[gstreamer-bugs] [Bug 592787] a52dec: Allow liba52 to use djbfft based IMDCT transform

[GStreamer (bugzilla.gnome.org)]

http://bugzilla.gnome.org/show_bug.cgi?id=592787



--- Comment #2 from Mart Raudsepp <leio at gentoo.org> 2009-08-23 10:14:30 UTC ---
I have anecdotal evidence of a 20% increase in speed of a52 decoding with this
change based on very very crude and quick measurement.

Just demuxing of a 45 minute test file seems to take 1.15 seconds
Decoding without djbfft patch seems to take 13.722 - 1.15 = ~12.57 seconds
Decoding with djbfft patch seems to take 11.6 - 1.15 = ~10.45 seconds  (assumes
a system liba52 with djbfft library usage enabled)

Note that a52_init isn't passed any SSE flag if the CPU supports it, but liba52
does have SSE code for downmixing. I might do a patch for that later, or not..

All of this was done while ensuring test.avi is in disk cache through multiple
runs and taking the last. In the end there's an excerpt from mplayer on the
same file, to demonstrate that with the patched liba52 in mplayer, the result
would be even better (if liba52 would be patched with mplayer patches and the
plugin would pass SSE flag to a52_init):

$ time gst-launch-0.10 filesrc location=test.avi ! avidemux ! a52dec ! fakesink
Setting pipeline to PAUSED ...
No accelerated IMDCT transform found
Pipeline is PREROLLING ...
Pipeline is PREROLLED ...
Setting pipeline to PLAYING ...
New clock: GstSystemClock
Got EOS from element "pipeline0".
Execution ended after 13623398303 ns.
Setting pipeline to PAUSED ...
Setting pipeline to READY ...
Setting pipeline to NULL ...
Freeing pipeline ...

real    0m13.722s
user    0m13.482s
sys     0m0.220s


$ time gst-launch-0.10 filesrc location=test.avi ! avidemux ! a52dec ! fakesink 
Setting pipeline to PAUSED ...
Using djbfft for IMDCT transform
Pipeline is PREROLLING ...
Pipeline is PREROLLED ...
Setting pipeline to PLAYING ...
New clock: GstSystemClock
Got EOS from element "pipeline0".
Execution ended after 11475860134 ns.
Setting pipeline to PAUSED ...
Setting pipeline to READY ...
Setting pipeline to NULL ...
Freeing pipeline ...

real    0m11.599s
user    0m11.306s
sys    0m0.267s


$ time gst-launch-0.10 filesrc location=test.avi ! avidemux ! fakesink 
Setting pipeline to PAUSED ...
Pipeline is PREROLLING ...
Pipeline is PREROLLED ...
Setting pipeline to PLAYING ...
New clock: GstSystemClock
Got EOS from element "pipeline0".
Execution ended after 1018646297 ns.
Setting pipeline to PAUSED ...
Setting pipeline to READY ...
Setting pipeline to NULL ...
Freeing pipeline ...

real    0m1.146s
user    0m0.847s
sys    0m0.230s


$ time mplayer -vo null -vc null -ao pcm:fast -benchmark test.avi 
...
Opening audio decoder: [liba52] AC3 decoding with liba52
Using SSE optimized IMDCT transform
Using MMX optimized resampler
AUDIO: 48000 Hz, 2 ch, s16le, 192.0 kbit/12.50% (ratio: 24000->192000)
Selected audio codec: [a52] afm: liba52 (AC3-liba52)
...
BENCHMARKs: VC:   0.077s VO:   0.000s A:   5.751s Sys:   3.278s =    9.106s
BENCHMARK%: VC:  0.8491% VO:  0.0000% A: 63.1538% Sys: 35.9971% = 100.0000%

real    0m9.137s
user    0m6.013s
sys     0m1.077s

-- 
Configure bugmail: http://bugzilla.gnome.org/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are the QA contact for the bug.
You are the assignee for the bug.