Make a new GstVideoFormatinfo structure that contains the specific information
related to a format such as the number of planes, components, subsampling,
pixel stride etc. The result is that we are now able to introduce the concept of
components again in the API.
Use tables to specify the formats and its properties.
Use macros to get information about the video format description.
Move code to set strides, offsets and size into one function.
Remove methods that are not handled with the structures.
Add methods to retrieve pointers and strides to the components in the video.
Remove the GstVideoPlane structure and move the fields directly into the
GstVideoInfo structure. This makes things a little easier to read and also makes
it more likely that we can pass the stride array to external libraries.
This prevents the ugly hack where the text_sink pad template
was only added for textoverlay but not for the subclasses.
Also makes this work with the core change that made
subclasses inherit the templates of their parent class.
'A OVER B' compositing is explained at
http://en.wikipedia.org/wiki/Alpha_compositing.
Previously, overlaying text on a transparent background image left the
text overlay also transparent. This pipeline shows such an example:
gst-launch videotestsrc pattern=white ! video/x-raw-yuv,format=\(fourcc\)AYUV ! alpha alpha=0.0 ! textoverlay text=Testing auto-resize=False font-desc=60px ! videomixer ! ffmpegcolorspace ! autovideosink
With this patch, text is composited "OVER" the background image and
thus is visible regardless of the alpha of the background image. The
overlay in the above pipeline works after applying this patch.
Pango is not reentrant. Use a class wide mutex to protect pange use in
gst_text_overlay_render_pangocairo(). This works reliable in contrast to the
hack in my previous commit.
Fixes Bug #412678
In case of odd values for xpos or ypos, the division by two in CbCr
plane would result in an off-by-one error, which in the case of NV12,
NV21, or UYVY would cause inversion of blue and red colors. (And
would be not so easily noticed for I420 as it would just cause the
chroma to be offset slightly from the luma.)
This patch also fixes a silly typo from the earlier patch which
added NV12 support that broke UYVY support.
The textoverlay element will rerender the text string whenever
overlay sets the 'need_render' flag to TRUE. Previously, we
lazily set the flag to TRUE every time the time string was requested.
Now, we save a copy of the previously given string, and only set
'need_render' to TRUE if the string has changed.
In my tests with a 30fps video stream, and a time string including
a seconds field, this change reduced the CPU usage of the clockoverlay
element from 60% to 5%.
Fixes bug #627780.
