On Sun, Jan 18, 2015 at 02:18:19PM +0000, Kieran Kunhya wrote: > > iam not trying to look for anything, iam just trying to fix bugs > > and as is ffmpeg displays the wrong DAR in the printout for the > > overscan case (i belive this is a big part of the misuderstandings), > > you would get bt601 with some crazy nonsense DAR > > values instead of 16:9 and 4:3, this patch is intended to fix it > > Wrong.
Please calm down
ATM its this way:
Stream #0:0[0xd4]: Video: h264 (Main) ([27][0][0][0] / 0x001B), yuv420p(tv,
smpte170m), 720x480 [SAR 10:11 DAR 15:11], 29.97 fps, 59.94 tbr, 90k tbn, 59.94
tbc
after the patch its this way:
Stream #0:0[0xd4]: Video: h264 (Main) ([27][0][0][0] / 0x001B), yuv420p(tv,
smpte170m), 720x480 [SAR 10:11 DAR(overscan) 4:3], 29.97 fps, 59.94 tbr, 90k
tbn, 59.94 tbc
Thats what the H264 spec says in its table as well
If theres a problem with the patch please elaborate
>
> > internally ffmpeg only uses SAR which should already be correct for
> > all cases
>
> For BT601 you can only work on the basis that there is no direct
> relationship between SAR and DAR owing to approximations and the fact
> that the DAR applies to the active image.
yes, thats 100% true
but the specs require the mathematical relation, this is "normative"
not something you can ignore or you simply violate the specs
ISO/IEC 13818-2: 1995 (E)
6.3.3 Sequence header
...
* If sequence_display_extension() is not present then it is intended that the
entire reconstructed
frame is intended to be mapped to the entire active region of the display.
The sample aspect ratio
may be calculated as follows:
horizontal _ size
SAR = DAR * ------------------
vertical_ size
* If sequence_display_extension() is present then the sample aspect ratio may
be calculated as
follows:
display_ horizontal _ size
SAR = DAR * ------------------------------
display _ vertical _ size
...
display_horizontal_size -- See display_vertical_size.
display_vertical_size -- display_horizontal_size and display_vertical_size
together define a rectangle
which may be considered as the "intended display" active region. If this
rectangle is smaller than the
encoded frame size then the display process may be expected to display only
a portion of the encoded
frame. Conversely if the display rectangle is larger than the encoded frame
size then the display process
may be expected to display the reconstructed frames on a portion of the
display device rather than on the
whole display device.
i hope very much that we implement this correctly, if not i need
samples that are handled wrongly and ill try my best to fix them
the active area is stored in mpeg1/2 and should be used, its in the
pan scan variables IIRC, that way there is a very close to correct
mathematical relation between SAR, DAR and the active area in the
BT601 case
There should be no problem here with complying to BT601 and the
video coding specs
I hope i dont miss anything but its surely possible that i do and
i intend to fix (or help fix if its unexpectedly non trivial) any
issues that are in there if people report them
[...]
--
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
Avoid a single point of failure, be that a person or equipment.
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