Codecs: mp4: Accurate seek in large files with small lookup_table

Read sample_byte_sizes table on demand when it can't be cached

Change-Id: I2191be63ceebfd8b16e1e973e13c5b51986b6564

1 files changed, 10 insertions, 1 deletions

diff --git a/lib/rbcodec/codecs/libm4a/demux.c b/lib/rbcodec/codecs/libm4a/demux.c
index 25462db030..8a424c5187 100644
--- a/lib/rbcodec/codecs/libm4a/demux.c
+++ b/lib/rbcodec/codecs/libm4a/demux.c
@@ -400,7 +400,8 @@ static bool read_chunk_stsz(qtmovie_t *qtmovie, size_t chunk_len)
     }
     else
     {
-        DEBUGF("stsz too large, ignoring it\n");
+        qtmovie->res->sample_byte_sizes_offset = stream_tell(qtmovie->stream);
+        DEBUGF("stsz too large: %u, save sample_byte_sizes_offset\n", numsizes);
     }
 
     if (size_remaining)
@@ -481,6 +482,14 @@ static bool read_chunk_stco(qtmovie_t *qtmovie, size_t chunk_len)
         return false;
     }
 
+    // Reading sample_byte_sizes data on seek can lead to additional re-buffering.
+    // So skip it if we have good enough seek accuracy via lookup_table (3000 ms)
+    if (qtmovie->res->sample_byte_sizes_offset && ci->id3->length / fit_numentries <= 3000)
+    {
+        qtmovie->res->sample_byte_sizes_offset = 0;
+        DEBUGF("lookup_table seek accuracy %ld ms, ignoring sample_byte_sizes_offset \n", ci->id3->length / fit_numentries);
+    }
+
     /* Build up lookup table. The lookup table contains the sample index and
      * byte position in the file for each chunk. This table is used to seek
      * and resume (see m4a_seek() and m4a_seek_raw() in libm4a/m4a.c) and