Change decode_audio() interface

Rewrite decode_audio to better deal with filters that handle input in
large blocks. It now always places output in sh_audio->a_out_buffer
(which was always given as a parameter before) and reallocates the
buffer if needed. After the changes filters can return arbitrarily
large blocks of data without some of it being lost. The new version
also allows simplifying some code.


git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@24920 b3059339-0415-0410-9bf9-f77b7e298cf2

2 files changed, 102 insertions, 74 deletions

diff --git a/libmpcodecs/dec_audio.c b/libmpcodecs/dec_audio.c
index 5445eeac22..ee6295d2ca 100644
--- a/libmpcodecs/dec_audio.c
+++ b/libmpcodecs/dec_audio.c
@@ -1,6 +1,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
+#include <assert.h>
 
 #include "config.h"
 #include "mp_msg.h"
@@ -380,86 +381,113 @@ int init_audio_filters(sh_audio_t *sh_audio, int in_samplerate,
     return 1;
 }
 
-int decode_audio(sh_audio_t *sh_audio, unsigned char *buf, int minlen,
-		 int maxlen)
+static int filter_n_bytes(sh_audio_t *sh, int len)
 {
-    int declen;
-    af_data_t afd;		// filter input
-    af_data_t *pafd;		// filter output
-    ad_functions_t *mpadec = sh_audio->ad_driver;
-
-    if (!sh_audio->inited || !sh_audio->afilter)
-	abort();
-
-    declen = af_calc_insize_constrained(sh_audio->afilter, minlen, maxlen,
-					sh_audio->a_buffer_size -
-					sh_audio->audio_out_minsize);
-
-    mp_msg(MSGT_DECAUDIO, MSGL_DBG2,
-	   "\ndecaudio: minlen=%d maxlen=%d declen=%d (max=%d)\n", minlen,
-	   maxlen, declen, sh_audio->a_buffer_size);
-
-    if (declen <= 0)
-	return -1;		// error!
-
-    while (declen > sh_audio->a_buffer_len) {
-	int len = declen - sh_audio->a_buffer_len;
-	int maxlen = sh_audio->a_buffer_size - sh_audio->a_buffer_len;
-
-	mp_msg(MSGT_DECAUDIO, MSGL_DBG2,
-	       "decaudio: decoding %d bytes, max: %d (%d)\n", len, maxlen,
-	       sh_audio->audio_out_minsize);
-
-	// When a decoder sets audio_out_minsize that should guarantee it can
-	// write up to audio_out_minsize bytes at a time until total >= minlen
-	// without checking maxlen. Thus maxlen must be at least minlen +
-	// audio_out_minsize. Check that to guard against buffer overflows.
-	if (maxlen < len + sh_audio->audio_out_minsize)
+    assert(len-1 + sh->audio_out_minsize <= sh->a_buffer_size);
+
+    int error = 0;
+
+    // Decode more bytes if needed
+    while (sh->a_buffer_len < len) {
+	unsigned char *buf = sh->a_buffer + sh->a_buffer_len;
+	int minlen = len - sh->a_buffer_len;
+	int maxlen = sh->a_buffer_size - sh->a_buffer_len;
+	int ret = sh->ad_driver->decode_audio(sh, buf, minlen, maxlen);
+	if (ret <= 0) {
+	    error = -1;
+	    len = sh->a_buffer_len;
 	    break;
+	}
+	sh->a_buffer_len += ret;
+    }
 
-	len = mpadec->decode_audio(sh_audio,
-				   sh_audio->a_buffer + sh_audio->a_buffer_len,
-				   len, maxlen);
-	if (len <= 0)
-	    break;		// EOF?
-	sh_audio->a_buffer_len += len;
+    // Filter
+    af_data_t filter_input = {
+	.audio = sh->a_buffer,
+	.len = len,
+	.rate = sh->samplerate,
+	.nch = sh->channels,
+	.format = sh->sample_format
+    };
+    af_fix_parameters(&filter_input);
+    af_data_t *filter_output = af_play(sh->afilter, &filter_input);
+    if (!filter_output)
+	return -1;
+    if (sh->a_out_buffer_size < sh->a_out_buffer_len + filter_output->len) {
+	int newlen = sh->a_out_buffer_len + filter_output->len;
+	mp_msg(MSGT_DECAUDIO, MSGL_V, "Increasing filtered audio buffer size "
+	       "from %d to %d\n", sh->a_out_buffer_size, newlen);
+	sh->a_out_buffer = realloc(sh->a_out_buffer, newlen);
+	sh->a_out_buffer_size = newlen;
     }
-    if (declen > sh_audio->a_buffer_len)
-	declen = sh_audio->a_buffer_len;   // still no enough data (EOF) :(
-
-    // run the filters:
-    afd.audio = sh_audio->a_buffer;
-    afd.len = declen;
-    afd.rate = sh_audio->samplerate;
-    afd.nch = sh_audio->channels;
-    afd.format = sh_audio->sample_format;
-    af_fix_parameters(&afd);
-    pafd = af_play(sh_audio->afilter, &afd);
-
-    if (!pafd)
-	return -1;   // error
-
-    mp_msg(MSGT_DECAUDIO, MSGL_DBG2, "decaudio: declen=%d out=%d (max %d)\n",
-	   declen, pafd->len, maxlen);
-
-    // copy filter==>out:
-    if (maxlen < pafd->len) {
-	af_stream_t *afs = sh_audio->afilter;
-	maxlen -= maxlen % (afs->output.nch * afs->output.bps);
-	mp_msg(MSGT_DECAUDIO, MSGL_WARN,
-	     "%i bytes of audio data lost due to buffer overflow, len = %i\n",
-	       pafd->len - maxlen, pafd->len);
-    } else
-	maxlen = pafd->len;
-    memmove(buf, pafd->audio, maxlen);
+    memcpy(sh->a_out_buffer + sh->a_out_buffer_len, filter_output->audio,
+	   filter_output->len);
+    sh->a_out_buffer_len += filter_output->len;
 
     // remove processed data from decoder buffer:
-    sh_audio->a_buffer_len -= declen;
-    if (sh_audio->a_buffer_len > 0)
-	memmove(sh_audio->a_buffer, sh_audio->a_buffer + declen,
-		sh_audio->a_buffer_len);
+    sh->a_buffer_len -= len;
+    memmove(sh->a_buffer, sh->a_buffer + len, sh->a_buffer_len);
 
-    return maxlen;
+    return error;
+}
+
+/* Try to get at least minlen decoded+filtered bytes in sh_audio->a_out_buffer
+ * (total length including possible existing data).
+ * Return 0 on success, -1 on error/EOF (not distinguished).
+ * In the former case sh_audio->a_out_buffer_len is always >= minlen
+ * on return. In case of EOF/error it might or might not be.
+ * Can reallocate sh_audio->a_out_buffer if needed to fit all filter output. */
+int decode_audio(sh_audio_t *sh_audio, int minlen)
+{
+    if (!sh_audio->inited || !sh_audio->afilter)
+	abort();
+
+    // Decoded audio must be cut at boundaries of this many bytes
+    int unitsize = sh_audio->channels * sh_audio->samplesize;
+
+    /* Filter output size will be about filter_multiplier times input size.
+     * If some filter buffers audio in big blocks this might only hold
+     * as average over time. */
+    double filter_multiplier = af_calc_filter_multiplier(sh_audio->afilter);
+
+    /* If the decoder set audio_out_minsize then it can do the equivalent of
+     * "while (output_len < target_len) output_len += audio_out_minsize;",
+     * so we must guarantee there is at least audio_out_minsize-1 bytes
+     * more space in the output buffer than the minimum length we try to
+     * decode. */
+    int max_decode_len = sh_audio->a_buffer_size - sh_audio->audio_out_minsize;
+    max_decode_len -= max_decode_len % unitsize;
+
+    while (sh_audio->a_out_buffer_len < minlen) {
+	int declen = (minlen - sh_audio->a_out_buffer_len) / filter_multiplier
+	    + (unitsize << 5); // some extra for possible filter buffering
+	if (declen > max_decode_len) {  // Do it in several steps
+	    if (filter_n_bytes(sh_audio, max_decode_len) < 0)
+		return -1;
+	    continue;
+	}
+	declen -= declen % unitsize;
+	if (filter_n_bytes(sh_audio, declen) < 0)
+	    return -1;
+	if (sh_audio->a_out_buffer_len >= minlen)
+	    return 0;
+	/* Some filter must be doing significant buffering if the estimated
+	 * input length didn't produce enough output from filters.
+	 * Feed the filters 2k bytes at a time until we have enough output.
+	 * Very small amounts could make filtering inefficient while large
+	 * amounts can make MPlayer demux the file unnecessarily far ahead
+	 * to get audio data and buffer video frames in memory while doing
+	 * so. However the performance impact of either is probably not too
+	 * significant as long as the value is not completely insane. */
+	declen = min(2000, max_decode_len);
+	declen -= declen % unitsize;
+	while (sh_audio->a_out_buffer_len < minlen) {
+	    if (filter_n_bytes(sh_audio, declen) < 0)
+		return -1;
+	}
+	return 0;
+    }
+    return 0;
 }
 
 void resync_audio_stream(sh_audio_t *sh_audio)
diff --git a/libmpcodecs/dec_audio.h b/libmpcodecs/dec_audio.h
index d372a65fc8..e5d71b8792 100644
--- a/libmpcodecs/dec_audio.h
+++ b/libmpcodecs/dec_audio.h
@@ -2,7 +2,7 @@
 // dec_audio.c:
 extern void afm_help(void);
 extern int init_best_audio_codec(sh_audio_t *sh_audio,char** audio_codec_list,char** audio_fm_list);
-extern int decode_audio(sh_audio_t *sh_audio,unsigned char *buf,int minlen,int maxlen);
+extern int decode_audio(sh_audio_t *sh_audio, int minlen);
 extern void resync_audio_stream(sh_audio_t *sh_audio);
 extern void skip_audio_frame(sh_audio_t *sh_audio);
 extern void uninit_audio(sh_audio_t *sh_audio);