diff --git a/examples/makemovie.c b/examples/makemovie.c
index e748ad8..5cab39f 100644
--- a/examples/makemovie.c
+++ b/examples/makemovie.c
@@ -22,7 +22,6 @@
 
 #define WIDTH 1280
 #define HEIGHT 720
-#define FPS 30
 
 int main(int argc, char *argv[])
 {
@@ -30,12 +29,37 @@ int main(int argc, char *argv[])
     pipi_image_t *image;
     pipi_sequence_t *seq;
     pipi_pixels_t *p;
+    int width, height, fps, par_num, par_den, bitrate;
     int f;
 
+    width = 1280;
+    height = 720;
+    fps = 30;
+    par_num = 1;
+    par_den = 1;
+    bitrate = 16 * 1024 * 1024;
+
     if(argc < 2)
+    {
+        fprintf(stderr, "usage: makemovie FILE [width [height [fps [par_num [par_den [bitrate]]]]]]>\n");
         return EXIT_FAILURE;
+    }
+
+    if (argc > 2)
+        width = atoi(argv[2]);
+    if (argc > 3)
+        height = atoi(argv[3]);
+    if (argc > 4)
+        fps = atoi(argv[4]);
+    if (argc > 5)
+        par_num = atoi(argv[5]);
+    if (argc > 6)
+        par_den = atoi(argv[6]);
+    if (argc > 7)
+        bitrate = atoi(argv[7]);
 
-    seq = pipi_open_sequence(argv[1], WIDTH, HEIGHT, FPS);
+    seq = pipi_open_sequence(argv[1], width, height, fps,
+                             par_num, par_den, bitrate);
     if(!seq)
         return EXIT_FAILURE;
 
diff --git a/pipi/pipi.h b/pipi/pipi.h
index c177b8e..be24ad7 100644
--- a/pipi/pipi.h
+++ b/pipi/pipi.h
@@ -237,8 +237,9 @@ __extern int pipi_get_image_histogram(pipi_image_t *, pipi_histogram_t *, int);
 __extern int pipi_free_histogram(pipi_histogram_t*);
 __extern int pipi_render_histogram(pipi_image_t *, pipi_histogram_t*, int);
 
-__extern pipi_sequence_t *pipi_open_sequence(char const *, int, int, int);
-__extern int pipi_feed_sequence(pipi_sequence_t *, uint8_t *, int, int);
+__extern pipi_sequence_t *pipi_open_sequence(char const *, int, int, int,
+                                             int, int, int);
+__extern int pipi_feed_sequence(pipi_sequence_t *, uint8_t const *, int, int);
 __extern int pipi_close_sequence(pipi_sequence_t *);
 
 #ifdef __cplusplus
diff --git a/pipi/sequence.c b/pipi/sequence.c
index 67b8cc9..57034e1 100644
--- a/pipi/sequence.c
+++ b/pipi/sequence.c
@@ -54,12 +54,9 @@ typedef struct
 ffmpeg_codec_t;
 #endif
 
-#define PAR_NUM 1
-#define PAR_DEN 1
-#define BITRATE (16 * 1024 * 1024)
-
 pipi_sequence_t *pipi_open_sequence(char const *file,
-                                    int width, int height, int fps)
+                                    int width, int height, int fps,
+                                    int par_num, int par_den, int bitrate)
 {
 #if defined USE_FFMPEG
     static int initialised = 0;
@@ -104,18 +101,18 @@ pipi_sequence_t *pipi_open_sequence(char const *file,
     if (!ff->stream)
         goto error;
 
-    ff->stream->sample_aspect_ratio.num = PAR_NUM;
-    ff->stream->sample_aspect_ratio.den = PAR_DEN;
+    ff->stream->sample_aspect_ratio.num = par_num;
+    ff->stream->sample_aspect_ratio.den = par_den;
 
     ff->cod_ctx = ff->stream->codec;
 
     ff->cod_ctx->width = width;
     ff->cod_ctx->height = height;
-    ff->cod_ctx->sample_aspect_ratio.num = PAR_NUM;
-    ff->cod_ctx->sample_aspect_ratio.den = PAR_DEN;
+    ff->cod_ctx->sample_aspect_ratio.num = par_num;
+    ff->cod_ctx->sample_aspect_ratio.den = par_den;
     ff->cod_ctx->codec_id = ff->fmt_ctx->oformat->video_codec;
     ff->cod_ctx->codec_type = CODEC_TYPE_VIDEO;
-    ff->cod_ctx->bit_rate = BITRATE;
+    ff->cod_ctx->bit_rate = bitrate;
     ff->cod_ctx->time_base.num = 1;
     ff->cod_ctx->time_base.den = fps;
     ff->cod_ctx->gop_size = fps * 3 / 4; /* empirical */
@@ -168,7 +165,8 @@ error:
 #endif
 }
 
-int pipi_feed_sequence(pipi_sequence_t *seq, uint8_t *buffer, int width, int height)
+int pipi_feed_sequence(pipi_sequence_t *seq, uint8_t const *buffer,
+                       int width, int height)
 {
 #if defined USE_FFMPEG
     AVPacket packet;