[Bug 775437] New: bayer2rgb: vectorized horiz_upsample cannot be compiled on arm7a

[GStreamer (GNOME Bugzilla)]

https://bugzilla.gnome.org/show_bug.cgi?id=775437

            Bug ID: 775437
           Summary: bayer2rgb: vectorized horiz_upsample cannot be
                    compiled on arm7a
    Classification: Platform
           Product: GStreamer
           Version: 1.4.5
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: Normal
         Component: gst-plugins-bad
          Assignee: gstreamer-bugs at lists.freedesktop.org
          Reporter: robin.haberkorn at googlemail.com
        QA Contact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---

Created attachment 341096
  --> https://bugzilla.gnome.org/attachment.cgi?id=341096&action=edit
Log of running a pipeline with bayer2rgb and ORC_DEBUG=10

I've filed this for v1.4.5 (since this is what I'm using now), but I checked
upstream. There is no difference in the relevant code.
The version of liborc used is 0.4.23, but again there does not seem to be any
commit upstream that could affect this.

When running a pipeline with bayer2rgb and ORC_DEBUG=10 on an embedded platform
(armv7a), bayer_orc_horiz_upsample() cannot be compiled, so orc will use the
fallback C version (see orc-log.txt).

I've patched gstbayer2rgb.c, so the alternative
bayer_orc_horiz_upsample_unaligned() is used on ARMv7a (see attached patch).
This JIT-compiles fine. But frankly, I do not understand the difference between
the two variants and why this did the trick. There are no code comments and no
explanations. Perhaps one of the maintainers could elaborate on this.

To my even bigger surprise, using the vectorized
bayer_orc_horiz_upsample_unaligned() seems to bring no significant speed
increase versus the fallback bayer_orc_horiz_upsample() version. But with about
90MB/s of debayered buffers being produced by my pipeline, I might also have
run into a memory bandwidth bottleneck here (although the bottleneck would be
unlikely low) or into some other bottleneck of course.
In general, the liborc vectorizations do speed up things at least 1,7 times.

-- 
You are receiving this mail because:
You are the QA Contact for the bug.
You are the assignee for the bug.