Codecs: mpa: Improve seek in large mp3 vbr files

Use current position as toc mark and use it if it gives better accuracy.

Continuation of 3883c978

Change-Id: Ic6e8192fc43061f3c07128486dbefba7382be5ce

1 files changed, 16 insertions, 13 deletions

diff --git a/lib/rbcodec/codecs/mpa.c b/lib/rbcodec/codecs/mpa.c
index c5d47a6791..5fdcb38da8 100644
--- a/lib/rbcodec/codecs/mpa.c
+++ b/lib/rbcodec/codecs/mpa.c
@@ -176,6 +176,8 @@ static int get_file_pos(int newtime)
     struct mp3entry *id3 = ci->id3;
 
     if (id3->vbr) {
+        int curpos = ci->curpos - id3->first_frame_offset;
+        long skipms_from_curpos = curpos > 0 ?  (long) (id3->elapsed - newtime) : - newtime;
         if (id3->has_toc) {
             /* Use the TOC to find the new position */
             unsigned int percent = ((uint64_t)newtime * 100) / id3->length;
@@ -183,28 +185,29 @@ static int get_file_pos(int newtime)
                 percent = 99;
 
             unsigned int pct_timestep = id3->length / 100;
-            unsigned int toc_sizestep = id3->filesize / 256;
-            unsigned int cur_toc = id3->toc[percent];
-            unsigned int next_toc = percent < 99 ? id3->toc[percent+1] : 256;
-            unsigned int plength = (next_toc - cur_toc) * toc_sizestep;
-
-            /* Seek to TOC mark */
-            pos = cur_toc * toc_sizestep;
 
             /* Interpolate between this TOC mark and the next TOC mark */
-            int newtime_toc = newtime - percent * pct_timestep;
-            pos += (uint64_t)plength * newtime_toc / pct_timestep;
-        } else {
+            int skipms_from_toc = newtime - percent * pct_timestep;
+            if (skipms_from_toc < abs(skipms_from_curpos)) 
+            {
+                unsigned int toc_sizestep = id3->filesize / 256;
+                unsigned int cur_toc = id3->toc[percent];
+                unsigned int next_toc = percent < 99 ? id3->toc[percent+1] : 256;
+                unsigned int plength = (next_toc - cur_toc) * toc_sizestep;
+
+                pos = cur_toc * toc_sizestep + (uint64_t) plength * skipms_from_toc / pct_timestep;
+            }
+        } else if (newtime < abs(skipms_from_curpos)) {
             /* No TOC exists, estimate the new position */
             pos = (uint64_t)newtime * id3->filesize / id3->length;
         }
         // VBR seek might be very inaccurate in long files 
         // So make sure that seeking actually happened in the intended direction 
         // Fix jumps in the wrong direction by seeking relative to the current position
-        long delta = id3->elapsed - newtime;
-        if ((delta >= 0 && pos > ci->curpos) || (delta < 0 && pos < ci->curpos))
+        if (pos == -1 || (skipms_from_curpos >= 0 && pos > curpos) || (skipms_from_curpos < 0 && pos < curpos))
         {
-            pos = ci->curpos - delta * id3->filesize / id3->length;
+            pos = curpos - skipms_from_curpos * (id3->filesize / id3->length);
+            //LOGF("сurpos relative seek: %d, curpos: %d, newtime: %d", pos, curpos, newtime);
         }
     } else if (id3->bitrate) {
         pos = newtime * (id3->bitrate / 8);