Everything you used to want to know about TV transmission, but too late now... - Page 1
Forum section: electronics / general

author: IanB
author_rank: Super Contributor
timestamp: October 05, 2016, 02:34:15 am
content: ...because analog TV is obsolete.But this is a seriously interesting video. Someone put a huge amount of effort into it:https://youtu.be/3GJUM6pCpew

author: albert22
author_rank: Regular Contributor
timestamp: October 05, 2016, 06:04:13 pm
content: Nice basic video but with some inaccuracies: At 4:40 when discussing NTSC he mentions "line by line phase reversal" that is not used in NTSC it is used in PAL.

author: Gyro
author_rank: Super Contributor
timestamp: October 05, 2016, 06:48:39 pm
content: That's why NTSC was 'Never Twice the Same Colour' ... No cancellation of phase errors (hence the need for a tint control on NTSC sets).

author: jonovid
author_rank: Super Contributor
timestamp: October 05, 2016, 07:29:56 pm
content: it was all so simple back then. only two major video formats. Now try recovering Digital family videos that are more then 10 yrs old.or unlocking DVD region codes and all the disc file BS , the many digital Video codecs used by home digital video cameras, then you have all the odd-ball compression formats used by Microsoft. standardizing of digital video formats has failed.

author: IanB
author_rank: Super Contributor
timestamp: October 05, 2016, 08:25:26 pm
content: Quote from: albert22 on October 05, 2016, 06:04:13 pmKeep in mind that Matt started out with zero knowledge of the subject and had to research everything from scratch before creating the video.

author: alanb
author_rank: Frequent Contributor
timestamp: October 05, 2016, 09:57:46 pm
content: The follow on video where he shows the set up that he has used together with an explanation of the way he achieved some of the effects is well worth viewing. In some respects it is more interesting than the initial video.

author: timb
author_rank: Super Contributor
timestamp: October 06, 2016, 09:00:02 am
content: Quote from: jonovid on October 05, 2016, 07:29:56 pmNot really... H.264 is pretty much *the* standard now. I haven't had to download a codec or special plugin in well over 10 years.

author: rfeecs
author_rank: Frequent Contributor
timestamp: October 06, 2016, 09:08:01 pm
content: Quote from: IanB on October 05, 2016, 08:25:26 pmYes, it's a well produced video, but his explanation is at least partially wrong, and he admits he doesn't really understand the real reason.Even Wikipedia has a decent explanation:https://en.wikipedia.org/wiki/ColorburstQuoteAnother explanation here:http://www.extron.com/company/article.aspx?id=ntscdb1cAnd another nice image:

author: C
author_rank: Super Contributor
timestamp: October 06, 2016, 09:52:54 pm
content: At 9:45 he is suggesting a change from 525 to 625 horizontal lines while keeping the same BWNTSC is not dots on a screen, it has a limit of rate of change.thinking In digital terms, You can have any number of starting points on a line but are limited in rate of change. If you can get say 400 dots per line, you can do 1600 starting points as long as the signal remains on for 4 or more of those starting points.In simple terms a shift from 525 to 625 horizontal lines while keeping the same BW would result in a loss of luminance detail on a line. If this was not a problem then old computers would display more characters per line when using a Tv display.NTSC is a great match to your eye.luminance signal has a wide bandwidth while lesser bandwidths for colorjust like your eye.

author: IanB
author_rank: Super Contributor
timestamp: October 06, 2016, 10:31:06 pm
content: Quote from: C on October 06, 2016, 09:52:54 pmQualitatively I would find it hard to agree with this. Comparing an analog NTSC TV picture with an analog PAL picture made the PAL picture look like HDTV in comparison. The difference in sharpness and overall picture quality was enormous.

author: Red Squirrel
author_rank: Super Contributor
timestamp: October 06, 2016, 11:45:15 pm
content: That was really interesting. Actually analog TV as a whole is a really interesting thing, I never knew much about it until it was obsolete. I watched Dave's video on the analog TV station tour and that was quite fascinating to see. It's actually what got me to sub the channel.

author: C
author_rank: Super Contributor
timestamp: October 07, 2016, 12:20:30 am
content: Quote from: IanB on October 06, 2016, 10:31:06 pmYou need to think of PAL being a later generation of matched to the eye system.The Eye is most sensitive to luminance, both NTSC & PAL cater to this unlike the RGB.

author: Someone
author_rank: Super Contributor
timestamp: October 07, 2016, 12:45:40 am
content: Quote from: C on October 07, 2016, 12:20:30 amAnd the following digital standards kept the reduced bandwidth chroma channels:https://en.wikipedia.org/wiki/Chroma_subsamplingAnd restrictions in pixel rate (bandwidth) lead to the 720p/1080i argument.

author: SL4P
author_rank: Super Contributor
timestamp: October 07, 2016, 06:44:30 am
content: Quote from: jonovid on October 05, 2016, 07:29:56 pmI'm fascinated by the confusion generated by MS and many others - incorrectly referring to codecs and media containers interchangeably... !Then you have long-GOP codecs, and some that derive stream timing from the audio - hence heavy compression has benefits, but the video suffers dramatically - all in pursuit of the almighty dollar saved in distribution bandwidth (thanks MS and Apple).Honest quality-based video compression left the room about 5-10 years ago.

author: vk6zgo
author_rank: Super Contributor
timestamp: October 07, 2016, 08:06:15 am
content: Quote from: C on October 06, 2016, 09:52:54 pmAgreed!To fit 625 lines into a vertical scan period of approx 33.334ms,gives us a line period of 53.334us approx.A vertical line on the screen (what we used to call a resolution line) would need the beam to complete its transition faster,hence requiring wider bandwidth.If we retained the 4.5MHz video bandwidth,it ,as you say,it would,indeed, result in decreased horizontal resolution.The ratio between Luma & Chroma bandwith is very similar in NTSC & PAL.As you implied,it is due to the characteristics of the human eye.By the way,he got the bandwidth thing a bit wrong:- the "window" between the Vision & Sound Carriers of 625 line PALeverywhere else than the UK,is 5.5 MHz,so the top 0.5MHz is thrown away---another compromise!The ideal is to have equal vertical & horizontal resolutions,so the Brits took it on themselves to go it alone.The actual video signal is completely compatible,but the TV's were not.A person in the UK trying to watch French TV would end up watching a BW program with no sound.France used SECAM for their colour transmissions,& their sound carrier offset was 5.5 MHz.the same as European PAL.