[Ffmpeg-devel] Modifing output_example.c for Sony PSP support

[Lars Blumberg]

Hello newsgroup,

I made a few changes to output_example.c to create a test video for "Sony 
Play Station Portable" Devices.
So I had to change the screen size and some compression values (bit rate, 
sample rate, ...).

Now the problem is, that output_example does not generate a valid audio 
stream. The audio stream is correctly played with VLC, but the Sony PSP 
device only plays very strange noises. output_example uses the right codecs 
for encoding, but there is something wrong with the audio.

Can anyone check my changes, please? I want to know, what I did wrong in 
order to create a test video for Sony PSP devices.

Here are the differences between the original, current output_example.c and 
my changes:

--- output_example.c    Sun Apr  2 09:46:56 2006
+++ output_example_psp.c        Mon Apr  3 16:53:40 2006
@@ -35,8 +35,9 @@

 /* 5 seconds stream duration */
 #define STREAM_DURATION   5.0
-#define STREAM_FRAME_RATE 25 /* 25 images/s */
-#define STREAM_NB_FRAMES  ((int)(STREAM_DURATION * STREAM_FRAME_RATE))
+#define STREAM_FRAME_RATE_DEN 2997 /* 25 images/s */
+#define STREAM_FRAME_RATE_NUM 100
+#define STREAM_NB_FRAMES  ((int)(STREAM_DURATION * STREAM_FRAME_RATE_DEN / 
STREAM_FRAME_RATE_NUM))
 #define STREAM_PIX_FMT PIX_FMT_YUV420P /* default pix_fmt */

 /**************************************************************/
@@ -68,7 +69,7 @@

     /* put sample parameters */
     c->bit_rate = 64000;
-    c->sample_rate = 44100;
+    c->sample_rate = 24000;
     c->channels = 2;
     return st;
 }
@@ -195,16 +196,16 @@
     c->codec_type = CODEC_TYPE_VIDEO;

     /* put sample parameters */
-    c->bit_rate = 400000;
+    c->bit_rate = 480000;
     /* resolution must be a multiple of two */
-    c->width = 352;
-    c->height = 288;
+    c->width = 320;
+    c->height = 240;
     /* time base: this is the fundamental unit of time (in seconds) in 
terms
        of which frame timestamps are represented. for fixed-fps content,
        timebase should be 1/framerate and timestamp increments should be
        identically 1. */
-    c->time_base.den = STREAM_FRAME_RATE;
-    c->time_base.num = 1;
+    c->time_base.den = STREAM_FRAME_RATE_DEN;
+    c->time_base.num = STREAM_FRAME_RATE_NUM;
     c->gop_size = 12; /* emit one intra frame every twelve frames at most 
*/
     c->pix_fmt = STREAM_PIX_FMT;
     if (c->codec_id == CODEC_ID_MPEG2VIDEO) {
@@ -218,7 +219,7 @@
         c->mb_decision=2;
     }
     // some formats want stream headers to be seperate
-    if(!strcmp(oc->oformat->name, "mp4") || !strcmp(oc->oformat->name, 
"mov") || !strcmp(oc->oformat->name, "3gp"))
+    if(!strcmp(oc->oformat->name, "mp4") || !strcmp(oc->oformat->name, 
"mov") || !strcmp(oc->oformat->name, "3gp") || !strcmp(oc->oformat->name, 
"psp"))
         c->flags |= CODEC_FLAG_GLOBAL_HEADER;

     return st;
@@ -420,7 +421,7 @@

     /* auto detect the output format from the name. default is
        mpeg. */
-    fmt = guess_format(NULL, filename, NULL);
+    fmt = guess_format("psp", NULL, NULL);
     if (!fmt) {
         printf("Could not deduce output format from file extension: using 
MPEG.\n");
         fmt = guess_format("mpeg", NULL, NULL);
@@ -438,6 +439,7 @@
     }
     oc->oformat = fmt;
     snprintf(oc->filename, sizeof(oc->filename), "%s", filename);
+    snprintf(oc->title, sizeof(oc->title), "test video");

     /* add the audio and video streams using the default format codecs
        and initialize the codecs */

Best regards

Lars