From b5b9cb031d0b1b3c802fde2f33e27ecf7d166778 Mon Sep 17 00:00:00 2001
From: Mohamed Tarek <mt@rockbox.org>
Date: Mon, 13 Jul 2009 10:06:19 +0000
Subject: Modified the code for seeking to speed it up a bit. Instead of
 searching the file for the required timestamp, we seek directly to a
 calcualted position. If we go to a point beyond the desired seek_time, we
 seek back in blocks (normally one or two blocks to the back) to get the
 required block.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@21836 a1c6a512-1295-4272-9138-f99709370657
---
 apps/codecs/cook.c | 70 ++++++++++++++++++++++++++----------------------------
 1 file changed, 34 insertions(+), 36 deletions(-)

(limited to 'apps')

diff --git a/apps/codecs/cook.c b/apps/codecs/cook.c
index 5efb797fdd..fe818be905 100644
--- a/apps/codecs/cook.c
+++ b/apps/codecs/cook.c
@@ -41,12 +41,12 @@ static void init_rm(RMContext *rmctx)
 enum codec_status codec_main(void)
 { 
     static size_t buff_size;
-    int datasize, res, consumed, i, j, time_offset;
+    int datasize, res, consumed, i, time_offset;
     uint8_t *bit_buffer;
     int16_t outbuf[2048] __attribute__((aligned(32)));
     uint16_t fs,sps,h;
     uint32_t packet_count;
-    int scrambling_unit_size, flag_seek_block = 0;
+    int scrambling_unit_size, num_units;
 
 next_track:
     if (codec_init()) {
@@ -102,51 +102,49 @@ seek_start :
             if (ci->stop_codec || ci->new_track)
                 goto done;
 
-             if (ci->seek_time) {
+            if (ci->seek_time) {
+                ci->set_elapsed(ci->seek_time);
+
+                /* Do not allow seeking beyond the file's length */
+                if ((unsigned) ci->seek_time > ci->id3->length) {
+                    ci->seek_complete();
+                    goto done;
+                }       
+
                 ci->seek_buffer(rmctx.data_offset + DATA_HEADER_SIZE);
                 packet_count = rmctx.nb_packets;
                 rmctx.audio_pkt_cnt = 0;
                 rmctx.frame_number = 0;
+
+                /* Seek to the start of the track */
                 if (ci->seek_time == 1) {
                     ci->set_elapsed(0);
                     ci->seek_complete();
                     goto seek_start;           
-                }                                
-                j = 0;
-                while(1) {
+                }                                                                
+                num_units = ((ci->seek_time)/(sps*1000*8/rmctx.bit_rate))/(h*(fs/sps));                    
+                ci->seek_buffer(rmctx.data_offset + DATA_HEADER_SIZE + consumed * num_units);
+                bit_buffer = (uint8_t *) ci->request_buffer(&buff_size, scrambling_unit_size);
+                consumed = rm_get_packet(&bit_buffer, &rmctx, &pkt);
+                if(consumed < 0) {
+                     DEBUGF("rm_get_packet failed\n");
+                     return CODEC_ERROR;
+                } 
+                packet_count = rmctx.nb_packets - rmctx.audio_pkt_cnt * num_units;
+                rmctx.frame_number = ((ci->seek_time)/(sps*1000*8/rmctx.bit_rate)); 
+                while(rmctx.audiotimestamp > (unsigned) ci->seek_time) {
                     rmctx.audio_pkt_cnt = 0;
-                    bit_buffer = (uint8_t *) ci->request_buffer(&buff_size, scrambling_unit_size);                    
-                    consumed = rm_get_packet(&bit_buffer, &rmctx, &pkt);
-                    if(consumed < 0) {
-                        DEBUGF("rm_get_packet failed\n");
-                        return CODEC_ERROR;
-                    }     
-                    if(rmctx.audiotimestamp < (unsigned) ci->seek_time) {
-                        ci->advance_buffer(consumed); 
-                        packet_count -= rmctx.audio_pkt_cnt;   
-                        rmctx.frame_number += h*(fs/sps); 
-                        j+= consumed;                          
-                    }                 
-                    if(rmctx.audiotimestamp > (unsigned) ci->seek_time) {
-                        flag_seek_block = 1;
-                        rmctx.audio_pkt_cnt = 0;
-                        break;
-                    }                                                          
-                }
-
-                if(flag_seek_block) {   
-                    ci->seek_buffer(rmctx.data_offset + DATA_HEADER_SIZE + j - consumed);
-                    bit_buffer = (uint8_t *) ci->request_buffer(&buff_size, scrambling_unit_size);                                      
-                    consumed = rm_get_packet(&bit_buffer, &rmctx, &pkt);
+                    ci->seek_buffer(rmctx.data_offset + DATA_HEADER_SIZE + consumed * (num_units-1));
+                    bit_buffer = (uint8_t *) ci->request_buffer(&buff_size, scrambling_unit_size); 
+                    consumed = rm_get_packet(&bit_buffer, &rmctx, &pkt);                                                                             
                     packet_count += rmctx.audio_pkt_cnt;
-                    rmctx.frame_number -= h*(fs/sps);
-                    time_offset = ci->seek_time - rmctx.audiotimestamp;
-                    i = (time_offset/((sps * 8 * 1000)/rmctx.bit_rate));
-                    flag_seek_block = 0;
-                    ci->set_elapsed(rmctx.audiotimestamp+(1000*8*sps/rmctx.bit_rate)*i);
-                    ci->seek_complete();                    
+                    num_units--;
                 }
-             }    
+                time_offset = ci->seek_time - rmctx.audiotimestamp;
+                i = (time_offset/((sps * 8 * 1000)/rmctx.bit_rate));
+                ci->set_elapsed(rmctx.audiotimestamp+(1000*8*sps/rmctx.bit_rate)*i);
+                ci->seek_complete(); 
+            }    
             res = cook_decode_frame(&rmctx,&q, outbuf, &datasize, pkt.frames[i], rmctx.block_align);
             rmctx.frame_number++;
 
-- 
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