[MPlayer-dev-eng] [Patch] Audio detection

[Michael Behrisch]

Hello,
this patch cleans up the detection loop
in demux_audio and enhances mp3 detection.

Michael
-------------- next part --------------
--- libmpdemux/demux_audio.old	2003-10-09 10:02:45.000000000 +0200
+++ libmpdemux/demux_audio.c	2004-02-10 09:49:35.000000000 +0100
@@ -21,6 +21,7 @@
 
 
 #define HDR_SIZE 4
+#define MIN_VALID_HEADERS 6
 
 typedef struct da_priv {
   int frmt;
@@ -37,7 +38,8 @@
   stream_t *s;
   sh_audio_t* sh_audio;
   uint8_t hdr[HDR_SIZE];
-  int st_pos = 0,frmt = 0, n = 0, pos = 0, step, mp3_freq,mp3_chans;
+  int frmt = 0, n = 0, pos = 0, bytes_to_read = HDR_SIZE;
+  int len, mp3_freq, mp3_chans;
   da_priv_t* priv;
 #ifdef MP_DEBUG
   assert(demuxer != NULL);
@@ -46,49 +48,59 @@
   
   s = demuxer->stream;
 
-  while(n < 5 && ! s->eof) {
-    st_pos = stream_tell(s);
-    step = 1;
-    if(pos < HDR_SIZE) {
-      stream_read(s,&hdr[pos],HDR_SIZE-pos);
-      pos = HDR_SIZE;
-    }
+  while(n < 50 && ! s->eof) {
+    pos = stream_tell(s);
+    stream_read(s,&hdr[HDR_SIZE-bytes_to_read],bytes_to_read);
+    bytes_to_read = 1;
 
     if( hdr[0] == 'R' && hdr[1] == 'I' && hdr[2] == 'F' && hdr[3] == 'F' ) {
       stream_skip(s,4);
-      if(s->eof)
-	break;
-      stream_read(s,hdr,4);
-      if(s->eof)
-	break;
+      if(s->eof) break;
+      stream_read(s,hdr,HDR_SIZE);
+      if(s->eof) break;
       if(hdr[0] != 'W' || hdr[1] != 'A' || hdr[2] != 'V'  || hdr[3] != 'E' )
 	stream_skip(s,-8);
       else
       // We found wav header. Now we can have 'fmt ' or a mp3 header
       // empty the buffer
-	step = 4;
+        bytes_to_read = HDR_SIZE;
     } else if( hdr[0] == 'I' && hdr[1] == 'D' && hdr[2] == '3' && (hdr[3] >= 2)) {
-      int len;
       stream_skip(s,2);
-      stream_read(s,hdr,4);
+      if(s->eof) break;
+      stream_read(s,hdr,HDR_SIZE);
+      if(s->eof) break;
       len = (hdr[0]<<21) | (hdr[1]<<14) | (hdr[2]<<7) | hdr[3];
       stream_skip(s,len);
-      step = 4;
+      bytes_to_read = HDR_SIZE;
     } else if( hdr[0] == 'f' && hdr[1] == 'm' && hdr[2] == 't' && hdr[3] == ' ' ) {
       frmt = WAV;
       break;      
-    } else if((n = mp_get_mp3_header(hdr,&mp3_chans,&mp3_freq)) > 0) {
+    } else if((len = mp_get_mp3_header(hdr,&mp3_chans,&mp3_freq)) > 20) {
+      int i, mp3_freq2, mp3_chans2;
+      for(i = 1; i < MIN_VALID_HEADERS ; i++) {
+        stream_skip(s,len-HDR_SIZE);
+        if(s->eof) break;
+        stream_read(s,hdr,HDR_SIZE);
+        if(s->eof) break;
+        len = mp_get_mp3_header(hdr,&mp3_chans2,&mp3_freq2);
+        if(len < 21 || mp3_chans != mp3_chans2 || mp3_freq != mp3_freq2) break;
+      }
+      if(i == MIN_VALID_HEADERS) {
       frmt = MP3;
       break;
+      }
+      if(s->eof || !s->end_pos) break;
+      stream_seek(s, pos+1);
+      bytes_to_read = HDR_SIZE;
     } else if( hdr[0] == 'f' && hdr[1] == 'L' && hdr[2] == 'a' && hdr[3] == 'C' ) {
       frmt = fLaC;
       stream_skip(s,-4);
       break;
     }
     // Add here some other audio format detection
-    if(step < HDR_SIZE)
-      memmove(hdr,&hdr[step],HDR_SIZE-step);
-    pos -= step;
+    if(bytes_to_read < HDR_SIZE)
+      memmove(hdr,&hdr[bytes_to_read],HDR_SIZE-bytes_to_read);
+    n++;
   }
 
   if(!frmt)
@@ -99,7 +111,7 @@
   switch(frmt) {
   case MP3:
     sh_audio->format = 0x55;
-    demuxer->movi_start = st_pos-HDR_SIZE+n;
+    demuxer->movi_start = pos; // first frame gets skipped in mp3lib
     sh_audio->audio.dwSampleSize= 0;
     sh_audio->audio.dwScale = 1152;
     sh_audio->audio.dwRate = mp3_freq;
@@ -110,6 +122,7 @@
     sh_audio->wf->nBlockAlign = 1152;
     sh_audio->wf->wBitsPerSample = 16;
     sh_audio->wf->cbSize = 0;    
+    //following loop can be removed after testing new detection
     for(n = 0; n < 5 ; n++) {
       pos = mp_decode_mp3_header(hdr);
       if(pos < 0)