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

    From J. P. Gilliver@21:1/5 to All on Fri Feb 16 12:25:20 2024
    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

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  • From J. P. Gilliver@21:1/5 to Andy Burns on Fri Feb 16 13:47:38 2024
    In message <l395gmFi50fU1@mid.individual.net> at Fri, 16 Feb 2024
    13:16:06, Andy Burns <usenet@andyburns.uk> writes
    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 ...

    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.

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  • From Andy Burns@21:1/5 to J. P. Gilliver on Fri Feb 16 13:16:06 2024
    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 ...

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  • From Andy Burns@21:1/5 to J. P. Gilliver on Fri Feb 16 14:17:52 2024
    J. P. Gilliver wrote:

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

    What it serves up to me is 636x480

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  • From NY@21:1/5 to Andy Burns on Fri Feb 16 16:44:40 2024
    "Andy Burns" <usenet@andyburns.uk> wrote in message news:l3994fFie2eU1@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.

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  • From J. P. Gilliver@21:1/5 to me@privacy.invalid on Fri Feb 16 17:43:24 2024
    In message <uqo3ej$3ucaj$1@dont-email.me> at Fri, 16 Feb 2024 16:44:40,
    NY <me@privacy.invalid> writes
    "Andy Burns" <usenet@andyburns.uk> wrote in message >news:l3994fFie2eU1@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

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  • From Andy Burns@21:1/5 to J. P. Gilliver on Fri Feb 16 19:12:10 2024
    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.

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  • From NY@21:1/5 to J. P. Gilliver on Sun Feb 18 16:53:37 2024
    "J. P. Gilliver" <G6JPG@255soft.uk> wrote in message news:dBGcG1h865zlFwlN@255soft.uk...
    In message <uqo3ej$3ucaj$1@dont-email.me> at Fri, 16 Feb 2024 16:44:40, NY <me@privacy.invalid> writes
    "Andy Burns" <usenet@andyburns.uk> wrote in message >>news:l3994fFie2eU1@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.

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  • From J. P. Gilliver@21:1/5 to Andy Burns on Wed Feb 21 21:09:20 2024
    In message <l3n505F39snU3@mid.individual.net> at Wed, 21 Feb 2024
    20:33:07, Andy Burns <usenet@andyburns.uk> writes
    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

    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.

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  • From John Williamson@21:1/5 to wrightsaerials@aol.com on Wed Feb 21 20:34:38 2024
    On 21/02/2024 20:18, wrightsaerials@aol.com wrote:
    On Friday 16 February 2024 at 13:16:09 UTC, Andy Burns wrote:

    360p is a quarter of 720p

    I don't understand

    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.

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  • From Andy Burns@21:1/5 to Bill Wright on Wed Feb 21 20:33:07 2024
    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

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