vlc 0.2.90 observations on ppc

Jack Howarth howarth at bromo.msbb.uc.edu
Fri Oct 12 17:13:07 CEST 2001

    I wanted to pass along a few observations about the
improved performance of vlc 0.2.90 on a G4/450 running
Debian ppc sid. The new version seems to play without
any noticable artifacts. Before with 0.2.83 and some
test altivec patches from Michel Lanners I would get
noticable jerkiness in playback and a variation in the
framerate from between 16-17 to 24 fps. Now on this
new release with both the imdct and motion compensation
altivec codecs in use I get a rock solid 23.98 fps as
measured using the -v flag and the patch below...

--- vlc-0.2.83/src/video_output/video_output.c.org	Fri Aug 31 19:21:54 2001+++ vlc-0.2.83/src/video_output/video_output.c	Sat Sep  1 17:17:31 2001
@@ -954,6 +954,7 @@
  * terminated. It handles the pictures arriving in the video heap and the
  * display device events.
  *****************************************************************************/+static mtime_t olddate = 0;
 static void RunThread( vout_thread_t *p_vout)
     int             i_index;                                /* index in heap */@@ -1049,6 +1050,15 @@
                 p_pic =         NULL;
                 display_date =  0;
+           {
+               double frames_per_sec;
+               if ((p_vout->c_fps_samples % VOUT_FPS_SAMPLES) == 0) {
+                       frames_per_sec = (double)1000000 / ((double)(display_date - olddate) / (double)VOUT_FPS_SAMPLES);
+                       intf_WarnMsg(1, "vout warning: now = %lld, then = %lld, fps = %2.2f", display_date, olddate, frames_per_sec);
+                       olddate = display_date;
+               }
+           }

At this frame rate on a PowerMac G4/450 I am getting (using Xvideo)
this 23.98 fps framerate at about 30% cpu usage on vlc and 25% cpu
usage on XFree86 4.1. If I stress the machine I don't see any measured
change in fps (although I may be sampling to coarsely for that) but
I see a couple late frames skipped. However the video still looks pretty
     I do have one question. It seems that the only plugin we don't have
accelerated compared to mmx on our altivec equiped machines is the yuv
one. Does anyone know how much that would help and what sort of cpu load
reduction we should expect if we had it?

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