Where did (476 by) 360 come from? (And strange audio tones!)

[J. P. Gilliver]

I'm just watching a clip - obviously from someone's home recording -
that's, according to VLC:

Video resolution: 476x360
Buffer dimensions: 480x368
Frame rate: 29.970029
(I don't think VLC shows me whether it's interlaced or not.)

I deduce from the frame rate (and that the uploader said it was "on
Vera's 9/24/75 show"), that it was recorded in 525-land. (The clip is
https://www.youtube.com/watch?v=Y5cmBtMWMnM, if anyone's interested.) [I
presume it was originally BBC, so had been converted (not by the
uploader).]

It occurred to me that I've seen 360 quite often in low-quality clips on
YouTube, and I wondered where that number came from? AIUI, 525-land is
480 same as we in 625 were 576. I could understand if it was 240 -
discarding one field, or some other simple interpolation, but 360
implies a moderate amount of processing.

The audio (of course, encoded as 44100 stereo as usual on YouTube) is
mono, mostly below about 9 kHz, but I noticed (in GoldWave - I don't
hear that high nowadays!) it has two quite clear tones. Oh, I thought -
timebase breakthrough (virtually any YouTube audio that comes from video
- and much that doesn't! - has a line around 15½ kHz) from both the
standards: interesting! But then I looked more carefully, and they're at
10xxx Hz (no, it's in colour, so not from 405-line! [1975, anyway.]) and
11xxx - I'd guess about 10 and a third and 11 and two thirds. (I don't
think GoldWave has a frequency counter that'd tell me for sure.)
Thoughts as to their source?
--
J. P. Gilliver. UMRA: 1960/<1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf

While no one was paying attention, weather reports became accurate and the
news became fiction. Did not see that coming. - Scott Adams, 2015

[Andy Burns]

J. P. Gilliver wrote:

> It occurred to me that I've seen 360 quite often in low-quality clips on
> YouTube

360p is a quarter of 720p which is the "non full" HD 1280x720 that was
used more in NTSC land than in PAL land ...

[J. P. Gilliver]

In message <l395gm...@mid.individual.net> at Fri, 16 Feb 2024
13:16:06, Andy Burns <use...@andyburns.uk> writes

Ah, that would make sense as a source of the number. Though I'm still
curious as to why it's what something clearly off a non-HD-at-all home
video recording was uploaded as! I suppose the uploader _could_ have his
old video recorder connected via an "upscaler", and have sampled _that_
at half-rate.

--
J. P. Gilliver. UMRA: 1960/<1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf

the plural of 'anecdote' is not 'evidence'. Professor Edzart Ernst, prudential
magazine, AUTUMN 2006, p. 13.

[Andy Burns]

J. P. Gilliver wrote:

> https://www.youtube.com/watch?v=Y5cmBtMWMnM

What it serves up to me is 636x480

[NY]

"Andy Burns" <use...@andyburns.uk> wrote in message
news:l3994f...@mid.individual.net...

> J. P. Gilliver wrote:
>
>> https://www.youtube.com/watch?v=Y5cmBtMWMnM
>
> What it serves up to me is 636x480

N x 360 (eg 540x360 or 480x360) seems to be one of the common resolutions
that Youtube rescales video to when it is supplied with 720x576 "PAL" video.
It is a shame (and very NTSC-centric) that Youtube does not seem to allow
one of the various resolutions that it offers to be the native resolution
that was uploaded - it rescales 576i to 640x480 and 480x360. I have a lot of
Youtube videos which are either 540x360 or 480x360, depending on what was
the highest resolution that was offered for download.

[J. P. Gilliver]

In message <uqo3ej$3ucaj$1...@dont-email.me> at Fri, 16 Feb 2024 16:44:40,
NY <m...@privacy.invalid> writes

>"Andy Burns" <use...@andyburns.uk> wrote in message
>news:l3994f...@mid.individual.net...
>> J. P. Gilliver wrote:
>>
>>> https://www.youtube.com/watch?v=Y5cmBtMWMnM
>>
>> What it serves up to me is 636x480
>

Ah - I downloaded with yt-dlp with no parameters, as it was my
understanding that that usually gets the best available. (Was your one
also about 30fps, suggesting the upload - clearly from a home VCR, as
the colour was blotchy and it has slight tearing at the bottom - was
from someone in NTSCland?)

>
>N x 360 (eg 540x360 or 480x360) seems to be one of the common
>resolutions that Youtube rescales video to when it is supplied with
>720x576 "PAL" video. It is a shame (and very NTSC-centric) that Youtube
>does not seem to allow one of the various resolutions that it offers to
>be the native resolution that was uploaded - it rescales 576i to
>640x480 and 480x360.

Does it also rescale 25 to 30 fps? If so, very NTSC-centric indeed!

> I have a lot of Youtube videos which are either 540x360 or 480x360,
>depending on what was the highest resolution that was offered for
>download.

--
J. P. Gilliver. UMRA: 1960/<1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf

"Do you want to be right, or friends?"
- a friend quoted by Vicky Ayech in UMRA, 2018-12-4

[Andy Burns]

J. P. Gilliver wrote:

> Andy Burns wrote:
>
>> What it serves up to me is 636x480
>
> Ah - I downloaded with yt-dlp with no parameters, as it was my
> understanding that that usually gets the best available. (Was your one
> also about 30fps

yes

> suggesting the upload - clearly from a home VCR, as
> the colour was blotchy and it has slight tearing at the bottom

also yes.

[NY]

"J. P. Gilliver" <G6...@255soft.uk> wrote in message
news:dBGcG1h8...@255soft.uk...

> In message <uqo3ej$3ucaj$1...@dont-email.me> at Fri, 16 Feb 2024 16:44:40, NY
> <m...@privacy.invalid> writes
>>"Andy Burns" <use...@andyburns.uk> wrote in message
>>news:l3994f...@mid.individual.net...
>>> J. P. Gilliver wrote:
>>>
>>>> https://www.youtube.com/watch?v=Y5cmBtMWMnM
>>>
>>> What it serves up to me is 636x480
>>
> Ah - I downloaded with yt-dlp with no parameters, as it was my
> understanding that that usually gets the best available. (Was your one
> also about 30fps, suggesting the upload - clearly from a home VCR, as the
> colour was blotchy and it has slight tearing at the bottom - was from
> someone in NTSCland?)
>>
>>N x 360 (eg 540x360 or 480x360) seems to be one of the common resolutions
>>that Youtube rescales video to when it is supplied with 720x576 "PAL"
>>video. It is a shame (and very NTSC-centric) that Youtube does not seem to
>>allow one of the various resolutions that it offers to be the native
>>resolution that was uploaded - it rescales 576i to 640x480 and 480x360.
>
> Does it also rescale 25 to 30 fps? If so, very NTSC-centric indeed!

That's one thing it doesn't seem to do. I've seen a lot of 25 fps videos on
Youtube, though I've seen a fair number of UK programmes (and therefore made
in 25 fps) which are 30 on Youtube. Either they've been converted
(surprisingly well) to 30 fps (eg for a US audience/DVD) and then uploaded
to Youtube from there, or else Youtube is converting some 25 videos to 30
but leaving others alone.

Be nice if it would do 576i as one of the resolutions, then you knew you
were getting the source material without any interpolation to scale down
each frame to 480 or 360 or 240.

[wrights...@f2s.com]

On Friday 16 February 2024 at 13:16:09 UTC, Andy Burns wrote:

> 360p is a quarter of 720p

I don't understand

Bill

[Andy Burns]

Bill Wright wrote:

> Andy Burns wrote:
>
>> 360p is a quarter of 720p
>
> I don't understand

640x360 = 230,400 pixels

1280x720 = 921,600 pixels

230,400 / 921,600 = 1/4

[John Williamson]

If you preserve the dot pitch, the area of a 480 x 360p image is a
quarter of the area of a 960 x 720p image.

--
Tciao for Now!

John.

[J. P. Gilliver]

In message <l3n505...@mid.individual.net> at Wed, 21 Feb 2024
20:33:07, Andy Burns <use...@andyburns.uk> writes

Or, to put it another way, if you halve the resolution in one direction,
it is reasonable to assume you are also halving it in the other.

Hence QVGA (I think it was VGA: it certainly was Q), which is what a
very early cheap digital camera I had took as an option - the Q being
for quarter (though I don't think they ever actually said so).

--
J. P. Gilliver. UMRA: 1960/<1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf

When you are in it up to your ears, keep your mouth shut.