Re: [libdv-dev] Re: Should dv1394 work on PPC?

[Bill F. <bil...@mi...>]

On Wed, 19 Jun 2002, Bill Fink wrote:

> On 19 Jun 2002, Dan Dennedy wrote:
> 
> > On Wed, 2002-06-19 at 14:49, Bill Fink wrote:
> > > Also related to the audio, how difficult would it be to add an option
> > > --skip-video=n that would only decode and display every nth video frame,
> > > since at the moment if I try and do both audio and video, the audio is
> > > very stuttery and not understandable because my processor can't keep up
> > > with the demands of decoding the full frame rate video?
> > 
> > Do you care to contribute that yourself? Currently, we are trying to
> > release libdv 0.9.6, and I thought we were ready until these issues
> > popped up--particularly the endian detection issues. So, this is a lower
> > priority right now.
> 
> I'll take a look at it.  I admit that this part's not a high priority
> though.

OK.  I'm attaching a patch that implements the --skip-video option.
It didn't work quite as well as I had hoped, but I still think it's
useful (you can also use it to control how much CPU playdv consumes).
I guess you really need separate audio and video threads to do this
properly, but that's a much larger task.

						-Bill



playdv-skip-video.patch:
--------------------------------------------------------------------------------
--- .orig/playdv.c	Sun May 26 17:02:42 2002
+++ .mod/playdv.c	Thu Jun 20 00:25:14 2002
@@ -56,13 +56,14 @@
 #define DV_PLAYER_OPT_DISABLE_AUDIO   1
 #define DV_PLAYER_OPT_DISABLE_VIDEO   2
 #define DV_PLAYER_OPT_NUM_FRAMES      3
-#define DV_PLAYER_OPT_OSS_INCLUDE     4
-#define DV_PLAYER_OPT_DISPLAY_INCLUDE 5
-#define DV_PLAYER_OPT_DECODER_INCLUDE 6
-#define DV_PLAYER_OPT_AUTOHELP        7
-#define DV_PLAYER_OPT_DUMP_FRAMES     8
-#define DV_PLAYER_OPT_NO_MMAP         9
-#define DV_PLAYER_NUM_OPTS            10
+#define DV_PLAYER_OPT_SKIP_VIDEO      4
+#define DV_PLAYER_OPT_OSS_INCLUDE     5
+#define DV_PLAYER_OPT_DISPLAY_INCLUDE 6
+#define DV_PLAYER_OPT_DECODER_INCLUDE 7
+#define DV_PLAYER_OPT_AUTOHELP        8
+#define DV_PLAYER_OPT_DUMP_FRAMES     9
+#define DV_PLAYER_OPT_NO_MMAP         10
+#define DV_PLAYER_NUM_OPTS            11
 
 /* Book-keeping for mmap */
 typedef struct dv_mmap_region_s {
@@ -82,6 +83,7 @@
   gint             arg_disable_video;
   gint             no_mmap;
   gint             arg_num_frames;
+  gint             arg_skip_video;
   char*            arg_dump_frames;
 #if HAVE_LIBPOPT
   struct poptOption option_table[DV_PLAYER_NUM_OPTS+1]; 
@@ -127,6 +129,15 @@
     descrip:    "stop after <count> frames",
   }; /* number of frames */
 
+  result->option_table[DV_PLAYER_OPT_SKIP_VIDEO] = (struct poptOption) {
+    longName:   "skip-video", 
+    shortName:  's', 
+    argInfo:    POPT_ARG_INT, 
+    arg:        &result->arg_skip_video,
+    argDescrip: "n",
+    descrip:    "only process every <n>th video frame",
+  }; /* number of video frames to skip */
+
   result->option_table[DV_PLAYER_OPT_DUMP_FRAMES] = (struct poptOption) {
     longName:   "dump-frames", 
     argInfo:    POPT_ARG_STRING,
@@ -368,6 +379,9 @@
     if(!(audio_buffers[i] = malloc(DV_AUDIO_MAX_SAMPLES*sizeof(gint16)))) goto no_mem;
   } /* if */
 
+  if (!dv_player->arg_skip_video)
+    dv_player->arg_skip_video = 1;
+
   gettimeofday(dv_player->tv+0,NULL);
 
   dv_player->decoder->prev_frame_decoded = 0;
@@ -412,7 +426,7 @@
       } /* if */
     } /* if */
 
-    if(!dv_player->arg_disable_video) {
+    if((!dv_player->arg_disable_video) && ((frame_count % dv_player->arg_skip_video) == 0)) {
 #if 0
       if (dv_format_wide (dv_player->decoder))
         fprintf (stderr, "format 16:9\n");