How do I increase the playback size of a video without rescaling it?

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How do I increase the playback size of a video without rescaling it?

Chris Wood
I have a 720x576 video that when played in VLC fills the window
horizontally, so if I maximise the window it effectively fills the display.
When played on TV (via my PS/3) it plays full screen.

I have another video 1280x720 that plays back in a small rectangle, ditto
on the TV. Why? I can use ffmpeg to resize this video to make the image
larger by using the scale function, but this adds pixels by interpolation
and makes the file larger - pointlessly in a way because no new information
is being added that couldn't be added by the video player itself.

This can't be an issue about the lack of pixels, because the 720x576 video
plays back larger than the 1280x720 video. I've experimented with the DAS
and SAR values, which change the shape of the image but not make it bigger.
What am I not understanding?

Chris
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Re: How do I increase the playback size of a video without rescaling it?

Jim DeLaHunt-2
On 2020-07-15 14:02, Chris Wood wrote:

> I have another video 1280x720 that plays back in a small rectangle, ditto
> on the TV. Why?

It seems like this is a question for the playback app, not for ffmpeg.
What are you using to play back the video? VLC? FFplay? Whatever player
the PS/3 has?

     —Jim DeLaHunt

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Re: How do I increase the playback size of a video without rescaling it?

fowman
Jim DeLaHunt-2 wrote
> It seems like this is a question for the playback app, not for ffmpeg.
> What are you using to play back the video? VLC? FFplay? Whatever player
> the PS/3 has?

I'm on Linux (Mint) and I've used VLC and Xplayer; on the PS/3 it's whatever
it uses natively to play the mp4 file. Since they all show the same
behaviour, the common factor would appear to be the mp4 file, not the
player.

The 720x576 video is a broadcast transmission recorded on a Humax box. The
1280x720 video is the output from OpenShot after editing the same file. I've
found that if I use the scale function in OpenShot and export the video
using a scale factor of 1.4 on both dimensions I get a video that plays with
the full horizontal width, and is still 1280x720 i.e. the scaling has done
something other than increase the number of pixels, and I don't understand
what this is.

OpenShot does not set the DAR in the exported file, I have to set it
subsequently using ffmpeg, but then I get a file that plays pretty much like
the original.

I agree it's not an ffmpeg issue /per se/, but I'm hoping that with the
video knowledge around this forum someone can tell me what the issue is and
how to fix it using ffmpeg.

Chris



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Re: How do I increase the playback size of a video without rescaling it?

Mark Filipak
On 07/16/2020 02:04 AM, fowman wrote:
> Jim DeLaHunt-2 wrote
>> It seems like this is a question for the playback app, not for ffmpeg.
>> What are you using to play back the video? VLC? FFplay? Whatever player
>> the PS/3 has?
>
> I'm on Linux (Mint) and I've used VLC and Xplayer; on the PS/3 it's whatever
> it uses natively to play the mp4 file. Since they all show the same
> behaviour, the common factor would appear to be the mp4 file, not the
> player.

Isn't there another common factor? How about the display device? Are you playing to the same TV? Can
that TV scale up 1280x720?
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Re: How do I increase the playback size of a video without rescaling it?

fowman
Mark Filipak wrote
> Isn't there another common factor? How about the display device? Are you
> playing to the same TV? Can
> that TV scale up 1280x720?

VLC and Xplayer are playing to my computer screen, and the PS/3 to my TV, so
no, not the same.

With the small mp4 (1280x720) playing through the PS/3, I can change the TV
display settings with "stretch" or "best fit" etc options to make the
picture bigger, but with the normal settings it's just a rectangle that
doesn't fill the screen. The TV is full HD 1080p.

Are you suggesting that the players may up-scale automatically under certain
circumstances? I can see how that's possible, but if so, are these
circumstances "standard" so that the players all behave in the same way, and
could I know what they are so I can engineer a predictable result?

Thanks,
Chris



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Re: How do I increase the playback size of a video without rescaling it?

Moritz Barsnick
On Thu, Jul 16, 2020 at 06:55:55 -0500, fowman wrote:
> VLC and Xplayer are playing to my computer screen, and the PS/3 to my TV, so
> no, not the same.

Only the PS/3 is the issue, right?

> With the small mp4 (1280x720) playing through the PS/3, I can change the TV
> display settings with "stretch" or "best fit" etc options to make the
> picture bigger, but with the normal settings it's just a rectangle that
> doesn't fill the screen. The TV is full HD 1080p.
>
> Are you suggesting that the players may up-scale automatically under certain
> circumstances? I can see how that's possible, but if so, are these
> circumstances "standard" so that the players all behave in the same way, and
> could I know what they are so I can engineer a predictable result?

This is only an issue between your player and your screen, from all I
have read here. If their configurations don't match, you won't get a
full-screen display. This has nothing to do with any "settings" or
metadata in the video file.

Here are the PS/3 settings for upscaling, if you TV doesn't manage:
Games:
https://manuals.playstation.net/document/en/ps3/current/settings/gamesettings.html
DVD/BD:
https://manuals.playstation.net/document/en/ps3/3_15/settings/bdsettings.html

I can't find any settings for the video player, but it should have some
as well, or one of the above might apply?

Moritz
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Re: How do I increase the playback size of a video without rescaling it?

fowman
Moritz Barsnick wrote
> Only the PS/3 is the issue, right?

No, I have the same on all three.



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Re: How do I increase the playback size of a video without rescaling it?

Peter van den Houten
On 16/07/2020 14:22, fowman wrote:
> Moritz Barsnick wrote
>> Only the PS/3 is the issue, right?
>
> No, I have the same on all three.
>
>
Does your video not need [black bar] cropping? Easiest is to open in HandBrake and select Preview, then Show Crop.

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Re: How do I increase the playback size of a video without rescaling it?

Moritz Barsnick
In reply to this post by fowman
On Thu, Jul 16, 2020 at 07:22:39 -0500, fowman wrote:
> No, I have the same on all three.

Ah, okay. *All* you players are able to scale the 720x576 video to
fullscreen (automatically?), and *NONE* of them manages that with the
1280x720 video? That seems very unlikely. With every 1280x720 video? Or
just this one?

I'm guessing the latter video is letterboxed, i.e. a large black box
around it is encoded in the video. If you can share, we could tell.

If not, I know of no such property which would prevent such a video
from being scaled. Generally speaking, all these players should somehow
decode into a framebuffer, and then scale that, regardless of what the
original video file says.

Moritz
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Re: How do I increase the playback size of a video without rescaling it?

kumowoon1025
Hi,

> On Jul 16, 2020, at 08:39, Moritz Barsnick <[hidden email]> wrote:
>
> On Thu, Jul 16, 2020 at 07:22:39 -0500, fowman wrote:
>> No, I have the same on all three.
>
> Ah, okay. *All* you players are able to scale the 720x576 video to
> fullscreen (automatically?), and *NONE* of them manages that with the
> 1280x720 video? That seems very unlikely. With every 1280x720 video? Or
> just this one?
>
> I'm guessing the latter video is letterboxed, i.e. a large black box
> around it is encoded in the video. If you can share, we could tell.
>
> If not, I know of no such property which would prevent such a video
> from being scaled. Generally speaking, all these players should somehow
> decode into a framebuffer, and then scale that, regardless of what the
> original video file says.
>
> Moritz

I don't know if they are not used in all players but MP4 file format can contain the "clean-aperture" region info as well as matrices to specify sample transformations before the presentation should be displayed by default.

Regards,
Ted Park

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Re: How do I increase the playback size of a video without rescaling it?

Moritz Barsnick
On Thu, Jul 16, 2020 at 09:20:31 -0400, Edward Park wrote:
> I don't know if they are not used in all players but MP4 file format
> can contain the "clean-aperture" region info as well as matrices to
> specify sample transformations before the presentation should be
> displayed by default.

Ah, interesting. At the same time, VLC's trac ticket system indicates
that this has not been implemented in VLC. (ffmpeg doesn't tell me
about this, while mediainfo shows both dimensions.) [*]

I stand with my remarks:
> > With every 1280x720 video? Or just this one?
> [...]
> > If you can share, we could tell.

Moritz


[*]
https://trac.videolan.org/vlc/ticket/21179
https://streams.videolan.org/issues/21179/clap.mov
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Re: How do I increase the playback size of a video without rescaling it?

fowman
Moritz Barsnick wrote
> With every 1280x720 video? Or just this one?

Just this, but then it's the only one I have :-)

> I'm guessing the latter video is letterboxed, i.e. a large black box
> around it is encoded in the video. If you can share, we could tell.

Yes it is. My description of being displayed in a small rectangle was trying
to say this. I'm struggling to describe the problem in the correct
terminology so please bear with me.

Here is ffprobe info:

Original .ts file recorded by my Humax:
Stream #0:0[0x931]: Video: mpeg2video (Main) ([2][0][0][0] / 0x0002),
yuv420p(tv), 704x576 [SAR 16:11 DAR 16:9], max. 15000 kb/s, 25 fps, 25 tbr,
90k tbn, 50 tbc

1280x720 .mp4 exported from OpenShot:
Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1280x720,
14925 kb/s, 30 fps, 30 tbr, 15360 tbn, 60 tbc (default)

The OpenShot export parameters used DAR 16:9 and Pixel Ratio (which I assume
is the same as SAR) of 64:45, although it doesn't set the DAR or SAR in the
file metadata (I did this subsequently with ffnpeg).

I realise that the original .ts video is actually letterboxed, although the
vertical side bars are pretty narrow. I've always assumed that letterboxing
referred to the top and bottom horizontal bars and was just a side effect of
playing a widescreen movie in a 16:9 or 4:3 display. I also did wonder how
the how this original movie played with the correct (at least correct
looking) AR when the DAR is set to 16:9 - the measured AR on my computer
screen is more like 24:10. So it occurred to me - has this video been
letterboxed to play in an AR of 16:9 when its real AR is greater?



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Re: How do I increase the playback size of a video without rescaling it?

Mark Filipak
On 07/16/2020 01:39 PM, fowman wrote:
> Moritz Barsnick wrote
>> With every 1280x720 video? Or just this one?
>
> Just this, but then it's the only one I have :-)
>
>> I'm guessing the latter video is letterboxed, i.e. a large black box
>> around it is encoded in the video. If you can share, we could tell.
-snip-
> I realise that the original .ts video is actually letterboxed, although the
> vertical side bars are pretty narrow. I've always assumed that letterboxing
> referred to the top and bottom horizontal bars
-snip-

You are correct regarding letterbox. What you see, black areas top-bottom-left-right, is called
"pillarbox".
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Re: How do I increase the playback size of a video without rescaling it?

Moritz Barsnick
In reply to this post by fowman
On Thu, Jul 16, 2020 at 12:39:03 -0500, fowman wrote:
> Just this, but then it's the only one I have :-)

It can't be that difficult to find other 1280x720 recodings, can it? Or
to create your own?

> Here is ffprobe info:
>
> Original .ts file recorded by my Humax:
> Stream #0:0[0x931]: Video: mpeg2video (Main) ([2][0][0][0] / 0x0002),
> yuv420p(tv), 704x576 [SAR 16:11 DAR 16:9], max. 15000 kb/s, 25 fps, 25 tbr,
> 90k tbn, 50 tbc
>
> 1280x720 .mp4 exported from OpenShot:
> Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1280x720,
> 14925 kb/s, 30 fps, 30 tbr, 15360 tbn, 60 tbc (default)

That doesn't tell me whether the content includes boxes. Unless you run
it through the cropdetect filter.

> I realise that the original .ts video is actually letterboxed, although the
> vertical side bars are pretty narrow. I've always assumed that letterboxing
> referred to the top and bottom horizontal bars and was just a side effect of
> playing a widescreen movie in a 16:9 or 4:3 display.

I'm not referring to a side effect. I meant true black "boxes" or
borders, included in the encoded frames.

What often used to happen was that (true) 16:9 content was amended with
bars to make it 4:3. If you then play that (4:3 enconding) fullscreen
on a 16:9 screen, you will have the explicit top/bottom bars, and newly
introduced left/right bars, to fill the encoded 4:3 back up to 16:9,
instead of snipping something away, obviously. In total, this would
give you a big box around your content, despite full screen.

In your case, there might be a big box there (which we could see if we
saw the actual viedo), or said "clean-aperture" (CLAP) marking, which
could have funny effects. Come to think of it, those effects should be
opposite, i.e. the clean aperture should enforce cropping of
non-displayable segments.

Moritz
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Re: How do I increase the playback size of a video without rescaling it?

fowman
This command:
 > ffmpeg -i p.mp4 -t 1 -vf cropdetect -f null - 2>&1 | awk '/crop/ { print
$NF }' | tail -1
gives:
   crop=880:528:200:96
which I think confirms what you are saying: that the pillarboxing is the
result of cropped content and not something introduced by the metadata.

I will experiment with OpenShot. I'm guessing now that the scale function in
this editor can control the amount of cropping without changing the overall
resolution of the video, although why it crops in the first place is
something I still don't understand.

Many thanks for your help




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