[Mplayer-cvslog] CVS: main/libao2 ao_sdl.c,1.35,1.36
Reimar Döffinger CVS
syncmail at mplayerhq.hu
Sun Oct 31 22:02:49 CET 2004
CVS change done by Reimar Döffinger CVS
Update of /cvsroot/mplayer/main/libao2
In directory mail:/var2/tmp/cvs-serv15052/libao2
Modified Files:
ao_sdl.c
Log Message:
Different buffering scheme, avoiding possible races (SDL is using threads!).
Index: ao_sdl.c
===================================================================
RCS file: /cvsroot/mplayer/main/libao2/ao_sdl.c,v
retrieving revision 1.35
retrieving revision 1.36
diff -u -r1.35 -r1.36
--- ao_sdl.c 18 Sep 2004 20:31:27 -0000 1.35
+++ ao_sdl.c 31 Oct 2004 21:02:47 -0000 1.36
@@ -46,68 +46,78 @@
#define SAMPLESIZE 1024
#endif
-// General purpose Ring-buffering routines
-
-#define BUFFSIZE 4096
-#define NUM_BUFS 8
-
-static unsigned char *buffer[NUM_BUFS];
-
-static unsigned int buf_read=0;
-static unsigned int buf_write=0;
-static unsigned int buf_read_pos=0;
-static unsigned int buf_write_pos=0;
+#define CHUNK_SIZE 4096
+#define NUM_CHUNKS 8
+// This type of ring buffer may never fill up completely, at least
+// one byte must always be unused.
+// For performance reasons (alignment etc.) one whole chunk always stays
+// empty, not only one byte.
+#define BUFFSIZE ((NUM_CHUNKS + 1) * CHUNK_SIZE)
+
+static unsigned char *buffer;
+
+// may only be modified by SDL's playback thread or while it is stopped
+static volatile int read_pos;
+// may only be modified by mplayer's thread
+static volatile int write_pos;
#ifdef USE_SDL_INTERNAL_MIXER
static unsigned char volume=SDL_MIX_MAXVOLUME;
#endif
-static int full_buffers=0;
-static int buffered_bytes=0;
+// may only be called by mplayer's thread
+// return value may change between immediately following two calls,
+// and the real number of free bytes might be larger!
+static int buf_free() {
+ int free = read_pos - write_pos - CHUNK_SIZE;
+ if (free < 0) free += BUFFSIZE;
+ return free;
+}
+
+// may only be called by SDL's playback thread
+// return value may change between immediately following two calls,
+// and the real number of buffered bytes might be larger!
+static int buf_used() {
+ int used = write_pos - read_pos;
+ if (used < 0) used += BUFFSIZE;
+ return used;
+}
static int write_buffer(unsigned char* data,int len){
- int len2=0;
- int x;
- while(len>0){
- if(full_buffers==NUM_BUFS) break;
- x=BUFFSIZE-buf_write_pos;
- if(x>len) x=len;
- memcpy(buffer[buf_write]+buf_write_pos,data+len2,x);
- if (buf_write_pos==0)
- ++full_buffers;
- len2+=x; len-=x;
- buffered_bytes+=x; buf_write_pos+=x;
- if(buf_write_pos>=BUFFSIZE){
- // block is full, find next!
- buf_write=(buf_write+1)%NUM_BUFS;
- buf_write_pos=0;
- }
+ int first_len = BUFFSIZE - write_pos;
+ int free = buf_free();
+ if (len > free) len = free;
+ if (first_len > len) first_len = len;
+ // till end of buffer
+ memcpy (&buffer[write_pos], data, first_len);
+ if (len > first_len) { // we have to wrap around
+ // remaining part from beginning of buffer
+ memcpy (buffer, &data[first_len], len - first_len);
}
- return len2;
+ write_pos = (write_pos + len) % BUFFSIZE;
+ return len;
}
static int read_buffer(unsigned char* data,int len){
- int len2=0;
- int x;
- while(len>0){
- if(buffered_bytes==0) break; // no more data buffered!
- x=BUFFSIZE-buf_read_pos;
- if(x>len) x=len;
- if (x>buffered_bytes) x=buffered_bytes;
+ int first_len = BUFFSIZE - read_pos;
+ int buffered = buf_used();
+ if (len > buffered) len = buffered;
+ if (first_len > len) first_len = len;
+ // till end of buffer
#ifdef USE_SDL_INTERNAL_MIXER
- SDL_MixAudio(data+len2,buffer[buf_read]+buf_read_pos,x,volume);
+ SDL_MixAudio (data, &buffer[read_pos], first_len, volume);
#else
- memcpy(data+len2,buffer[buf_read]+buf_read_pos,x);
+ memcpy (data, &buffer[read_pos], first_len);
+#endif
+ if (len > first_len) { // we have to wrap around
+ // remaining part from beginning of buffer
+#ifdef USE_SDL_INTERNAL_MIXER
+ SDL_MixAudio (&data[first_len], buffer, len - first_len, volume);
+#else
+ memcpy (&data[first_len], buffer, len - first_len);
#endif
- len2+=x; len-=x;
- buffered_bytes-=x; buf_read_pos+=x;
- if(buf_read_pos>=BUFFSIZE){
- // block is empty, find next!
- buf_read=(buf_read+1)%NUM_BUFS;
- --full_buffers;
- buf_read_pos=0;
- }
}
- return len2;
+ read_pos = (read_pos + len) % BUFFSIZE;
+ return len;
}
// end ring buffer stuff
@@ -168,9 +178,8 @@
/* SDL Audio Specifications */
SDL_AudioSpec aspec, obtained;
- int i;
/* Allocate ring-buffer memory */
- for(i=0;i<NUM_BUFS;i++) buffer[i]=(unsigned char *) malloc(BUFFSIZE);
+ buffer = (unsigned char *) malloc(BUFFSIZE);
mp_msg(MSGT_AO,MSGL_INFO,MSGTR_AO_SDL_INFO, rate, (channels > 1) ? "Stereo" : "Mono", audio_out_format_name(format));
@@ -272,6 +281,7 @@
mp_msg(MSGT_AO,MSGL_V,"SDL: buf size = %d\n",obtained.size);
ao_data.buffersize=obtained.size;
+ reset();
/* unsilence audio, if callback is ready */
SDL_PauseAudio(0);
@@ -281,7 +291,7 @@
// close audio device
static void uninit(int immed){
mp_msg(MSGT_AO,MSGL_V,"SDL: Audio Subsystem shutting down!\n");
- while(buffered_bytes > 0)
+ while(buf_free() < BUFFSIZE - CHUNK_SIZE)
usec_sleep(50000);
SDL_CloseAudio();
SDL_QuitSubSystem(SDL_INIT_AUDIO);
@@ -292,15 +302,11 @@
//printf("SDL: reset called!\n");
+ SDL_PauseAudio(1);
/* Reset ring-buffer state */
- buf_read=0;
- buf_write=0;
- buf_read_pos=0;
- buf_write_pos=0;
-
- full_buffers=0;
- buffered_bytes=0;
-
+ read_pos = 0;
+ write_pos = 0;
+ SDL_PauseAudio(0);
}
// stop playing, keep buffers (for pause)
@@ -322,7 +328,7 @@
// return: how many bytes can be played without blocking
static int get_space(){
- return NUM_BUFS*BUFFSIZE - buffered_bytes;
+ return buf_free();
}
// plays 'len' bytes of 'data'
@@ -348,7 +354,8 @@
// return: delay in seconds between first and last sample in buffer
static float get_delay(){
- return (float)(buffered_bytes + ao_data.buffersize)/(float)ao_data.bps;
+ int buffered = BUFFSIZE - CHUNK_SIZE - buf_free(); // could be less
+ return (float)(buffered + ao_data.buffersize)/(float)ao_data.bps;
}
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