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Code Issues 1 Projects Releases Wiki Activity

design: subtitle-overlays: add missing markup

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Reynaldo H. Verdejo Pinochet 2016-12-30 00:40:41 -08:00
parent 8cc223c9bc
commit e7ba83d049
1 changed files with 13 additions and 7 deletions
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markdown/design/subtitle-overlays.md
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@ -106,7 +106,7 @@ Multiple possible solutions come to mind:
accommodate all the different cases and formats one would end up accommodate all the different cases and formats one would end up
with quite convoluted/tricky API. with quite convoluted/tricky API.
(Of course there could also be a GstFancyVideoBuffer that provides (Of course there could also be a `GstFancyVideoBuffer` that provides
an abstraction for such video accelerated objects and that could an abstraction for such video accelerated objects and that could
provide an API to add overlays to it in a generic way, but in the provide an API to add overlays to it in a generic way, but in the
end this is just a less generic variant of (c), and it is not clear end this is just a less generic variant of (c), and it is not clear
@ -221,7 +221,7 @@ overlay in the middle of the pipeline has other advantages:
We need to pass the overlay pixels from the overlay element to the We need to pass the overlay pixels from the overlay element to the
sink somehow. Whatever the exact mechanism, let's assume we pass a sink somehow. Whatever the exact mechanism, let's assume we pass a
refcounted GstVideoOverlayComposition struct or object. refcounted `GstVideoOverlayComposition` struct or object.
A composition is made up of one or more overlays/rectangles. A composition is made up of one or more overlays/rectangles.
@ -234,7 +234,8 @@ overlay in the middle of the pipeline has other advantages:
cases such as e.g. logo overlays or so. It is not designed for cases such as e.g. logo overlays or so. It is not designed for
full-fledged video stream mixing full-fledged video stream mixing
though. though.
```
// Note: don't mind the exact implementation details, they'll be hidden // Note: don't mind the exact implementation details, they'll be hidden
// FIXME: might be confusing in 0.11 though since GstXOverlay was // FIXME: might be confusing in 0.11 though since GstXOverlay was
@ -353,6 +354,7 @@ overlay in the middle of the pipeline has other advantages:
} else { } else {
video_buffer_attach_composition (logoverlay->cached_composition); video_buffer_attach_composition (logoverlay->cached_composition);
} }
```
FIXME: also add some API to modify render position/dimensions of a FIXME: also add some API to modify render position/dimensions of a
rectangle (probably requires creation of new rectangle, unless we rectangle (probably requires creation of new rectangle, unless we
@ -375,8 +377,9 @@ overlay in the middle of the pipeline has other advantages:
if e.g. a screnshotter gets the last buffer via the last-buffer if e.g. a screnshotter gets the last buffer via the last-buffer
property of basesink, it would get an image without the subtitles on property of basesink, it would get an image without the subtitles on
top. This could probably be fixed by re-implementing the property in top. This could probably be fixed by re-implementing the property in
GstVideoSink though. Playbin2 could handle this internally as well). `GstVideoSink` though. Playbin2 could handle this internally as well).
```
void void
gst_video_overlay_composition_blend (GstVideoOverlayComposition * comp gst_video_overlay_composition_blend (GstVideoOverlayComposition * comp
GstBuffer * video_buf) GstBuffer * video_buf)
@ -411,6 +414,7 @@ overlay in the middle of the pipeline has other advantages:
gst_buffer_unref (pixels); gst_buffer_unref (pixels);
} }
} }
```
3) Flatten all rectangles in a composition 3) Flatten all rectangles in a composition
@ -427,8 +431,8 @@ overlay in the middle of the pipeline has other advantages:
4) query support for the new video composition mechanism 4) query support for the new video composition mechanism
This is handled via GstMeta and an ALLOCATION query - we can simply This is handled via `GstMeta` and an ALLOCATION query - we can simply
query whether downstream supports the GstVideoOverlayComposition meta. query whether downstream supports the `GstVideoOverlayComposition` meta.
There appears to be no issue with downstream possibly not being There appears to be no issue with downstream possibly not being
linked yet at the time when an overlay would want to do such a linked yet at the time when an overlay would want to do such a
@ -518,6 +522,7 @@ our new API for non-raw video.
TEST: should these look (roughly) alike (note text distortion) - needs TEST: should these look (roughly) alike (note text distortion) - needs
fixing in textoverlay fixing in textoverlay
```
gst-launch-1.0 \ gst-launch-1.0 \
videotestsrc ! video/x-raw,width=640,height=480,pixel-aspect-ratio=1/1 \ videotestsrc ! video/x-raw,width=640,height=480,pixel-aspect-ratio=1/1 \
! textoverlay text=Hello font-desc=72 ! xvimagesink \ ! textoverlay text=Hello font-desc=72 ! xvimagesink \
@ -525,3 +530,4 @@ fixing in textoverlay
! textoverlay text=Hello font-desc=72 ! xvimagesink \ ! textoverlay text=Hello font-desc=72 ! xvimagesink \
videotestsrc ! video/x-raw,width=640,height=240,pixel-aspect-ratio=1/2 \ videotestsrc ! video/x-raw,width=640,height=240,pixel-aspect-ratio=1/2 \
! textoverlay text=Hello font-desc=72 ! xvimagesink ! textoverlay text=Hello font-desc=72 ! xvimagesink
```