From 19f9fd0f5feaf329a6e386eb859e0700b6e8dcc6 Mon Sep 17 00:00:00 2001
From: Andree Buschmann <AndreeBuschmann@t-online.de>
Date: Sat, 16 Apr 2011 19:08:50 +0000
Subject: Refactor alac decoder as preparation for upcoming m4a changes. The
 alac decoder does not need to use get_sample_info() to gather frame size or
 the number of consumed bytes.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@29724 a1c6a512-1295-4272-9138-f99709370657
---
 apps/codecs/alac.c           | 21 +++++----------------
 apps/codecs/libalac/alac.c   |  9 +++++++++
 apps/codecs/libalac/decomp.h |  1 +
 3 files changed, 15 insertions(+), 16 deletions(-)

diff --git a/apps/codecs/alac.c b/apps/codecs/alac.c
index 3721f04f1f..428fc59836 100644
--- a/apps/codecs/alac.c
+++ b/apps/codecs/alac.c
@@ -35,8 +35,6 @@ enum codec_status codec_main(void)
   stream_t input_stream;
   uint32_t samplesdone;
   uint32_t elapsedtime;
-  uint32_t sample_duration;
-  uint32_t sample_byte_size;
   int samplesdecoded;
   unsigned int i;
   unsigned char* buffer;
@@ -112,18 +110,9 @@ enum codec_status codec_main(void)
       ci->seek_complete();
     }
 
-    /* Lookup the length (in samples and bytes) of block i */
-    if (!get_sample_info(&demux_res, i, &sample_duration, 
-                         &sample_byte_size)) {
-      LOGF("ALAC: Error in get_sample_info\n");
-      retval = CODEC_ERROR;
-      goto done;
-    }
-
     /* Request the required number of bytes from the input buffer */
-
-    buffer=ci->request_buffer(&n,sample_byte_size);
-    if (n!=sample_byte_size) {
+    buffer=ci->request_buffer(&n, demux_res.sample_byte_size[i]);
+    if (n!=demux_res.sample_byte_size[i]) {
         retval = CODEC_ERROR;
         goto done;
     }
@@ -132,15 +121,15 @@ enum codec_status codec_main(void)
     ci->yield();
     samplesdecoded=alac_decode_frame(&alac, buffer, outputbuffer, ci->yield);
 
-    /* Advance codec buffer n bytes */
-    ci->advance_buffer(n);
+    /* Advance codec buffer by amount of consumed bytes */
+    ci->advance_buffer(alac.bytes_consumed);
 
     /* Output the audio */
     ci->yield();
     ci->pcmbuf_insert(outputbuffer[0], outputbuffer[1], samplesdecoded);
 
     /* Update the elapsed-time indicator */
-    samplesdone+=sample_duration;
+    samplesdone+=samplesdecoded;
     elapsedtime=(samplesdone*10)/(ci->id3->frequency/100);
     ci->set_elapsed(elapsedtime);
 
diff --git a/apps/codecs/libalac/alac.c b/apps/codecs/libalac/alac.c
index a7d7448b97..38fd6e1cdf 100644
--- a/apps/codecs/libalac/alac.c
+++ b/apps/codecs/libalac/alac.c
@@ -1108,10 +1108,14 @@ int alac_decode_frame(alac_file *alac,
 {
     int channels;
     int outputsamples;
+    int input_buffer_start;
 
     /* setup the stream */
     alac->input_buffer = inbuffer;
     alac->input_buffer_bitaccumulator = 0;
+    
+    /* save to gather byte consumption */
+    input_buffer_start = (int)alac->input_buffer;
 
     channels = readbits(alac, 3);
 
@@ -1127,6 +1131,11 @@ int alac_decode_frame(alac_file *alac,
         default: /* Unsupported */
             return -1;
     }
+    
+    /* calculate consumed bytes */
+    alac->bytes_consumed = (int)alac->input_buffer - input_buffer_start;
+    alac->bytes_consumed += (alac->input_buffer_bitaccumulator>5) ? 2 : 1;
+
     return outputsamples;
 }
 
diff --git a/apps/codecs/libalac/decomp.h b/apps/codecs/libalac/decomp.h
index bd476804cd..d7abd4db34 100644
--- a/apps/codecs/libalac/decomp.h
+++ b/apps/codecs/libalac/decomp.h
@@ -20,6 +20,7 @@ typedef struct
     int samplesize;
     int numchannels;
     int bytespersample;
+    int bytes_consumed;
 
     /* stuff from setinfo */
     uint32_t setinfo_max_samples_per_frame; /* 0x1000 = 4096 */    /* max samples per frame? */
-- 
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