i was working on openAL and found one bug which would cause infinite

loop when if avcodec_decode_audio (ffmpeg function) returned  0 in the
loop its in and when fixed in the loop above it.
see post  http://panda3d.org/phpbb2/viewtopic.php?p=30331#30331

most changes are to   ffmpegAudioCursor.cxx and movieAudio.h

It basically changes to proper error handling with 0 as DONE

-      if (len < 0) {
+      if (len <= 0) {

and create a give up counter

+  // give up after 100 tries to fetch data
+  int give_up_after = 100;
+
+  while (desired && give_up_after > 0) {
+    give_up_after --;

and some helpful debug messages for the next poor coder to step into this code.

panda/src/movies/ffmpegAudioCursor.cxx

@@ -179,6 +179,8 @@ fetch_packet() {
 ////////////////////////////////////////////////////////////////////
 void FfmpegAudioCursor::
 reload_buffer() {
+
+
   while (_buffer_head == _buffer_tail) {
     // If we're out of packets, generate silence.
     if (_packet->data == 0) {
@@ -190,7 +192,8 @@ reload_buffer() {
       int bufsize = _buffer_size * 2;
       int len = avcodec_decode_audio(_audio_ctx, _buffer, &bufsize,
                                      _packet_data, _packet_size);
-      if (len < 0) {
+      movies_debug("avcodec_decode_audio returned " << len);
+      if (len <= 0) {
         break;
       }
       _packet_data += len;
@@ -257,10 +260,20 @@ seek(double t) {
 ////////////////////////////////////////////////////////////////////
 void FfmpegAudioCursor::
 read_samples(int n, PN_int16 *data) {
+
+  //movies_debug("here!!! FfmpegAudioCursor n="<<n);
+
   int desired = n * _audio_channels;
-  while (desired) {
+
+  // give up after 100 tries to fetch data
+  int give_up_after = 100;
+
+  while (desired && give_up_after > 0) {
+
     if (_buffer_head == _buffer_tail) {
       reload_buffer();
+      give_up_after --;
+      movies_debug("reload_buffer will give up in "<<give_up_after);
     }
     int available = _buffer_tail - _buffer_head;
     int ncopy = (desired > available) ? available : desired;
@@ -272,6 +285,7 @@ read_samples(int n, PN_int16 *data) {
       desired -= ncopy;
       _buffer_head += ncopy;
     }
+
   }
   _samples_read += n;
 }

panda/src/movies/movieAudio.h

@@ -21,6 +21,19 @@
 #include "typedWritableReferenceCount.h"
 class MovieAudioCursor;
 
+
+#ifdef NOTIFY_DEBUG //[
+  // Non-release build:
+  #define movies_debug(msg) \
+  if (movies_cat.is_debug()) { \
+	  movies_cat->debug() << msg << endl; \
+  } else {}
+#else //][
+  // Release build:
+  #define movies_debug(msg) ((void)0);
+#endif //]
+
+
 ////////////////////////////////////////////////////////////////////
 //       Class : MovieAudio
 // Description : A MovieAudio is actually any source that provides