[Ffmpeg-devel] [PATCH] grabbing with V4L

[Flavio Pimentel Duarte]

I have reported that capturing movies with ffmpeg and Creative Notebook 
Webcam produces a very dark movie. Later I saw the same problem with 
Creative NX PRO. I took a look at V4L documentation and at the mplayer 
source code and realized that the problem was some initialization was 
missing or misplaced. I reorganized the code in grab.c to solve the 
problem. The patch is attached.

Flavio
-------------- next part --------------
Index: libavformat/grab.c
===================================================================
RCS file: /cvsroot/ffmpeg/ffmpeg/libavformat/grab.c,v
retrieving revision 1.39
diff -u -p -r1.39 grab.c
--- libavformat/grab.c	22 Dec 2005 01:10:11 -0000	1.39
+++ libavformat/grab.c	9 Jan 2006 18:25:34 -0000
@@ -65,6 +65,7 @@ static int grab_read_header(AVFormatCont
     int desired_palette;
     struct video_tuner tuner;
     struct video_audio audio;
+    struct video_picture pict;
     const char *video_device;
     int j;
 
@@ -135,11 +136,36 @@ static int grab_read_header(AVFormatCont
     audio.flags &= ~VIDEO_AUDIO_MUTE;
     ioctl(video_fd, VIDIOCSAUDIO, &audio);
 
+    ioctl(video_fd, VIDIOCGPICT, &pict);
+#if 0
+    printf("v4l: colour=%d hue=%d brightness=%d constrast=%d whiteness=%d\n",
+           pict.colour,
+           pict.hue,
+           pict.brightness,
+           pict.contrast,
+           pict.whiteness);
+#endif
+    /* try to choose a suitable video format */
+    pict.palette = desired_palette;
+    if (desired_palette == -1 || (ret = ioctl(video_fd, VIDIOCSPICT, &pict)) < 0) {
+        pict.palette=VIDEO_PALETTE_YUV420P;
+        ret = ioctl(video_fd, VIDIOCSPICT, &pict);
+        if (ret < 0) {
+            pict.palette=VIDEO_PALETTE_YUV422;
+            ret = ioctl(video_fd, VIDIOCSPICT, &pict);
+            if (ret < 0) {
+                pict.palette=VIDEO_PALETTE_RGB24;
+                ret = ioctl(video_fd, VIDIOCSPICT, &pict);
+                if (ret < 0)
+                    goto fail1;
+            }
+        }
+    }
+
     ret = ioctl(video_fd,VIDIOCGMBUF,&s->gb_buffers);
     if (ret < 0) {
         /* try to use read based access */
         struct video_window win;
-        struct video_picture pict;
         int val;
 
         win.x = 0;
@@ -151,32 +177,6 @@ static int grab_read_header(AVFormatCont
 
         ioctl(video_fd, VIDIOCSWIN, &win);
 
-        ioctl(video_fd, VIDIOCGPICT, &pict);
-#if 0
-        printf("v4l: colour=%d hue=%d brightness=%d constrast=%d whiteness=%d\n",
-               pict.colour,
-               pict.hue,
-               pict.brightness,
-               pict.contrast,
-               pict.whiteness);
-#endif
-        /* try to choose a suitable video format */
-        pict.palette = desired_palette;
-        if (desired_palette == -1 || (ret = ioctl(video_fd, VIDIOCSPICT, &pict)) < 0) {
-            pict.palette=VIDEO_PALETTE_YUV420P;
-            ret = ioctl(video_fd, VIDIOCSPICT, &pict);
-            if (ret < 0) {
-                pict.palette=VIDEO_PALETTE_YUV422;
-                ret = ioctl(video_fd, VIDIOCSPICT, &pict);
-                if (ret < 0) {
-                    pict.palette=VIDEO_PALETTE_RGB24;
-                    ret = ioctl(video_fd, VIDIOCSPICT, &pict);
-                    if (ret < 0)
-                        goto fail1;
-                }
-            }
-        }
-
         s->frame_format = pict.palette;
 
         val = 1;