The vim2m driver has some issues...
It currently fakes supporting two video formats, when in fact, it just
copies the data to the buffer;
It says it supports hflip, when, in fact, it does a 8 tiles flip...
that doesn't end well, though, due to the lack of proper video
format;
If more than one open() is called, it sometimes go to some dead lock,
preventing to stop all pipelines;
By default, it can be used only one instance, as it takes too long
to generate data (40 msecs). This is actually by purpose, as it
uses a delay work queue for that.
This patch series solve all the above issues. For the last one, a
new modprobe parameter was added, in order to allow changing the
default. For example, with this:
# sudo modprobe vim2m default_transtime=1
the delay is reduced to 1 ms. On my tests with this pipeline:
$ gst-launch-1.0 videotestsrc ! video/x-raw,format=YUY2 ! v4l2video0convert disable-passthrough=1 extra-controls="s,horizontal_flip=0,vertical_flip=0" ! video/x-raw,format=YUY2 ! videoconvert ! fpsdisplaysink
and a similar one:
$ gst-launch-1.0 videotestsrc ! video/x-raw,format=YUY2 ! v4l2video0convert disable-passthrough=1 extra-controls="s,horizontal_flip=1,vertical_flip=1" ! video/x-raw,format=RGB16 ! videoconvert ! ximagesink
I was able to create 17 such pipelines keeping the frame rate at 30
frames per second, and up to 27 pipelines without losing frames, with
a framerate close to 20 fps.
My tests were done on a 3rd generation i7core machine (i7-3630QM).
So, it sounds good enough to be used for testing m2m, even on nowadays
CPUs with less performance.
I opted to keep the default time to 40 ms to 1 ms, in order to allow
multiple streams, but, in practice, I suspect that just one instance
should be enough for most usecases. So, I ended by keping the 40 ms
timing.
PS.: the first patch is identical to the one I submitted before,
except for a minor change on its description.
This patch series can be found on my development tree:
https://git.linuxtv.org/mchehab/experimental.git/log/?h=vim2m
Mauro Carvalho Chehab (3):
media: vim2m: fix driver for it to handle different fourcc formats
media: vim2m: use per-file handler work queue
media: vim2m: allow setting the default transaction time via parameter
drivers/media/platform/vim2m.c | 434 ++++++++++++++++++++-------------
1 file changed, 270 insertions(+), 164 deletions(-)
--
2.20.1
