Since Blu-Rays are sold as high resolution, and since the filmmakers probably put a lot of effort/expense into the pan shot, be it via helicoper or matte, I reckon they're going to go with the jerky pan most of the time.

It's as if something isn't quite keeping up with the demand. Could this be the HDMI lead

Not gonna be the HDMI lead- albeit that you very occasionally get odd quirks, HDMI leads basically work or they don't. HDMI is a variant of the DVI standard- I.E. completely uncompressed digital RGB video (hence they're rated to gigabits of data transfer per second, versus 30-50 megabits coming off the disc). if we leave aside the question of HDCP, which I don't understand TBH, the TV just gets told what value to put on each of its red, green and blue pixels, there is no decoding going on whatsoever, it's all done by the player. The lead cannot cause a jerky pan, which is why the most expensive HDMI lead plugged into my £1k 60" plasma cost 3 quid, and only then because I needed an angled plug, thanks to the stupid design of the inputs on the telly :rolleyes: ).

that Blu-Ray player again?

It is certainly possible that some players are clever enough to apply their own smoothing if they detect a jerky moving scene, simply by moving the picture a few pixels in the direction of travel in between the key frames coming off the disc. But why your cheap but crash prone player would do this better than your expensive one, I don't know!

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Movies will always judder a bit with panning - 24 Hz is just too slow to get good panning, but it's what is used for filming movies, so it's here to stay.

Maybe I have slow eyes, but I watched a lot of films projected in 35mm as a member of my university's film society, and never once noticed juddering pans, or any other kind of juddering movement for that matter, whereas I notice judder on digital video and am annoyed by it.

The problem of 24 fps conversion to 60Hz TV (NTSC or Brazilian PAL) was referred to as "3:2 pulldown" I believe. I never owned enough NTSC Laserdiscs or DVDs to come to a definitive concusion about whether it annoyed me or not! :D In any case, I don't think it's a problem on a properly 24p capable screen. Both the big tellies in my house are new enough to have the problem licked, I think!

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Maybe I have slow eyes, but I watched a lot of films projected in 35mm as a member of my university's film society, and never once noticed juddering pans, or any other kind of juddering movement for that matter, whereas I notice judder on digital video and am annoyed by it.

The problem of 24 fps conversion to 60Hz TV (NTSC or Brazilian PAL) was referred to as "3:2 pulldown" I believe. I never owned enough NTSC Laserdiscs or DVDs to come to a definitive concusion about whether it annoyed me or not! :D In any case, I don't think it's a problem on a properly 24p capable screen. Both the big tellies in my house are new enough to have the problem licked, I think!

It's not very obvious on properly shown films; but maybe it's because I have quite sensitive eyes, because I can definitely notice it, although it's not obvious if the pan has been well photographed.

But then I projected 35mm for years at my University's film society, and could see and hear all the technical flaws in the format by the end of it.

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It's not very obvious on properly shown films; but maybe it's because I have quite sensitive eyes, because I can definitely notice it, although it's not obvious if the pan has been well photographed.

But then I projected 35mm for years at my University's film society, and could see and hear all the technical flaws in the format by the end of it.

Yeah? Good stuff! I was too lazy to complete the projectionists course (seemed like it would be a lot of effort spooling films up and down to earn your credit towards a free pass next term anyway, easier just to check tickets or sell confectionary, drinks and ice-creams, which as a shy extrovert I enjoyed anyway!).

Mind if I ask which film society? Me: Southampton, joined in 1998 in my second year. We had a pretty great setup; Vic-5, Dolby Digital, and even DTS when most commercial cinemas didn't yet have it (albeit that the DTS CDs turned up with the films once or twice a season at most :rolleyes: ). Unfortunately it was all installed in the Debating Chamber, so 50% of the seats were at right angles to the screen, and those that weren't had one or other of the side speakers blocked by the projection box, which meant to get the full big screen and 5.1 experience you had to sit on the floor :rolleyes: . I'm 70% deaf in my left ear, so the crew seats to the left of the projection box were not too bad for me, but for proper epic actioners I did the floor a couple of times!

We were always jealous of Warwick, who had a Vic-8, and did a 70mm jamboree each Easter. I never made it to one of those, but did have a great weekend at the BFI student film weekend. Ridiculously though, the best time I had there was seeing a preview VHS of Dobermann in a tiny little room with about 5 other people, on a 25" telly.

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Thanks everyone.

My blu-ray player was a bit buggy at first, it let me do firmware upgrades through an ethernet port on the back which sorted things out.

Have you looked into if the firmware can be updated? Maybe burn a disc or something?

I must admit I haven't. The TV, Humax box and the Blu-Ray player all have ports for internet connections but only the TV is ever connected since none of the others can do anything that the TV can't. So this might be one to look at. I did patch the Humax box but there may well be updates for the player.

I'm very surprised that a Panasonic is crap at all! :huh:

Mind you there is a difference between a £80 one and a £250 one! ;)

I think it was about £60 and came from Tesco!

Have you tried updating the BR player firmware?

I connect my Panasonic BR player to my router every so often and check for firmware updates. However, if the crashes appear to be random, firmware might not be the answer - but possibly overheating - is the unit well ventilated?

I get the panning issue in some cases (also with a decent Panasonic TV), and haven't found a solution for it. Luckily it's not often a problem. It might be worth experimenting with the frame creation/refresh rate/24p settings on the TV, and seeing if the BR player has any options toggling 24p output. I doubt it will eliminate the issue, but it might improve it.

Shall have a look.. It doesn't actually have any vents on the top. Because of the way the room is, it has to go quite near the fireplace - we haven't used it in ages, but soot does fall down it now and again and some might have got into it.

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It's as if something isn't quite keeping up with the demand. Could this be the HDMI lead, the TV trying to "reframe" the picture, that Blu-Ray player again?

Couple of things.

If you smoke you've probably destroyed the laser because the chemicals from tobacco smoke permanently alter the chemistry of the facet coating. Chuck it.

HDMI lead. No chance unless its got a break in the lead and you are wiggling it.

Dodgy discs? Are any of these movies burned yourself or bought at a car boot sale?

The TV... well, does it glitch on an HD tv channel as well? If so, the guts of it are probably defective. Get a new one.

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Couple of things.

If you smoke you've probably destroyed the laser because the chemicals from tobacco smoke permanently alter the chemistry of the facet coating. Chuck it.

Well some happy chuffers who I had staying for a bit, certainly bogged up mine! :blink:

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Movies will always judder a bit with panning - 24 Hz is just too slow to get good panning, but it's what is used for filming movies, so it's here to stay.

However, there is a problem, in that TV broadcasting is done at either 50 Hz or 60 Hz. On DVDs, UK films were played back at 104% speed - barely noticeable, but it would shave a few minutes of running time, unless the film was a musical and you are a musician with perfect pitch (in which case it is a disaster as all the music is out of tune).

However, with Blu-ray, 50 Hz is reserved for UK/Europe/Aus sourced TV. Movies will be played back at the correct speed, and this means that 24 Hz has to be forced into 60 Hz. This is a problem, as the 2 speeds are not directly compatible. The only way to do it, is to vary the time each movie frame is shown, alternating between 30 Hz and 20 Hz. This gives a horrible juddering experience, which is almost certainly what you've spotted. The trouble is that once you've seen it, you can't unsee it.

HDTV and Blu-ray does have a way around this. Blu-ray players can produce a 24 Hz signal, and HDTVs are capable of accepting a 24Hz (also called 24p) signal. If all is well, this should work fine, with each movie frame being shown for exactly the correct time. In practice, this isn't always the case, especially with cheap TVs; the TV may be able to accept a 24 Hz signal, but cheap TVs will often convert it to 60 Hz internally (using the uneven time method). Better TVs will take the 24 Hz signal all the way to the actual screen.

Unfortunately, there is no easy way to check that a TV works properly without testing it. All the specification sheets will say 24p compatible - but that means nothing, what matters is the internal processing in the TV. This usually means testing it out with a Blu-ray disc that you know shows the problem up. (I know I ended up buying a very expensive TV a couple of 3 or 4 years ago, specifically looking for 24p compatibility, and I was furious when I found out after a lot of fannying around that the TV juddered horribly with 24p because of the internal processing).

You may find that your blu-ray player, if it is a modern one, has better internal frame rate conversion than your TV. In which case, you may get better results, by choosing "always use 60 Hz" or whatever the option is called in your blu-ray player's settings.

Having worked on broadcast standard framestores and standards converters about 30 years ago, I think it's a shame that we still have this problem foisted upon us.

BTW, US Colour NTSC TV actually used a frame rate of about 29.97 FPS, not 30 FPS. This tweak to the original 30 frames/sec used in monochrome was in order to reduce the 3.58MHz subcarrier's interference with the audio FM component of the signal.

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Having worked on broadcast standard framestores and standards converters about 30 years ago, I think it's a shame that we still have this problem foisted upon us.

BTW, US Colour NTSC TV actually used a frame rate of about 29.97 FPS, not 30 FPS. This tweak to the original 30 frames/sec used in monochrome was in order to reduce the 3.58MHz subcarrier's interference with the audio FM component of the signal.

Everyone knows that! :blink:;)

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Everyone knows that! :blink:;)

Heh. I knew that, but for a long time I struggled to understand why it was an issue, as these are all independently adjustable parameters.

I presume it was something to do with undesirable intermodulation distortion (in lower quality receivers) between the colour and sound signals showing up in the luminance signal - don't really see how such a tiny change in frequency would really help, unless there was some sort of funny phase locking effect. But I suppose, that was the reason for chosing 30 Hz in the first place, electrical line noise would be phase locked to the signal.

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America runs on 60 Hz, we do 50 Hz here! I have no idea why this is connected to TV scan rates! USA got "color" in 1957, but it took us another ten years to get "colour"! I also have no idea why the 24 frames per second is any better than 25 or 60! If it looks good, I don't care! The PAL sub-carrier is 4.43 MHz BTW! :blink:

We should all talk loudly about "Test Card F"! :lol:

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  • 243 Brexit, House prices and Summer 2020

    1. 1. Including the effects Brexit, where do you think average UK house prices will be relative to now in June 2020?


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