How 16:9 can be 4:3?

[JosephTocco]

ID                          : 1
Format                      : AVC
Format/Info                 : Advanced Video Codec
Format profile              : Baseline@L2
Format settings             : 1 Ref Frames
Format settings, CABAC      : No
Format settings, Reference  : 1 frame
Muxing mode                 : Header stripping
Codec ID                    : V_MPEG4/ISO/AVC
Duration                    : 2 h 54 min
Nominal bit rate            : 2 000 kb/s
Width                       : 1 920 pixels
Height                      : 1 080 pixels
Display aspect ratio        : 4:3
Frame rate mode             : Constant
Frame rate                  : 23.976 (23976/1000) FPS
Color space                 : YUV
Chroma subsampling          : 4:2:0
Bit depth                   : 8 bits
Scan type                   : Progressive
Bits/(Pixel*Frame)          : 0.040
Writing library             : x264 core 148 r2665 a01e339
Encoding settings           : cabac=0 / ref=1 / deblock=1:0:0 / analyse=0x1:0x1 / me=hex / subme=1 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=0 / me_range=16 / chroma_me=1 / trellis=0 / 8x8dct=0 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=0 / threads=6 / lookahead_threads=1 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=0 / weightp=0 / keyint=250 / keyint_min=25 / scenecut=40 / intra_refresh=0 / rc=abr / mbtree=0 / bitrate=2000 / ratetol=1.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / ip_ratio=1.40 / aq=1:1.00
Language                    : Italian
Default                     : Yes
Forced                      : No

This video is reported as 1080p, snapshot shows it is really streched to 1080p, but player displays it normally as 4:3 (about 1480x1080). Mopic is true 4:3 without black lines. So why frame is supposedly 16:9, but in fact is 4:3?

[DB83]

The Aspect Ratio flag (4:3) has over-ridden the Sample Aspect Ratio (16:9)


But not all players will recognise the AR flag and stretch the image.

[jagabo]

Any frame size can be displayed with any aspect ratio. The container can flag the aspect ratio by specifying a display aspect ratio (the shape of the displayed picture) directly or by specifying a sample aspect ratio (the "shape" of individual pixels).

[Alwyn]

Another example: HDV, which is video from a consumer HD video camera, is 16:9 format but 1440x1080 pixels.

[johns0]

1440x1080 pixels is 4:3,to be 16:9 it need to have black bars on the sides.

[jagabo]

1440x1080 pixels is 4:3,to be 16:9 it need to have black bars on the sides.

No it doesn't. It can be flagged as 16:9 DAR or 4:3 SAR. The player should then display it as 16:9.

[hello_hello]

1440x1080 with a 16:9 display aspect ratio is an official, if rarely seen, Bluray resolution/aspect ratio.
https://en.wikipedia.org/wiki/Blu-ray#Video

[DB83]

^^ Important to point out the rider attached to that AR


"c These resolutions are stored anamorphically, i.e. they are stretched to the display aspect ratio by the player or display."


Which kinda confirms what has been already written.

[Cornucopia]

Strange thing is that one can regularly find 1440x1080 - with a 16:9 DAR flag - displayed as 1920x1080. But what we see here in post #1 is 1920x1080 but with a supposed 4:3 DAR flag. Doing what? the reverse (displaying as 1440x1080)? Sounds like a case of bad re-encoding (notice the telltale x264 metadata).

Scott

[johns0]

So can a 1440x1080 video be authorized as a 16:9 video in an blu-ray authoring program?

[Cornucopia]

Been a while since I authored BD, but IIRC yes. Depends on the app.


Scott

[Sharc]

So can a 1440x1080 video be authorized as a 16:9 video in an blu-ray authoring program?

Yes, 1440x1080 its Blu ray compliant, and when encoded with SAR=4:3 (SAR=SampleAspectRatio) the player will play it at DAR 16:9, because 4/3*1440=1920. I have done it many times. One can author it with TSMuxeR.
It's actually an "anamorphic BluRay" which is fully legal but perhaps a bit unusual for commercial releases.