api-example: Try to avoid decoding incomplete frames

Use a larger input audio buffer, refill it when it has less than 4 KB data
left.

Originally committed as revision 23323 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/api-example.c

@@ -39,6 +39,8 @@
 #include "libavutil/mathematics.h"
 
 #define INBUF_SIZE 4096
+#define AUDIO_INBUF_SIZE 20480
+#define AUDIO_REFILL_THRESH 4096
 
 /*
  * Audio encoding example
@@ -118,7 +120,7 @@ static void audio_decode_example(const char *outfilename, const char *filename)
     int out_size, len;
     FILE *f, *outfile;
     uint8_t *outbuf;
-    uint8_t inbuf[INBUF_SIZE + FF_INPUT_BUFFER_PADDING_SIZE];
+    uint8_t inbuf[AUDIO_INBUF_SIZE + FF_INPUT_BUFFER_PADDING_SIZE];
     AVPacket avpkt;
 
     av_init_packet(&avpkt);
@@ -155,12 +157,8 @@ static void audio_decode_example(const char *outfilename, const char *filename)
 
     /* decode until eof */
     avpkt.data = inbuf;
-    for(;;) {
-        avpkt.size = fread(inbuf, 1, INBUF_SIZE, f);
-        if (avpkt.size == 0)
-            break;
+        avpkt.size = fread(inbuf, 1, AUDIO_INBUF_SIZE, f);
 
-        avpkt.data = inbuf;
         while (avpkt.size > 0) {
             out_size = AVCODEC_MAX_AUDIO_FRAME_SIZE;
             len = avcodec_decode_audio3(c, (short *)outbuf, &out_size, &avpkt);
@@ -174,6 +172,17 @@ static void audio_decode_example(const char *outfilename, const char *filename)
             }
             avpkt.size -= len;
             avpkt.data += len;
+            if (avpkt.size < AUDIO_REFILL_THRESH) {
+                /* Refill the input buffer, to avoid trying to decode
+                 * incomplete frames. Instead of this, one could also use
+                 * a parser, or use a proper container format through
+                 * libavformat. */
+                memmove(inbuf, avpkt.data, avpkt.size);
+                avpkt.data = inbuf;
+                len = fread(avpkt.data + avpkt.size, 1,
+                            AUDIO_INBUF_SIZE - avpkt.size, f);
+                if (len > 0)
+                    avpkt.size += len;
             }
         }